Evaluation Report - ImPACT CT Scanner Evaluation Centre

March 2002 

Evaluation Report 

NUMBER 

MDA 02023 

Dual Slice CT Scanner Comparison Report 

ImPACT report 

MDA Evaluation Report 

MDA 02023 

© Crown Copyright 

£75

© Crown Copyright 2002 

Apart from any fair dealing for the purposes of research or private 

study, or criticism, or review, as permitted under the Copyright, 

Designs & Patents Act, 1988, this publication may only be reproduced, 

stored or transmitted in any form or by any means with the prior 

permission, in writing, of the Controller of Her Majesty's Stationery 

Office (HMSO). 

Enquiries concerning reproduction outside those terms should be sent 

to HMSO at the undermentioned address: 

The Copyright Unit, 

The Stationery Office, 

St Clements House, 

2 - 16 Colegate, 

NORWICH, 

NR3 1BQ

ImPACT – Imaging Performance Assessment of CT Scanners 

Dual Slice CT Scanner Comparison Report 

Version 6.01, March 2002 

A report comparing the specification and imaging performance of the following CT 

scanners: 

Manufacturer 

GE 

GE 

Marconi 

Siemens 

Toshiba 

Scanner model 

NX/i 

NX/i Pro 

Mx8000D 

Somatom Emotion Duo 

Asteion Dual 

Compiled and prepared by members of the ImPACT group 

www.impactscan.org 

© 2002, Crown Copyright

Table of Contents 

TABLE OF CONTENTS....................................................................................................2 

INTRODUCTION...............................................................................................................3 

Purpose of this report ................................................................................................................... 3 

Comparison methods.................................................................................................................... 3 

Specification comparison................................................................................................................. 3 

Scanner performance ...................................................................................................................... 3 

Scanners covered in this report................................................................................................... 4 

SPECIFICATION COMPARISON.....................................................................................5 

SCANNER PERFORMANCE ...........................................................................................8 

Introduction .................................................................................................................................... 8 

Dose efficiency............................................................................................................................... 9 

Head scanning ................................................................................................................................. 9 

Body scanning ................................................................................................................................. 9 

Spatial resolution......................................................................................................................... 10 

Limiting resolution.......................................................................................................................... 10 

Geometric efficiency.................................................................................................................... 11 

Clinical scan tables...................................................................................................................... 12 

Standard brain ............................................................................................................................... 12 

Standard abdomen ........................................................................................................................ 12 

Helical abdomen ............................................................................................................................ 12 

Inner ear (1mm) ............................................................................................................................. 12 

High resolution spine ..................................................................................................................... 12 

APPENDIX 1: EXTENDED SPECIFICATION COMPARISON.......................................13 

Scanner gantry............................................................................................................................. 13 

Patient couch ............................................................................................................................... 14 

X-ray generator ............................................................................................................................ 15 

X-ray tube...................................................................................................................................... 15 

Detection system ......................................................................................................................... 16 

System start-up and calibration .................................................................................................16 

Scan parameters.......................................................................................................................... 17 

Helical scanning........................................................................................................................... 17 

Scan projection radiograph (SPR) ............................................................................................. 18 

Manufacturers’ performance data.............................................................................................. 19 

Factors affecting image quality.................................................................................................. 20 

Operator’s console ...................................................................................................................... 21 

Main computer ............................................................................................................................. 22 

Image storage............................................................................................................................... 23 

Image reconstruction .................................................................................................................. 24 

3D reconstruction ........................................................................................................................ 25 

Optional features ......................................................................................................................... 26 

Installation requirements ............................................................................................................ 27 

Independent workstation ............................................................................................................ 28 

Image transfer and connectivity.................................................................................................29 

APPENDIX 2: IMAGE QUALITY ASSESSMENT AND Q ..............................................30 

APPENDIX 3: MANUFACTURERS’ COMMENTS .........................................................31 

Response from GE Medical Systems ........................................................................................ 32 

Response from Philips Medical Systems.................................................................................. 33 

Response from Siemens Medical Solutions ............................................................................. 34 

APPENDIX 4: IMPACT AND THE MDA.........................................................................35 

Background .................................................................................................................................. 35 

ImPACT ......................................................................................................................................... 35 

MDA support to purchasers and users ..................................................................................... 35 

2 ImPACT Dual Slice CT Scanner Comparison v 6.01

Introduction 

• Purpose of this report 

In January 2000, the UK government announced the funding for the replacement, over a three-year 

period, of all non-helical CT scanners in use in England. 

ImPACT has produced comparison reports for each phase of the purchase. The primary aim of 

these reports is to aid the equipment selection process by providing comparisons of CT scanners 

that are currently on the market. 

The scope of this report is limited to CT scanners that are capable of acquiring two sets of 

attenuation data per tube rotation, known as ‘dual’ or ‘two slice’ scanners. Single slice and four 

slice scanners are covered in separate reports. 

The scanners included in the report are those that are currently on the market, and in particular, 

that will generally be considered for purchase by NHS hospitals in the UK. 

• Comparison methods 

The data given in this report are representative of the scanners as of January 2002, and are liable to 

change as the performance of individual scanner models is changed and upgraded. In particular, 

optional features such as workstations and software packages may be listed as standard for the 

scanner replacement programme, but may not be included in other, separate scanner purchases. 

There are two main areas for comparison of the scanners: specification and performance 

Specification comparison 

The specification comparison is presented in two sections. The first is a side-by-side summary 

comparison of the specification of each scanner, workstation and related equipment, showing the 

parameters that are considered to be most important for inter-scanner comparison. An extended 

version of the first, giving greater detail can be found in Appendix 1 – Extended Specification 

Comparison. 

Scanner performance 

This section presents the results of ImPACT’s imaging and dose performance assessment of each 

of the scanners. Although manufacturers generally publish image and dose characteristics of their 

scanners, different measurement techniques and phantoms often make it very difficult to compare 

results from one scanner against another. The ImPACT performance assessments utilise standard 

techniques, and allow a fair, like-with-like comparison. 

ImPACT Dual Slice CT Scanner Comparison v 6.01 3

Introduction 

• Scanners covered in this report 

At the time of writing, there are five manufacturers of medical CT scanners; (in alphabetical order) 

GE Medical Systems, Philips Medical Systems, Shimadzu, Siemens AG and Toshiba Medical 

Systems. Of these, IGE, Philips, Siemens and Toshiba produce dual slice scanners. The scanner 

models in this report are listed in the table below. 

Manufacturer 

GE 

GE 

Philips 

Siemens 

Toshiba 

Scanner model 

NX/i 

NX/i Pro 

Mx8000D 

Somatom Emotion Duo 

Asteion Dual 

The GE NX/i and NX/i Pro are very similar, the main difference being the larger tube and 

generator on the NX/i Pro. The specification comparison section lists them in a single column, 

with the differences shown where relevant. The performance data comes from an assessment of an 

NX/i Pro, but the NX/i has identical imaging performance. 

Philips acquired Marconi Medical in October 2001. The Philips Mx8000D was formerly marketed 

as the Marconi Mx8000D. 

The Philips Mx8000D and the Toshiba Asteion Dual have not yet been evaluated by ImPACT, 

therefore no imaging performance measurements are available. The limiting resolution data for the 

Mx8000D came from the assessment of the Marconi Mx8000 (a four slice scanner), which is also 

applicable to the Mx8000D. 

Siemens’ dual slice scanner is the Somatom Emotion Duo, which replaces the Somatom Volume 

Access. The single slice version of the Somatom Emotion has been assessed, and the results are 

presented in the ImPACT Single Slice CT Scanner Comparison Report (MDA02020), however, 

the filtration of the Emotion has changed since this assessment. The Emotion Duo has not yet 

been assessed by ImPACT. 



GE NX/i 

[and NX/i Pro] 

Marconi 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Scanner gantry 

Generation 3rd 3rd 3rd 3rd 

Aperture (cm) 70 70 70 72 

Maximum scan field of view (cm) 50 50 50 50 

Nominal slice widths for axial scans 

(mm) 

Couch 

2 x 1, 2, 3, 4, 5, 6, 

7, 10, [2 x 0.5] 

2 x 0.5,1, 2.5, 5, 8, 

10 

2 x 1, 1.5, 2.5, 3, 

4. 1 x 6, 8 ,10 

2 x 0.5, 1, 2, 3, 4, 

5, 8, 10 

Length and width (cm) 

224 x 65 (or 42 just 

for cradle) 

243 x 67.5 217.5 x 43 200 x 47 

Horizontal movement range (cm) 162 200 153 182 

Vertical movement range out of 

gantry (cm) 

40 - 95 48 - 100.8 45 - 83 30 - 87 

Maximum weight on couch (kg) 180 200 200 205 

Tube and generator 

Generator power rating (kW) 42 or 53.2 60 40 36 

Anode heat capacity (MHU) 3.5 [6.3] 6.5 3.5 MHU 

Maximum anode cooling rate 

(kHU/min) 

Guaranteed tube life 

Detection system 

4.0 (nominal) 

(claimed 

equivalent to 6.5) 

820 [840] 735 700 864 

200,000 rotations 

160,000 scan 

revolutions 

130,000 scan 

seconds 


Number of elements along z-axis 2 2 2 22 

Effective length of each element at 

isocentre (mm) 

2 x 10 2 x 10 2 x 5 4 x 0.5, 18 x 1 

Total effective length of detector 

array at isocentre (mm) 

20 20 10 20 

Future option for more slices / 

rotation 

Yes (4) 

Yes (4, 16). 

4 slice takes 

1 day. 

32/64 slices WIP 

N/A 

Yes (4). (not 

'forklift', 3 - 4 

days) 



GE NX/i 


Marconi 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

System start-up and calibration 

Total start-up time (in routine use) 

Total time from fully off to scanning 

in an emergency (mins) 

Recommended frequency for any 

additional calibration by the 

radiographer 

Scanning 

Scan times (s) 

* = Partial scans 

Helical pitches (range and 

increment) 

5 mins from fully 

off, 3 mins from 

standby 

8 - 9 mins from 

fully off, 4 - 5 mins 

from standby 



standby 



standby 

5 8 - 9 17 2 

Included in tube 

warm up, no 

additional cals are 

normally required 

0.46*, 0.7, 1, 1.5, 

2, 3 

NX/i: optional 0.8 

1.5 and 3 

(0.75 and 1.5) 

1 per week 

0.3*, 0.5, 0.75, 1, 

1.5, 2 

0.5 to 4 (0.25 to 

2) (0.1 steps) 

Advised 2 hrs post 

switch on 

0.5*, 0.67*, 0.8, 

0.1, 1.5 

1 to 4 (0.25 to 2) 

(freely selectable) 

1 per week 

0.5*, 0.75, 1, 1.5, 

2, 3 

1.25 to 3 (0.63 to 

1.5) (0.25 steps) 

Maximum continuous scan time (s) 120 100 100 standard 100 

Operator's console 

Number of monitors at console 1 

2 (patient set up 

and 

acquisition/image 

review, recon and 

filming) 

1 Standard , 

(acquisition/review 

and processing). 

2nd optional 

(shared database) 

2 


and processing) 

Control methods Mouse, keyboard Mouse, keyboard Mouse, keyboard 

Image storage 

Total hard disk storage capacity 

supplied as standard (Gbytes) 

27 72 

Archive options MOD (standard) MOD (standard) 

Image reconstruction 

Minimum time taken (secs) for the 

30th image of a series to appear for: 

18 GByte system 

disk, 2 x 18 GByte 

data disk 

MOD and CD-R 

(standard) 

(i) standard axial brain scan 60 (with IBO) 40 45 

(iii) helical abdomen scan 48 23 45 

Simultaneous scanning and 

reconstruction 

Mouse, cursor, 

keyboard 

45 

Rewritable MOD 

(standard) 

50 prospective, 

65 retro. 


50 retro. 

Yes Yes Yes Yes 



GE NX/i 


Marconi 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

3D reconstruction 

3D reconstruction software 

MIPs, SSD, 

volume rendering, 

MPR, virtual 

endoscopy 

MIPs, SSD, 


MPR, virtual 

endoscopy 

MIPs, SSD, 


MPR, virtual 

endoscopy 

MIPs, SSD, 


MPR, virtual 

endoscopy 

Additional facilities 

Independent workstation Standard Standard Standard Standard 

Contrast injector Optional Optional Optional Optional 

Contrast media bolus tracking Standard Standard Standard Standard 

CT fluoroscopy software and 

hardware 

Optional Optional Optional 

Level 1 standard, 

level 2 optional 

Hard-copy imaging device Optional Optional Optional Optional 

Bone mineral densitometry Optional Optional Optional Optional 

CT angiography Standard Standard Standard Standard 

Dental Optional Optional Optional Optional 

Radiotherapy CT simulation 

software 

Prospective ECG-triggered cardiac 

software 

Retrospective ECG-gated cardiac 

software 

Image transfer/connectivity 

DICOM service classes provided by 

CT console (SCP and SCU) 


Independent workstation (SCP and 

SCU) 

Speed of scanner/workstation 

connections to local area networks 

(Mbits/s) 

Standard 

Optional 

Available from 3rd 

party 

Optional 

N/A Optional Optional Optional 

Optional Optional N/A Optional 

Storage SCU and 

SCP, 

Query/Retrieve 


SCP, 



SCP, 

Query/Retrieve, 

Print 


SCP, 


Print 


SCP, 


Print, Modality 

Worklist 


SCP, 


Print 


Print (standard), 

Storage SCP and 

Modality Worklist 

(Optional) 


SCP, Print, 


(standard) 

100 100 100 100 



• Introduction 

In order to compare the performance of CT scanners, the ImPACT evaluation programme has 

developed a range of assessment techniques. These were described in detail in MDA98/25, Type 

Testing of CT Scanners: Methods and Methodology for Assessing Imaging Performance and 

Dosimetry. The results of this testing are presented in this section, which consists of four sets of 

data regarding different aspects of scanner performance. 

The dose efficiency section looks at the overall image quality of the scanner relative to the 

radiation dose delivered to the patient, for both head and body scanning. This is presented in terms 

of the ImPACT Q value. 

Spatial resolution compares the ability of the scanners to reproduce fine detail within an image, 

usually referred to as the high contrast spatial resolution. This is presented as the MTF 50 and 

MTF 10 values for inner ear and high contrast spine clinical studies, as well as the limiting clinical 

resolution of the scanner. 

Geometric efficiency examines the z-axis dose utilisation of the scanners. This is expressed as the 

ratio of the imaged slice thickness to the x-ray beam thickness. In general, scanners with a high 

geometric efficiency will not produce large patient doses, particularly for narrow slice thicknesses, 

where geometric efficiencies are normally lowest. 

Clinical scan tables lists the measured image quality and dose parameters for the standard 

ImPACT clinical scans. 



• Dose efficiency 

Dose efficiency is a term used to describe the quality of a scanner's images relative to the radiation 

dose to the patient. It can be expressed in a number of ways, ImPACT normally use the 'Q-value', 

which combines measurements of noise, high contrast resolution, slice thickness and dose to 

produce an imaging figure of merit (see Appendix 2 for more details). 

The Q 2 values presented in this section are for head and body imaging. The imaging parameters 

used for these scans are chosen to minimise slight variations that occur for different kV, slice 

thicknesses, scan times and reconstruction algorithm, by using standard values where possible: 

kV: 120 kV or 130 kV when this is the ‘standard’ operating kV for the scanner 

Slice thickness: 2 x 5 mm for head, 2 x 10mm for body. 

Scan time: 1.5 or 2 s for head, 1s for body. 

Reconstruction algorithm: the algorithm chosen for each scanner is the one that most closely 

matches the average ‘standard’ head and body algorithm (MTF 50 of 3.4 c/cm, MTF 10 of 6.0 c/cm). 

Reconstruction field of view: 250 mm (head) and 380 mm (body). 

The mAs setting that would result in a CTDI w of 50mGy for head and 15mGy for body scanning is 

listed. Z-sensitivity, image noise at 50 or 15 mGy and MTF values are also shown. 

Head scanning 

Scanner 

Recon 

Algorithm 

mAs for 

50mGy 

z-sens 

(mm) 

Noise 

(%) 

MTF 50 

(c/cm) 

MTF 10 

(c/cm) 

GE NX/i Std+ 337 5.0 0.30 3.3 6.2 7.1 

Q 2 

Body scanning 


Recon 

Algorithm 

mAs for 

15mGy 

z-sens 

(mm) 

Noise 

(%) 

MTF 50 

(c/cm) 

MTF 10 

(c/cm) 

GE NX/i Detl 229 9.4 1.3 3.3 6.1 2.1 

Q 2 



• Spatial resolution 

The spatial resolution figures given below show the capabilities of the scanners to reproduce fine 

detail within an image. 

Limiting resolution looks at the highest spatial resolution that can be achieved with the scanner, 

using a clinical reconstruction algorithm. 

Limiting resolution 


Recon. MTF50 MTF10 

filter (lp/cm) (lp/cm) 

Marconi Mx8000D E 8.9 17.8 

GE NX/i Edge 10.2 12.1 

The scan parameters used for limiting resolution table are those that produce the highest spatial 

resolution i.e. fine focal spot, long (>1 s) scan time, sharpest reconstruction algorithm, small 

reconstruction field of view. 



• Geometric efficiency 

Geometric efficiency is a measure of the scanners dose utilisation in the z-axis. This is expressed 

as the ratio of the axial imaged slice section thickness relative to the z-axis dose profile. For 

optimum imaging, the geometric efficiency should be 1, but it is often less, especially for narrow 

beam collimations where post-patient collimation may be necessary to bring the imaged slice 

thickness closer to the nominal value. Geometric efficiency values of greater than 1 are due to the 

accuracy limits of the measurements. 

The data is presented in the form of a table and a graph. The table gives geometric efficiency 

values both for the setting closest to 2 x 1 mm slice thickness and also, where applicable, for the 

slice narrower than 1 mm. The graph presents data for all slice widths, showing how geometric 

efficiency varies with nominal imaged slice width. The total z-sensitivity figure is measured using 

fused slices. 


Slice 

Thickness 

(mm) 

Imaged 

width (mm) 

Total z- 

sensitivity 

(mm) 

Dose 

profile 

(mm) 

Geometric 

efficiency 

GE NX/i 2 x 1 1.2 2.3 2.2 1.07 

1.2 

1.0 

0.8 

0.6 

0.4 

GE NX/i 

0.2 

0.0 

0 2 4 6 8 10 

Nominal Imaged Slice Width (mm) 



• Clinical scan tables 

These are a sub-set of the standard ImPACT clinical scan tables for a range of examination types. 

It should be noted that exposure parameters listed were those suggested by the manufacturer, but in 

practice they will vary from site to site. In particular, the settings for mA and scan time, which 

define patient dose, may vary widely from one centre to another. 

Standard brain 

Head scan reconstructed to show low contrast brain detail. 

Scan Slice FOV Conv. CTDI W z-sens. Noise MTF 50 MTF 10 

Scanner kVp mAs 

time (s) (mm) (mm) Filter (mGy) (mm) (%) (c/cm) (c/cm) 

GE NX/i 120 240 2 2 x 10 250 Std+ 35 9.4 0.26 3.3 6.2 

Standard abdomen 

Axial abdomen scan. 




GE NX/i 120 175 0.7 2 x 10 380 Std+ 11 9.4 1.2 2.7 4.8 

Helical abdomen 

Helical abdomen scan. 




GE NX/i 120 175 0.7 10 380 Std+ 8 10.4 1.1 2.5 4.5 

Inner ear (1mm) 

High contrast inner ear exam, using a narrow slice for good resolution in the z-axis. 

Scan Slice FOV Conv. CTDI W z-sens. Noise MTF 50 MTF 10 MTF 10 


time (s) (mm) (mm) Filter (mGy) (mm) (%) (c/cm) (c/cm) as mm 

GE NX/i 120 100 1 2 x 1 120 Edge 16 1.2 8.4 10.2 12.1 0.41 

High resolution spine 

High contrast spine examination. 

Scan Slice FOV Conv. CTDI W z-sens. Noise MTF 50 MTF 10 MTF 10 


time (s) (mm) (mm) Filter (mGy) (mm) (%) (c/cm) (c/cm) as mm 

GE NX/i 120 170 1 2 x 3 120 Bone 12 3.1 13.82 7.5 10.1 0.50 


Appendix 1: Extended specification comparison 

• Scanner gantry 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Generation 3rd 3rd 3rd 3rd 

Slipring Low voltage Low voltage Low voltage Low voltage 

Aperture (cm) 70 70 70 72 

Scan fields of view (cm) 18, 25, 35, 50 25 and 50 50 18, 24, 32, 40, 50 

Nominal slice widths for axial scans 

(mm) 

2 x 1, 2, 3, 4, 5, 6, 

7, 10, [2 x 0.5] 

2 x 0.5,1, 2.5, 

5, 8, 10 

2 x 1, 1.5, 2.5, 3, 

4. 1 x 6, 8 ,10 

2 x 0.5, 1, 2, 3, 4, 

5, 8, 10 

Tilt range (degrees) ± 30 ± 30 ± 30 ± 30 

Type of positioning lights Laser Laser Laser Laser 



• Patient couch 

Couch top 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Material Carbon fibre Carbon fibre Carbon fibre Carbon Fibre 

Length and width (cm) 

Horizontal movement 

224 x 65 (or 42 just 

for cradle) 

243 x 67.5 217.5 x 43 200 x 47 

Horizontal movement range (cm) 162 200 153 182 

Horizontal movement speeds 

(mm/sec) 

20, 100 0.5 - 100 1 - 100 10, 100 

Accuracy/reproducibility of table 

positioning (mm) 

± 0.25 ± 0.25 ± 0.5 ± 0.25 

Scannable horizontal range (cm): 

(i) without table top extension 162 165 153 144 

(ii) with table top extension(s) 162 187 153 155 

Vertical movement 

Vertical movement range out of 

gantry (cm) 

Vertical movement range in gantry 

(cm) 

Minimum couch top height outside 

gantry (cm) 

Weight bearing properties 

Maximum weight allowed on couch 

(kg) 

Maximum weight on couch which 

still achieves stated performance 

specifications (kg) 

40 - 95 48 - 100.8 45 - 83 30 - 87 

81 - 95 86 - 100.8 18.6 73 - 87 

40 48 45 30 

205 200 200 500 

180 200 200 205 



• X-ray generator 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Type High frequency High frequency High frequency High frequency 

Location 

Rotation assembly Rotation assembly Rotation assembly Rotation assembly 

Power rating (kW) 42 or 53.2 60 40 36 

kV settings available 80, 120, 140 90, 120, 140 80, 110, 130 80, 100, 120, 135 

mA range and step size 

Max. mA allowed for each kV 

10 - 350 [10 - 440] 

(5mA steps) 

80kV:350 [400]mA 

120kV:350 

[440]mA 

140kV:300 

28 - 500 

( 5.5 6.4mm (at 80kV) > 1 (inh) + 1.5 

Anode heat capacity (MHU) 3.5 [6.3] 6.5 3.5 MHU 

Maximum anode cooling rate 

(kHU/min) 

Method of cooling 

Guaranteed tube life 

4.0 (nominal) 

(claimed 

equivalent to 6.5) 

820 [840] 735 700 864 

Oil to air 


Pumped oil/forced 

air 

160,000 scan 

revolutions 

Oil to air 

130,000 scan 

seconds 

Oil/forced air with 

liquid metal 

bearings 




• Detection system 

Detector type 

Number of detectors per row 

GE NX/i 


Solid state (HiLight 

/ Lumex) 

789 (plus 23 

reference 

elements) 

Philips 

Mx8000D 

Solid state (High 

speed ceramic) 

672 (plus 2 

reference 

elements) 

Siemens 

Emotion Duo 

Solid state (Ultra 

Fast Ceramic) 

2 x 672 

Toshiba 

Asteion Dual 

Solid state 

896 (plus 1 pair ref 

detectors) 

Number of elements along z-axis 2 2 2 22 

Effective length of each element at 

isocentre (mm) 

2 x 10 2 x 10 2 x 5 4 x 0.5, 18 x 1 

Total effective length of detector 

array at isocentre (mm) 

20 20 10 20 

Future option for more 

slices/rotation 

Yes (4) 

Yes (4, 16). 

4 slice takes 

1 day. 

32/64 slices WIP 

N/A 

Yes (4). (not 

'forklift', 3 - 4 days) 

• System start-up and calibration 

Power-on to warm-up time (mins) 

Tube warm-up time from 'cold' to 

operating temperature (mins) 

Time to perform detector 

calibrations at warm-up (mins) 

Recommended frequency for any 

additional calibration by the 

radiographer 

Time to perform these additional 

calibrations (mins) 

Total time from fully off to scanning 

in an emergency (mins) 

GE NX/i 


3 from fully off, 1 

from standby 

Philips 

Mx8000D 

6 from fully off, 

approx. 2 from 

standby 

Siemens 

Emotion Duo 


from standby 

2 2 - 3 3 

Included in 2 mins 

tube warm-up 

Included in tube 

warm up, no 

additional cals. are 


5 mins but not 


Toshiba 

Asteion Dual 


from standby 

2 (0 in an 

emergency) 

3 2 1 

1 per week 

Advised 2 hrs post 

switch on 

1 per week 

2 2 Up to 20 

5 8 - 9 17 2 



• Scan parameters 

GE NX/i 


Reconstruction fields of view (cm) 4.8 - 50 

Nominal slice widths (mm) and 

2 x 0.5*, 2 x 1, 

number of simultaneous slices (axial 

2 x 2, 2 x 3, 2 x 5, 

scans) 

2 x 7, 2 x 10, 9 + 1 

* = Optional 

Scan times for axial scans (s) 

* = partial scans 

0.46*, 0.7, 1, 1.5, 

2, 3 


Philips 

Mx8000D 

2.5 - 50 (0.1 

steps) 

2 x 0.5, 2 x 1, 

2 x 2.5, 2 x 5, 

2 x 8, 2 x 10 

0.3*, 0.5, 0.75, 1, 

1.5, 2 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

5 - 50 0 - 50 

2 x 1, 2 x 1.5, 

2 x 2.5, 2 x 4, 

6, 8, 10 

0.5*, 0.67*, 0.8, 

0.1, 1.5 

2 x 0.5, 2 x 1, 

2 x 2, 2 x 3, 2 x 4, 

2 x 5, 2 x 8, 2 x 10 

0.5*, 0.75, 1, 1.5, 

2, 3 

kV settings available 80, 120, 140 90, 120, 140 80, 110, 130 80, 100, 120, 135 

mA range and step size 

Max. mA allowed for each kV 

10 - 350 [10 - 440] 

(5mA steps) 

80kV:350 [400]mA 

120kV:350 

[440]mA 

140kV:300 

[380]mA 

28 - 500 

(1mA steps) 

90 kV: 500 mA 

120 kV: 500 mA 

140 kV: 425 mA 

30 - 240 (10 mAs) 

80 kV: 228 mA 

110 kV: 236 mA 

130 kV: 240 mA 

10 - 400 

(10mA steps) 

80-120 kV: 400 

mA 

135 kV: 350 mA 

• Helical scanning 

Rotation times for helical scanning 

(s) 

Pitches available for routine 

scanning (range and increment) 

Recommended pitches for optimal 

image quality 

Helical interpolation algorithms 

available 

Maximum number of rotations in 

one helical run at standard 

abdomen parameters 

GE NX/i 


0.7, 1. 1.5 


1.5 and 3 

(0.75 and 1.5) 

1.5 and 3 

180º LI, 360° & z- 

filter interpolation 

39 (300mA), 

56 (250 mA), 

>60 (210mA) 

[99 (300mA), 

110 (270 mA), 

120 (250mA)] 

All 0.7s scan time 

Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

0.5, 0.75, 1, 1.5 0.8, 1, 1.5 0.75, 1, 1.5 

0.5 to 4 (0.25 to 

2) (0.1 steps) 

0.5, 0.75, 1, 1.25, 

1.75, 2.5, 3.5, 4 

180º, 360º, high 

order non linear 

filters 

200 

1 to 4 (0.25 to 2) 

(freely selectable) 

2 to 4 

Adaptive axial 

interpolator 

100 (100mA) 

100 (150mA) 

45 (200mA) 

All 0.8s scan time 

1.25 to 3 (0.63 to 

1.5) (0.25 steps) 

1.25, 1.5, 1.75, 

2.25, 2.5, 2.75, 3 

180º, 360º, 

Muscot 

115 

(190mA, 0.75s) 

133 

(160mA, 0.75s) 

Maximum continuous scan time (s) 120 100 100 100 

Gantry tilt for helical scanning 

(degrees) 

30 30 



• Scan projection radiograph (SPR) 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Maximum SPR length (mm) 1000 1024 1024 1390 

SPR field dimensions (mm x mm) 500 x 1000 

Angular positions of x-ray tube 

available for SPR (degrees) 

Real time image 

Accuracy of slice prescription from 

the scanogram (mm) 

Any angle from 0 - 

355 (5º steps) 

Yes 

width: 500 

length: 100 - 1024 

(1mm steps) 

512 x 1024 

0, 90, 180, 270 AP, PA, LAT 

Available next s/w 

release. (Recon 

time curently 2s) 

Standard 

width: 240, 400, 

500, 

length: 200 - 1,390 

0, 90, 180, 270 

(oblique in 5º 

steps) 

Yes 

± 0.25 < ± 1 ± 0.5 ± 0.25 

Accuracy of distance measurements 

from SPR's taken at isocentre 

(lateral and axial directions) (mm) 

± 0.25 ± 0.25 ± 0.5 < +/- 0.5 mm 



• Manufacturers’ performance data 

High contrast spatial resolution 

Resolution (lp/cm) for sharpest 

clinical algorithm 

Low contrast resolution 

Smallest rod size (mm) discernable 

at given parameters in 20 cm 

CATPHAN 

Dose 

GE NX/i Plus 


15 lp @ 0% MTF 

13 lp @ 10% MTF 

8.5 lp @ 50% MTF 

Performance 

algorithm, 0.7 sec 

scan time, small 

focus 

5.0mm @ 0.3% 

Philips 

Mx8000D 

24.0 lp/cm @ cut 

off, Ultra-high 

mode 

5 mm @ 0.3%, 

120 kVp, 250 

mAs, 2 x 10 mm 

slice 

Siemens 

Emotion Duo 

0% MTF 15.5 

lp/cm. 60 mA 

130 kV, 0.8sec, 

1mm. Large f.s. 

Alg: U90S. 

5 mm 3 HU 15.8 

mGy at 90 mAs, 

0.8 sec, 10 mm at 

130 kv 

Toshiba 

Asteion Dual 

18 lp/cm @ cut off, 

14.5 lp/cm @ 2% 

MTF, 12.5 lp/cm 

@ 10% MTF, 

FC90 

1 sec. 

Directly 

comparable data 

not available 

CTDI for axial standard brain scans 

at given parameters: 

Info. not available 


130 kV 140 mA 

1.5 s scan time 

8 mm slice 

thickness (fused 

from 2 x 4 mm) 

focal spot (normal) 


- centre of CTDI phantom 

(mGy/100 mAs) 

- periphery of CTDI phantom 

(mGy/100 mAs) 

14.7 Info. not available 21.7 Info. not available 


CTDI for axial standard abdomen 

scans 



130 kV 100 mA 

1 s scan time 

8 mm slice 

thickness (fused 

from 2 x 4 mm) 

focal spot (normal) 


- centre of CTDI phantom 

(mGy/100 mAs) 

- periphery of CTDI phantom 

(mGy/100 mAs) 



Dose profile FWHM (mm) Info. not available Info. not available 

1 mm = 1.1 mm, 

1.5 mm = 1.4 mm, 

2.5 mm = 2.5 mm, 

4 mm = 3.9 mm, 

5 mm = 4.9 mm 




• Factors affecting image quality 

Dose 

Post-patient collimation for narrow 

slices 

Automatic mA adjustment according 

to body dimensions or density 

during examination 

Noise 

Adaptive filtration for noise 

reduction 

Resolution 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

No Yes Yes No 

Smart mA 

(standard) 

Advanced noise 

reduction 

N/A 

Adaptive image 

enhancement or 

smoothing for up 

to three density 

ranges 

Yes, mA 

modulation 

Yes (automatic) 

Yes 

Yes (user 

programmable) 

Quarter detector shift Yes Yes Yes Yes 

Moving (dynamic/flying) focal spot No Yes Yes No 

Number of imaging detectors per 

row 

Sampling frequency 

Artefacts 

Artefact reduction algorithms 

789 672 672 896 

972 views/rotation 

Advanced artefact 

reduction, 

advanced noise 

reduction, 

interative bone 

option (IBO), 

motion correction 

2,320 views (in 

standard imaging 

mode of 0.75s 

rotation time) 

Iterative bone 

correction 

2 x 1344 1200 views/sec 

Modified beam 

hardening 

(abdomen, pelvis, 

shoulder), motion 

correction 

(sequential 

modes) 

Beam hardening 

correction, raster 

artefact 

suppression 

protocol (RASP), 

stack scanning, 

automatic patient 

motion correction 



• Operator’s console 

Image monitor 

Diagonal dimension of image 

screen (inches) 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

21 20 18.1 21 

Number of monitors at console 

(functions of each if > 1) 

1 

2 (patient set up 

and 

acquisition/image 

review, recon and 

filming) 

1 standard , 


and processing). 

2nd optional 

(shared database) 

2 


and processing) 

Image display 

Image display matrix dimensions 512, 768, 1024 

Usual range of CT number 

displayed (HU) 

Dose information 

Weighted CTDI (CTDI W ) diplayed on 

console 

340, 512, 768, 

1024 

-1024 to +3071 -1000 to +3094 

1024 

-1024 to +3071 

(-10,240 to 30,710 

if metal implants) 

512, 512 x 1024, 

1024 

-1024 to +8191 


Dose Length Product (DLP) 

displayed on console 

No No Yes Info. not available 

Geometric efficiency displayed on 

console when 70% for all 

collimations) 

Not applicable 

(>70% for all 

collimations) 

Not applicable 

(>70% for all 

collimations) 

Control methods Mouse, keyboard Mouse, keyboard Mouse, keyboard 


Mouse, cursor, 

keyboard 



• Main computer 

Make and model 

GE NX/i 


Silicon Graphics 

O 2 

Philips 

Mx8000D 

2 x Silicon 

Graphics O 2 

Siemens 

Emotion Duo 

Siemens PC with 

array processor; 

IRS - 2 x Pentium 

III, ICS - Pentium 

III, G200 graphic 

card ( 2nd console 

'Wizard' is option) 

Toshiba 

Asteion Dual 

2 x Silicon 

Graphics O 2 

Operating system IRIX Unix Windows NT IRIX 

Type and speed of CPU 

Amount of computer RAM (Mbytes): 

RU5200, 300 MHz 

2 x RISC 

processor 

300 MHz (one for 

each console) 

(i) supplied as standard 512 2 x 1024 

(ii) maximum 512 2 x 1024 

Navigator: 

Primergy CISC 

CPU is 933 MHz 

Navigator: 1024, 

Optional Wizard: 

1536 

Navigator: 1024, 

optional Wizard: 

1536 

R5000 (scan 

console) R12000 

(display console) 

300 MHz 

2 x 1024 

2 x 1024 



• Image storage 

Hard disk storage 

Total standard hard disk capacity 

(Gbytes) 

Maximum hard disk capacity 

(Gbytes) 

Hard disk capacity for image 

storage (Gbytes and no. of 

uncompressed 512 x 512 images) 

Hard disk capacity for storage of 

raw data files (Gbytes and no. of 

data files) 

Archive options 

GE NX/i 


Philips 

Mx8000D 

27 72 

Siemens 

Emotion Duo 

18 GByte system 

disk, 2 x 18 GByte 

data disk 

Toshiba 

Asteion Dual 

27 72 36 90 

18, 

20,000 images 

18, 6000 data files 

72, 

54,000 images 

72, approx. 1800 

data files 

Archive options MOD (standard) MOD (standard) 

Capacity of a single archive disk 

(Gbytes and no. of images) 

Time to mount an archive disk or 

tape (s) 

Archive data transfer rate 

(images/s) 

2.3 (12,000 JPEG 

losslessly 

compressed 

512 x 512 images 

or 600 raw data 

files) 

5 - 6 in background 

operation 

4.1 (15,650 

512 x 512 images. 

Factor 2-3 

compression) 

Immediate (disk 

continually 

accessible) 

9, 

13,000 images 

18, 8,000 raw 

data files 

MOD and CD-R 

(standard) 

MOD: 4.1Gb 

(26,000 losslessly 

compressed 

images), CD-R: 

0.65Gb (4800 

compressed 

images) 

256 x 256 matrix 

approx 30 for full 

disk 

45 

16,000 images 


Rewritable MOD 

(standard) 

2.6 (9600 

512 x 512 images - 

slightly 

compressed) 

1 (read), 0.7 (write) > 3 2 - 3 Approx. 1 

. 



• Image reconstruction 

GE NX/i 


Reconstruction matrix 256, 512 

Minimum reconstruction interval in 

helical scanning (mm) 

Reconstruction times 

Time (secs) from the start of data 

acquisition to the appearance of the 

30th image of a series: 

Philips 

Mx8000D 

340, 512, 768, 

1024 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

256, 512 256, 512 

0.1 0.1 0.1 0.1 

(i) standard axial brain scan 60 (with IBO) 40 45 

(ii) axial spine scan 47 40 45 

(iii) helical abdomen scan 48 23 45 

Parallel processing details 


reconstruction 

Any delay in either scanning or 

reconstruction when performed 

concurrently 

Simultaneous scanning and routine 

analysis 


archiving and/or hard copying 

Simultaneous scanning and transfer 

to second console/workstation 


65 retro. 


60 retro. 


50 retro. 


No No No No 






• 3D reconstruction 

3D Reconstruction on main 

console (MC) and workstation 

(WS) 

MIPs and MinIPs (maximum and 

minimum intensity projections) 

SSD (3D shaded surface display) 

3D volume rendering software 

3D virtual endoscopy 

MPR (multi-planar reconstruction) 

Planes available in MPR 

GE NX/i 


MC - standard, 

WS - standard 

(MIP & MinIP) 

MC - optional, 

WS - otandard 

(3D) 

MC - N/A, 

WS - standard 

(Volume 

Rendering) 


WS - standard 

(Navigator) 


WS - standard 

(MPR & MPVR) 

All planes as 

defined by 

operator in real 

time. MPVR is 

also std & real time 

Philips 

Mx8000D 


WS - standard 

(Angio MIP) 


WS - standard 

(3D SSD) 


WS - standard 

(Vol Rend 4D 

Angio) 


WS - standard 

(V-endo Voyager) 


WS - standard 

(MPR) 

All planes, any 

oblique (identical 

on console and 

workstations) 

Siemens 

Emotion Duo 


WS - standard 


WS - standard 


WS - standard 

MC - released Q2 

2002, 

WS - standard 


WS - standard 

Axial, sagittal, 

coronal, oblique, 

curvilinear 

Toshiba 

Asteion Dual 


WS - standard 


WS - standard 


WS - standard 


WS - standard 


WS - standard 

Axial, sagittal, 

coronal, oblique, 

curved with cross 

cut through the 

curved reformat 



• Optional features 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Contrast injector Optional Optional Optional Optional 

Contrast media bolus tracking 

CT fluoroscopy software and 

hardware 

Standard 

(SmartPrep) 

Optional 

Standard 

(BolusPro Ultra) 

Optional 

(Continuous CT 

Imaging) 

Standard 

(CARE Bolus) 

Optional (CARE 

Vision) 

Standard 

Level 1 standard, 

level 2 optional 

Hard-copy imaging device Optional Optional Optional Optional 

Radiotherapy planning 

accessories 

Radiotherapy planning table top 

Optional (RT flat 

pad and 'Exact' 

couch top) 

Optional (RTP) Optional Optional 

Carbon fibre breast board Optional N/A Optional N/A 

Means for attaching patient 

immobilisation devices and a 

stereotactic frame to the end of the 

couch 

Software packages on main 

console (MC) and workstation 

(WS) 

Bone mineral densitometry 

CT angiography 

Dental 

Radiotherapy CT simulation 

software 

Prospective ECG-triggered cardiac 

software 

Retrospective ECG-gated cardiac 

software 

Optional (Exact 

couch E8505M) 

MC - N/A, 

WS - optional 

(PC option) 

BMD 


WS - standard 

(including MIP 

MinIP Average) 


WS - optional 

(Dentascan) 

MC - N/A, 

WS - standard for 

CT Sim purchase, 

otherwise optional 

N/A 

MC - N/A, 

WS - optional 

Optional 

(Stereotaxis) 


WS - optional 

(Q BMAP II) 


WS - standard 

(Angio MIP) 


WS - optional 

(DENT -3) 


WS - optional 

(ACQSim) 


WS - N/A 


WS - N/A 

Optional 


(Osteo CT) 

WS - N/A 


WS - standard 


(Dental CT) 

WS - N/A 

Available from 3rd 

party 


WS - N/A 

N/A 

Optional 


WS - N/A 

MC-standard, 

WS-standard 


WS - optional 


WS - N/A 


WS - N/A 


WS - N/A 



• Installation requirements 

Environmental requirements 

(max/min temperature, humidity) in 

scanner room 


(max/min temperature, humidity) in 

scanner control room 

Peak heat output from system 

during scanning (kW) 

System cooling method 

Air conditioning requirements for 

scanner room of minimum floor area 

Minimum floor area required for the 

system (m 2 ) 

Dimensions of: 

(i) Gantry (H x W x D (mm)) and 

weight 

(ii) Couch (H xW x L (mm)) and 

weight 

(iii) Supplementary units (H x W x D 

(mm)) and weight 

Power supply requirements 

GE NX/i 


20-28 ºC, 30-70% 

non condensing 

humidity 

20-28 ºC, 30-70% 

non condensing 

humidity 

3.9 (120kV, 

300mA, 1s scan 

time, 280 scans 

per hour) 

Output to air 

Recommended 

Philips 

Mx8000D 

15-30 °C, relative 

humidity 40-60% 

15-30 °C, relative 

humidity 40-60% 

Siemens 

Emotion Duo 

18 - 30 ºC, relative 

humidity 15-75%, 

15-28 ºC, relative 

humidity 15-75 % 

Toshiba 

Asteion Dual 

16-28 ºC, humidity 

40-80% 

18-28 ºC, humidity 

40-80% 

13.5 4.7 10.6 max 

Water/water or 

water/air 

Not required other 

than for patient 

comfort 

18 25 

1850 x 1820 x 911 

1190 kg 

995 x 650 x 2240 

295 kg 

Power Distribution 

Unit: 

820 x 550 x 700, 

157kg 

3 phase 380-480V, 

100kVA 

2050 x 2290 x 980 

2100kg 

480 x 670 x 2550 

500kg 

Power Cabinet: 

1800 x 900 x 750 

550kg, 

Cooling Unit: 

1800 x 900 x 750, 

500kg 

3 phase 380- 

480V, 90kVA 

Output to air 

None 

18, though 22 

recommended 

1780 x 770 x 2300 

1200kg 

890 x 680 x 2260 

400kg 

None 

3 phase 200- 

480V, 48kVA 

Output to air 

Not necessary but 

recommended 

20 

1760 x 1970 x 870 

1300kg 

390 x 620 x 2390 

330kg 

Transformer: 

980 x 800 x 770, 

550kg 

3 phase 380- 

440V, 75kVA 



• Independent workstation 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Is a workstation provided? 

Standard 

Standard 

(MX VIEW) 

Standard 

(Leonardo) 

Standard 

(AlatoView) 

Computer make and model 

Sun UltraSPARC 

60 


O 2 

Siemens Fujitsu 

Pentium 4 


O 2 

Operating system Solaris 2.7 Unix NT Unix 

Type and speed of CPU 

Two 450 MHz 

ultraSPARC II 

RISC processor, 

300MHz 

2 x Pentium (at 

least 850 MHz) 

R12000, 300 MHz 

Amount of computer RAM (Mbytes): 

(i) supplied as standard 1024 1024 1024 1024 

(ii) maximum 2048 1024 3 GB 1024 

Total hard disk storage capacity 

(Gbytes): 

(i) supplied as standard 36 18 36 27 

(ii) maximum 36 18 36 27 

Archive options 

Capacity of a single archive disk 

(Gbytes) 


(max/min temperature, humidity) for 

workstation 

MOD or CD-R/W 

(optional) 

MOD: 2.3 (9400 

losslessly 

compressed 

512 x 512 images 

or 700 raw data 

files) 

10 - 40 ºC, 

20 - 80 % relative 

non-condensing 

humidity at 40 ºC 

MOD Drive 

utilising R/W disks 

(Standard) (Data CD standard MOD 

is stored with (optional) 

lossless 

compression) 

4.1 (15,650 

512 x 512 images. 

Factor 2-3 

compression) 

0 - 40° C 

MOD: 4.1Gb 

(26,000 losslessly 

compressed 

images) CD-R: 

0.65Gb (4800 

compressed 

images) 

256 x 256 matrix 

15 - 30 ºC, 

20 - 85% relative 

humidity 

MOD (optional) 

2.6 (9600 

512 x 512 images - 

slightly 

compressed) 

16 - 28 ºC, 

humidity 40 - 80% 



• Image transfer and connectivity 

GE NX/i 


Philips 

Mx8000D 

Siemens 

Emotion Duo 

Toshiba 

Asteion Dual 

Speed of scanner/workstation 

connections to local area networks 

(Mbits/s) 

Remote PC access to images on 

workstation 


CT console (SCP and SCU) 


Independent workstation (SCP and 

SCU) 

100 100 100 100 

Optional 


SCP, 



SCP, 


JPACS or 

Radworks 

(optional). 

Radworks 

provides full image 

distribution 


SCP, 


Print 


SCP, 


Print 

Optional 


SCP, 


Print, Modality 

Worklist 


SCP, 


Print 

Optional 


Print (standard), 

Storage SCP and 

Modality Worklist 

(Optional) 


SCP, Print, 


(standard) 


Appendix 2: Image quality assessment and Q 

Statistical noise, spatial resolution and slice sensitivity are fundamental parameters describing the 

amount of object information retrievable from an image, or its image quality. X-ray dose can be 

regarded as a 'cost' of this information. In general, it is meaningless to quote any one of these 

measurements without reference to the others. The Q-value incorporates the dose, noise, spatial 

resolution and slice width into one number. This figure is derived from a relationship between 

image quality and dose received. 

A dose efficiency factor has a fundamental meaning, in that a dose efficient scanner will produce 

good resolution at minimum dose and noise. However, it can take a number of forms depending on 

how the various parameters are measured and quoted. 

The Q-value used in this comparison report, Q 2 , is the same one used in Comparison Report 12 

(MDA/00/11), which was modified from the previous value used by ImPACT, Q 1 . 

Q 2 is defined as follows: 

Q 

2 

= 

f 

av 

2 

σ z CTDI 

1 

3 

w 

where: 

σ = image noise, expressed as a percentage for a 5cm 2 region of interest at the centre of the field of 

view in the standard ImPACT water phantoms. 

f av = spatial resolution, given as (MTF 50 + MTF 10 )/ 2 

Where MTF 50 and MTF 10 are the spatial frequencies corresponding to the 50% and 10% 

modulation transfer function values respectively (in line pairs per cm). 

z 1 = the full width at half maximum (FWHM) of the imaged slice profile (z-sensitivity). This is 

measured using the inclined plates method for axial imaging, and using a 0.1mm thickness, 6mm 

diameter tungsten disc for helical scanning 

CTDI w = weighted CT dose index, as defined in EUR 16262 

The Q-factor is in part empirical and it should be used with caution. It is not an absolute figure, as 

its derivation relies on assumptions of the shape of convolution filter used. Comparisons between 

scanners will be more reliable when comparing scans reconstructed with similar convolution 

filters. It is of most importance when considering the standard scans for head or body. The 

uncertainty in this value is up to about ±15%, with a conservative estimate of ±10%. 


Appendix 3: Manufacturers’ comments 

• Responses are included from the following manufacturers : 

GE Medical Systems 

Philips Medical Systems 

Siemens Medical Solutions 



• Response from GE Medical Systems 

2nd May 2001 

ImPACT 2-Slice CT Comparison Reports 

Dear Sue 

Thank you, for the draft version of the report. 

We were pleased with the results of the comparison, which confirm the high image quality and low 

dose nature of these scanners. 

We are happy that these measurements are representative of the NX/i CT Scanners. 

Please note that the horizontal movement range is in fact 160cm, and not 162cm as stated. The 

figure of 162cm has been taken from a service manual, as this range is possible in service mode 

only 

Kind regards 

Yours sincerely 

Paul Morgan 

CT Clinical Scientist 



• Response from Philips Medical Systems 

Dear Sue, 

Thank you and all the ImPACT team for all your work on producing a thorough Blue Cover 

Report for the CT scanner comparison and assessment. 

On behalf of Marconi Medical Systems we have no additional comments to make and look 

forward to receiving a hardback copy and working with you all in the future. 

Best Regards 

Derek Tarrant 

CT Product Manager 

Marconi Medical Systems UK 

28/05/01 



• Response from Siemens Medical Solutions 

10/05/01 

ImPACT Comparison Reports; Manufacturer's Response 

Dear Sue, 

Thank you for your invitation to respond to the ImPACT Comparison report. Firstly, we would 

like to acknowledge the work and effort that you and your team have put into these reports. 

Tremendous efforts have been made by all involved to deal with this. 

Of course specifications are changing as each CT system evolves. For example the Emotion CT 

system is now delivered with a new filter which results in reduced dose. Thus, I realise it is simply 

not possible to provide a continuous comprehensive report with the rate of change taking place. So 

I think it is reasonable to recognise the work done and propose not to comment on, for example, 

specifications that may have changed between original report and this version of the publication in 

relation to each individual system. 

However, whilst you do not wish for a detailed response from us, there is one general aspect we 

would wish to highlight in some reasonable detail and I hope that you agree that this is 

appropriate. I am referring to the 'Q' factor, which reduces a complex issue of image quality to a 

single number combining spatial resolution, dose and noise level at the centre of rotation. We note 

that you do point out the limitations of the 'Q' factor in the appendices, however, it could be 

possible for some clinical teams to take this factor and regard it as a categorical statement 

regarding dose efficiency. Perhaps I could focus on the Volume Zoom, though this would affect 

any system. Since this 'Q' factor places the Volume Zoom in a ranking amongst different 

manufacturers in a poor position, we believe that the performance of this system in delivering 

outstanding clinical images is not properly reflected in this ranking.''' 

We look forward to continuing to work with you in the future. 

Yours sincerely 

David Forrest 

Product Manager CT 


Appendix 4: ImPACT and the MDA 

• Background 

One of the roles of the Medical Devices Agency (MDA) is to fund evaluation programmes for 

medical devices and equipment. The programme includes evaluation of x-ray Computed 

Tomography Equipment currently available on the UK market. 

MDA aims to ensure that evaluation techniques keep abreast of improvements in CT imaging 

performance and that MDA reports present evaluation information that is timely, useful and 

readily understood. 

• ImPACT 

ImPACT (Imaging Performance Assessment of Computed Tomography) is the MDA's CT 

evaluation facility. It is based at St George's Hospital, London, part of St George's Healthcare NHS 

Trust. 

ImPACT have developed test objects and measurement procedures suitable for inter-comparing 

CT scanner performance. For each CT evaluation hundreds of images are obtained from the system 

under test and subsequently analysed using custom written software. Dose measurements are made 

using ion chambers, and x-ray film is used to obtain additional x-ray dose information. 

Members of ImPACT contributing to and writing this report: N. Keat, A. L. Hill, M. A. Lewis, J. 

F. Barrett and S. Edyvean (ImPACT Group Leader). 

• MDA support to purchasers and users 

The ImPACT team is available to answer any queries with regard to the details of this report, and 

also to offer general technical and user advice on CT purchasing, acceptance testing and quality 

assurance. 

ImPACT 

Bence-Jones Offices 

St. George's Hospital 

London SW17 0QT 

Tel: 020 8725 3366 

Fax: 020 8725 3969 

email: impact@impactscan.org 

web site: http://www.impactscan.org 

MDA contact point for general information on the CT evaluation programme: 

Debbie Smith 

Programme Manager 

Room 1207, Hannibal House 

Elephant and Castle 

London SE1 6TQ 

Tel: 020 7972 8155 

Fax: 020 7972 8105 


MEDICAL DEVICES AGENCY 

MDA Evaluation Reports 

MDA evaluation reports are published by the Medical Devices Agency, an Executive Agency of the Department of 

Health. They are available free of charge to the UK National Health Service (NHS), and are for sale to commercial 

organisations and other interested parties. A free catalogue of available reports can be obtained from the Orders 

Department, or downloaded from the MDA web site: 

http://www.medical-devices.gov.uk 

Ordering 

Send your order to the address given below, stating the number, title and quantity of each report required. Your 

reports will be despatched by second class post the following working day. If you are not a representative of the 

NHS, you will be invoiced separately. Non-NHS customers are reminded that it is not possible to offer refunds for 

reports ordered in error. 

Enquiries 

Orders Department 

Room 1207 

Medical Devices Agency 

Hannibal House 

Elephant and Castle 

London 

SE1 6TQ 

Tel: 020-7972 8181 

Fax: 020-7972 8105 

E-mail: dep@medical-devices.gov.uk 

General publication enquiries should be directed to the Orders Department: 

Tel: 020-7972 8181 

Fax: 020-7972 8105 

E-mail: dep@medical-devices.gov.uk

ISBN 1 84182 515 8 

Smart number 36 26637 1

Evaluation Report - ImPACT CT Scanner Evaluation Centre

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?