Study Guide RADIOLOGY - UMF

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Study Guide – Radiology – Faculty of Medicine - IV th Year 20• Long TE: 120 ms• Fluids = hypersignal• Fat = less intense signal compared to T1• Mucin = hyposignal• PD (proton density) weighting• Conditioned by the proton density• Characterized by long TR and short TEo MR Artifacts• Metallic - lack of signal (signal void) of large size, with peripheralenhancement• truncation = false bands or hyper - or hyposignal occurring where there is asharp transition in the signal - eg CSF-spinal cord (false appearance ofsyringomyelia)• Aliasing: object larger than FOV (field of view)• Chemical shift artifacts = band of hyposignal at the water-fat interface• Magnetic susceptibility: broad areas of hyposignal generated by theappearance of a magnetic field gradient at the interface of two structures withvery different magnetic susceptibility: ex air-watero Contraindications:• Absolute:• Cardiac pace-maker• Ferro-magnetic foreign body• Relative:• Pregnant women in the I trimester• Claustrophobia• Patients who are intubated, ventilatedSample Questions for the written exam of Radiology1. On standard sequences a subcutaneous lypoma appears:a. hypersignal T1b. black on T2c. hyposignal T1 and T2d. black on T1 and white on T2 weighted sequencese. It has an aspect of signal voidAnswer: a2. T1 weighting is:a. Conditioned by TRb. Conditioned by TEc. Proton density conditioned on the examined regiond. Characterized by long TR and TEe. Characterized by short TR and long TEAnswer: a3. The following statements are true, except one:a. Transverse magnetization can be measuredb. Longitudinal magnetization increases when a radio-frequency pulse isappliedc. Relaxation times are long for fluids compared to solid state.d. Adipose tissue has short relaxation timesAnswer: b
Study Guide – Radiology – Faculty of Medicine - IV th Year 21TOPIC 7. THE DIGITAL IMAGETable of ContentsI. Definitions.II. Image ProcessingIII. Image formatsIV. Sample questionsEducational objectives• The student must know:o Pixel definition• Two-dimensional picture element (monochrome square)o voxel definition• Volume element corresponding to a pixelo digital image definition• Picture which was digitized both in spatial coordinates (pixel-x, y, voxel - x,y, z) and in intensity• By digitization, the real scene is converted into an image composed of pixelsin the 2D space, respectively voxels in 3D, which have an associated grayvalue (usually ranging between 0 and 255) representing the intensity of thelight spot converted.o Image processing steps• Image acquisition• Preprocessing (improvement of primary acquisition):• noise removal• Isolation of the regions whose pixel structure indicate a similaritywith alphanumeric information required• Image Segmentation• Recognition and interpretation of data• Storage - storage of digital imageso Image formats• Binary images - the color of each pixel is expressed by a value (bit), 1 or 0. Ifit is monochrome the intensity of each pixel will be in the range of 0-255(usually)• True Color Image - the color of each pixel is expressed in terms of RGBintensities, red, green and blue• Image based on a variety of colors (Colormap) - each pixel value isinterpreted as an index into a table of RGB values• Common formats:• BMP• TIFF• GIF• JPEGo Image compression methods• Lossy compression – leads to decay of non-essential and redundantinformation (unpercievable by the human eye) at decompression• Lossless compression - does not lead to decay of information ondecompression, less used, low efficiency
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Study Guide RADIOLOGY - UMF

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