Parathyroid Scintigraphy - European Association of Nuclear Medicine

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the operation, the time necessary for frozen section examination can be used by the surgeon for inspection of the other parathyroid glands, also reducing surgeon anxiety. Important points to know when proceeding with parathyroid imaging • Imaging is not for diagnosis. The increase in plasma levels of calcium (normal value 88–105 mg/l) and PTH (normal value 10–58 ng/l) establishes the diagnosis. • • • • • Imaging does not identify normal parathyroid glands, which are too small (20–50 mg) to be seen. Imaging should detect abnormal parathyroid(s) and indicate the approximate size and the precise relationship to the thyroid (the level of the thyroid at which the parathyroid lesion is seen on the anterior view; and whether it is proximal to the thyroid or deeper in the neck on the lateral or oblique view or SPECT) (Fig. 1). Imaging should identify ectopic glands (add SPECT in cases of a mediastinal focus, and ask for additional CT or MRI for confirmation and anatomical landmarks) (Fig. 2). Imaging should be able to differentiate patients with a single adenoma from those with MGD (Fig. 3). Imaging should identify thyroid nodules that may require concurrent surgical resection. The choice of imaging technique The most common preoperative localisation methods are radionuclide scintigraphy and ultrasound. As stated before, the two main reasons for failed surgery are ectopic glands and undetected MGD (Levin and Clark 1989). Because high-resolution ultrasound would, even in skilled hands, fail to detect the majority of these cases, it is not optimal for preoperative imaging as a single technique. In the study by Haber et al. (2002), ultrasound missed six of eight ectopic glands and five of six cases of MGD. Ultrasound may, however, be useful in combination with 99m Tc-sestamibi imaging (Rubello et al. 2003). 99m Tc-sestamibi scanning is now considered the most sensitive imaging technique in patients with pHPT (Giordano et al. 2001; Mullan 2004). Whatever the protocol used, 99m Tc-sestamibi scanning will usually meet the requirement of detecting ectopic glands (all eight were detected in the study by Haber et al.). With regard to the recognition of MGD, however, the protocol in use will determine the sensitivity. When 99m Tc-sestamibi is used as a single tracer with planar imaging at two time points -- the “dual-phase” (or washout) method – the sensitivity for primary hyperplasia is very low (Taillefer et al. 1992; Martin et al. 1996). Better results can be obtained by adding SPECT. Subtraction scanning, using either 123 I (Borley
et al. 1996; Hindié et al. 2000; Mullan 2004) or 99m Tc-pertechnetate (Rubello et al. 2003) in addition to 99m Tc-sestamibi, improves the sensitivity for hyperplastic glands. One difficulty with subtraction imaging is keeping the patient still for the time necessary to scan the thyroid, to inject 99m Tc-sestamibi and to record images of this second tracer. Simultaneous recording of 123 I and 99m Tc-sestamibi can be a simple answer to these difficulties. It prevents artefacts on subtraction images due to patient motion, and shortens the imaging time (Hindié et al. 1998; Mullan 2004). Preoperative imaging has opened a new era of minimally invasive parathyroid surgery Conventional bilateral exploration is still considered the gold standard in parathyroid surgery. However, the introduction of 99m Tcsestamibi scanning, the availability of intraoperative adjuncts such as the gamma probe and intraoperative monitoring of PTH to help detect MGD have challenged the dogma of routine bilateral exploration. When preoperative imaging points to a single well-defined focus, unequivocally suggesting a “solitary adenoma”, the surgeon may now choose focussed surgery instead of bilateral exploration. Focussed excision can be made by open surgery through a mini-incision, possibly under local anaesthesia, or by video-assisted endoscopic surgery under general anaesthesia (Lee and Inabnet 2005). Compared with patients who undergo bilateral surgery, those in whom focussed parathyroid surgery is successfully Chapter 1: Applications of parathyroid imaging completed enjoy a shorter operation time, the possibility of local anaesthesia, a better cosmetic scar, a less painful postoperative course, less profound postoperative “transient” hypocalcaemia and an earlier return to normal activities. The fact that many clinicians now use a lower threshold for surgery is partly due to the perception that parathyroid surgery is easier than in the past (Utiger 1999). Patients at specific risk of failure of minimal surgery are those with unrecognised MGD. Therefore, when choosing minimal surgery, the surgeon is committed to distinguishing cases of MGD either preoperatively, through an appropriate imaging protocol, or by intraoperative monitoring of PTH plasma levels, or by a combination of both. The true sensitivity of intraoperative PTH for MGD is still under debate. What raises concern is that studies relying solely on intraoperative measurements report a low percentage of MGD, only 3% (Molinari et al. 1996), which is three to four times lower than is generally observed during routine bilateral surgery. Whether this will lead to higher rates of late recurrence is not known. It is thus important that imaging methods used to select patients for focussed surgery have a high sensitivity for detecting MGD. In this new era of focussed operations, the success of parathyroid surgery depends not only on an experienced surgeon but also on excellent interpretation of images. A localisation study with high accuracy is mandatory to EANM
Page 1 and 2: European Association of Nuclear Med
Page 3 and 4: Contents Foreword 4 Sylviane Prévo
Page 5 and 6: Introduction Sue Huggett The first
Page 7: frequently (about 15% of cases) by
Page 11 and 12: patients with renal failure (Hindi
Page 13 and 14: Radiopharmaceuticals Linda Tutty Ra
Page 15 and 16: pertechnetate/ 99m Tc-sestamibi com
Page 17 and 18: 1 Chapter 2: Radiopharmaceuticals T
Page 19 and 20: y recording the time needed to acqu
Page 21 and 22: 1a) is defined by a fixed distance
Page 23 and 24: Obviously the maximum value of the
Page 25 and 26: • • • Language difficulties:
Page 27 and 28: Chapter 4: Patient preparation I ha
Page 29 and 30: Imaging protocols Nish Fernando and
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Page 33 and 34: Technical aspects of probe-guided s
Page 35 and 36: of preoperative scintigraphy is ver
Page 37 and 38: tamibi dose protocol, with a succes
Page 39 and 40: Chapter 6: Technical aspects of pro
Page 41 and 42: the role of surgery in the asymptom
Page 43 and 44: hyperparathyroidism: optimization o

Parathyroid Scintigraphy - European Association of Nuclear Medicine

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