Thesis

143 Review of the role of bone-SPECT/CT in tarsal coalitions Delayed ‘mineralization’ images were acquired 3-4 hours p.i. including bone-SPECT/ CT with low-dose CT for all patients, with the settings as follows: Table 3. Parameters and settings of the two used SPECT/computed tomography systems for acquisition Philips BrightView XCT Siemens Symbia Intevo bold SPECT SPECT matrix CT slice thickness CT basic parameters CT exposure time CT pitch CT matrix CTreconstruction increment 64 views 20 s per view 128 × 128 0.33 mm 120 kV, 30 mA 7.2 s N/A 512 × 512 60 views, 15 s per view 256 × 256 0.75 mm 110 kV, 120 mAs dose modulation 13.4 s 0.9 512 × 512 0.5 mm CT, computed tomography. The effective dose from the radiotracer administered for bone scintigraphy for an adult is approximately 3.0 to 4.0 mSv, whereas that in children is around 2.5 mSv [15]. Both feet can be imaged in the same session after a single injection of the radiopharmaceutical with no extra radiation burden when compared to imaging one foot and also at no extra time spent for the patient or the department. The amount of radiation burden for the CT-part of the study is very low for the distal lower extremities, leading to an additional effective dose of less than 0.1 mSv [16]. For standardized positioning and avoiding motion artifacts, an immobilization device is advised in order to position the feet and the ankles appropriately. This dedicated foot support should consist of synthetic materials that do not introduce artefacts on the CT and should both immobilize with upper ankle joint in 90-degree position and be comfortable enough to stimulate immobilization. Quantification of bone-SPECT/CT On the Siemens Symbia Intevo system we performed quantification additionally to visual interpretation in patients with scans pre- and post-therapy, as only visual evaluation is often inconsistent in objectifying change in the disease activity [34]. Different techniques exist to reconstruct bone-SPECT/CT images to be used for quantification and specific Bayesian methods may outperform the more often used OSEM-reconstructions with improved quantitative accuracy [35]. Both research and clinical practice on quantitative bone-SPECT/CT have worldwide gained the most experience with analysis of bone metastases in prostate (and to lesser extent breast) cancer [36]. 5

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