As compared to images on a conventional SPECT camera, stress myocardial perfusion images acquired on a CZT camera are more frequently interpreted as normal with identical clinical outcome after 1-year follow-up. This lowers the need for additional testing, results in lower mean radiation dose and shortens imaging time.

Also in CZT SPECT image quality decreases with weight. The use of a tracer dose and scan time that depends linearly on patient's body weight corrected for the varying image quality in CZT-SPECT MPI. This leads to better radiation exposure justification.

A major disadvantage of 18 F-FDG PET involves poor detection of small lesions and lesions with low metabolism, caused by limited spatial resolution and relatively large image voxel size. As spatial resolution and sensitivity are better in new PET systems, it is expected that small-lesion detection could be improved using smaller voxels. The aim of this study was to test this hypothesis using a state-of-the-art time-of-flight PET/CT device. Methods: 18 F-FDG PET scans of 2 image-quality phantoms (sphere sizes, 4-37 mm) and 39 consecutive patients with lung cancer were analyzed on a time-of-flight PET/CT system. Images were iteratively reconstructed with standard 4 · 4 · 4 mm voxels and smaller 2 · 2 · 2 mm voxels. For the phantom study, we determined contrast-recovery coefficients and signal-to-noise ratios (SNRs). For the patient study, 18 F-FDG PET-positive lesions in the chest and upper abdomen with a volume less than 3.0 mL (diameter, ,18 mm) were included. Lesion mean and maximum standardized uptake values (SUV mean and SUV max , respectively) were determined in both image sets. SNRs were determined by comparing SUV max and SUV mean with background noise levels. A subanalysis was performed for lesions less than 0.75 mL (diameter, ,11 mm). For qualitative analysis of patient data, 3 experienced nuclear medicine physicians gave their preference after visual side-by-side analysis. Results: For phantom spheres 13 mm or less, we found higher contrast-recovery coefficients and SNRs using small-voxel reconstructions. For 66 included 18 F-FDG PET-positive lesions, the average increase in SUV mean and SUV max using the small-voxel images was 17% and 32%, respectively (P , 0.01). For lesions less than 0.75 mL (21 in total), the average increase was 21% and 44%, respectively. Moreover, averaged over all lesions, the mean and maximum SNR increased by 20% and 27%, respectively (P , 0.01). For lesions less than 0.75 mL, these values increased up to 23% and 46%, respectively. The physicians preferred the small-voxel reconstructions in 76% of cases. Conclusion: Supported by a phantom study, there was a visual preference toward 18 F-FDG PET images reconstructed with 2 · 2 · 2 mm voxels and a profound increase in standardized uptake value and SNR for small lesions. Hence, it is expected that small-lesion detection improves using smallvoxel reconstructions. Whole-body 18 F-FDG PET integrated with CT is widely used for primary tumor analysis and mediastinal lymph node staging in patients with non-small cell and small cell lung cancer (1,2). For these patients, accurate lymph node staging is of high importance because both prognosis and therapeutic management depend on the tumor stage (3). A major disadvantage of 18 F-FDG PET involves poor detection of small lesions and lesions with low metabolism. With a sensitivity of 76% and specificity of 88% (4), PET/ CT is less sensitive for nodal involvement of small nodes (diameter, ,10 mm) (3,5). This poor detection is caused by limited spatial resolution and sensitivity (3,6). To impro...

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After orthotopic liver transplantation (OLT) bone mass rapidly declines and vertebral fracture rate increases. We studied bone loss and parameters of bone turnover in 53 consecutive patients. In an attempt to reduce bone loss the patients were prophylactically treated with cyclical etidronate in addition to daily 1 alpha-hydroxyvitamin D3 and calcium. During the first 3 months after transplantation median lumbar spinal bone mineral density (BMD) decreased 4.5%; subsequently no significant changes occurred. Median hip BMD continued to fall during the first post-transplantation year and deteriorated 7% over the whole study period. New vertebral fractures were seen in 25% of the patients, which is not lower than previously reported rates in patients not receiving cyclical etidronate. Parathyroid hormone levels increased after OLT (p = 0.01), but remained within normal ranges. Urinary hydroxyproline levels were increased and normalized in the second half-year after OLT. Elevated fasting calciuria increased further after OLT. 1,25-Dihydroxy-vitamin D3 levels were lowered pre-OLT (25 vs 66 pmol/ 1, p< 0.001) and normalized at 3 months after OLT. Serum osteocalcin concentrations remained unchanged and were reduced compared with levels in healthy controls. In summary, increased bone resorption occurs after OLT with persistent decreased bone formation, leading to vertebral fracture in 25% of patients. Etidronate, 1 alpha-calcidol and calcium treatment did not prevent bone loss.