Various methodologies for 99m Tc-sestamibi parathyroid scintigraphy are in clinical use. There are few direct comparisons between the different methods and even less evidence supporting the superiority of one over another. Some reports suggest that SPECT is superior to planar imaging. The addition of CT to SPECT may further improve parathyroid adenoma localization. The purpose of our investigation was to compare hybrid SPECT/CT, SPECT, and planar imaging and to determine whether dual-phase imaging is advantageous for the 3 methodologies. Methods: Scintigraphy was performed on 110 patients with primary hyperparathyroidism and no prior neck surgery. Of these, 98 had single adenomas and are the subject of this review. Planar imaging and SPECT/CT were performed at 15 min and 2 h after injection. Six image sets (early and delayed planar imaging, SPECT, and SPECT/CT) and combinations of the 2 image sets were reviewed for adenoma localization at 13 possible sites. Each review was scored for location and certainty of focus by 2 reviewer groups. Surgical location served as the standard. Sensitivity, specificity, area under the curve, positive predictive value, negative predictive value, and k-values were determined for each method. Results: The overall k-coefficient (certainty of adenoma focus) between reading groups was 0.68 (95% confidence interval, 0.66-0.70). The highest values were for dualphase studies that included SPECT/CT. Dual-phase planar imaging, SPECT, and SPECT/CT were statistically significantly superior to single-phase early or delayed imaging in sensitivity, area under the curve, and positive predictive value. Neither single-phase nor dual-phase SPECT was statistically superior to dual-phase planar imaging. Early-phase SPECT/CT in combination with any delayed imaging method was superior to dualphase planar imaging or SPECT for sensitivity, area under the curve, and positive predictive value. Conclusion: Early SPECT/ CT in combination with any delayed imaging method was statistically significantly superior to any single-or dual-phase planar or SPECT study for parathyroid adenoma localization. Localization with dual-phase acquisition was more accurate than with singlephase 99m Tc-sestamibi scintigraphy for planar imaging, SPECT, and SPECT/CT.

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FDG-PET/CT parameters were best for assessing tumor down-staging and percentage of residual tumor after neoadjuvant treatment of rectal cancer and can potentially assist in treatment planning.

The accuracy of myocardial perfusion SPECT improves with attenuation correction. Algorithms for attenuation correction in hybrid SPECT/CT systems have the potential for misregistration of emission and transmission scans because CT and SPECT are obtained sequentially. Misregistration will influence regional tracer distribution and may reduce diagnostic accuracy. This study focused on the role of misregistration in cardiac SPECT/ CT and the performance of a software-based approach for reregistration. Methods: We included 105 consecutive patients who underwent clinical myocardial perfusion imaging on a SPECT/ CT system. Images were quantitatively assessed for misregistration using fusion software. Results were recorded in millimeters in the x-, y-, and z-axes. Regional tracer uptake in 6 segments (anterior, septal, inferior, lateral, anteroapical, and inferoapical) for noncorrected and attenuation-corrected images before and after reregistration was obtained from polar maps. To determine the relative influence of misregistration, we correlated individual differences between noncorrected and attenuation-corrected images, as well as between attenuation-corrected images before and after reregistration, with the degree of misregistration in a multivariate analysis including additional clinical variables such as sex and body weight. Results: The difference in regional radiotracer uptake was significant between noncorrected and attenuationcorrected images in all 6 segments and was most pronounced in the inferior wall. On multivariate analysis, misregistration contributed significantly to changes in radiotracer distribution in the anterior (P 5 0.038), septal (P 5 0.011), and inferior (P 5 0.006) segments. The mean misregistration was 8.6 6 3.8 mm (1.25 6 0.55 pixel). Misregistration of one or more pixels was observed in 64% of studies. Reregistration of misalignment significantly affected regional radiotracer distribution in the segments shown to be influenced by misregistration. Conclusion: Misregistration occurs with SPECT/CT systems and influences regional tracer distribution on attenuation-corrected myocardial images. Reregistration of misaligned studies may be a useful tool for correction. The impact of this strategy on the diagnostic and prognostic accuracy of cardiac hybrid imaging needs to be determined. Formyocardi al perfusion SPECT, professional societies recommend incorporation of attenuation correction to improve diagnostic accuracy (1). On standalone SPECT scanners, the transmission scans necessary for determining tissue density maps for attenuation correction are obtained with an external radionuclide line or point source. With the advent of SPECT/CT hybrid systems, however, CT is now increasingly used for transmission scanning. Advantages of the CT method include higherquality attenuation maps secondary to higher photon flux, lower noise, and improved resolution (2). Additionally, especially when using multislice CT in SPECT/CT systems, coronary calcium scoring or coronary angiography can be performed t...

Sincalide-stimulated cholescintigraphy is performed to quantify gallbladder contraction and emptying. However, different infusion methods are used for this study. Our purpose was to determine the infusion method with the least variability (smallest coefficient of variation [CV]) for calculation of the gallbladder ejection fraction (GBEF) in healthy subjects and to establish normal values. Methods: Sixty healthy volunteers at 4 medical centers were injected intravenously with 99m Tc-mebrofenin. After gallbladder visualization had been confirmed at 60 min, 0.02 mg of sincalide per kilogram was administered using 3 different infusion durations, 15, 30, and 60 min, each performed on separate days. The CV, mean, SD, first to 99th percentile, and fifth to 95th percentile were calculated. GBEF normal values were determined for the different infusion durations. Results: The CV was smallest for the 60-min infusion at 60 min (19%; 95% confidence interval [CI], 16%223%), compared with the 30-min infusion at 30 min (35%; 95% CI, 29.2%242.1%) and the 15-min infusion at 15 min (52%; 95% CI, 44%263%). These were all significantly different (P , 0.0007). For the 60-min infusion at 60 min, the lower limit of normal for the GBEF was 38% defined at the 1% CI. Conclusion: The GBEF at 60 min has the lowest CV in healthy subjects, compared with shorter infusions of 15 or 30 min. This multicenter trial establishes a GBEF lower limit of normal of 38% (first percentile) for a 60-min infusion of 0.02 mg of sincalide per kilogram, quantified at 60 min. Using this infusion method minimizes the variability in measured GBEFs. This sincalide infusion method should become the standard for routine clinical use.