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To evaluate the repeatability of gallium-68 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic (DOTA)-D-Phe1-Try3-octreotide (68Ga-DOTATOC) positron emission tomography (PET) in neuroendocrine tumors.Five patients with neuroendocrine tumors were imaged with 68Ga-DOTATOC PET twice within 5 days. Maximum and mean standardized uptake values (SUVmax and SUVmean) and kinetic parameters (K-Patlak and K-influx) of target lesions were measured. The repeatability of these measurements was investigated.Forty-seven target lesions were identified on whole-body PET and 21 lesions on dynamic images. There was excellent repeatability with intraclass correlation coefficient of 0.99 for SUVmax, SUVmean, and K-Patlak, and 0.85 for K-influx. The median absolute percent differences and the interquartile ranges (IQR) between 2 scans for SUVmax and SUVmean were 7.4% (IQR, 14.1%) and 9.3% (IQR, 10.6%), respectively. The median absolute percent differences for K-Patlak and K-influx were 12.5% (IQR, 12.6%) and 29.9% (IQR, 22.4%), respectively. The SUVmax of target lesions did not differ by more than 25% between the 2 scans.68Ga-DOTATOC PET imaging of neuroendocrine tumors is highly reproducible. A difference of more than 25% in SUVmax represents a change that is larger than the measurement error observed on repeated studies and should reflect a significant change in the biological character of the tumor.

Reflux grade predicts resolution and influences followup and treatment. Bladder pressure at the onset of reflux may reflect the ureterovesical junction competence. By combining simultaneous cystometry with nuclear cystography (nuclear cystometrogram) we determined bladder pressure at the onset of reflux.Nuclear cystometrograms were performed in 40 children to determine bladder pressure at the onset of reflux, reflux volume and bladder capacity at the onset of reflux. The effect of bladder pressure and capacity at the onset of reflux was assessed with a reflux pressure volume index.A weak inverse correlation existed between bladder pressure at the onset of reflux and a normalized volume of reflux (r = -0.32, p = 0.018). A stronger correlation existed between reflux pressure and bladder volume at reflux (r = 0.47, p = 0.0002). An inverse correlation of the reflux pressure-volume index and reflux volume was significant (r = -0.49, p = 0.0002) as was the correlation between bladder volume at reflux and amount of reflux (r = -0.47, p = 0.0003). The reflux pressure-volume index for patients with persistent reflux at followup (median 1.89) was significantly smaller than that for those without reflux (median = 8.71, p = 0.02). A difference existed in normalized bladder volume at reflux between resolved and persistent reflux (p = 0.003). No difference was detected with respect to reflux volume and resolution (p = 0.738).A nuclear cystometrogram is no more invasive than a standard cystogram and permits determination of bladder pressure at the onset of reflux. Factors such as reflux pressure and bladder volume at reflux provide additional characterization of the ureterovesical junction and may help determine the prognosis for reflux resolution.

Bone scintigraphy (BS) is widely utilized for the assessment of bone metastases (BMs) of neuroblastoma (NB). Since 111 In-pentetreotide scintigraphy (PS) has been used to image NB with high sensitivity, we compared the sensitivity and specificity of PS with that of BS for the detection of BMs of NB. Nine patients with NB underwent both PS and BS for staging and/or restaging of their disease. The sensitivity and specificity of both imaging approaches were compared based on the findings of histopathology, other conventional imaging methods and subsequent clinical follow-up. In five of the nine patients, both PS and BS were negative for BMs. Radiographic bone surveys (RBSs) were also negative in these patients, except in one who showed a suspicious tibial lesion, but a computed tomography-guided biopsy failed to show evidence of disease. These patients remained without clinical evidence of BMs after a median duration of more than 15 months (range, 6-19 months). In three of four remaining patients, both PS and BS were positive for BMs, whilst only PS was positive in one patient. Overall, PS showed a greater number of BMs (30 vs. 7) with greater conspicuity compared with BS. The initial experience comparing BS with PS suggests that PS may provide a better assessment of the extent of BMs of NB, and that it may be useful as an adjunct to BS at institutions in which 131 I- or 123 I-metaiodobenzylguanidine is not available, particularly if BS is negative. In patients with similarly positive BS, PS might still provide unique prognostic information beyond that provided by BS. Further studies are therefore warranted.

Objective Standard uptake values (SUVs) are widely used for quantifying the uptake of 18 F-fluorodeoxyglucose ( 18 F-FDG) in tumours. The objective of this study was to evaluate the accuracy of SUVs for malignancy in lung nodules/masses and to analyse the effects of tumour size, blood glucose levels and different body weight corrections on SUV. Methods One hundred and twenty-seven patients with suspicious lung lesions imaged with 18 F-FDG positron emission tomography (PET) were studied retrospectively. Pathology results were used to establish lesion diagnosis in all cases. SUVs based on maximum pixel values were obtained by placing regions of interest around the focus of abnormal 18 F-FDG uptake in the lungs. The SUVs were calculated using the following normalizations: body weight (BW), lean body weight (LBW), scaled body surface area (BSA), blood glucose level (Glu) and tumour size (Tsize). Receivers operating characteristic (ROC) curves were generated to compare the accuracy of different methods of SUV calculation. Results The areas under the ROC curves for SUV BW , SUV BW+Glu , SUV LBW , SUV LBW+Glu , SUV BSA , SUV BSA+Glu and SUV BW+Tsize were 0.915, 0.912, 0.911, 0.912, 0.916, 0.909 and 0.864, respectively. Conclusion The accuracy of SUV analysis for malignancy in lung nodules/masses is not improved by correction for blood glucose or tumour size or by normalizing for body surface area or lean body weight instead of body weight.

Although standardized uptake values (SUV) are widely used to quantify the uptake of 18F-fluorodeoxyglucose (18F-FDG) in tumours, there are systematic differences in the way this index is applied by different investigators. The aims of this study were to compare the effects of using maximum or mean region counts in the calculation of SUV and to investigate an alternative technique based on a fixed fraction of the maximum counts. Simulated PET projections of the thorax were generated together with spherical lesions that varied in diameter from 1.6 to 4.8 cm with uptake values of 2, 4 and 8. The lesion SUVs were determined using either the maximum (SUVmax) or mean count (SUVmean) values found in regions circumscribing the lesion. In addition, average values were calculated that only included region pixels that exceeded a selected fraction of maximum value (SUV0.6max or SUV0.75max). These methods were also applied to six clinical 18F-FDG PET studies with a total of 12 lesions. The SUVs for these lesions were determined independently by four observers. Decreases with respect to SUVmax of 57%, 23% and 14% were found for SUVmean, SUV0.6max and SUV0.75max approaches respectively in the simulation study. The variation in SUVmean with region size was 35%, while the SUV0.6max and SUV0.75max was less than 3%. Similar results were obtained for the clinical data. We conclude that the proposed technique produces SUVs that are essentially independent of lesion region size and shape. It is expected that this will provide a more stable and reliable result than current approaches.

Following androgen ablation therapy, skeletal metastases from prostate cancer appear in some instances to show an increase in 99 Tc m -methylene diphosphonate ( 99 Tc m -MDP) uptake. Such a phenomenon could represent a mechanism to increase delivery of bone-seeking therapeutic agents to skeletal metastatic sites. The aim of this study was to characterize more precisely the potential increase in 99 Tc m -MDP in skeletal metastases from prostate cancer following initiation of hormone therapy. Baseline bone scans were performed within 1 week of onset of hormone therapy in patients with stage D2 prostate cancer followed by multiple repeat bone scans for up to 4-6 weeks. The count density within metastatic lesions was divided by the average count density from several areas of normal bone to obtain a lesion to normal bone uptake ratio (L/N) for each lesion in each scan. Altogether, 61 skeletal metastases were identified on bone scans from five subjects. Eighty-four percent (51/61) of these lesions showed an increase in 99 Tc m -MDP activity relative to normal bone following initiation of hormone therapy with a mean peak increase of 39%. Thirty-nine of these 51 metastatic lesions showed maximum uptake at 3 weeks post-onset of hormone treatment. From our findings, it appears that approximately 3 weeks following initiation of hormone blockade, most skeletal metastases from prostate cancer will demonstrate significantly enhanced 99Tcm uptake relative to normal bone. Consequently, it may be possible to improve the uptake and effectiveness of therapeutic bone-seeking radiopharmaceuticals by administering these agents following hormone therapy in patients with prostate cancer metastases.

This pilot study was undertaken to generate preliminary data on the accuracy of captopril-enhanced renal scintigraphy with a relatively new radiopharmaceutical, 99Tcm-mercaptoacetyltriglycine (99Tcm-MAG3) for detecting significant renal artery stenosis. Truth data was based either on arteriographic or outcome criteria (blood pressure response to therapy). Twenty-seven subjects with suspected renovascular hypertension were studied with baseline and captopril-enhanced 99Tcm-MAG3 renal scintigraphy and renal arteriography. Scan interpretations were expressed as a probability of a significant renal artery stenosis. Scan interpretations were compared with renal arteriographic results, renal vein renin levels, blood pressure values after renal artery repair, and blood pressure control after 4-26 months of clinical follow-up. Using > or = 50% luminal obstruction on arteriography as the reference standard for renal artery stenosis and a high probability scan representing a positive test, the test sensitivity and specificity were 33 and 97%, respectively (using high or indeterminate probability to represent a positive scan, the test sensitivity and specificity were 67 and 83%, respectively). The negative predictive value of a low probability scan for renal artery stenosis was 80%. However, including a measure of renovascular hypertension (blood pressure response to renal artery repair) as the reference standard, the accuracy of the scan improves, with the negative predictive value of a low probability scan for renovascular hypertension increasing to 97%. Scintigraphic results were also positively correlated with renal vein renin values in a statistically significant fashion (two-tailed Fisher exact test statistic = 6.43, P = 0.0219). Captopril-enhanced 99Tcm-MAG3 renal scintigraphy is a moderately accurate technique for detecting renal artery stenosis. More importantly, our preliminary findings suggest that the scintigraphic technique using 99Tcm-MAG3 appears to predict the blood pressure response to renal artery repair in subjects with suspected renovascular hypertension, thereby separating subjects with haemodynamically insignificant renal artery stenosis from those with renovascular hypertension.

The physical considerations of using dual isotope brain SPECT imaging to monitor blood flow changes during cognitive activation studies were investigated. These factors included field uniformity, spatial resolution and crosstalk. Serial dual isotope single photon emission computed tomographic (SPECT) studies of a test tube phantom and an anthropomorphic brain phantom filled with 99Tcm and 123I were made over a 10 h period. The reconstructed counts in the 99Tcm and 123I windows were corrected for crosstalk and were plotted as a function of time. The plotted data from each window decreased over time with a half-life characteristic of each radionuclide. The relative difference between true 123I and 99Tcm region counts has to be of the order of 10% to be statistically significant at the P < 0.05 level.

A dual isotope, single photon emission tomography (SPECT) technique using 99Tcm-hexamethylpropyleneamine oxime (HMPAO) and 123I-iodoamphetamine (IMP) was investigated to determine its suitability for assessing regional cerebral blood flow (rCBF) changes resulting from cognitive activation. The similarity of the 123I-IMP and 99Tcm-HMPAO distributions under the same physiological conditions was first investigated by administering the two agents to human subjects (n = 8) either simultaneously or at different times but during the performance of the same task. Normalized ratio images generated from the 99Tcm and 123I data showed that the two tracers distributed similarly in the left and right cerebral hemispheres when administered under similar physiological conditions. There was, however, a significant anterior/posterior gradient that appears to be the result of partial volume effects due to small differences in spatial resolution of the two agents. In two subjects, 99Tcm-HMPAO was administered during a resting period with eyes-closed and 123I-IMP was injected later during visual checkerboard stimulation. Ratio images showed a localized increase in the occipital lobes during the visual stimulation consistent with the expected increase in rCBF. The dual isotope strategy appears promising for study of changes in rCBF due to cognitive activation.

SPECT brain imaging using Iofetamine HC1 I-123 (IMP) has a great potential in the evaluation of various neurologic disorders. Transverse, coronal, and sagittal sectional IMP images obtained using a single head rotating gamma camera system are correlated with corresponding normal brain slices in this atlas.