European Journal of Nuclear Medicine

A comparison has been made between three gamma camera methods for estimation of glomerular filtration rate (GFR) using 99mTc-DTPA in a group of 27 patients with widely different renal function. Plasma clearance of 99mTc-DTPA by multiple blood sampling was used as the reference. Percentage uptake of chelate in the bladder and kidneys at 20 min after injection gave the lowest standard error of 8.0 ml/min. Techniques using early uptake of isotope in the kidneys at 2 min after injection gave less accurate estimates. Correction for the vascular activity in the renal region of interest improved the results for the 2 min uptake technique. Gamma camera techniques provide rapid estimates of GFR which are less accurate than those obtained by plasma clearance of labelled chelate.

The aim of the present study was to assess and compare the diagnostic performance of integrated PET/MRI and MRI alone for local tumor evaluation and whole-body tumor staging of primary cervical cancers. In addition, the corresponding impact on further patient management of the two imaging modalities was assessed. A total of 53 consecutive patients with histopathological verification of a primary cervical cancer were prospectively enrolled for a whole-body 18F-FDG PET/MRI examination. Two experienced physicians analyzed the MRI data, in consensus, followed by a second reading session of the PET/MRI datasets. The readers were asked to perform a dedicated TNM staging in accordance with the 7th edition of the AJCC staging manual. Subsequently, the results of MRI and PET/MRI were discussed in a simulated interdisciplinary tumor board and therapeutic decisions based on both imaging modalities were recorded. Results from histopathology and cross-sectional imaging follow-up served as the reference standard. PET/MRI allowed for a correct determination of the T stage in 45/53 (85%) cases, while MRI alone enabled a correct identification of the tumor stage in 46/53 (87%) cases. In 24 of the 53 patients, lymph node metastases were present. For the detection of nodal-positive patients, sensitivity, specificity and accuracy of PET/MRI were 83%, 90% and 87%, respectively. The respective values for MRI alone were 71%, 83% and 77%. In addition, PET/MRI showed higher values for the detection of distant metastases than MRI alone (sensitivity: 87% vs. 67%, specificity: 92% vs. 90%, diagnostic accuracy: 91% vs. 83%). Among the patients with discrepant staging results in the two imaging modalities, PET/MRI enabled correct treatment recommendations for a higher number (n = 9) of patients than MRI alone (n = 3). The present results demonstrate the successful application of integrated PET/MRI imaging for whole-body tumor staging of cervical cancer patients, enabling improved treatment planning when compared to MRI alone.

A method of superimposing computed tomography (CT) and immunoscintigraphic (IS) single photon emission tomography (SPET) slices is presented and has been applied to 10 patients with suspected cancer recurrence. IS was performed with carcinoembryonic antigen (CEA)-specific indium-111 monoclonal antibodies (MoAbs) in 5 patients with colorectal cancer, and with OC125 111In-MoAbs in 5 patients with ovarian cancer. All patients had an abnormal CT image result in the pelvis, which was interpreted 5 times as recurrence, once as doubtful and four times as scar fibrosis. Recurrence was subsequently proven in all patients. Bone scintigraphy (BS) SPET was recorded at the same time as IS. No special technique was used during BS, IS or CT acquisition. CT images were fed into a computer using a CCD camera. Using the internal anatomical landmarks provided by the pelvic bone structures seen on CT and BS, an operator had to select corresponding fiducial points, which were used by the software to register the images. The final results were CT-BS and CT-IS superimposed images. CT-BS images were used for quality control. In all patients, the inspection of CT-BS and CT-IS showed that the registration process is accurate and assists in the co-interpretation of CT and IS images.

The aim of this study was to elucidate further the causative mechanism of abnormal coronary vasomotion in patients with syndrome X. In patients with syndrome X, defined as angina pectoris and documented myocardial ischaemia during stress testing with normal findings at coronary angiography, abnormal coronary vasomotion of either the micro- or the macrocirculation has been suggested as the causative mechanism. Accordingly, we evaluated endothelial function, vasodilator reserve, and perfusion heterogeneity in these patients. Twenty-five patients with syndrome X (definitely normal coronary arteriogram, group A), 15 patients with minimal coronary artery disease (group B) and 21 healthy volunteers underwent [13N]ammonia positron emission tomography at rest, during cold pressor stimulation (endothelial function) and during dipyridamole stress testing (vasodilator reserve). Heterogeneity of myocardial perfusion was analysed by parametric polar mapping using a 480-segment model. In both patient groups, resting perfusion was increased compared to the normal subjects: group A, 127±31 ml·min−1·100 g−1; group B, 124±30 ml·min−1·100 g−1 normal subjects, 105±21 ml·min−1·100 g−1 (groups A and B vs normals,P<0.05). These differences were abolished after correction for rate-pressure product. During cold pressor stimulation, the perfusion responses (ratio of cold pressor perfusion to resting perfusion) were similar among the patients and the control subjects (group A, 1.20±0.23; group B, 1.24±0.22; normal subjects, 1.23±0.14). Likewise, during dipyridamole stress testing, perfusion responses were similar among the three groups (group A, 2.71±0.67; group B, 2.77±1.29; normal subjects, 2.91±1.04). In group A the heterogeneity of resting perfusion, expressed as coefficient of variation, was significantly different from the volunteers (20.1±4.5 vs 17.0±3.0,P<0.05). In group B (coefficient of variation 19.4±3.9) the difference from normal volunteers was not significant. In this study, patients with syndrome X and patients with minimal coronary artery disease showed normal perfusion responses during cold pressor stimulation and dipyridamole stress testing. Our findings therefore suggest that endothelial dysfunction and impaired vasodilator reserve are of no major pathophysiological relevance in patients with syndrome X. Rather, other mechanisms such as increased sympathetic tone and focal release of vasoactive substances may play a role in the pathogenesis of syndrome X.

The clearance of125I-sodium iothalamate,131I-sodium hippurate,99mTc-DMSA, and β2-microglobulin were determined in 20 patients with proven or suspected proximal tubular dysfunction and in 18 control patients with various renal diseases. A clear distinction in the relative99mTc-DMSA clearance was observed between patients with proximal tubulopathy (14%–35%) and control patients (>14%). A similar difference between the two groups was found in the relative β2-microglobulin clearance. Nine patients with proximal tubulopathy showed an elevated filtration fraction versus only two control patients. The renal handling of99mTc-DMSA seems to be an indicator of proximal tubular function.