Pinhole versus parallel-hole collimators for parathyroid imaging: an intraindividual comparison.

UNLABELLED: This study was undertaken to determine the effects of collimators on the accuracy of preoperative sestamibi parathyroid imaging of the neck. METHODS: Forty-nine patients with primary hyperparathyroidism underwent preoperative (99m)Tc-sestamibi parathyroid imaging. The protocol included early and late pinhole and parallel-hole imaging. One experienced nuclear physician, without knowledge of other test results or final diagnoses, interpreted studies. For both pinhole and parallel-hole images, focally increased sestamibi accumulation outside the normal tracer biodistribution that persisted or increased in intensity from early to late images was interpreted as positive for a parathyroid lesion. Final diagnoses were operatively confirmed in all patients. RESULTS: Fifty-four parathyroid lesions were resected from the 49 patients. Forty-five patients had single-gland disease. Four patients had multigland disease: 3 had 2 lesions and 1 had 3 lesions. Median lesion weight was 840 mg. Pinhole imaging was significantly more sensitive than parallel-hole imaging (89% vs. 56%; P = 0.0003) for all 54 lesions. Specificity did not significantly differ between pinhole and parallel-hole imaging (93% vs. 96%, P = 0.29). Pinhole imaging was significantly more sensitive than parallel-hole imaging for lesions above (100% vs. 68%, P = 0.003) and below (77% vs. 42%, P = 0.03) the median weight and for single-gland disease (96% vs. 67%, P = 0.001). Pinhole imaging also was more sensitive for multigland disease, although the difference was only marginally significant (55% vs. 0%, P = 0.037). CONCLUSION: Because sensitivity is significantly higher, sestamibi parathyroid imaging of the neck should be performed with a pinhole collimator.

Diagnosing prosthetic vascular graft infection with the antigranulocyte antibody 99mTc-fanolesomab.

AIM: The objectives of this retrospective investigation were to determine the accuracy of 99mTc-fanolesomab, an antigranulocyte antibody, for diagnosing prosthetic vascular graft infection, ascertain optimum imaging times for this indication, and assess safety of this agent. METHODS: Eighteen patients with 19 prosthetic vascular grafts were included. Indications for graft placement included peripheral vascular disease (8), haemodialysis (7), and aneurysm (4). Patients were imaged 2-5 h and 18-30 h after injection of 555-740 MBq (75-125 microg) 99mTc-fanolesomab. One experienced nuclear physician reviewed images in three separate sessions, early alone, late alone and early plus late images together. When early and late images were read alone, graft activity more intense than native blood pool activity was classified as positive for infection. When early and late images were interpreted together, graft activity which persisted or which increased in intensity over time was classified as positive for infection. Patient records were reviewed for adverse events up to 30 days after injection. RESULTS: Five (26%) prosthetic grafts were infected. Early, late and early plus late imaging were equally sensitive (1.00). Early images were significantly less specific (0.50), than late and early plus late images (0.93) (P<0.05, analysis of proportions). Accuracy of late imaging and early plus late imaging were the same: 0.93. No patient experienced adverse events following radiopharmaceutical injection. CONCLUSIONS: 99mTc-fanolesomab imaging, performed 18-30 h after injection, diagnosed prosthetic vascular graft infection safely and accurately (95%). (Although safety was not an issue in this investigation, following reports of serious, including two fatal, events after administration, 99mTc-fanolesomab was withdrawn from the United States market).

PET with FDG-labeled leukocytes versus scintigraphy with 111In-oxine-labeled leukocytes for detection of infection.

PURPOSE: To compare prospectively the accuracy of positron emission tomography (PET) with leukocytes labeled in vitro with (18)F fluorodeoxyglucose (FDG) versus that of conventional scintigraphy with leukocytes labeled in vitro with (111)In oxine in patients suspected of having infection. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; informed consent was obtained from all patients. Patients were 25 men and 26 women aged 32-86 years. In vitro labeling of autologous human leukocytes with FDG and (111)In-oxine was performed according to published methods. Labeling efficiencies and cell viability were determined. Imaging was performed 2.5-5.8 hours after injection of 196-315 MBq of FDG-labeled leukocytes and approximately 24 hours after injection of 17-25 MBq of (111)In-oxine-labeled leukocytes. Forty-three (20 men, 23 women; mean age, 59 years; range, 32-86 years) patients could be successfully imaged with both tracers. Six patients were not injected with FDG-labeled leukocytes because of low labeling efficiency (<35%). Two patients were injected with FDG-labeled leukocytes but were not imaged. One reader interpreted all results as positive or negative for infection. Imaging results were compared with final diagnoses. Labeling efficiencies and cell viabilities were compared by using the paired t test. Differences between PET and scintigraphy were determined by using the McNemar test. RESULTS: For the 43 patients who were imaged with both tracers, labeling efficiency of FDG was lower than that of (111)In oxine (72% +/- 8 [standard deviation] vs 90% +/- 5, P < .001). Viability of FDG-labeled leukocytes was not different from that of (111)In-oxine-labeled leukocytes (98% +/- 1 vs 97% +/- 3). There were no differences between FDG PET and (111)In scintigraphy in terms of sensitivity (87% vs 73%), specificity (82% vs 86%), or accuracy (84% vs 81%). CONCLUSION: PET with FDG-labeled leukocytes was comparable to scintigraphy with (111)In-oxine-labeled leukocytes. Further investigation in a larger population with dedicated PET or PET/computed tomography seems warranted.

Pulmonary activity on labeled leukocyte images: physiologic, pathologic, and imaging correlation.

Accurate interpretation of labeled leukocyte images requires knowledge of pulmonary labeled leukocyte uptake: its prevalence and patterns and its correlation with technical, physiologic, and pathologic conditions as well as with other imaging findings. Images obtained shortly after injection of labeled cells are characterized by diffuse pulmonary activity, which decreases over time, until about 4 hours after injection when it becomes indistinguishable from background activity, remaining constant thereafter. Focal pulmonary uptake that is segmental or lobar in appearance is most often associated with bacterial pneumonia. Focal pulmonary uptake that is not segmental or lobar results from technical problems during labeling or reinfusion and is not usually associated with infection. Diffuse pulmonary uptake on images obtained more than 4 hours after reinjection of labeled cells is associated with a variety of pathologic conditions, some of the more common being opportunistic infection, radiation pneumonitis, pulmonary drug toxicity, adult respiratory distress syndrome, and sepsis. However, this pattern is almost never seen in bacterial pneumonia. When pulmonary uptake patterns are analyzed and correlated with the clinical situation, labeled leukocyte scintigraphy can provide useful information about pulmonary disease.