Galina Iosilevsky

Single-photon emission computed tomography quantitation of gallium citrate uptake for the differentiation of lymphoma from benign hilar uptake

PURPOSE To assess the role of quantitative gallium citrate (Ga 67) single-photon emission computed tomography (SPECT) in differentiating lymphoma from benign hilar uptake, concentrations of Ga 67 in 29 sites of documented lymphoma and in 75 benign lesions were compared. PATIENTS AND METHODS One hundred seven thoracic Ga 67 SPECT studies obtained in 101 consecutive lymphoma patients were reviewed. Fifty-nine studies detected Ga 67 uptake in the hilar and or mediastinal regions. Forty-eight studies showed no such abnormality. The concentration of Ga 67 in the thoracic lesions was measured using a quantitative SPECT technique and its nature was determined by correlation with computed tomographic (CT) scans and follow-up evaluation of the sites. RESULTS In 20 of 59 abnormal studies (34%), there was lymphoma in the hilar and or mediastinal regions. In the remaining 39 abnormal studies (66%), Ga 67 uptake was benign. There were 29 sites of lymphoma and 75 benign lesions. The concentration of Ga 67 in lymphoma was significantly higher than in benign hilar uptake (13.2 +/- 5.4 %ID/mL x 10(-3) v 5.6 +/- 1.5 % injected dose (ID)/mL x 10(-3); P < .001). A concentration value of 8.3 %ID/mL x 10(-3) was found to best separate lymphoma and benign uptake, with a sensitivity of 90%, a specificity of 93%, a positive predictive value of 84%, and a negative predictive value of 96%. CONCLUSION Lymphoma and benign hilar uptake differ significantly in their concentration of Ga 67. The present study shows that quantitative Ga-67 SPECT reliably differentiates lymphoma and benign uptake.

Permeability of blood vessels in experimental gliomas: uptake of 99mTc-glucoheptonate and alteration in blood-brain barrier as determined by cytochemistry and electron microscopy.

Experimental gliomas were induced in rats by prenatal exposure to ethyl nitrosourea. Changes in the blood-brain barrier were determined by the uptake of a water-soluble compound, 99mTc-glucoheptonate. Increased uptake of 99mTc-glucoheptonate was measured in intact tumors and in various sectors of dissected tumors. The extent of 99mTc-glucoheptonate uptake greatly varied among different tumors and among different sectors of the same tumor. Ultrastructural and cytochemical analysis of the capillary endothelial wall revealed major alterations in tight junctions, which became permeable to horseradish peroxidase. In brain tissue around the tumors, uptake of 99mTc-glucoheptonate and ultrastructure of tight junctions were comparable to normal brain capillaries. The results of the present study indicate that altered endothelial tight junctions may provide the main route of transport of 99mTc-glucoheptonate through the endothelial wall.

Ga-67 scintigraphy with a dual-head camera.

High quality images are necessary for correct interpretation of Ga-67 studies in lymphoma. The authors were interested if there is a significant change in the quality of the Ga-67 images using a newly introduced dual-head camera compared with a conventional single-head camera. The tomographic spatial resolution, full width at half maximum, was found to be 9.63 mm compared with 13.7 for a single-head camera. The volume sensitivity was 380 cps/μCi/ml per axial cm as compared with 333 cps/μCi/ml, and point source sensitivity was 5.6 cps/μCi compared with 3.8. There was a significant difference (P < 0.001), when using the threshold technique, in the number of counts per pixel over a wide range of volumes and concentrations in phantoms when the two cameras were compared. There was also a significant difference (P < 0.001) in Ga-67 uptake in lymphoma lesions in patients when the same parameters were used for both cameras when using SPECT. The average uptake in lymphoma lesions, using a dual-head camera, was 529 counts/pixel with a range of 112 to 1275 counts/pixel in different tumors. With a single-head camera, the average for the same tumor was 216 counts/pixel with a range of 59 to 469 counts/pixel. The high sensitivity of the dual-head camera enabled high-quality, whole body scintigraphy, including the limbs, in 20 minutes compared with the 35 minutes necessary for the single-head camera for images which did not include the legs. Whole body Ga-67 scintigraphy is shown to be important in patients with lymphoma of the upper and lower limbs. The high sensitivity of the dual-head camera enables the performance of SPECT studies at 7 days after injection and planar studies of satisfactory quality at 14 days, resulting in clearance of the colonic activity and better evaluation of the abdomen. The authors conclude that, at the present time, a dual-head camera appears to be the most appropriate equipment to use for Ga-67 scintigraphy.

The concentration of bleomycin labeled with Co‐57 in primary and metastatic tumors

The concentration over time of bleomycin labeled with Co‐57 was measured in 39 primary and metastatic tumor sites in 16 patients using a newly developed and validated single photon emission computed tomography (SPECT) method. There were nine primary tumors, 15 metastatic tumors, and five multifocal lymphomas. Co‐bleomycin concentrations also were measured in primary and metastatic B‐16 melanoma tumors in mice. In humans, metastases to lymph nodes (1.58 ± 0.51 %ID/ml × minutes) showed significantly higher (P < 0.01) tumor cumulative concentrations of Co‐bleomycin than metastases to liver, bone, lung, and brain (0.76 ± 0.20 %ID/ml × minutes). The cumulative concentrations of Co‐bleomycin in human lymphomas (1.1 ± 0.25 %ID/ml × minutes) also were significantly higher (P < 0.01) than the concentrations in human metastases other than lymph nodes. The cumulative concentration in cerebral metastases (0.65 ± 0.18 %ID/ml × minutes) was significantly lower (P < 0.05) than in noncerebral metastases (1.22 ± 0.53 %ID/ml × minutes). Primary tumors in humans showed higher concentrations of Co‐bleomycin than metastases, except for lymph nodes. In contrast with humans, murine metastases showed higher concentrations of Co‐bleomycin (6.20 ± 2.65 %ID/g) than primary tumors (2.94 ± 0.90 %ID/g) (P < 0.001). The concentrations of Co‐bleomycin in murine tumors that were affected by bleomycin were about three orders of magnitude higher than in human tumors. The results of this in vivo study document the differences in drug delivery of Co‐57‐labeled bleomycin to human primary and metastatic tumors and show differences in drug delivery between human and murine tumors.

Scintigraphic assessment of technetium 99m-diphosphonate uptake, vascularlty and vessel permeability in human bone tumours

Differences in the rate of uptake of 99Tcm-diphosphonate were found in 20 human bone tumours investigated. As some tumours have a slow rate of uptake it is suggested that the time used for routine scintigraphy at 3 hours is not always optimal and a further study should be performed in some cases. Various degrees of tumour vascularity and vessel permeability were found. The rate of diphosphonate uptake correlates with the vascularity, while it does not correlate with permeability which is generally increased as compared to normal bone.