Satish G. Jhingran

Poststress redistribution of thallium-201 in patients with coronary artery disease, with and without prior myocardial infarction☆

Abstract To elucidate patterns of thallium-201 redistribution with and without myocardial infarction, to determine the value of thallium-201 redistribution scintigrams in identifying additional ischemic myocardium in the presence of prior myocardial infarction and to delineate the relation of collateral vessels to redistribution, thallium-201 myocardial perfusion scintigraphy was performed immediately after exercise and 4 to 6 hours after exercise in 46 patients with coronary artery disease and 12 normal control subjects. Scintigrams were interpreted in the conventional visual manner as well as with use of computer-processed myocardial perfusion ratios. Normal control subjects demonstrated uniform thallium-201 distribution with regional perfusion ratios approximating unity in both the early and delayed scintigrams. Of 27 patients with prior myocardial infarction, 5 (19 percent) had complete redistribution on delayed imaging, 17 (62 percent) had partial redistribution and 5 (19 percent) had no redistribution. Of 25 regions corresponding to electrocardiographlc evidence of infarction, 8 (32 percent) had total, 8 (32 percent) had partial and 9 (36 percent) had no redistribution. Collateral vessels were absent or of poor quality in seven of eight infarct areas with no redistribution; three of four infarct regions with normal early thallium uptake were supplied by collateral vessels of good quality. Of 12 regions supplied with good collateral vessels, 9 had complete redistribution, 2 partial and 1 no redistribution. In contrast, only 2 of 21 hypoperfused zones without redistribution (10 percent) were supplied by good collateral vessels. Of 19 patients without prior myocardial infarction, 10 (53 percent) had complete redistribution, 6 (31 percent) had partial redistribution and 3 (16 percent) had no redistribution. Of the 34 abnormal areas in the immediate postexercise image, 22 (65 percent) showed total redistribution, 3 (9 percent) showed partial redistribution and 9 (26 percent) showed no redistribution. Thus, considerable overlap in redistribution scintigrams occurs in patients with coronary artery disesase with and without prior infarction; a high incidence rate of transient stress-induced hypoperfusion occurs in both infarcted and noninfarcted myocardium. Further, good quality collateral vessels afford redistribution, even to some areas of prior infarction. These data indicate that because delayed postexercise redistribution imaging may not discriminate between myocardial scar and ischemia resting scintigrams may be needed in a substantial number of patients.

Spinal bone mineral after 5 weeks of bed rest

SummaryPatients put at bedrest for medical reasons lose 1–2% of spinal bone mineral per week. Losses of this magnitude during even shortterm space flights of a few months would pose a serious limitation and require countermeasures. The spinal bone mineral (L2–L4) was determined in 6 healthy males (precision=2%) before and after 5 weeks of complete bed rest. Only one individual had a significant loss (3%) and the −0.9% mean change for the 6, was not significant (P=0.06). The average negative clacium balance during the 5 weeks was 4 g or 0.36% of total body calcium, similar to that reported in other bed-rest studies. Spinal bone loss, however, in healthy bed-rested males is significantly less than reported for bed-rested patients, suggesting that a large loss of spinal bone mineral does not occur during space flight missions lasting 5 weeks or less.

Technetium-99m labeled red blood cells in the evaluation of hemangiosarcoma

Imaging with Tc-99m labeled red blood cells (RBC) is increasingly being used in the detection of acute gastrointestinal bleeding, especially in patients with intermittent bleeding. A patient is presented in whom the labeled RBC scan was helpful in the incidental discovery of a previously unsuspected probable angiosarcoma of the right femur and adjacent soft tissues of the right hip due to the “blood pool” or “blush effect” of the labeled cells. The labeled RBC scan also identified extravasation due to active gastrointestinal bleeding from a previously unknown angiosarcoma of the ascending colon. Thus, the Tc-99m labeled RBC scan was useful in simultaneously detecting extravasation and blood pool effect at two remote tumor sites in the same patient.

Selective in vitro labeling of white blood cells using 99mTc-labeled liposomes

We describe a method by which endocytosis-based radiolabeling of WBC is achieved using 99mTc-liposomes of optimal size and charge, and of a composition that assures both in vitro (whole blood) and intracellular stability of the radiopharmaceutical. In our study, excellent in vitro stability of 99mTc-liposomes with 95% labeling efficiency was observed with >90% stability up to 6 h and a minimum of 85% after 24 h of incubation either in normal saline or serum. Total WBC labeling efficiency using 99mTc-liposomes determined by radio-thin layer chromatographic analysis was 30.6 +/- 2.21%, 20.89 +/- 1.31% for monocytes and 9.7 +/- 1.74% for polymorphonuclears. Negligible activity was bound to red blood cells. The procedure did not affect the cell viability and the separation of the free 99mTc-liposomes from the cells was done by centrifugation.

High resolution bone mineral densitometry with a gamma camera

A technique is described by which the regional distribution of bone mineral can be determined in bone samples from small animals. The technique employs an Anger camera interfaced to a medical computer. High resolution (less than 1 mm) imaging is possible by producing magnified images of the bone samples. Regional densitometry of femurs from oophorectomised and bone grafted rats demonstrated significant heterogenity of bone mineral loss.

Scintigraphic assessment of pericardio-peritoneal window patency. Relevance to peritoneal dialysis.

To alleviate recurrent pericardial effusion secondary to systemic lupus erythematosus, pericardio-peritoneal window was performed. Subsequently, end stage renal disease developed and the patient required peritoneal dialysis. Patency of the pericardio-peritoneal window was demonstrated by intraperitoneal injection of Tc-99m SC through a Tenckhoff catheter, which prompted special counsel to the patient in order to prevent infectious pericarditis potentially complicating peritoneal dialysis induced-peritonitis.

Technetium-99m labeled RBC imaging in gastrointestinal bleeding from gastric leiomyoma.

Tc-99m labeled RBC imaging is becoming increasingly useful in detecting gastrointestinal (Gl) bleeding sites. A patient is presented who had massive Gl bleeding from an unsuspected gastric leiomyoma in whom a Tc-99m sulfur colloid Gl bleed image was negative. The Tc-99m labeled RBC imaging done on the day after sulfur colloid imaging revealed increased gastric activity due to active bleeding from an intragastric leiomyoma. Tc-99m labeled RBC imaging helped in early detection of the bleeding site resulting in its successful treatment. This experience also reinforces the assertion that Tc-99m labeled RBC imaging may be more helpful than Tc-99m sulfur colloid imaging in patients with upper Gl or intermittent bleeding.

Diffuse pancreatic Ga-67 uptake in pancreatitis with markedly elevated Ca 19-9 tumor marker

A 73-year-old woman, who was nonethanollc, experienced recent onset of right upper abdominal pain, fever, obstructive jaundice with normal serum amylase, elevated liver function test results, and markedly elevated Ca 19-9 tumor marker. Abdominal CT scan showed diffusely enlarged pancreas with a questionable mass in the pancreatic head. Ga-67 imaging showed persistent marked diffuse pancreatic uptake on 24-hour and 96-hour scans. Exploratory laparotomy and cholecystojejunostomy for obstructive jaundice with transduodenal biopsies from four different areas of diffusely enlarged, hard pancreas revealed acute and chronic pancreatitis and fibrosis, but no malignancy. The patient was in good health 3 years after surgery. In such situations, diffuse pancreatic uptake of Ga-67 can help strengthen diagnosis of pancreatitis over pancreatic cancer, despite normal amylase and high tumor marker levels.

Chloramine-T induced binding of monoclonal antibody B72.3 to concanavalin-A

The effects of chloramine-T (CT) on monoclonal antibody B72.3 were studied with particular reference to Con-A lectin binding. After exposure to chloramine-T concentrations from 0.8 to 4.0 mg/mL (115-574 mol CT/mol B72.3), B.72.3 showed progressive binding to agarose-linked Con-A. This behavior was paralleled by decreasing immunoreactivity and increasing fragmentation and aggregation of B72.3 demonstrated by SDS-PAGE and size exclusion HPLC.

New 111In labeling of IgG: 111In-oxine mediated chelation

Current methods of 111In chelate conjugation labeling of antibodies expose the protein to pH 5-6 during 111In chelation. These conditions could be detrimental if the antibody is acid labile. We have successfully labeled human IgG via the cyclic anhydride of DPTA and 111In-oxyquinoline(oxine). Chelation was achieved at pH 6.9-8.4 and was complete within 1 min at room temperature. The chelation was sensitive to trace metal contamination on labware and in some reagents (including commercial 111In-oxine).