Biomedical subjects
Publications and source records attributed to V V Sagar.
Radioguided surgery has slowly gained acceptance since the first gamma probe directed sentinel node lymph node biopsy in a patient with melanoma in 1993. We describe how the intraoperative gamma probe is used to localize a rib with abnormal uptake on the bone scan in a patient with rib pain.
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Abdominal scanning using sodium pertechnetate Tc 99m is useful in demonstrating Meckel's diverticula containing ectopic gastric mucosa. However, other structures like the uterus may also concentrate 99mTc. We present a case which showed a focal area of increased uptake in the pelvis due to an infected ovarian cyst.
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The value of Ga-67 images in identifying unsuspected locations of subcutaneous Staphylococcus aureus abscess is presented. Many of the lesions detected on the Ga-67 study were not clinically evident. In addition, follow-up studies show resolution of the changes after antibiotic therapy.
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The effect of cimetidine, an H2-receptor blocking agent, on the secretion of 99mTc-pertechnetate was studied in 11 dogs. In cimetidine-treated animals, there was increased retention of 99mTc-pertechnetate by the gastric wall as compared with the untreated animals. The results indicate the potential use of cimetidine for enhanced visualization of Meckel's diverticulum, Barrett's esophagus, and the stomach, with 99mTc-pertechnetate.
Spleen scan demonstration of space-occupying lesions in patients with histiocytic lymphoma is a sensitive but not a specific finding. However, response to therapy could be evaluated if pretreatment scans show well-defined space-occupying lesions and posttreatment scans showed resolution of those changes.
Experiments were performed in 14 dogs to study the effect of changes in bone blood flow on the tibial uptake of the skeletal tracer Tc-99m(Sn)methylenediphosphonate (Tc-99m MDP). Aortic blood was diverted through a pulsatile-flow pump in order to monitor and control femoral arterial blood flow. Tibial nutrient perfusion, as measured with labeled microspheres, paralleled the changes in arterial flow. We found that increments in bone blood flow up to four times normal produced only minimal augmentation of Tc-99m MDP uptake (mean = 33%), a markedly nonproportional relationship. The data points clustered about a predicted curve produced by perturbing the rate constants of a seven-compartment model obtained in normal dogs. These findings indicate that bone uptake of Tc-99m MDP is diffusion-limited, and they therefore cast doubt upon the validity of a method used for many years for estimating bone blood flow, the so-called skeletal tracer clearance technique. Nerve section, performed in 14 other dogs, augmented Tc-99m MDP uptake by about 50% at supranormal flows, suggesting a parallel-flow model of the microcirculation in bone, under sympathetic control. Such a model satisfactorily explains many scintigraphic findings in disease states.