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Biomedical subjects

J A Ponto

Publications and source records attributed to J A Ponto.

At least 37 records · Page 2Linked to original sources
PubMed1988

Dosimetry of technetium-99m red blood cells labeled in vivo.

Mean organ doses received from Tc-99m red blood cells labeled in vivo were calculated by the MIRD method using biodistribution data reported in the literature. The organ receiving the greatest dose was found to be the heart, followed closely by the bladder and stomach. Relatively high doses are also received by the blood, spleen, and lungs. Intermediate absorbed doses are received by the thyroid and kidneys, whereas organs with small blood concentrations and the remainder of the body receive the smallest doses. The major portion of the absorbed doses delivered to the stomach and the thyroid is due to the presence of free pertechnetate.

Erythrocytes↗
PubMed1988

Pitfalls in establishing the diagnosis of deep venous thrombophlebitis by indium-111 platelet scintigraphy.

Forty-seven 111In-platelet scintigraphs (In-PS) were analyzed retrospectively to identify sources of diagnostic error and to optimize the diagnostic criteria for active deep venous thrombophlebitis (DVT). The results of In-PS were compared with contrast venography, additional diagnostic studies, and clinical outcome. Three patterns of platelet localization emerged as the best predictors of active DVT: (a) focal or (b) linear 4-hr localization, or (c) an asymmetric blood-pool pattern on 4-hr imaging that evolved into a focal or linear pattern by 16 to 24 hr. All false-positive studies had abnormal patterns confined to the inguinal region at 24 hr. All patients with false-negative studies had received heparin between 4 and 24 hr. The potential pitfalls encountered in the evaluation of the iliac, femoral, and popliteal veins are reviewed and the importance of delayed imaging in selected cases is emphasized.

Blood Platelets↗
PubMed1987

Deep venous thrombophlebitis: detection with 4-hour versus 24-hour platelet scintigraphy.

Thirty-one nonheparinized patients with suspected deep venous thrombophlebitis (DVT) underwent contrast venography and indium-111 platelet scintigraphy (In-111 PS). Venography permitted identification of acute DVT in 12 of 31 cases (39%). One additional patient was considered to have acute DVT despite nonconclusive venography results. In-111 PS results were positive at 4 hours in nine of 13 cases (69%) and at 24 hours in 12 of 13 cases (92%). Two of four patients with false-negative 4-hour In-111 PS studies had received warfarin. Thus, the sensitivity of 4-hour In-111 PS in patients not receiving anticoagulants was 82%. Venography results were negative for acute DVT in 18 cases, and 4-hour In-111 PS studies were negative or equivocal in each. In-111 PS is an alternative to contrast venography for detecting acute DVT. If 4-hour In-111 PS results are positive, anticoagulation can be initiated. Delayed images are necessary if the 4-hour images are negative or equivocal.

Aged↗
PubMed1986

Fetal dosimetry from pulmonary imaging in pregnancy. Revised estimates.

Fetal dose estimates from Tc-99m MAA and Tc-99m DTPA aerosol were calculated using two methods. These calculations show that the average fetal dose decreases as gestational age (or fetal size) increases. Although the resultant dose estimates exceed those previously reported by severalfold, the risk to mother and fetus from undiagnosed pulmonary embolism far outweighs the risk to the fetus from the radiation exposure.

Female↗
PubMed1986

Cost-effectiveness of routine radiochemical quality assurance testing of technetium Tc 99m radiopharmaceuticals.

The cost-effectiveness of performing routine radiochemical quality assurance (QA) testing of technetium Tc 99m radiopharmaceuticals was evaluated. Data were collected retrospectively on use and failures of radiopharmaceuticals over a 30-month period at a university hospital. Cost of quality assurance testing of the radiopharmaceuticals and cost of not performing this routine testing (e.g., repetition of invalid studies) were compared. Possible reasons for failure of radiopharmaceuticals to meet QA standards were examined. Based on these data and an informal survey of the incidence of failures at other nuclear pharmacies, expected radiopharmaceutical failure rates were calculated. The incidence of failures at the study institution was 0.56% (20 of 3775); the other nuclear pharmacies reported similar data. Based on these data, 6 failures per 1000 technetium Tc 99m radiopharmaceuticals prepared were predicted. "Low tin" kits (e.g., albumin aggregated) with low-specific-activity sodium pertechnetate Tc 99m were associated with failure to meet QA standards. Direct costs of QA testing were slightly less than direct costs associated with not testing; however, consideration of indirect costs confirmed the cost-effectiveness of QA testing. Routine radiochemical QA testing of technetium Tc 99m radiopharmaceuticals appears to be cost-effective.

Cost-Benefit Analysis↗
PubMed1984

Common uses of nonradioactive drugs in nuclear medicine.

A variety of nonradioactive pharmaceuticals commonly used in patients who receive nuclear medicine diagnostic tests are described. Nonradioactive drugs used in thyroid, brain, hepatobiliary, cardiac, renal, Meckel's diverticulum, gallium, adrenal, and hematological studies are described. Pharmaceutical necessities used as disinfectants, diluents, and anticoagulants are also described. Hospital pharmacists should be familiar with the uses of commonly prescribed nonradioactive drugs in nuclear medicine studies.

Adrenal Glands↗
PubMed1981

Time dependence of iprofenin-labeling with technetium Tc 99m.

The incubation time required to attain 90% labeling efficiency (90% radiochemical purity) for technetium Tc 99m labeling of iprofenin (PIPIDA, Diagnostic Isotopes, Inc.), was investigated. Thirty iprofenin vials were prepared according to the manufacturer's instructions. Aliquots were withdrawn from 12 vials at times 0.5, 1, 2, 3, 5, 7, 10, 12, 15, 20, 30, 45, and 60 minutes after mixing. Aliquots were withdrawn from 18 vials at 1, 2, 3, 5, 7, and 10 minutes. Free pertechnetate and reduced/hydrolyzed technetium were isolated from aliquots with instant thin-layer chromatography and quantified with a scintillation well counter. Based on the 30 vials, a mean (+/- S.E.M.) of 5.83 +/- 4.32 minutes was required to attain 90% labeling efficiency. Using tolerance limits calculations, the incubation time required to be assured that 95% of vials have achieved 90% labeling is 16.8 minutes. It is concluded that 99mTc iprofenin vials should be incubated 17 minutes to be assured of 90% labeling efficiency.

Imino Acids↗