Sensitivity of Kr-81m and Xe-127 in evaluating nonembolic pulmonary disease.

The relative sensitivities of Kr-81m and Xe-127 in detecting lung ventilation defects was evaluated in 80 patients with nonembolic pulmonary diseases. Krypton-81m ventilation images (500,000 count) were interdigitated with Tc-99m MAA perfusion images; both were compared with Xe-127 images. The distributions of the two gases were also compared on the basis of point-by-point computer analyses. Xenon-127 was found to be more sensitive than Kr-81m in clinical evaluations of scintiphotos--although they were equivalent by computer analyses--in indicating regions of impaired ventilation in patients with obstructive airways disease.

Ruthenium-97 DTPA: a new radiopharmaceutical for cisternography.

Ruthenium-97 DTPA (diethylenetriamine penta-acetic acid) was evaluated for its possible use as a cerebrospinal fluid imaging agent. Ru-97 has favorable physical properties that are highly suitable for imaging: decay by electron capture; gamma energy = 216 keV, 85%; T 1/2 = 2.9 days. Dogs were injected with 0.4 mCi Ru-97 DTPA or In-111 DTPA into the cisterna magna. The movement of the agents was monitored with a camera interfaced to a computer, or with a dual-probe system placed over the head and urinary bladder. In addition, blood and urine samples were collected at fixed intervals for 6 hr. High-quality images were obtained up to 48 hr after injection. The results show that the kinetics and excretion of Ru-97 DTPA are similar to those of In-111 DTPA. Radiation dose for identical activities is twice as high for In-111, in part because of greater abundance of the low-energy electron emission of In-111.

The diagnosis of hypertension.

An argument can be made for modifying the recommendation in the sixth report of the Joint National Committee for Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI) for the measurement of blood pressure. If the blood pressure is taken in the erect position immediately after the patient enters the examination room, a much closer approximation of the ambulatory blood pressure is obtained. Another blood pressure taken immediately after assuming the supine position, and a third blood pressure 3-5 minutes after assuming the supine position, will then yield a basal equivalent to the JNC VI recommendation. Postural hypotension in older and diabetic patients can be unmasked by a final erect blood pressure. These procedures will allow a spectrum of blood pressures sufficient to establish the diagnosis of hypertension and monitor its treatment, without resorting to ambulatory blood pressure monitoring.

Detection of gastrointestinal blood loss with 99mTc-labeled, heat-treated red blood cells.

Studies in dogs showed that heat-treated 99mTc-labeled red blood cells (HT/RBC) afford a highly sensitive means of detecting gastrointestinal bleeding as low as 0.12 ml/min., which could not be seen with unheated 99mTc-RBC, 99mTc-sulfur colloid, or 99mTc-DTPA. In addition, as the right upper quadrant and epigastrium remained free of activity, only one fifth to one tenth of the dose of 99mTc was needed. The safety of HT/RBC in humans has been documented, and the experiments in dogs suggest that it may have advantages over other agents in detecting gastrointestinal bleeding.

Splenic sequestration of 99mTc labeled, heat treated red blood cells.

The rates of blood clearance and splenic uptake as well as the total splenic uptake of heat damaged red blood cells labeled with 99mTc were determined in eight patients. Splenic uptake at two hours was 72.0 +/- 18.5%. Approximately 82.6% of the initial radioactivity was cleared from the blood by two hours, with a rapid T1/2 component of 6.3 +/- 4.7 minutes. The T1/2 of splenic uptake was 8.3 +/- 4.6 minutes, and splenic radioactivity reached a plateau by 30 minutes. The results indicate that the method of preparation is reliable, but its usefulness for evaluating spleen function remains to be determined.

97Ru-DMSA for delayed renal imaging.

Dimercaptosuccinic acid (DMSA) was labeled with 97Ru both with and without the addition of SnCl.2H2O. The tin-containing preparation was found to induce higher cortical deposition of 97Ru-DMSA than the tin-free preparation. Visualization of the renal cortex was excellent 4 to 48 hours after injection in normal dogs with renal insufficiency. It is concluded that 97Ru-(Sn+2)-DMSA is a potentially useful renal imaging agent when delayed scintigraphy is necessary because of decompensaton of the kidneys.