Radioisotopic pulmonary lobectomy: feasibility study in dogs.

In search for an alternate treatment for inoperable cancer of the lung in humans, we investigated the possibility that introduction of radioactive material into a selected lobe of the canine lung would effectively destroy that lobe without systemic effects or radiation injury to adjacent organs. Ten million ion exchange microspheres labeled with 740 MBq of phosphorus-32 (32P) were injected through a catheter placed in a selected lobar branch of a pulmonary artery in 12 anesthetized dogs. Six additional dogs served as controls and received 10 million microspheres not labeled with 32P. Organs were harvested from 1 wk to 12 mo after injection and examined grossly and histologically. There was progressive organization and contraction of each necrosed 32P treated lobe which was reduced to a scarred remnant by 12 mo, whereas only minimal inflammatory changes occurred in controls. Of the 32P injected dose, 94% remained in injected lobe, 4%-5% in nontargeted lobes and less than 0.08% in blood. Radioactivity in liver, kidneys, spleen, heart, and bone marrow was less than 0.1% for each organ. Thus, large doses of radiation in the order of 1,500 Gy can be effectively delivered to a selected lobe to produce a "radioisotopic pulmonary lobectomy."

Synthesis and quality control testing of 32P labeled ion exchange resin microspheres for radiation therapy of hepatic neoplasms.

Commercial cation exchange resin beads (200--400 mesh) are separated into narrow particle size ranges by sieving and differential sedimentation. These microspheres are converted into the chromic form by reaction with Cr(NO2)3, labeled with 20 mCi 32P phosphate by exchange at pH 2--4, and converted to a stable product at pH 9. Chemical stability ahd biological behavior of these microspheres suspended in physiological saline is measured before administration through a hepatic artery catheter for radiation therapy of the liver and hepatic neoplasms.

Collimator and xenon-127 for ventilation studies.

In comparison with xenon-133, the more energetic emissions from xenon-127 suffer less attenuation by tissues and should therefore provide images with better resolution in ventilation studies. However, the better resolution of the low-energy collimator used with xenon-133 may outweigh such advantages of the more energetic emission of xenon-127, which requires a medium or high-energy collimator.

The health physics of xenon-127.

Dosimetry calculations were performed for clinical ventilation studies in which xenon-127 was used in place of xenon-133. A graphical method for obtaining the maximum permissible concentrations for a facility that uses both isotopes is presented. Shielding requirements are also described.

Renal clearance and extraction parameters of ortho-iodohippurate (I-123) compared with OIH(I-131) and PAH.

o-[131I] iodohippurate [OIH(I-131)] has been used for many years in the estimation of effective renal plasma flow. This compound suffers from low photon yield and poor images when the quantity used is limited to stay within a reasonable radiation dose. To test the validity of substituting I-123 for I-131, a series of experiments was performed in a surgically prepared dog model. The extraction ratios and clearance values OIH(I-123) prepared from radionuclidically pure I-123 were compared with those of commercial OIH(I-131) and PAH. The extraction ratios for OIH(I-123) and OIH(I-131) were 0.65 and 0.67, representing 0.86 and 0.88 that of PAH, respectively. The clearance values (cc/min/kg) for the I123 and I-123) can be used to estimate effective renal plasma flow; moreover, because of the high yield within an acceptable radiation dose range, images of good quality can be produced.

Scintillation camera imaging with I-123.

Iodine-123 produced from three different nuclear targets (Te-122, Te-124, and I-127) was evaluated for spatial resolution and sensitivity with an Anger scintillation camera. Te-122 targets generated a substantial amount of I-130, which necessitated use of a medium-energy collimator. Te-124 targets produced solutions with significant amounts of I-124. Shortly after the end of bombardment, a 4,000-hole (4KH) collimator was satisfactory; at 30 hours, a medium-energy collimator was required. High-purity I-123 from an I-127 target gave excellent spatial resolution when the 4KH collimator was used, but low-energy "foil" collimators were not adequate.

Total and individual kidney function assessment with iodine-123 ortho-iodohippurate.

A simple and reliable method of preparing 123l o-iodohippurate (l-123 OIH) is described. The agent was used to evaluate renal function in 329 patients; its use results in significant dose reduction for those with obstruction, hypertension, or transplant. Images from l-123 OIH provide 2.4 times more detectable photons per mCi administered to the patient than images obtained from l-131 OIH. Diagnoses are expected to be more reliable with l-123 OIH due to the decreased random variation of each data point.

Myocardial imaging with 123I-hexadecenoic acid.

123I-hexadecenoic acid is a terminally iodinated, 17-carbon fatty acid analog which is rapidly degraded in the myocardium. By determining regional myocardial distribution patterns and clearance rates, it may become useful as a single agent for estimating regional myocardial perfusion and for distinguished viable ischemic tissue from infarcted tissue. The high count rates obtainable with the iodine label permit acquisition of qualitative multiprojection images in only 3 min. per view, or quantifiable single projection high count images in 10 min. Ischemic defects may be observed in anginal patients without subjecting them to stress.

Production by compact cyclotron of radiochemically pure iodine-123 as iodide for synthesis of radiodiagnostic agents.

Iodine-123-labeled radiopharmaceuticals are desirable because they give a high flux of 159-keV photons and a low radiation exposure per millicurie. Procedures suited to a compact cyclotron were developed to produce 50-mCi batches of radiochemically pure iodine-123 as iodide. Iodine-123 is separated from proton-irradiated tellurium-124 by distillation. Aqueous iodide is readily obtained by reduction with thiosulfate. Anhydrous iodide is extracted from the distillate iwth methyl ethyl ketone. The procedures for isolating radiochemically pure iodide are trouble-free, convenient, and reliable. Iodine-123-labeled o-iodohippurate and 16-iodo-9-hexadecenoic acid prepared from our iodide are now being used in clinical trials.