Use of a paramagnetic substance, colloidal manganese sulfide, as an NMR contrast material in rats.

Paramagnetic pharmaceuticals ( magnetopharmaceuticals ) that are suitably distributed into specific organ systems or diseased sites might be clinically useful for tissue contrast enhancement in nuclear magnetic resonance images. To determine whether an insoluble magnetopharmaceutical might be useful in such service, we investigated the effect of a colloidal preparation of manganese sulfide ( MnSC ) upon liver and lung spin-lattice relaxation times (T1) in rats following intravenous administration. NMR tissue sample measurements were made at 24 MHz, ahd showed that after MnSC treatment, liver T1 values--and to a lesser extent lung T1 values--were depressed below control values. Liver manganese content (as determined by flame atomic absorption spectrophotometry) increased in proportion to the dose of MnSC , and the reciprocal of the liver T1 values also increased in proportion to the dose of MnSC .

Alteration of gallium-67 distribution in tumor-bearing mice following treatment with methotrexate: concise communication.

The effect of methotrexate (MTX) treatment upon Ga-67 distribution was investigated. Tumor bearing mice were injected with Ga-67 citrate at varying time intervals following MTX treatment administered either as a single dose or in multiple doses. Altered Ga-67 distribution was observed following MTX therapy, the general pattern showing decreased levels in blood and increased uptake in bone. MTX therapy decreased Ga-67 uptake in liver, tumor, and muscle. The effects of MTX are related to the dose and time interval between the administrations of MTX and Ga-67. The serum of MTX-treated mice had lower unsaturated iron-binding capacities and higher levels of unbound Ga-67. Serum iron and iron binding in rats determined 20 hr after MTX therapy showed significantly higher levels of serum iron and lower levels of Ga-67 in blood, and the percent transferrin saturation was approximately 95%. These observations suggest that MTX inhibition of erythropoiesis elevates serum iron levels and decreases the availability of gallium-binding sites in serum, resulting in altered Ga-67 tissue distribution.

Relative lesion detection ability of Tc-99m HMDP and Tc-99m MDP: concise communication.

To compare the efficacy of Tc-99m HMDP and Tc-99m MDP to define skeletal lesions, 28 adult patients were examined in a double-blind, randomized, crossover study. Each patient was imaged with both agents over a period of 7-14 days. Both quantitative and qualitative evaluations were performed on the resulting images. Both agents detected the same number of skeletal lesions, and the number of lesions detected was the same whether the imaging was performed 2 or 4 hr after injection. Relative uptake of the tracer in the lesion relative to normal bone was also the same for both agents. Lesions were easier to see at 4 hr after injection than at 2 hr, presumably because soft-tissue levels were lower. Retention of tracer in bone compared with soft tissue was greater, and image quality was judged to be better, with Tc-99m HMDP than with Tc-99m MDP.

Comparison of Tc-99m pyrosphosphate and Tc-99m hydroxymethylene diphosphonate in acute myocardial infarction: concise communication.

A clinical comparison between a new bone seeking radiopharmaceutical, Tc-99m hydroxymethylene diphosphonate (TcHMDP) and the standard agent, Tc-99m pyrophosphate (TcPPi), was performed in 18 patients with acute myocardial infarction. Each patient was imaged initially with either TcHMDP or TcPPi, and imaged 24 hr later with the other tracer. All 18 patients had images positive for acute myocardial infarction with TcPPi, whereas 16 of 18 patients (89%) had positive studies with TcHMDP. The TcPPi images were graded significantly superior to those obtained with TcHMDP in 61% of the patients, and they were equal in 33%. In only one patient (6%) was TcHMDP better. The results indicate that compared with TcHMDP, TcPPi not only has a superior sensitivity for acute myocardial infarction but also has a significantly increased intensity of uptake in positive areas. TcPPi remains the agent of choice for myocardial infarct imaging.

The utility of adrenal scintigraphy in Cushing's syndrome and hyperaldosteronism.

Thirty-three adrenal scintigrams in 30 patients were reviewed to determine the utility of this noninvasive imaging technique. It was found to be very accurate in distinguishing bilateral from unilateral hyperfunction in patients who have clinical and biochemical evidence of adrenal cortical hyperfunction. The technique proved correct in 12 of 12 cases of Cushing's syndrome and 14 of 19 cases of hyperaldosteronism. Specific clinical questions were also answered in three miscellaneous cases.

Hematologic depression following therapy with strontium-89 chloride.

Initial clinical trials using strontium-89 (Sr-89) chloride for the treatment of painful skeletal metastases have observed minimal or no hematological depression secondary to the radiostrontium. A patient with marked bone marrow depression temporally related to the administration of the Sr-89 is reported, and the need for close hematological monitoring is emphasized. Bone marrow tumor replacement may predispose patients to marrow depression from radiostrontium, and such patients should be treated with caution.

Principles and applications of nuclear magnetic resonance imaging.

The physics, instrumentation, and general aspects of nuclear magnetic resonance (NMR) imaging are discussed. NMR images are constructed from magnetic signals emitted by certain atomic nuclei when they are subjected to simultaneously applied magnetic fields and externally generated radiofrequency (r.f.) energy. Hydrogen (the nucleus of which is a single proton) is sensitive to NMR and sufficiently abundant in tissues to produce the signals necessary for image formation. The NMR imaging device consists of a large magnet, a radiofrequency-transmitter coil, and computer hardware. Following r.f. pulsing, the strength and origin of the magnetic signals can be determined by magnetic field gradients that are superimposed on a magnetic field. Then this spatial information can be encoded electronically and reconstructed into a cross-sectional image. NMR imaging is valuable for the diagnosis of a variety of diseases and traumas since a high level of lesion and soft tissue contrast is possible in most types of pathology. Compounds containing paramagnetic elements (magnetopharmaceuticals) may be useful to enhance tissue contrast and organ detail. The high level of tissue detail, sensitivity to pathology, and apparent lack of hazard make NMR an important addition to the existing diagnostic modalities.

Effects of liquid versus solid diet on colonic transit in humans. Evaluation by standard colonic transit scintigraphy.

The effects of liquid versus solid diet on human colonic transit were investigated, and transit following cecal instillation of tracer was compared with transit following instillation in the proximal jejunum. In a randomized cross-over, single-blind fashion, 6 normal volunteers ingesting either normal solid foods or a liquid diet were studied using colonic transit scintigraphy. 111In-DTPA was instilled either into the cecum via a long intestinal tube or into the proximal jejunum via a feeding tube. Compared with the liquid diet, the solid diet slowed transit in the cecum and ascending colon (p less than 0.025) and delayed progression of the geometric center (p less than 0.05) during the first 4 h of the study. Transit from 18 to 48 h was similar on the 2 diets. On the solid diet, transit was similar whether 111In-DTPA was instilled into the proximal jejunum or into the cecum. Transit from the terminal ileum to the cecum was assessed in an additional 5 volunteers following jejunal instillation of 99mTc-DTPA. Cecal filling was rapid (T1/2 = 0.49 h) and complete in all subjects before the onset of cecal emptying. These results suggest that colonic transit is slower on a solid than a liquid diet and that jejunal instillation of radiopharmaceuticals should be suitable for colonic transit studies in most subjects.