John G. McAfee

99mTc-Labeled Polyphosphate as a Skeletal Imaging Agent1

A new complex of 99mTc with a synthetic linear long-chain polyphosphate shows excellent potential as a skeletal imaging agent on the basis of preliminary animal tissue radio-assay and imaging studies. Skeletal metastases were demonstrated by rectilinear scanning and gamma camera imaging. The quality of the scans were comparable with those obtained with 18F.

Correlation of computed tomography, gray scale ultrasonography, and radionuclide imaging of the liver in detecting space-occupying processes.

The abilities of computed tomography (CT; scanning time=2.7 min), gray scale ultrasonography, and radionuclide imaging to detect and characterize space-occupying processes in the liver were compared. A numerical rating scale which emphasized detection abilities resulted in ultrasonography scoring 3.5 CT 3.2, and radionuclide imaging 2.9. CT resulted in no false positives and 6 false negatives, caused mainly by motion artifacts. The simplest technique, radionuclide imaging, also had the smallest number (2) of false negatives; it is therefore recommended as the screening procedure of choice. Sonography or CT should be done for those patients with a prior suspicious finding.

Work in Progress: Visualization of Renal Parenchyma by Scintiscanning with Hg203 Neohydrin1

Radioactive contrast media, such as I131-labeled Diodrast, Miokon, or Hippuran, have been widely used for renal function studies. They are entirely unsatisfactory, however, for renal scintillation scanning because they are rapidly excreted by the kidneys, without retention in the renal parenchyma (Fig. 1, A). In contrast, mercurial diuretics labeled with radioactive mercury are concentrated to a high degree in the renal tubular cells (2), chiefly in the cortex, prior to their appearance in the urine (Fig. 1, B). Furthermore, the nuclide Hg203 has a single, rather weak gamma emission (280 kev) that enables good resolution when a multihole focusing collimator and gamma spectrometry are used (1). These pharmacological and physical characteristics make it possible to obtain a clearly delineated spatial image of the kidneys in man by means of scintillation scanning. The mercurial diuretic is retained in the renal parenchyma long enough to permit completion of the procedure. The effective half-life of the com p...

COMPARISON OF RADIOISOTOPE SCANNING WITH CEREBRAL ANGIOGRAPHY AND AIR STUDIES IN BRAIN TUMOR LOCALIZATION

In this paper, cerebral scintillation scans in 400 brain tumor suspects are evaluated and compared with the results of conventional neuroradiologic methods. Although the scanning technic has been applied to the diagnosis of intracerebral lesions for many years, it has failed to gain widespread use as a diagnostic tool (6). The opinion of the pioneer workers in this field differed widely on the clinical value of the procedure. There was almost uniform agreement, however, that scanning instruments could be greatly improved. Those developed for thyroid and hepatic lesions proved disappointing for cerebral lesions. Coincident scanners for positron-emitting nuclides reached a high degree of development at an early stage (3) but failed to gain popularity because of their complexity and expense. During the past ten years, steady progress has been made in the development of scintiscarmers. The detailed requirements for a satisfactory instrument will be published elsewhere. At the present time, commercial units ar...

VISUALIZATION OF THE SPLEEN IN MAN BY RADIOISOTOPE SCANNING

To visualize an organ by scintillation scanning, a gamma-emitting radioisotope must reach a considerably higher concentration within the organ than in the surrounding tissues. A method for scanning the spleen has recently been reported (2). Cr51-labeled Rh0(D) positive red blood cells, “sensitized” for splenic trapping by coating with incomplete anti-Rh0(D) antibody, were administered intravenously to Rh0(D) positive persons. This method, however, could not be used in Rh negative patients and necessitated typing of each patients blood. On the basis of the observation that heated red blood cells concentrate in the spleen (1), a simple technic which gave a good spatial image of the spleen was developed. Ten cubic centimeters of the patients blood were withdrawn into a sterile syringe containing 2 c.c . of ACD anticoagulant. Two hundred microcuries of Cr51 sodium chromate were added. After incubation at room temperature for fifteen minutes, 50 mg. of ascorbic acid were added to reduce residual chromate to ...

LOCAL RADIATION DAMAGE TO BONE AND MARROW DEMONSTRATED BY RADIOISOTOPIC IMAGING.

The effects of irradiation on the skeleton and the bone marrow have been extensively studied for many years. Most of this early work has been concerned with total-body irradiation rather than with localized fields commonly used in radiation therapy. As a rule, clinical evidence of radiation damage to bone does not present without either secondary infection or pathological fractures. In addition, roentgenographic evidence of this type of osseous damage is notoriously late in appearing. The changes following irradiation, however, are shown early by imaging the skeleton after the administration of short-lived radionuclides which selectively localize in either the skeleton or the reticuloendothelial system. These changes are apparent when neither clinical nor roentgenographic changes of radiation damage are present. The distribution of bone-seekers such as fluorine 18 within the skeleton is markedly affected by a variety of pathological states. Abnormal concentrations have been shown, for example, in areas of...

Experimental and clinical trials of new 99mTc-labeled hepatobiliary agents.

Several new derivatives of lidocaine were synthesized and used to examine the intra- and extrahepatic bile ducts and gallbladder. Diisopropyl-IDA exhibited approximately twice the bile concentration of 131I-rose bengal during the first hour after injection. P-butyl-IDA also concentrates moderately well in the bile and has the added advantage of very low excretion into the urine (2%). It seems more effective than the other IDA derivatives at high bilirubin levels.

Measurement of Hg203 Chlormerodrin Accumulation by the Kidneys for Detection of Unilateral Renal Disease

It has long been recognized that a reliable screening procedure is needed for hypertensive patients, in order that a minority whose disease is due to unilateral renal ischemia may be selected. A popular technic for this purpose has been the “radioisotope renogram,” whereby the rate of accumulation and excretion of I131 o-iodohippuric acid2, injected intravenously, is measured by paired scintillation detectors external to the kidneys, (3, 4). Since 1959, the mercurial diuretic chlormerodrin (Neohydrin) labeled with Hg203 has been used for delineation of localized renal lesions by scintillation scanning (2). In addition, renal function may be assessed with this material by measuring its rate of accumulation by a technic similar to the I131 Hippuran studies. To perform this “chlormerodrin uptake test,” the patient is positioned supine on a modified x-ray table tilted 30° from the horizontal. A preliminary radiograph is obtained for accurate localization of two scintillation detectors under the kidneys. The s...

Radionuclide Imaging in the Assessment of Primary Chronic Pyelonephritis

The diagnostic value of radionuclide imaging as a supplement to excretory urography was assessed in 33 patients with primary chronic pyelonephritis. Both 99mTc-glucoheptonate and 131I-Hippuran were used. Radionuclide imaging did not improve the sensitivity of detection by urography alone (31 of 33 patients). Nevertheless, in one third of cases the radionuclide studies demonstrated certain abnormalities more readily, including focal parenchymal damage, renal functional impairment, and decreased renal perfusion. Radionuclide imaging is useful when minimal or no abnormalities are observed on the excretory urogram or nephrotomogram.

Experimental Models and Evaluation of Animal Data for Renal Radiodiagnostic Agents

After a new gamma-emitting radiodiagnostic agent is synthesized and its chemical structure defined, serial camera imaging following administration to experimental animals can quickly determine its major organ localization. Blood and plasma disappearance curves and urinary excretion at different time intervals are also measured. For renal agents, with negligible extrarenal concentration or excretion, a double exponential analysis of the plasma disappearance curve may be used to quantitate renal clearance, in dogs (Blaufox et al., 1963) or even in small animals like the rat (Blaufox et al., 1970). If a new agent appears promising for eventual human use, more detailed concentration values are required for various organs at different time intervals. These are generally obtained by direct tissue radioassay following the sacrifice of a series of animals. It is frequently rewarding to compare (by dual channel pulse height analysis) the distribution of a new agent with that of an older one with similar organ localization, simultaneously injected and labeled with a radionuclide of different gamma energy. These tissue concentration data from animals are essential to calculate preliminary radiation dose estimates, before administration to humans is considered.