Scintigraphic detection of intrapulmonary bleeding using technetium-99m sulfur colloid: concise communication.

Radionuclide imaging has been successfully used clinically to determine sites of gastrointestinal hemorrhage, but its use in hemoptysis has not been studied. A dog model of intrapulmonary hemorrhage was devised. Utilizing technetium sulfur colloid, at doses of 4 and 15 mCi, bleeding rates of 0.1--0.2 cc/min were detected. In some dogs, however, significantly higher bleeding into a large bronchus, which causes a diffuse distribution of the radionuclide.

Distribution of 67-Ga following intravenous administration: effects of disodium edetate therapy.

Following intravenous administration of 67Ga-citrate to normal and abscessed rats, the colon content of 67Ga decreased with increasing oral doses of Na2EDTA. The effects observed, however, were not thought to be of potential clinical value.

Monitoring of I-125 contamination using a portable scintillation camera.

A technique has been developed using a portable scintillation camera to monitor I-125 contamination of personnel. The procedure takes less than a minute to complete and can detect 3 nanocuries; its use minimizes dissemination of I-125 throughout the hospital, emphasizes safe iodination practices and proper handling of radioactive materials, and reduces radiation exposure by undetected contamination.

Peritoneal fluid causing inferior attenuation on SPECT thallium-201 myocardial imaging in women.

On SPECT thallium images, myocardial left ventricular (LV) anterior wall attenuation due to breast tissue is common in women. In contrast, in men, inferior wall counts are normally decreased compared to anterior counts. The purpose of this report is to describe cases of inferior wall attenuation of counts in women caused by peritoneal fluid, not myocardial disease. Twelve consecutive SPECT thallium myocardial studies performed in women on peritoneal dialysis, being evaluated for kidney transplant, were included in this study. For all studies, 3.5 mCi 201Tl were injected intravenously. Thirty-two images were acquired over 180 degrees (45 degrees RAO progressing to 45 degrees LPO) at 40 sec per stop. SPECT images were reviewed in short axis, horizontal long and vertical long axes. Data were also displayed in "bullseye" format with quantitative comparison to gender-matched normal files. Ten of 12 female patients studied had inferior wall defects on images, confirmed by bullseye display. All patients had approximately 2 liters of peritoneal fluid. Review of planar rotational views showed diaphragm elevation and fluid margin attenuations affecting left ventricular inferior wall. Thus, peritoneal fluid is a cause of inferior attenuation on 201Tl cardiac imaging.

No difference in sensitivity for occult infection between tropolone- and oxine-labeled indium-111 leukocytes.

There is considerable disagreement as to whether oxine or tropolone is the best labeling agent for indium leukocytes. We have previously looked at the sensitivity of oxine-labeled 111In leukocyte scans for occult infections and now present a similar group of patients imaged with tropolone-labeled 111In leukocytes. Thirty-four patients (38 studies) with possible occult infection were prospectively studied. Patients were imaged 1-4 hr after injection and again at 24 hr postinjection. The early tropolone images had a sensitivity of 53% while the delayed images at 24 hr had a sensitivity of 93%. Based on a previous study, oxine-labeled leukocyte scans have an early sensitivity of 33% and a delayed sensitivity (at 24 hr) of 95%. The differences in sensitivity between oxine and tropolone when imaged early and at 24 hr were not statistically significant. We conclude that there is no significant difference in the ability to detect infection between oxine- and tropolone-labeled leukocytes, both early at 1-4 hr, and on delayed imaging 24 hr after injection.

SPECT thallium-201 scintigraphy for the detection of left-ventricular aneurysm.

We have noted that the presence of left ventricular anterior/apical aneurysm on contrast ventriculography or echocardiography correlates well with the finding of failure of convergence of the left ventricular walls toward the apex on single photon emission computed tomography (SPECT) thallium-201 images. To assess this observation, we analyzed the SPECT thallium scans of 74 sequential patients who had SPECT thallium scintigraphy and contrast ventriculography and/or echocardiography for evaluation of coronary artery disease. Immediate post-stress and 4-hr redistribution thallium-201 SPECT images, obtained following i.v. administration of 2 mCi of thallium-201, were reconstructed with no attenuation correction using three-dimensional linear and nonlinear filters and displayed in short, vertical-long, and horizontal-long axes. Of the 74 patients, contrast ventriculography and/or echocardiography showed anterior/apical aneurysms in 15 and a posterolateral aneurysm in one. SPECT thallium scans detected 14 of the 16 aneurysms, based on the criterion of failure of convergence of the ventricular walls toward the apex. There were two false-positives. Thus SPECT thallium-201 scintigraphy for the detection of left-ventricular aneurysm in this series had a sensitivity of 94%, a specificity of 97%, and an accuracy of 96%.

Tumor model studies of 131I-tetracycline and other compounds.

Iodine-131-tetracycline (131I-TET) was prepared by allowing tetracycline hydrochloride to react with radioiodide in acidic methanol (labeling efficiency greater than 85%). This preparation was found to be stable at--4 degrees C for at least 72 hr. Some minimal in vivo breakdown did occur. The 131I-TET, 67Ga, and several 99mTc compounds were studied in a rat hepatoma model. The incorporation of the radiopharmaceuticals into the tumor occurred rapidly, with peak levels at 0.5 and 24 hr after injection for 131I-TET and 67Ga, respectively. The clearnace of the radiopharmaceutical from nonviable tumor was slower than for viable tumor, and by 72 hr after injection the greatest concentration of radioactivity appeared in the nonviable fraction. All normal tissues showed faster clearance than did tumor tissue, regardless of viability. Decreasing the quantity of 131I-TET injected increased the percent of uptake in the nonviable tumor tissue but had no effect on the viable tumor uptake. Of the 99mTc compounds studied, the phosphates developed the highest tumor-to-background ratios. Unfortunately these ratios were not as high as those achieved for 67Ga or 131I-TET.

Reproducibility of thallium-201 exercise SPECT studies.

UNLABELLED: A detailed analysis of intrapatient reproducibility of exercise SPECT thallium studies is presented. METHODS: Twenty patients in stable condition were re-examined with exercise-redistribution SPECT201 Tl within 3-9 days without intervening procedures. At peak stress, 3.5 mCi 201Tl were given intravenously 1 min prior to exercise termination. SPECT imaging started at 5 and 180 min. Acquisition and processing protocols were the same for all studies. Coronary angiography was performed on 19 patients and showed coronary artery disease (CAD) in 18, and no CAD in one; one patient did not have coronary arteriography. RESULTS: For 16 of 20 patients, exercise levels and ECG were comparable for both studies. Ten patients reproduced ST-segment depression; two reproduced angina; one had left bundle branch block (LBBB) on both studies after 1 min of exercise. The remaining seven patients had no ECG changes or symptoms during exercise. Four of 20 (20%) thallium scans differed: three in degree of redistribution and one (5%) in presence of a second stress defect. In three of four patients whose thallium studies showed some nonreproducibility, there were differences in exercise. Thallium results were identical in 15 of 16 patients whose ECG/exercise tests were reproducible (94%). Interobserver agreement was 95%. CONCLUSION: There was excellent reproducibility of 201Tl SPECT scintigraphy in patients who reproduced exercise test performance and symptoms.

Technetium-99m-sulfur colloid for lymphoscintigraphy: effects of preparation parameters.

UNLABELLED: There has been a resurgence in the use of lymphoscintigraphy for the external detection of lymph nodes for metastatic melanoma and breast tumors. Technetium-99m-antimony trisulfide colloid was the radiopharmaceutical developed for this procedure and was found to have a narrow distribution of small particles, 0.003-0.03 microns, but it was never approved by the FDA. Technetium-99m-sulfur colloid also forms particles and this article reports on the effects different preparation parameters have on its particle size distribution and stability. METHODS: Four groups of kits were evaluated, kits which utilized: (a) a reduced heating protocol with a new 99mTc-elution, (b) a reduced heating protocol with an old 99mTc-elution, (c) a prolonged heating protocol with a new 99mTc-elution and (d) a prolonged heating protocol with an old 99mTc-elution. The particle size distribution and the stability of the different 99mTc-sulfur colloid kit preparations were evaluated over 6 hr utilizing polycarbonate filters ranging from 0.03 to 10 microns. RESULTS: In vitro studies demonstrated no significant change in the particle size distribution over a 6-hr period and all 99mTc-sulfur colloid preparations had a bimodal particle size distribution pattern. Importantly, heating the kit for shorter periods of times utilizing [99mTc]pertechnetate, which had a longer ingrowth of [99mTc]pertechnetate, produced a formulation which had the largest percentage of particles smaller than 0.03 microns. CONCLUSION: In our clinical setting, 99mTc-sulfur colloid prepared with the reduced heating protocol and utilizing [99mTc]pertechnetate, which has the highest ingrowth of [99mTc]pertechnetate has proved to be an excellent agent for lymphoscintigraphy studies. This preparation has demonstrated rapid movement of the particles from the primary site to the lymph nodes in over 97% (106/109) of the patients we have studied.

Left ventricular dilatation and multivessel coronary artery disease on thallium-201 SPECT are important prognostic indicators in patients with large defects in the left anterior descending distribution.

This study examines the importance of left ventricular (LV) dilatation, and evidence of multivessel coronary artery disease identified on thallium-201 (TI-201) single-photon emission computed tomographic (SPECT) scintigrams, for predicting long-term outcome in patients with an extensive left anterior descending (LAD) perfusion deficit. Impaired contractility of the left ventricle determined by low ejection fraction, elevated LV end-systolic volume, and dilatation of the left ventricle are known as major predictors of mortality after myocardial infarction. TI-201 single-photon emission computed tomography primarily reveals status of perfusion/redistribution, but also contains indirect information on LV function. To date, there are no TI-201 SPECT data on impaired function of the left ventricle (LV dilatation) and extent of perfusion deficits, discussed together as correlates of survival. Patient data were prospectively collected in the computer data base at Emory University. A large perfusion defect involving more than one third of the LAD territory was identified in 291 of 2,652 consecutive patients examined with TI-201 SPECT initial and 3-hour redistribution studies. Follow-up data were obtained for 284 patients (98%) at 38 +/- 14 months. Of the 291 patients, 58 died. The most powerful multivariate correlates of death were LV dilatation, multivessel disease, and the ratio of the LAD severity stress score to total severity of SDs stress score. Cox model analysis was used to determine correlates of survival. Three-year survival for patients with LV dilatation was 73% versus 89% without LV dilatation (p < 0.001). Three-year survival in patients with 1-vessel disease ("LAD only") was 94% versus 78% for multivessel disease (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Prognosis in patients with left ventricular apical aneurysm diagnosed by thallium-201 or Tc-99m sestamibi SPECT images.

The prognosis of patients with left ventricular (LV) aneurysm diagnosed by thallium single-photon emission computed tomography (Tl-SPECT) or technetium-99m sestamibi SPECT (MIBI) has not previously been defined. Of 9,505 Tl or MIBI patients, 139 with apical infarct and probable LV aneurysm on tomographic images were identified. Patients were grouped by the presence of divergent versus parallel LV walls. Divergent walls show increasing separation of the walls as they approach the apex on vertical or horizontal long-axis slices. The degree of the deformation at the apex (divergent vs parallel walls), extent of impaired myocardium (total number of pixels in the defect/total number of pixels in the myocardium x 100%), percentage of reversibility, and segmental and total severity of standard deviations of perfusion defects were calculated. Seventy-six patients underwent contrast ventriculography. Patients with divergent walls (n = 57) were older (p = 0.05), had lower ejection fractions (p = 0.012), higher lung uptake (only Tl patients (p = 0.06), and more frequent ST elevation on the resting electrocardiogram (p = 0.009) than patients with nondivergent (parallel) walls. For both groups, the percent impaired myocardium was comparably high (44 +/- 9% vs 46 +/- 10%). Analysis of asynergic segments in 76 patients who underwent contrast ventriculography showed more akinetic, paradoxical, or aneurysmal segments in the apical region of the left ventricle in the group with SPECT divergent walls. Cox model analysis showed divergence as the significant correlate of death. At 5 years, survival for the group with divergent walls was 52% compared with 75% for those with nondivergent walls (p = 0.008). Despite significant apical LV impairment in both groups, mortality was almost twice as high in the group with divergent walls compared with patients with parallel walls. Thus, patients with LV aneurysm diagnosed by radionuclide SPECT perfusion imaging have a higher mortality when displaying a divergent wall pattern than patients with lesser deformity.

Prognostic value of thallium-201 single-photon emission computed tomography for patients with multivessel coronary artery disease after revascularization (the Emory Angioplasty versus Surgery Trial [EAST]).

The aim of this study was to investigate the relation between reversible thallium single-photon emission computed tomography (SPECT) myocardial perfusion defects at 1-year after revascularization and quantitative indexes in Emory Angioplasty versus Surgery Trial (EAST) and outcomes 3 years after revascularization in 336 patients. EAST was a randomized controlled trial assessing cardiac outcomes for angioplasty versus bypass surgery for patients with multivessel coronary artery disease. During this prospective trial, a substudy included the evaluation of the prognostic value of reversible defects on quantitative thallium SPECT. At 1-year after revascularization, 336 patients underwent SPECT thallium-201 stress myocardial perfusion and 3-hour delayed imaging. Subsequent events, percutaneous transluminal coronary angioplasty, coronary artery bypass graft surgery, myocardial infarction, and death, were recorded at 3 years. A stress-induced reversible thallium-201 defect was defined using a quantitative index of a reversibility score >30% and severity score >500. Reversible defects were observed more frequently in the percutaneous transluminal coronary angioplasty than in the coronary artery bypass graft surgery treatment groups (46% vs 27%, p <0.001). A total of 123 patients had stress-induced, reversible thallium defects and more events than patients with other perfusion results (freedom from all events was 81.3% vs 94% [p <0.001], and freedom from myocardial infarction and death 88.3% vs 95.5% [p = 0.031]). Quantitative thallium SPECT at 1 year after revascularization risk stratifies patients as to their likelihood of major cardiac outcomes.

Sentinel node staging of early breast cancer using lymphoscintigraphy and the intraoperative gamma-detecting probe.

Sentinel node staging for breast cancer is increasingly used in place of axillary lymph node dissection but is not yet universally accepted. The problems of non-standardized methodologies and lack of consensus on the optimum techniques to identify sentinel nodes are being addressed. Complementary use of radionuclide imaging before surgery, intraoperative probe detection, and blue dye have yielded the best reported sensitivities for finding a sentinel node (94%). The importance of imaging is summarized as identifying sentinel node(s), distinguishing sentinel from secondary nodes, guiding surgical incision planning, and facilitating lower doses. The learning curve phenomenon, which applies to the surgeon and the nuclear medicine physician, has been recognized; measures to minimize it are being implemented. Radiation exposure to operating room and pathology personnel is very low; estimates of exposure to the surgeon's hands are 0.2% of the annual whole body dose received by every human being from natural background and cosmic sources.

Lymphoscintigraphy, the sentinel node concept, and the intraoperative gamma probe in melanoma, breast cancer, and other potential cancers.

There is a resurgence of interest in lymphoscintigraphy because of attention to the sentinel node concept and the availability of the surgical gamma probe that can be used in the operating room to localize radiolabeled sentinel nodes. Conventional surgical management of melanoma has been altered for intermediate thickness tumors such that lymph node dissection is performed for a lymph node bed only if the sentinel node is tumor positive on histological exam after gamma probe-guided excision. This approach is cost effective, saving about 80% of these patients (sentinel node tumor negative) the cost and morbidity of unnecessary "elective lymph node dissection." In addition, a biopsy can be performed on all lymph node beds that receive lymphatic drainage from the tumor site thereby improving staging and perhaps survival by providing the most appropriate therapy. Substantial work has been done to develop optimum imaging techniques and the best radiopharmaceutical preparation to achieve accurate, reproducible lymphatic drainage images. Our methodology includes the following intradermal injections of a technetium 99m sulfur colloid (modified preparation) are followed by dynamic imaging (10 seconds per frame); static imaging up to 30 minutes and late imaging at 1 to 2 hours. Images show lymphatic channels that lead to sentinel nodes in 1, 2, 3, or more anatomic locations. Surgical management is altered to include sampling sentinel nodes of nodal beds, many of which would not have been sampled by previous conventional surgical estimates of lymphatic drainage. While clinical success of lymphoscintigraphy and intraoperative probe localization of the sentinel node in melanoma is evident, use of lymphoscintigraphy and the sentinel node concept in breast cancer is investigative, but promising. The radiopharmaceutical is injected around the tumor in the breast followed by imaging to delineate lymphatic drainage to the sentinel node(s). Optimum methodologies for radiopharmaceutical, volume and/or activity of injectate, and imaging have yet to be determined. Breast lymphatic drainage can be to axilla, internal mammary, and/or supraclavicular nodes in any combination.

The importance of work-up (verification) bias correction in assessing the accuracy of SPECT thallium-201 testing for the diagnosis of coronary artery disease.

Noninvasive testing is often evaluated by the sensitivity and specificity in comparison with a more invasive, but more definitive "gold" standard. However, work-up or verification bias, which occurs when the results of a noninvasive test impact the decision to perform the gold standard invasive test, increases the "observed" sensitivity and decreases the "observed" specificity of the noninvasive test. Most large clinical studies utilizing a noninvasive technique to diagnose coronary artery disease have biases, particularly work-up bias. To obtain more accurate measurements of sensitivity and specificity, we determined the observed sensitivity and specificity of stress (exercise and dipyridamole) single photon emission computed tomographic (SPECT) thallium testing for the detection of coronary artery disease by angiography, and then applied previously published equations to correct for work-up bias. From a computerized data base, reports of 4354 stress SPECT thallium studies from January 1, 1986 through December 31, 1992 were reviewed. All patients with a known history of myocardial infarction or prior coronary angiography were excluded, leaving 2688 patients. From this total, 471 patients underwent coronary angiography within 90 days following stress SPECT thallium testing. Coronary artery disease was defined as a visually assessed stenosis of a coronary artery or a major branch > 50%. Of the 2688 stress SPECT thallium studies, 1265 were normal and 1423 were abnormal. For the 471 patients who underwent catheterization within 90 days following stress SPECT thallium testing. the "observed" sensitivity and specificity were 98 and 14%, respectively. After correction for work-up bias, the corrected sensitivity and specificity were 82 +/- 6% and 59 +/- 2%, respectively. Most studies utilizing noninvasive technologies for the detection of coronary artery disease include patients with known coronary artery disease and have work-up bias as well. By knowing the thallium results of patients with and without catheterization, we were able to correct for work-up bias. These data provide better estimate of the sensitivity and specificity of stress SPECT thallium testing.

Multiorgan scans for staging lung cancer. Correlation with clinical evaluation.

One hundred consecutive patients with findings suggestive of resectable bronchogenic carcinoma were studied prospectively to determine if routine liver, brain, and bone scans (multiorgan scans) detected metastases which were not suggested by a history, physical examination, and serum chemistries. Multiorgan scans were compared with clinical evaluations in 52 patients found to have operable bronchogenic carcinoma. There was a discordance between scans and clinical evaluations in 25/153 scans (16 per cent). Two of the 22 negative scans in patients with abnormal clinical findings were false negative. Sixteen of the 17 positive scans in patients with normal clinical findings were false positive. One of the 131 scans done in patients with no evidence of metastases on clinical evaluation was true positive. These data indicate that the routine use of multiorgan scans in the initial staging of potentially resectable bronchogenic carcinoma is not justified.

Latissimus dorsi dynamic cardiomyoplasty of the right ventricle. Potential for use as a partial myocardial substitute.

Full-thickness right ventricular latissimus dorsi dynamic cardiomyoplasty with the Medtronic Cardiomyostimulator (Medtronic, Inc., Minneapolis, Minn.) was performed in a chronic canine model. In one group (n = 2) the latissimus dorsi was electrically preconditioned before cardiomyoplasty. In a second group (n = 3) cardiomyoplasty was performed and the muscle was progressively stimulated, with conditioning accomplished while the latissimus dorsi was functioning on the ventricle. The contribution of the stimulated latissimus dorsi to global ventricular function was assessed, and the effects of varying muscle stimulation parameters on latissimus dorsi function and hemodynamics were examined. Right ventricular systolic pressure increased 8%, from 23.2 +/- 0.95 to 25.1 +/- 1.5 mm Hg. The rate of pressure rise increased 37% from 226 +/- 13 to 309 +/- 12 mm Hg/sec. Right ventricular ejection fraction was measured in two dogs and increased 29% with latissimus dorsi stimulation, from 51.5% +/- 13.5% to 66.5% +/- 14.5%. Although the sample size was small, there was no difference observed between the preconditioned and nonpreconditioned groups. Right ventricular systolic pressure, rate of pressure rise, and percent latissimus dorsi fiber shortening increased as voltage and burst frequency of the muscle stimulus increased, whereas increasing the burst duration had little effect in two dogs so studied. Latissimus dorsi dynamic cardiomyoplasty can function as a partial myocardial replacement in a chronic canine model, apparently without preconditioning of the muscle. The degree of cardiac assist obtained with cardiomyoplasty appears to be influenced by the voltage and frequency of the stimulus applied to the muscle. Although it is unclear whether these results can be extrapolated to the left ventricle, this technique may find application in the treatment of ventricular aneurysm or ventricular tumor.

Effects of dynamic cardiomyoplasty on indices of left ventricular systolic and diastolic function in a canine model of chronic heart failure.

The effects of cardiomyoplasty were evaluated with multiple-gated equilibrium radionuclide angiocardiography and catheterization in a canine model of chronic heart failure. Doxorubicin was administered to 12 dogs at a dose of 1 mg/kg/wk intravenously for 10 weeks. Left ventricular ejection fraction was reduced from a mean of 53.6% +/- 3.4% to 33.5% +/- 2.3% preoperatively. Two dogs died of presumed arrhythmia during this period. Cardiomyoplasty with the left latissimus dorsi muscle was performed on 10 dogs. The muscle was wrapped around both the left and right ventricles. Five dogs died of infection or arrhythmia after the operation. Postoperatively the muscle remained unstimulated for 2 weeks to allow adhesion to the heart. After this period, the latissimus dorsi muscle was conditioned by a progressive stimulation protocol. After the muscle was conditioned, multiple-gated equilibrium radionuclide angiocardiography studies showed that left ventricular global ejection fraction was 18.4% +/- 7.2% at 0 volts (nonstimulation), 26.2% +/- 3.7% at 5-volt stimulation (p less than 0.05), and 31.0% +/- 5.4% at 10-volt stimulation (p less than 0.05). Regional ejection fractions in low lateral, apical, and low septal regions at 5 volts and 10 volts were higher than those at 0 volts (p less than 0.05). Regional wall motion (percent radial shortening) of the low lateral region was higher than that during nonstimulation (p less than 0.05). Peak emptying rate was 2.07 +/- 0.95 end-diastolic counts per second at 0-volt, 3.10 +/- 0.67 at 5-volt, and 3.34 +/- 0.89 at 10-volt stimulation (p less than 0.05). Peak filling rate was 1.81 +/- 0.52 end-diastolic counts per second at 0-volt, 2.67 +/- 1.18 at 5-volt, and 3.11 +/- 0.65 at 10-volt stimulation (p less than 0.05). Cardiac catheterization data showed a nonsignificant increase in left ventricular rate of pressure rise with increasing voltage (1302 +/- 355 mm Hg/sec at 0 volts, 1450 +/- 413 mm Hg/sec at 5 volts, and 1568 +/- 455 mm Hg/sec at 10 volts). Left ventricular systolic pressures were unchanged. End-diastolic pressures decreased (11.2 +/- 1.48 mm Hg at 0 volts, 10.4 +/- 2.30 mm Hg at 5 volts, and 9.6 +/- 1.52 at 10 volts; p less than 0.05). These data show that cardiomyoplasty can improve indices of systolic and diastolic function in a canine model of chronic heart failure.

The effect of vasospasm on perfusion radionuclide imaging in experimental pulmonary embolism.

Experiments were conducted to further evaluate previously observed discrepancies between postembolic perfusion scans and angiograms, and the relationship of these discrepancies to pulmonary vasospasm. Nonresorbable emboli were formed from Ivalon, muscle, or heated autologous clot. Scans and angiograms were compared at 24-hour intervals for two to eight days. During the first two days after embolism, angiographic-scan discrepancies occurred in most dogs, characterized by decreased size of scintigraphically demonstrated perfusion defects at the same times that the angiogram showed stable or even progressive obstruction. This discordant behavior of scan and angiogram is thought to reflect subsidence of postembolic vasospasm. In the 17 experimental dogs, 13 showed evidence of vasospasm, and four did not. In those that developed spasm, direct angiographic evidence of such spasm was present in all but one, manifest as diffuse constriction of small arteries and diminished parenchymal stain in vascular beds that were not directly obstructed mechanically. Although spasm diminished rapidly during the first 6 hours, there was continued and appreciable further resolution for over 48 hours in some dogs. This study reconfirms the frequent existence of vasospasm in three different embolic models, and indicates subsidence of spasm over a much longer time frame than was formerly supposed. Regression of spasm over an interval of several days suggests that perfusion scans should be performed clinically as soon as possible after a suspected embolic episode, prior to subsidence of spasm, in order to exploit the added sensitivity provided by spasm.

Uptake of cadmium-109, a metallothionein-binding radiometal, by tumors in mice as a function of the transformed phenotype.

Metallothionein (MT) is an intracellular protein that binds many metals with isotopes having imaging or radiotherapeutic potential. To determine whether uptake of radioisotopes that bind to MT is increased in tumors, we measured the uptake of cadmium-109 (Cd-109) in tumors and in normal tissues of mice. Tumors were grown in Balb/C mice from cultured Balb/3T3 cells transformed by the Moloney murine sarcoma virus (MMSV). Uptake of Cd-109 by MMSV tumors exceeded that by normal tissues examined, with the exception of liver and kidney (the organs known to be richest in metallothionein). The MMSV tumor:background ratios of activity were greater for Cd-109 than for gallium-67 for many of the normal tissues examined. The magnitude of uptake of Cd-109 by tumors from four related cell lines paralleled their degree of expression of two indices of the transformed, or malignant, phenotype. We conclude that metals that bind to MT may be useful for imaging or radiotherapy of cancer.