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PubMed1988

Prognostic utility of the exercise thallium-201 test in ambulatory patients with chest pain: comparison with cardiac catheterization.

The goal of this study was to determine the prognostic utility of the exercise thallium-201 stress test in ambulatory patients with chest pain who were also referred for cardiac catheterization. Accordingly, 4 to 8 year (mean +/- 1SD, 4.6 +/- 2.6 years) follow-up data were obtained for all but one of 383 patients who underwent both exercise thallium-201 stress testing and cardiac catheterization from 1978 to 1981. Eighty-three patients had a revascularization procedure performed within 3 months of testing and were excluded from analysis. Of the remaining 299 patients, 210 had no events and 89 had events (41 deaths, nine nonfatal myocardial infarctions, and 39 revascularization procedures greater than or equal to 3 months after testing). When all clinical, exercise, thallium-201, and catheterization variables were analyzed by Cox regression analysis, the number of diseased vessels (when defined as greater than or equal to 50% luminal diameter narrowing) was the single most important predictor of future cardiac events (chi 2 = 38.1) followed by the number of segments demonstrating redistribution on delayed thallium-201 images (chi 2 = 16.3), except in the case of nonfatal myocardial infarction, for which redistribution was the most important predictor of future events. When coronary artery disease was defined as 70% or greater luminal diameter narrowing, the number of diseased vessels significantly (p less than .01) lost its power to predict events (chi 2 = 14.5). Other variables found to independently predict future events included change in heart rate from rest to exercise (chi 2 = 13.0), ST segment depression on exercise (chi 2 = 13.0), occurrence of ventricular arrhythmias on exercise (chi 2 = 5.9), and beta-blocker therapy (chi 2 = 4.3). The exclusion of myocardial revascularization procedures as an event did not change the results significantly. Although the number of diseased vessels was the single most important determinant of future events, the exercise thallium-201 stress test when considered as a whole (which included the number of segments demonstrating redistribution on delayed thallium-201 images, change in heart rate from rest to exercise, ST segment depression on the electrocardiogram, and ventricular premature beats on exercise) was equally powerful (chi 2 = 41.6). Combination of both catheterization and exercise thallium-201 data was superior to either alone (chi 2 = 57.5) for determining future events. Exercise stress test alone (without thallium-201 data) was inferior to the exercise thallium-201 stress test or cardiac catheterization for predicting future events (chi 2 = 30.6).(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiac Catheterization↗
PubMed1993

Concordance and discordance between stress-redistribution-reinjection and rest-redistribution thallium imaging for assessing viable myocardium. Comparison with metabolic activity by positron emission tomography.

BACKGROUND: Stress thallium scintigraphy provides important diagnostic and prognostic information in patients with coronary artery disease by demonstrating regional myocardial ischemia. However, if the clinical question being addressed is whether a region is viable and not whether there is inducible ischemia, then it may be more reasonable to perform rest-redistribution imaging rather than stress-redistribution imaging followed by either reinjection or late redistribution. Therefore, we determined whether stress-redistribution-reinjection and rest-redistribution imaging provide the same information regarding myocardial viability. METHODS AND RESULTS: Both stress-redistribution-reinjection and rest-redistribution thallium single photon emission computed tomographic imaging was performed in 41 patients with chronic stable coronary artery disease, with quantitative analysis of regional thallium activity. Thallium reinjection was performed immediately after the 3- to 4-hour redistribution images were completed. Of the 155 myocardial regions with perfusion defects on the stress images, 91 (59%) were irreversible on conventional 3- to 4-hour redistribution images. When the outcomes of these irreversible regions were assessed after reinjection and compared with rest-redistribution images, there was concordance of data regarding myocardial viability (normal/reversible or irreversible) in 72 of the 91 (79%) irreversible defects. Twenty of the 41 patients also underwent positron emission tomography at rest with [18F]fluorodeoxyglucose and [15O]water. In these patients, stress-redistribution-reinjection and rest-redistribution imaging provided concordant information regarding myocardial viability in 427 (72%) of 594 myocardial regions and discordance in 167 regions. However, when irreversible thallium defects were further analyzed according to the severity of the thallium defect in these discordant regions, 149 of 167 (89%) demonstrated only mild-to-moderate reduction in thallium activity (51% to 85% of normal activity), and positron emission tomography verified 98% of these regions to be metabolically active and viable. Thus, when the severity of thallium activity was considered within irreversible thallium defects, the concordance between stress-redistribution-reinjection and rest-redistribution imaging regarding myocardial viability increased to 94%. CONCLUSIONS: These data indicate that one of two imaging modalities, either stress-redistribution-reinjection or rest-redistribution imaging, may be used for identifying viable myocardium. However, if there are no contraindications to stress testing, stress-redistribution-reinjection imaging provides a more comprehensive assessment of the extent and severity of coronary artery disease by demonstrating regional myocardial ischemia without jeopardizing information on myocardial viability.

Coronary Angiography↗
PubMed1998

[18F]fluorodeoxyglucose single photon emission computed tomography: can it replace PET and thallium SPECT for the assessment of myocardial viability?

BACKGROUND: New high-energy collimators for single photon emission computed tomography (SPECT) cameras have made imaging of positron-emitting tracers, such as [18F]fluorodeoxyglucose (18FDG), possible. We examined differences between SPECT and PET technologies and between 18FDG and thallium tracers to determine whether 18FDG SPECT could be adopted for assessment of myocardial viability. METHODS AND RESULTS: Twenty-eight patients with chronic coronary artery disease (mean left ventricular ejection fraction [LVEF]=33+/-15% at rest) underwent 18FDG SPECT, 18FDG PET, and thallium SPECT studies. Receiver operating characteristic curves showed overall good concordance between SPECT and PET technologies and thallium and 18FDG tracers for assessing viability regardless of the level of 18FDG PET cutoff used (40% to 60%). However, in the subgroup of patients with LVEF< or =25%, at 60% 18FDG PET threshold value, thallium tended to underestimate myocardial viability. In a subgroup of regions with severe asynergy, there were considerably more thallium/18FDG discordances in the inferior wall than elsewhere (73% versus 27%, P<.001), supporting attenuation of thallium as a potential explanation for the discordant observations. When uptake of 18FDG by SPECT and PET was compared in 137 segments exhibiting severely irreversible thallium defects (scarred by thallium), 59 (43%) were viable by 18FDG PET, of which 52 (88%) were also viable by 18FDG SPECT. However, of the 78 segments confirmed to be nonviable by 18FDG PET, 57 (73%) were nonviable by 18FDG SPECT (P<.001). CONCLUSIONS: Although 18FDG SPECT significantly increases the sensitivity for detection of viable myocardium in tissue declared nonviable by thallium (to 88% of the sensitivity achievable by PET), it will occasionally (27% of the time) result in falsely identifying as viable tissue that has been identified as nonviable by both PET and thallium.

Adult↗
PubMed1997

Effects of Prussian blue and N-acetylcysteine on thallium toxicity in mice.

BACKGROUND: Thallium poisoning is now rare but still occurs as a result of homicide attempts. Prussian blue's efficacy in the treatment of experimental thallium poisoning has been demonstrated in animal models, and its use in humans is supported by anecdotal data. Since thallium binds sulfhydryl groups, the use of N-acetylcysteine is also considered as a potential antidote. STUDY OBJECTIVE: To compare the efficacy of Prussian blue and N-acetylcysteine in a murine model of thallium poisoning. METHODS: Female Swiss albino mice with free access to food and water were used. Two study doses of thallium, given as a subcutaneous injection of thallium acetate dissolved in sterile water, were chosen: 70 mg/kg (LD90) and 85 mg/kg (> LD100). A randomized, placebo controlled study was conducted with survival at 120 h chosen as the outcome measure. Four treatment groups were studied: control, Prussian blue, N-acetylcysteine, and the combination of Prussian blue and N-acetylcysteine. Prussian blue was dissolved in water and given by oral gavage at a dose of 50 mg/kg. N-acetylcysteine was diluted in normal saline and given as intraperitoneal injections of 200 mg/kg. Sterile water by gavage and normal saline by peritoneal injection were given as control treatments whenever an active agent was not given. Survival was recorded over a 120 h study period and compared at 120 h by a Fisher's exact test. RESULTS: At 120 h following subcutaneous injection of thallium 70 mg/kg, only 10% of the control animals survived. Treatment with N-acetylcysteine or Prussian blue increased survival to 35% (p = 0.13) and 50% (p = 0.014), respectively. The addition of N-acetylcysteine to Prussian blue offered no benefit over Prussian blue therapy alone. CONCLUSIONS: Prussian blue was found to decrease mortality from thallium poisoning at a dose equal to the LD90 in this model, but not a dose greater than the LD100. No role for N-acetylcysteine in the treatment of thallium poisoning was demonstrated by this study.

Acetylcysteine↗
PubMed1998

[Thallium poisoning a clinical analysis of 5 cases].

OBJECTIVE: To sumarize the clinical features, diagnosis and treatment of thallium poisoning by analysis of clinical cases. METHODS: Five cases of thallium poisoning were reported. The clinical manifestations, quantitative-analysed thallium level, methods and effect of treatment, and prognosis were analysed. RESULTS: Three of the 5 cases were acute, and the other two chronic. Four of them had a history of poison contact. The clinical features included alopicia (4 cases), transverse white stripes in the nails (Mee's stripes, 2) polyneuropathy, cranial nerve and central nervous system impairments (5), and abdominal pain and other digestion disturbances (3). All of the 5 cases were treated with antidotes and other methods to increase thallium excretion. One case died of lung infection 3 days after diagnosis. The serum and urine thallium levels of the 4 survivors decreased to normal after treatment (3 recovered, one had neurologic sequelae). CONCLUSION: It is not difficult to diagnose thallium poisoning by definite poison contact history, classical manifestation, and serum or urine thallium quantitative analysis. Attention should be paid to those patients with indefinite exposure to thallium. For those suspected cases, it is necessary to measure the thallium level in blood and urine in order to verify the diagnosis.

Adult↗
PubMed1992

Balanced triple-vessel disease: enhanced detection by estimated myocardial thallium uptake.

Maximal stress thallium scans may prove to be 'normal' in some patients with triple-vessel disease due to global reduction in flow resulting in no focal perfusion defect. The aim of this study was to attempt to identify patients with global reduction in flow by estimating total thallium delivery to the left ventricle. Myocardial thallium uptake was calculated as a percentage of injected dose as a mean of three projections in 90 patients undergoing diagnostic arteriography and in 10 normal volunteers. These volunteers and nine patients who proved to have normal coronary arteries established a normal range. Values for myocardial thallium uptake were: 1.166 +/- 0.352% in normals (n = 19); 0.671 +/- 0.184% in patients with single- or double-vessel disease (n = 26); 0.708 +/- 0.245% in patients with triple-vessel disease (n = 55). Thallium scans were normal in 11 of 55 patients with triple-vessel disease and eight of 26 with single- or double-vessel disease. However, eight of these 11 and 5 of the eight proved to have abnormal myocardial thallium uptake. Thus combining the tests improved sensitivity from 76.5% for the scan alone to 94.5% for the scan and myocardial thallium uptake, with no reduction in specificity. Measurement of myocardial thallium uptake is a readily and reliably quantified parameter from a thallium scan which leads to enhanced detection of coronary artery disease.

Adult↗
PubMed1989

Quantitation of postexercise lung thallium-201 uptake during single photon emission computed tomography.

To test the hypothesis that analysis of lung thallium uptake measured during single photon emission computed tomography (SPECT) yields supplementary clinical information as reported for planar imaging, quantitative analysis of lung thallium uptake following maximal exercise was performed in 40 clinically normal subjects (Group 1) and 15 angiographically normal subjects (Group 2). Lung thallium uptake was measured from anterior projection images using a ratio of heart-to-lung activities. Seventy subjects with coronary artery disease (CAD) (Group 3) determined by angiography (greater than or equal to 70% luminal stenosis) underwent thallium perfusion SPECT. Thirty-nine percent of these subjects had multivessel and 61% had single vessel CAD. Lung thallium uptake was elevated in 47 of 70 (67%) Group 3 subjects. Group 3 subjects with elevated lung thallium uptake did not differ from Group 3 subjects with normal lung thallium uptake with respect to extent or distribution of coronary artery disease, left ventricular function, or severity of myocardial ischemia as determined by exercise and redistribution thallium SPECT. Thus, the measurement of thallium lung uptake from anterior projection images obtained during SPECT frequently identifies patients with CAD, but it may not provide supplementary information regarding the extent of myocardial ischemia or ventricular dysfunction.

Adult↗
PubMed1989

Comparison of rest and exercise thallium-201 kinetics in man and implications for quantitation.

To develop a technique for quantitative analysis of resting thallium scintigrams, an understanding of thallium kinetics at rest is required. This study evaluates in normal man the thallium distribution and washout rates of thallium at rest and compares these findings to similar data obtained during exercise. The thallium half-life in normal resting myocardium is significantly longer than after exercise, 10.2 +/- 1.4 hours versus 3.9 +/- 0.3 hours (P less than .01). Differences in resting thallium half-life exist between the anterior, 45 degrees left anterior oblique (LAO), and 70 degrees LAO views and are 11.4 +/- 1.0, 10.6 +/- 1.0, 8.8 +/- 0.7 hours, respectively (all significantly different from each other by ANOVA, P less than or equal to .01); these differences are related to the imaging sequence. After exercise, the thallium half-life also varies according to imaging sequence, but in the opposite direction; i.e., anterior, 45 degrees LAO, and 70 degrees LAO views are 3.6 +/- 0.1, 3.9 +/- 0.3, 4.2 +/- 0.3 hours, respectively (P less than or equal to .01). Since imaging sequence and time of acquisition at rest and exercise were similar, this finding may be related to earlier maximal uptake of thallium after exercise as compared to rest. There are also significant segmental differences in thallium half-life at rest in the 45 degrees LAO view (9.8 +/- 0.9, septal vs. 11.0 +/- 0.9, posterolateral, P less than .01) and 70 degrees LAO view (8.3 +/- 0.4, anteroseptal vs. 9.2 +/- 0.6, inferior, P less than or equal to .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Quantitation of coronary artery lesions by 2-4 hour stress-myocardial clearance of thallium-201].

The stress-redistribution thallium-201 scintigraphy and thallium-201 washout method have limitations in their ability to detect individual coronary lesions in patients with multivessel coronary artery disease. The purpose of this study is to investigate the value of the quantitative planar method using the dynamics of thallium-201 redistribution after exercise. We observed the patterns of thallium clearance in the late stages (at 2 and 4 hrs) which are characteristic of decreased myocardial blood supply by the obstructed coronary arteries. In 20 subjects, quantitative thallium scintigrams (planar image and circumferential count profile) and blood samples for thallium concentration were obtained immediately, and 2 and 4 hrs after maximal treadmill exercise. Coronary angiography was performed in all subjects, and 16 patients had coronary artery disease (CAD) and four were normal. The rate of thallium clearance from the blood (TCB) was compared with the rate of thallium clearance from each segmental lesion of the myocardium (TCM) between the 2- and 4-hr images. The system adopted for assignment of myocardial regions to individual coronary arteries has been used as an approach to localization of anatomic disease. In the four patients with normal coronary arteries, TCM exceeded TCB in all regions of all images (specificity 100%). Fourteen of the 16 CAD patients had at least one region where TCM was less than TCB (sensitivity 88%). Ten of the 14 patients with multivessel CAD had multiple regions where TCM was less than TCB (sensitivity 71%). All of the six patients without multivessel CAD (four with normal coronary arteries and two with one vessel disease) did not have multiple regions where TCM was less than TCB (specificity 100%). Quantitative thallium scintigraphy showed sensitivities of 86%, 56% and 91% in the left anterior descending artery, the circumflex coronary artery and right coronary artery, respectively. These results showed that decreased TCM in the late stage is characteristic of myocardial regions where blood is supplied by the diseased coronary arteries. This finding may improve diagnostic sensitivity under the condition of multivessel coronary artery disease.

Adult↗
PubMedDate not supplied

Thallium loading in owls and other birds of prey in Denmark.

Due to previous findings of increased concentrations of the rodenticid, thallium, in free-living Danish carnivores, thallium analysis has been carried out on material from 77 owls and birds of prey. Thallium was found in 2/3 of the birds and in 10% the concentration was so high that the load of thallium may have caused the death of the birds. The load of thallium in birds of prey was lower than concentrations found in carnivores, probably because poisoning caused by direct intake of thallium baits placed for rodent control does not seem to occur among birds of prey. From the investigation of this limited number of birds, it is not possible to tell if thallium did have any influence on the maintenance of a healthy population of birds of prey, but the large number of thallium loaded birds also justify the restrictions in the sue of thallium which were given from the 1st of July, 1975.

Animals↗
PubMed1996

Preoperative grading of glioma malignancy with thallium-201 single-photon emission CT: comparison with conventional CT.

PURPOSE: To compare thallium-201 single-photon emission CT with conventional CT in grading the malignancy of gliomas and to determine the reliability of each in tumor assessment. METHODS: We studied 37 patients who had gliomas (31 high grade and 6 low grade) and compared the CT findings with the thallium-201 index, which we defined as tumor uptake relative to the uptake in the contralateral hemisphere. RESULTS: Among the high-grade gliomas, we observed a significant correlation between breakdown volume of the blood-brain barrier and thallium-201 uptake. However, 8 of the high-grade gliomas had low thallium-201 uptake, in the same range as the low-grade gliomas. Of these, 2 were nonenhancing and the other 6 showed ring enhancement on CT scans. Analysis of variance showed no significant difference in thallium-201 indexes between low-grade gliomas and highly malignant (grade II-III) gliomas. Accuracy of thallium-201 imaging was lower (78%) than that of CT (84%) in identifying high-grade gliomas. CONCLUSIONS: Damage to the blood-brain barrier is a prerequisite for uptake of thallium-201 in gliomas. Tumors with central necrotic areas and moderate ring enhancement tend to be underestimated when evaluated by means of thallium-201 scintigraphy. The results indicate a need for caution when interpreting findings on images obtained with thallium-201 single-photon emission CT in preoperative evaluation of brain tumors.

Adolescent↗
PubMed2001

Occult primary tumors of the head and neck: accuracy of thallium 201 single-photon emission computed tomography and computed tomography and/or magnetic resonance imaging.

OBJECTIVE: To determine the accuracy of thallium 201 single-photon emission computed tomography (thallium SPECT) and computed tomography and/or magnetic resonance imaging (CT/MRI) in the detection of occult primary tumors of the head and neck. DESIGN: Study of diagnostic tests. SETTING: National Cancer Institute, Amsterdam, the Netherlands. PATIENTS AND METHODS: Thirty-two patients with a neck node metastasis of an epithelial tumor and negative findings by mirror examination at initial presentation were included in the study. Twenty-nine patients underwent thallium SPECT and CT/MRI before examination under general anesthesia (EUA). In 3 patients only thallium SPECT was performed before EUA. Histological confirmation of an occult primary tumor during EUA was used as the gold standard. Negative radiodiagnostic and nuclear findings in the upper aerodigestive tract in the presence of a primary carcinoma other than of the head and neck were interpreted as true-negative findings. RESULTS: For thallium SPECT the following results were recorded: sensitivity, 67%; specificity, 69%; accuracy, 69%; positive predictive value, 33%; and negative predictive value, 90%. In 1 patient, thallium whole body scan indicated a primary carcinoma beyond the mucosal lining of the upper aerodigestive tract. The CT/MRI results were as follows: sensitivity, 71%; specificity, 73%; accuracy, 72%; positive predictive value, 45%; and negative predictive value, 89%. CONCLUSIONS: Thallium SPECT and CT/MRI showed comparable results for detection of occult primary tumors of the head and neck. A potential advantage of thallium SPECT is that it allows total body screening.

Adult↗
PubMed1994

Thallium imaging for brain tumors with results measured by a semiquantitative index and correlated with histopathology.

BACKGROUND: The optimal management of patients with brain tumors requires knowledge of the tumor characteristics upon presentation and the discovery of recurrence after therapy. Thallium-201 (Tl-201) chloride has shown varying uptake in tumors, depending on their viability and the type and degree of malignancy. This study explores the diagnostic potential of thallium imaging in patients with brain tumors. METHODS: Forty-three Tl-201 single photon emission computed tomographic scintigrams were performed on 40 patients with intracranial neoplasms, nearly equally divided between patients with no prior treatment and patients who had prior treatment and were suspected to have recurrent tumor and/or radiation necrosis. A thallium tumor index was calculated as the ratio of counts for a region of interest drawn in the lesion area and its mirror image in normal brain tissue. A two-tailed Student's t test was performed to compare the thallium index and histopathologic findings. RESULTS: A value of 1.5 for the thallium tumor index allowed for the best correlation between the prediction of malignancy and the histopathologic results. In the pretreatment group, a thallium tumor index greater than 1.5 correlated with high grade malignancy, and less than 1.5 correlated with either a well differentiated astrocytoma or benign cyst. In the posttreatment group, a thallium tumor index greater than 1.5 correlated with recurrent and/or residual malignant tumor. CONCLUSIONS: For those patients undergoing initial evaluation, the thallium study can help in the differential diagnosis of an intracranial mass lesion and offers confirmation of results of biopsy. For those patients who already have received treatment, the study can be used to detect recurrent or residual tumor.

Adult↗
PubMed1993

Time sequential single photon emission computed tomography studies in brain tumour using thallium-201.

Time sequential single photon emission computed tomography (SPECT) studies using thallium-201 were performed in 25 patients with brain tumours to evaluate the kinetics of thallium in the tumour and the biological malignancy grade preoperatively. After acquisition and reconstruction of SPECT data from 1 min post injection to 48 h (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 15-20 min, followed by 4-6, 24 and 48 h), the thallium uptake ratio in the tumour versus the homologous contralateral area of the brain was calculated and compared with findings of X-ray CT, magnetic resonance imaging, cerebral angiography and histological investigations. Early uptake of thallium in tumours was related to tumour vascularity and the disruption of the blood-brain barrier. High and rapid uptake and slow reduction of thallium indicated a hypervascular malignant tumour; however, high and rapid uptake but rapid reduction of thallium indicated a hypervascular benign tumour, such as meningioma. Hypovascular and benign tumours tended to show low uptake and slow reduction of thallium. Long-lasting retention or uptake of thallium indicates tumour malignancy.

Brain↗
PubMed1975

The cryptonephridial system in the mealworm Tenebrio molitor: transport of radioactive potassium, thallium and sodium; a functional and structural study.

Larvae of the mealworm Tenebrio molitor were injected with radioactive potassium, sodium or thallium solution. It was found that the rectal complex of the animal was labelled with potassium and thallium, but not with sodium. Potassium and thallium labelled the complex to the same level as if the two ions were tracers for each other. Ramsay has found that potassium is actively transported to the complex from the hemocoel and there are reasons to believe that T1+ follows the same pathway. Therefore animals injected with thallium were investigated both by light and electron microscopy. The results suggest that thallium spreads from the hemocoel through the leptophragma to the neighbouring ordinary tubular cells, and in moist mealworms thallium is further found in the perirectal space. Due to diffusion and washing out of thallium during fixation it can not be determined whether T1+ and K+ follow identical pathways, but it is possible to determine how far thallium has penetrated during the experiments.

Animals↗
PubMed1990

Preoperative evaluation of cardiac risk using dobutamine-thallium imaging in vascular surgery.

Coronary artery disease is frequently present in patients undergoing evaluation for reconstructive peripheral vascular surgery. Dobutamine-thallium imaging has been shown to be a reliable and sensitive noninvasive method for the detection of significant coronary artery disease. Eighty-seven candidates for vascular reconstruction underwent dobutamine-thallium imaging. Forty-eight patients had an abnormal dobutamine-thallium scan. Twenty-two patients had infarct only, while 26 had reversible ischemia demonstrated on dobutamine-thallium imaging. Fourteen of 26 patients with reversible ischemia underwent cardiac catheterization and 11 showed significant coronary artery disease. Seven patients underwent preoperative coronary bypass grafting or angioplasty. There were no postoperative myocardial events in this group. Three patients were denied surgery on the basis of unreconstructible coronary artery disease, and one patient refused further intervention. Ten patients with reversible myocardial ischemia on dobutamine-thallium imaging underwent vascular surgical reconstruction without coronary revascularization and suffered a 40% incidence of postoperative myocardial ischemic events. Five patients were denied surgery because of presumed significant coronary artery disease on the basis of the dobutamine-thallium imaging and clinical evaluation alone. Thirty-nine patients with normal dobutamine-thallium scans underwent vascular reconstructive surgery with a 5% incidence of postoperative myocardial ischemia. Dobutamine-thallium imaging is a sensitive and reliable screening method which identifies those patients with coronary artery disease who are at high risk for perioperative myocardial ischemia following peripheral vascular surgery.

Aged↗
PubMed1998

Usefulness of thallium-201 SPECT imaging for the evaluation of local recurrence of colorectal cancer.

PURPOSE: To clarify the accumulation of thallium-201 in recurrent tumors in patients who had undergone resection of colorectal cancer and to evaluate the usefulness of thallium-201 single photon emission computed tomography (SPECT) images for distinguishing recurrent tumors from postoperative changes. MATERIALS AND METHODS: Thallium-201 SPECT images and CT images of 22 consecutive patients suspected to have local recurrence of colorectal cancer based on clinical symptoms and signs were reviewed. CT was performed on all patients. RESULTS: In nine of the 11 patients who had local recurrence, SPECT images showed positive thallium uptake, but in 10 of the 11 patients confirmed to have no recurrence, SPECT images showed negative thallium uptake. Sensitivity was 81.8% (9/11) specificity was 90.9% (10/11), and accuracy was 86.4% (19/22). There were five patients in whom CT results were inconclusive. All of them had rectal cancer and had undergone Miles' operation, and all were correctly diagnosed by thallium-201 SPECT. CONCLUSION: Thallium-201 exhibited intense uptake in recurrent colorectal cancer. Thallium-201 SPECT is considered to be a useful diagnostic tool for the detection of recurrence of colorectal cancer, particularly in patients with inconclusive CT results.

Adult↗
PubMed1984

Serial thallium-201 imaging after dipyridamole for coronary disease detection: quantitative analysis using myocardial clearance.

After dipyridamole, canine studies have demonstrated a slower rate of myocardial thallium-201 clearance from zones distal to a coronary artery stenosis compared to normal zones. To determine if criteria based on canine myocardial thallium-201 clearance rates could be applied clinically, 40 patients with and 26 patients without coronary artery disease (CAD) had serial thallium-201 images obtained for 2 to 5 hours after dipyridamole. Regions of interest were manually placed over six left ventricular segments in two projections for each of three imaging times. The myocardial thallium-201 clearance rate was calculated for each of the six segments and, using the clearance rate criterion found in canine studies, was considered abnormal if less than 6.5%/hr. Using this criterion alone, 22 of 26 patients (85%) without CAD had normal and 30 of 40 patients (75%) with CAD had abnormal myocardial thallium-201 clearance rates. A quantitative analysis of regional inhomogeneity in tracer distribution (normal was greater than or equal to 25% difference between segments) was negative in 24 of 26 patients (92%) without CAD and positive in 20 of 40 patients (50%) with CAD. When both clearance rate and regional inhomogeneity were considered, 21 of 26 patients (81%) without CAD had negative and 36 of 40 patients (90%) with CAD had positive results. Thus, post-dipyridamole myocardial clearance rate criteria derived from canine studies can be applied to clinical thallium imaging. Quantitative analysis of serial thallium-201 images after dipyridamole is optimized by using myocardial thallium-201 clearance rates. Such an approach is independent of regional inhomogeneities in tracer distribution.

Adult↗