Effect of cardiac resynchronization therapy on septal perfusion and septal thickening: Association with left ventricular function, reverse remodelling and dyssynchrony.

BACKGROUND: We evaluated the effect of cardiac resynchronization therapy (CRT) on septal perfusion and thickening at 6 months post implantation assessed on Tc99m-MIBI Gated myocardial perfusion SPECT (GMPS).We also studied the association of change in septal perfusion and thickening with primary outcome defined as at least one [improvement in ≥1NYHA class, left ventricular ejection fraction (LVEF) by ≥ 5%, reduction of end-systolic volume (ESV) by ≥ 15%, and improvement ≥ 5 points in Minnesota living with heart failure questionnaire (MLHFQ)]. METHOD: One hundred and five patients underwent clinical and GMPS evaluation before and at 6 months post CRT. RESULT: Post CRT there was significant improvement in mean normalized septal perfusion uptake and in septal thickening (P value = 0.001, both). There was no significant relation between improvement in septal perfusion and primary outcome. However, improvement in septal thickening was statistically significant with favorable primary outcome (P = 0.001).There was no significant correlation between improvement of septal perfusion and improvement in LVEF, reduction in End diastolic volume (EDV), ESV, and Left ventricular Dyssynchrony (LVD). But, there was significant correlation between improvement of septal thickening and these parameters. CONCLUSION: Improvement in septal thickening was associated with reverse remodeling, improvement in LVEF, and reduction of LVD.

Influence of extracardiac activity and perfusion abnormalities on myocardial perfusion gated SPECT parameters: interobserver analysis.

OBJECTIVE: Extracardiac activity (ECA) may affect interpretation of gated SPECT myocardial perfusion studies (MPSs). To solve this problem, available softwares include myocardial edge delimitation. PURPOSE: To evaluate the influence of ECA in automatic myocardial edge detection under normal conditions and with abnormal perfusion and also evaluate the reproducibility of semi-automatic processing. METHODS: A total of 100 MPSs, 50 with ECA, were analyzed. Each subgroup included 25 cases with perfusion abnormalities. The cases were processed automatically and by 4 independent operators with different levels of experience. Commercial QGS and QPS softwares were used with tools to mask and relocate the left ventricle area. Functional parameters (final diastolic and systolic volumes and ejection fraction) and perfusion parameters such as the reversibility perfusion score and rest perfusion defect extension were analyzed. The data were compared with Pearson's correlation and Student's test. RESULTS: Interobserver correlation significantly worsened with the presence of ECA and was moderately affected by perfusion abnormalities. More experienced observers presented better correlation. Reproducibility was greater for the functional perfusion parameters, independently of the observer's experience. CONCLUSIONS: ECA significantly affects automatic edging delimitation, affecting the MPS values. Interobserver reproducibility with manual processing was more altered regarding functional parameters than in the perfusion scores. Perfusion abnormalities did not interfere with software reproducibility, and when present, better correlation was found. If ECA is not present, manual intervention should be avoided.

[Agreement between observers with different experience in the interpretation of the stress myocardial perfusion electrocardiogram in SPECT]. / Concordancia entre observadores con distinta experiencia en interpretación de electrocardiograma de esfuerzo en SPECT de perfusión miocárdica.

UNLABELLED: Coronary artery disease (CAD) is the leading cause of death in many countries. Stress electrocardiogram (ECG) is able to detect myocardial ischemia and also has prognostic value, which may be impaired in presence of electrical baseline abnormalities. Stress myocardial single photon emission tomography (SPECT) has recognized utility yield in assessment of CAD, requiring independent interpretation of ECG and myocardial images. PURPOSE: To analyze stress ECG interpretation reproducibility among observers with different training level, including pre- and post-graduate medical students, compared to an experienced cardiologist and also with SPECT. METHOD: We studied 95 patients under CAD evaluation, mean age 61+/-9.3 years (range: 42-85), 56% male. Interobserver correlation kappa (k) between perfusion gated (99m)Tc-Sestamibi SPECT and exercise ECG were calculated as normal/abnormal, presence of necrosis, ischemia or mixed pattern. Interobserver kappa (k) analysis was made. RESULTS: 49.5% stress ECG and 45% SPECT studies were abnormal at the initial report with 62.1% concordance (k: 0.24) for normal/abnormal and 58.9% for ischemia (k: 0.14). Agreement between stress ECG initial report and independent cardiologist was 89.5% (k: 0.78). The correlation between independent observers and the initial report ranged between 62.1% and 48.4%, for baseline ECG between 41.1% and 90.5% considering normal/abnormal, and between 80% and 93.7% (k: 0.59-0.87) for the presence of ischemia. CONCLUSION: Stress ECG interpretation presented adequate interobserver reproducibility with greater agreement in the most experienced observers, confirming the importance of training.

[Interobserver correlation in the interpretation of 99mTc-sestamibi SPECT in reperfused acute myocardial infarction]. / Correlación interobservadores en interpretación de SPECT de perfusión con 99mTc-sestamibi en infarto agudo de miocardio reperfundido.

INTRODUCTION AND OBJECTIVES: The correct interpretation of myocardial perfusion single photon emission computed tomography (SPECT) requires knowledge of the technique reproducibility. The objective was analyze the interobserver correlation of different experience in the interpretation of myocardial perfusion SPECT in patients following acute myocardial infarction (AMI) in order to improve the quality of our site. METHODS: Sixty cases (56 +/- 11 years, 87 % men) with transmural AMI who had recently undergone successful thrombolysis were included. Resting perfusion with (99m)Tc-sestamibi was performed at one week post-AMI. ANALYSIS: Semiquantitative interpretation using 17 segment-model by 2 independent specialists and 5 observers, was performed blindly. Left ventricular ejection fraction (LVEF) was measured with isotopic ventriculography one month after AMI, with a mean of 38 %. RESULTS: Using independent and then agreed on perfusion analysis, average involved segments/patient was 9.3 +/- 4 and the sum of severity 25 +/- 13. Readings of other observers ranged from 7 +/- 3.7 to 9.4 +/- 3.9 and 16.7 +/- 9.7 to 24.6 +/- 13, respectively, consistent with the reading of the specialists of between 0.779-0.871 (kappa: 0.565-0.741). There was no significant difference when the number of segments were analyzed in 40 % of the cases and for intensity in 60 % of them in more experienced observers. Correlation with consensus reading for the number of segments ranged from 0.84 to 0.94 and for severity from 0.79 to 0.89. Identification of culprit arteries was acceptable, with r values between 0.612 and 0.683 and kappas between 0.629 and 0.656. Correlation of the number of involved segments and severity with LVEF performed one month after AMI was 0.73 and 0.74, respectively. CONCLUSIONS: There was good correlation in the interpretation of myocardial perfusion SPECT, with a significantly better fit in more experienced observers. This academic exercise was also helpful in improving our residents' skills in cardiology.

Risk stratification of coronary artery disease using radionuclides. Current status of clinical practice. / Estratificación de riesgo de enfermedad coronaria con métodos isotópicos. Estado actual de la práctica clínica.

A discussion is presented on the current use of radioisotopes for evaluation of coronary artery disease in relation to other available techniques. The review is focused on coronary artery disease risk stratification employing single photon emission computed tomography and positron emission tomography, as well as on ischaemic cardiomyopathy and myocardial viability applications. Concepts are presented regarding coronary blood flow reserve, diagnostic and prognostic values, criteria for its appropriate use, as well as current methods to reduce unnecessary patient irradiation, in order to optimise nuclear cardiology practice.

201Tl myocardial SPECT detects significant coronary artery disease between 50% and 75% angiogram stenosis.

UNLABELLED: Coronary angiography is the "gold standard" for the diagnosis of coronary artery disease (CAD). The aim of this work was to compare 201Thallium SPECT with different coronary angiographic cutoff values. METHODS: Data pertaining to 145 patients were tabulated. All patients underwent stress ECG, 201Thallium SPECT and coronary angiography. To assess the cutoff impact, two criteria for coronary angiography diagnosis were used: a) > or = 50% and b) > or = 75% stenosis, and applied to data from patients and vessels. RESULTS: On a patient basis, 201Thallium SPECT sensitivity, specificity and accuracy were 87%, 57% and 81% with > or = 50% cutoff and 93%, 51% and 79% with > or = 75% cutoff, respectively (NS). When performing individual vessel analysis, sensitivity, specificity and accuracy were 59%, 78% and 68% for > or = 50% cutoff and 70%, 75% and 74% for > or = 75% cutoff, respectively (p < 0.029 for sensitivity). As expected, the severer the stenosis the higher the detection rate. There were 19 patients who had stenosis between 50% and 74%. Of these, 21% had abnormal stress ECG and 58% abnormal Thallium-201 SPECT. CONCLUSION: 201Thallium SPECT results support the use of > or = 50% stenosis cutoff criteria for CAD diagnosis and evaluation. Combined with coronary angiography, myocardial SPECT offers an excellent management strategy to patients.

Left ventricular volume calculation using a count-based ratio method applied to multigated radionuclide angiography.

The purpose of this study was to investigate the accuracy of a new count-proportional method for the measurement of left ventricular volume when applied to gated equilibrium blood-pool imaging. An equation is developed that relates total chamber volume, Vt, to the area of a pixel (M) and the ratio (R) of total counts within the chamber to the counts within the hottest pixel in the chamber such that Vt = 1.38 M3R3/2. The value of M is a constant for the particular scintillation camera-collimator system and R is obtained from observed count rates. All calculated volumes were compared to volumes measured using biplane contrast ventriculography. In 25 patients, the method for ventricular volumes gave an r of 0.95 and an s.e.e. of 23 ml [Volume (nuclear) = 0.94 Volume (cath) + 1.3]. Endsystolic volume was best calculated from end-diastolic volume and ejection fraction. Manual regions of interest were more accurate than automated regions of interest. This method appears to be as accurate as more complex approaches and has the advantage of not requiring attenuation correction or blood sampling.

Is (99m)Tc-sestamibi scintimammography complementary to conventional mammography for detecting breast cancer in patients with palpable masses?

UNLABELLED: The aim of this trial was to evaluate in developing countries from different regions the diagnostic performance of (99m)Tc-sestamibi scintimammography (SM) in palpable breast lesions and to verify the clinical usefulness of a joint evaluation with mammography and SM. METHODS: From 10 countries, a total of 238 patients with palpable breast masses (n = 245) were included in this prospective multicenter trial. Prone SM was performed 10 min and 60-90 min (157 patients) after injection using an isotime acquisition of 10 min. Mammography was assessed by the same dedicated imaging radiologist according to breast imaging reporting and data system (BI-RADS) categories for malignancy and breast density. Masked SM findings and mammography findings were checked for a correlation with histopathology findings for excisional biopsy samples. Diagnostic values for breast cancer detection were calculated per lesion. RESULTS: Histopathology revealed 189 cancerous lesions and 56 benign lesions. The sensitivity and specificity of SM were 0.83 and 0.77, respectively. SM diagnostic values did not depend on the incidence of breast cancer in the country of origin or on the timing of imaging (early vs. delayed scans). On mammography, the technique yielded a sensitivity and specificity of 0.85 and 0.66, with 27 mammograms classified as BI-RADS category 1, 33 as category 2, 5 as category 3, 56 as category 4, and 124 as category 5. Thirty-seven lesions were considered to show increased radiologic density. No significant difference was found in SM diagnostic values among different BI-RADS categories or between the groups with low and high breast density. A sensitivity of 96% was calculated when SM and mammography results were combined, with 75% of all false-negative mammography findings classified as true-positive results by SM. CONCLUSION: SM complements mammography in patients with palpable masses and negative mammography findings.

An assessment of wall motion, perfusion and glucose metabolism in recent myocardial infarction: a comparison in patients with and without revascularization.

The aim of this study was to compare the extent and severity of wall motion abnormalities, perfusion and glucose metabolism, in recent myocardial infarction in patients with and without revascularization. Forty-nine patients were studied (82% men; mean age 58 years) by using echocardiography, 201Tl single photon emission computed tomography (SPECT) rest and redistribution, and 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) SPECT at a mean of 9.2 days (range, 1-24 days) after myocardial infarction. Twenty-seven of the 49 patients underwent revascularization while the other 22 received medical therapy before echocardiography and studies using radionuclides. A contrast angiogram was obtained for each patient. A follow-up echocardiogram at 3 months was obtained for 44 patients. Images were read blindly, using a 17 segment model, with semi-quantitative analysis. In the whole group, the extent of hypokinesia was 15%+/-14 (mean+/-SD); the extent of mild defects was determined as 5%+/-6 by using 201Tl at rest, 6%+/-9 by using 201Tl redistribution, and 4%+/-6 by using 18F-FDG (P<0.0005, echocardiogram/radionuclides). Echocardiography showed that the extent of akinesia-dyskinesia was 16%+/-18 in revascularized patients and 28%+/-18 in non-revascularized patients (P=0.017). With regard to moderate and severe defects, 201Tl rest showed 19%+/-16 and 28%+/-17, respectively (P=0.047); 201Tl redistribution 17%+/-15 and 26%+/-15, respectively (P=0.043); and 18F-FDG 17%+/-13 and 24%+/-15, respectively (NS). In echocardiography, the extent of hypokinetic segments decreased from 16%+/-15 at baseline to 10%+/-11 at 3 months (P=0.045), in revascularized patients. It is concluded that, in recent myocardial infarction, hypokinesia extent on echocardiogram is greater than mild perfusion or metabolic defect extent, reflecting stunning and so the use of radionuclide techniques appear more accurate for defining the extent of myocardial infarction. Non-revascularized patients showed a significantly greater extent of akinesia-dyskinesia and moderate-severe perfusion defects than did revascularized patients, which can be considered a result of therapy. It is suggested that 201Tl rest perfusion be used for the assessment of myocardial infarction soon after revascularization.

Long-term prognostic value of a normal dipyridamole thallium-201 perfusion scan.

In a 4-year period, 84 patients who were referred for a dipyridamole thallium-201 stress test to rule out significant coronary artery disease had normal scans. A dipyridamole study was recommended instead of exercise because of arthritis, severe obesity, peripheral vascular disease, pulmonary disease, other chronic illnesses, or combinations of these problems. All patients had three-view (i.e., anterior, shallow left anterior oblique, and steep left anterior oblique) planar thallium-201 imaging 10 minutes and 3.5 hours after administration of 0.6 mg/kg of intravenous dipyridamole. The patients were followed for 42 +/- 13 (range 1-58) months to document the cardiac event rate. Of the 84 patients with normal results, 14 died during the follow-up period from noncardiac causes. Three other patients died 29-51 months after the test due to an acute myocardial infarction, a probable acute myocardial infarction, and sudden cardiac death, respectively. Of the survivors, 5 suffered an acute myocardial infarction 28-50 months after the dipyridamole thallium scan and 1 had coronary artery bypass grafting due to increasing angina pectoris 58 months after the scan (overall cardiac event rate of 0.4% per year). Of the remaining 61 patients, 39 (64%) were asymptomatic, 20 (33%) had the same symptoms they had at the time of testing without significant deterioration, while 2 patients (3%) had deterioration of their chest pains but no cardiac complication. Thus, in this group of patients, a normal dipyridamole thallium-201 perfusion scan predicted a good cardiovascular outcome for at least 24 months following the test.

Simultaneous assessment of function and perfusion during dipyridamole-handgrip Tc-99m sestamibi imaging in chronic coronary artery disease.

The main goal of this work was to know the value of ventricular function in addition to perfusion Tc-99m sestamibi images in the assessment of coronary artery disease (CAD) when using dipyridamole (DIP) associated to isometric exercise. We analyzed 52 patients with suspected CAD; 40 of them had coronary lesions > or = 50% and 12 patients without CAD, conforming study and control groups, respectively. Twenty-eight patients had prior myocardial infarction. A two-day sestamibi protocol was employed with i.v. DIP-handgrip and rest injections, acquiring ECG-gated first pass and planar perfusion images. Sensitivity for perfusion images was 85% and specificity was 91.7%. There was no change between rest and DIP ejection fraction (EF) in controls. CAD patients presented a significant EF decrease with DIP (p: 0.0015). Patients with ischemia in perfusion images had larger EF decrease (p: 0.0001). For the analysis, an EF drop > or = 5% and any wall motion abnormality (WMA) were considered as having an abnormal response to DIP. CAD sensitivity improved significantly to 92.5% when adding EF drop and to 90% when adding WMA parameters, but specificity decreased to 75% with EF drop, and to 58.3% with WMA. In conclusion, first pass parameters from DIP-isometric exercise in addition to perfusion images are not a significant help in the assessment of CAD.

Optimal imaging time for delayed images in the diagnosis of abnormal parathyroid tissue with Tc-99m sestamibi.

PURPOSE: Double-phase scintigraphy with Tc-99m sestamibi is a good method to detect hyperfunctioning parathyroid glands. This study tried to determine the best time for delayed images: 2 or 4 hours. METHODS: Fifty-six patients were studied, and 35 of them had primary hyperparathyroidism (mean age, 53 +/- 13 years; 54% were women). Cervical ultrasonography was performed on 29 of 56 (52%) patients and surgery in 16 of 56 (29%) patients. The dose was 740 MBq (20 mCi) given intravenously, and the acquisition was performed at 10 minutes, 2 h, and 4 h using anterior views, including the mediastinum. Studies that had positive results were analyzed blindly by two independent observers, who selected the best definition for abnormal activity. RESULTS: Nineteen of 56 (34%) studies were negative and 37 of 56 (66%) were positive, 25 of them with one focus and 12 with two or more parathyroid foci. Analysis revealed 76% agreement between the observers (the rest was classified by consensus). In 70% of the cases, the best delayed image was obtained at 2 hours, in 16% at 4 hours (P < 0.00001), and in 14% both images were similar. In those cases with better images at 4 hours, the 2-hour images also showed the lesions. In two patients, lesions were seen only at 2 hours. These results could be explained by tracer decay, washout of parathyroid activity, or both. CONCLUSIONS: The best protocol should include the early 10-minute image and the 2-hour delayed view. Further controls do not appear necessary. This may be important for patient throughput.

Dipyridamole thallium-201 myocardial imaging. Complications associated with oral and intravenous routes of administration.

Previous reports have shown that TI-201 myocardial imaging with either an oral or intravenous administration of dipyridamole is a suitable diagnostic examination for patients at risk for coronary artery disease who cannot perform treadmill exercise. To compare the incidence of complications associated with these two routes of drug administration, the records of 78 oral and 97 intravenous dipyridamole TI-201 imaging studies were reviewed. The oral administration is associated with a significantly higher incidence of nausea (15% vs. 4%). Despite the higher incidence of nausea, the percentage of patients having one or more dipyridamole-induced symptoms was no greater for the oral (29%) than for the intravenous (37%) administration. Intravenous administration produced both a significantly higher incidence of atypical angina (14% vs. 4%) and a significantly greater increase in heart rate (16.6 vs. 10.2 beats per minute). No patient in either the oral or intravenous dipyridamole protocols had life-threatening arrhythmias or myocardial infarctions. In clinical practice, the difference in complications associated with the oral and intravenous administration of dipyridamole for TI-201 imaging is not significant.

[Radioisotopic evaluation of alginic acid/antacid effect on the prevention of pathologic gastroesophageal reflux (GER)]. / Evaluación radioisotópica del efecto del ácido alginico/antiácido en la prevención del reflujo gastroesofágico (RGE) patológico.

In this study the antireflux effect of Antacid/Alginic Acid compound (Batynid (R)) was prospectively evaluated assessed by radionuclide technique. Patients were divided in 2 groups: mild esophagitis 13 patients and severe esophagitis 13 patients. The radionuclide study was done before and posterior ingestion of the compound evaluating duration, severity and number of the reflux episodes. The results show no significant differences comparing gastroesophageal reflux pre and post Batynid, in both group of patients, considering all parameters studied.

Estratificación de riesgo de enfermedad coronaria con métodos isotópicos. Estado actual de la práctica clínica / Risk stratification of coronary artery disease using radionuclides. Current status of clinical practice

Se discute el uso actual de los radioisótopos para la evaluación de la enfermedad coronaria con relación a otras técnicas disponibles. La revisión se centra en la estratificación de riesgo de enfermedad coronaria mediante tomografía de fotón único y de doble fotón, y su la aplicación en viabilidad miocárdica y miocardiopatía isquémica. Se presentan conceptos sobre flujo absoluto y reserva de flujo coronario, valor diagnóstico y pronóstico, así como criterios de uso apropiados de las pruebas y también los métodos actuales para disminuir la radiación innecesaria de los pacientes, optimizando la práctica de la cardiología nuclear (AU)

A discussion is presented on the current use of radioisotopes for evaluation of coronary artery disease in relation to other available techniques. The review is focused on coronary artery disease risk stratification employing single photon emission computed tomography and positron emission tomography, as well as on ischaemic cardiomyopathy and myocardial viability applications. Concepts are presented regarding coronary blood flow reserve, diagnostic and prognostic values, criteria for its appropriate use, as well as current methods to reduce unnecessary patient irradiation, in order to optimise nuclear cardiology practice (AU)

[Renovascular hypertension. Radionuclide renography for detection and prediction of clinical response to revascularization]. / Hipertensión arterial renovascular. Rol del cintigrama renal en su detección y en la predicción de la respuesta clínica a la revascularización.

The most frequently used non invasive tests in the diagnosis of renovascular hypertension are the measurement of peripheral blood renin before and after captopril administration, intravenous pyelogram, renal Doppler examination and radionuclide renography without and with angiotensin converting enzyme inhibitor administration. Measurement of renal vein renin levels and renal angiography are invasive tests commonly used. The latter allows an anatomical diagnosis of renal vein stenosis but does not give information about the functional consequences of such lesion and thus, does not predict the response of blood pressure to revascularization. Radionuclide renography has become the most useful non invasive diagnostic test, with a sensitivity and specificity of 83-94 and 85-97% respectively. It also predicts clinical response to revascularization and is useful for follow up after surgery or angioplasty. It also has good results in patients with renal failure, bilateral stenosis or stenosis in a solitary kidney and in transplanted patients.

[Cushing with transition from pituitary to adrenal origin. Study with SPECT scintigraphy of the adrenal cortex with norcholesterol-I 131 in a case]. / Transición de Cushing de causa hipofisiaria a suprarrenal. Estudio con cintigrafía SPECT de corteza suprarrenal con I131 norcolesterol en un caso.

The case of a 49 yr old alcoholic women with clinical and laboratory findings that suggested a Cushing syndrome is presented. The functional tests showed cortisol suppression greater than 50% of the basal value with 8 mg of dexamethasone and no response in the combined dexamethasone/desmopressin test. Pituitary Nuclear Magnetic Resonance (NMR) was negative, Abdominal Computed Axial Tomography suggested hyperplastic adrenal glands; adrenal nodules were not found in the NMR. Pituitary or hipothalamic Cushing with secondary autonomous micronodular adrenal hyperplasia was suspected. Norcholesterol-I131 SPECT scintigraphy under dexamethasone suppression demonstrated a functional adrenal hyperplasia which was hystologically confirmed.

[Predictive value of the ergometric test stress parameters for myocardial ischemia according to SPECT thallium-201 scintigraphy]. / Valor de los parámetros de la prueba ergométrica para predecir isquemia miocárdica de acuerdo a cintigrafía SPECT con Talio 201.

BACKGROUND: Exercise EKG is used as the test of choice in the diagnosis of coronary artery disease. Classical parameters are angor and ST depression representing myocardial ischemia. AIM: To correlate exercise EKG parameters with SPECT 201Thallium to know their likelihood ratios for ischemia. PATIENTS AND METHODS: Two hundred seventy four patients (171 men), aged 58 years old as a mean, were studied. Of these, 23% had a prior myocardial infarction. The likelihood ratios for the presence of ischemia of ST depression, failure to increase blood systolic pressure, the presence of angor and its duration during stress testing were calculated according to the results of SPECT 201Thallium. Seventy one patients were also subjected to a coronary angiography. RESULTS: Among men, likelihood ratios for the presence of angor, failure to increase systolic pressure, ST alterations and duration of angor were 6.9, 6.15, 1.77 and 1.27 respectively. Among women, the figures were 5.45, 1.77, 0.58 and 1.4 respectively. The diagnostic accuracy of SPECT 201Thallium, when correlated with the results of coronary angiography, was 85%. CONCLUSIONS: Among men, the best exercise EKG predictors for myocardial ischemia were the failure to increase systolic blood pressure and the presence of angor. Among women the only significant predictor was the presence of angor.

[Treatment of hyperthyroidism with radioiodine: effects of administered dose on complications and thyroid function]. / Tratamiento del hipertiroidismo con radioyodo: efecto de la dosis administrada sobre la función tiroidea y complicaciones asociadas.

BACKGROUND: Radio-iodine is a definite therapy for Graves disease hyperthyroidism. However, the optimal dosage is still debatable. AIM: To assess the effects of different radioiodine doses on thyroid function and complications in patients with hyperthyroidism. MATERIAL AND METHODS: A retrospective analysis of 139 patients with hyperthyroidism, treated with ratio-iodine between 1988 and 1998. Radio iodine dose used was classified as low (< 10 mCi), intermediate (10-14.9 mCi) or high (> or = 15 mCi). RESULTS: Thirty-five patients were treated with low doses, 33 with intermediate doses and 71 with high doses. There were no differences between these patients in age, disease severity, frequency of post treatment euthyroidism or complications. Patients treated with low doses had a higher frequency of persistent hyperthyroidism than patients treated with high doses (25.7 and 4.2% respectively, p < 0.001). Likewise, the frequency of subsequent hypothyroidism was 60% in patients treated with low doses and 84.5% of those with high doses, in whom it also appeared earlier. Associated complications were clinically irrelevant. In seven patients, Graves ophthalmopathy progressed after treatment, but this progression was not associated with the dose used. CONCLUSIONS: Radio iodine in high doses is useful, safe and effective for the treatment of Graves hyperthyroidism.