Dosimetric properties of new formulation of PRESAGE® with tin organometal catalyst: Development of sensitivity and stability to megavoltage energy.

AIM: Tin-base catalyst is one of the widely used organometallic catalysts in polyurethane technology. The purpose of this study was to evaluate the effect of tin organometallic catalyst in the radiation response and radiological properties of a new formula of PRESAGE®. MATERIALS AND METHODS: In the study, two types of PRESAGE were fabricated. A very little amount of dibutyltindillaurate (DBTDL) (0.07% weight) was used as a catalyst in the fabrication of new PRESAGE (i.e., PRESAGE with catalyst), which components were: 93.93% weight polyurethane, 5% weight tetrachloride, and 1% weight leucomalachite green (LMG). For PRESAGE without catalyst, 94% weight polyurethane, 4% weight tetrachloride, and 2% weight LMG were used. Radiochromic response and postirradiation stability of PRESAGEs were determined. Also, radiological characteristics of PRESAGEs, such as mass density, electron density, mass attenuation coefficient, and mass stopping power in different photon energies were assessed and compared with water. RESULTS: The absorption peak of new PRESAGE compared to PRESAGE without catalyst was observed without change. Sensitivity of new PRESAGE was higher than PRESAGE without catalyst and its stability after the first 1 h was relatively constant. Also, Mass attenuation coefficient of new PRESAGE in energy ranges <0.1 MeV was 10% more than water, whereas the maximum difference of mass stopping power was only 3%. CONCLUSIONS: Tin organometallic catalyst in very low concentration can be used in fabrication of radiochromic polymer gel to achieve high sensitivity and stability as well as good radiological properties in the megavoltage photon beam.

Optical computed tomography in PRESAGE® three-dimensional dosimetry: Challenges and prospective.

With the advent of new complex but precise radiotherapy techniques, the demands for an accurate, feasible three-dimensional (3D) dosimetry system have been increased. A 3D dosimeter system generally should not only have accurate and precise results but should also feasible, inexpensive, and time consuming. Recently, one of the new candidates for 3D dosimetry is optical computed tomography (CT) with a radiochromic dosimeter such as PRESAGE®. Several generations of optical CT have been developed since the 90s. At the same time, a large attempt has been also done to introduce the robust dosimeters that compatible with optical CT scanners. In 2004, PRESAGE® dosimeter as a new radiochromic solid plastic dosimeters was introduced. In this decade, a large number of efforts have been carried out to enhance optical scanning methods. This article attempts to review and reflect on the results of these investigations.

The combination of A-966492 and Topotecan for effective radiosensitization on glioblastoma spheroids.

Radiotherapy is one of the modalities in the treatment of glioblastoma patients, but glioma tumors are resistant to radiation and also chemotherapy drugs. Thus, researchers are investigating drugs which have radiosensitization capabilities in order to improve radiotherapy. PARP enzymes and topoisomerase I enzymes have a critical role in repairing DNA damage in tumor cells. Thus, inhibiting activity of these enzymes helps stop DNA damage repair and increase DSB lethal damages. In the current study, we investigated the combination of TPT as a topoisomerase I inhibitor, and A-966492 as a novel PARP inhibitor for further radiosensitization. U87MG cells (a human glioblastoma cell line) were cultured in Poly-Hema coated flasks to reach 300 µm-diameter spheroids. Treatments were accomplished by using non-toxic concentrations of A-966492 and Topotecan. The surviving fraction of treated cells was determined by clonogenic assay after treatment with drugs and 6 MV X-ray. The γ-H2AX expression was measured by an immunofluorescence staining method to examine the influence of A-966492, TPT and radiation on the induction of double stranded DNA breaks. Treatments using the A-966492 drug were conducted in concentration of 1 µM. Combining A-966492 and TPT with radiation yielded enhanced cell killing, as demonstrated by a sensitizer enhancement ratio at 50% survival (SER50) 1.39 and 1.16 respectively. Radio- and chemo-sensitization was further enhanced when A-966492 was combined with both X-ray and TPT, with SER50 of 1.53. Also γ-H2AX expression was higher in the group treated with a combination of drugs and radiation. A-966492 is an effective PARP inhibitor and has significant radio-sensitivity on U87MG spheroids. By accumulating cells in the S phase and by inhibiting the DNA damage repair, TPT enhanced radio-sensitivity. A-966492 combined with TPT as a topoisomerase I inhibitor had additive radio-sensitizing effects. As a result, applying PARP and topoisomerase I inhibitors can be a suitable strategy for improving radiotherapy in clinics.

Gastrointestinal Side Effects of the Radioiodine Therapy for the Patients with Differentiated Thyroid Carcinoma Two Days after Prescription.

Iodine-131 (I-131) therapy is one of the conventional approaches in the treatment of patients with differentiated thyroid carcinoma (DTC). The radioiodine agents also accumulate in the other organs that cause pain and damage to the patients. Radioiodine therapy is associated with various gastrointestinal (GI) toxicities. In this study, GI side effects of the radioiodine therapy were investigated. GI toxicities of the radioiodine therapy were studied in 137 patients with histologically proven DTC in Jun-Nov 2014. All the patients were treated by radioiodine agents in the research institute of Shariati Hospital, Tehran, Iran. The patients were examined 48 h after prescription (before discharge) and their GI side effects were registered. Correlation of the age, gender, administered dose, administered dose per body weight as the independent factors, and GI side effects were analyzed using the Pearson correlation test with Statistical Package for the Social Sciences (SPSS) version 20. Regression coefficients and linearity of the variable were investigated by MATLAB software. Line fitting was performed using MATLAB curve-fitting toolbox. From the subjects, 38 patients had GI complaints (30.4%). Significant factors influencing GI side effects were dose per body weight and administered doses. There was no significant correlation between age and gender as the independent parameters and GI complaints. The most prevalent GI side effect was nausea that occurs in 26.4% of the patients. From the results, it could be concluded that the GI side effects could be prevented by administering a safe radioiodine dose value less than 5,550 MBq.

Histopathological Evaluation of the Effectiveness of Glycyrrhizic Acid as a Radioprotector Against the Development of Radiation-Induced Lung Fibrosis.

BACKGROUND: Radiotherapy of the thorax often causes lung inflammation leading to fibrosis. OBJECTIVES: The aim of this study was to investigate whether the use of glycyrrhizic acid (GLA) could improve the development of lung fibrosis in irradiated animals. MATERIALS AND METHODS: Wistar rats were divided into four groups. Group A rats received thoracic irradiation. Rats in group B received GLA and irradiation. Group C received GLA and no irradiation. Group D received no GLA and irradiation. GLA was administered at a dose of 4 mg/kg body weight using an intraperitoneal injection one hour before thoracic irradiation. Radiation therapy was delivered on a Cobalt-60 unit using a single fraction of 16 Gy. The animals were sacrificed at 32 weeks following thoracic irradiation. The lungs were dissected and blind histopathological evaluation was performed. RESULTS: Histopathologically, a decrease (statistically not significant) in the thickening of alveolar or bronchial wall, formation of fibrous bands, and superimposed collagen were noted in the animals in group B as compared to the animals in group A. CONCLUSION: In this experimental study, administration of GLA one hour before thoracic irradiation may be a protective agent against radiation-induced fibrosis in animals and this model could be used in future studies.

The Effect of the Lumbar Vertebral Malpositioning on Bone Mineral Density Measurements of the Lumbar Spine by Dual-Energy X-Ray Absorptiometry.

A significant discrepancy between the results of previous human and phantoms studies is identified regarding the effects of vertebral positioning on bone mineral density (BMD) measurements. We aimed to evaluate the effects of lumbar vertebral positioning on BMD measurements by dual-energy X-ray absorptiometry in a human cadaveric spine phantom. A spine phantom was designed using L1-L4 vertebrae harvested from a 48-year-old male cadaver without coronal or sagittal deformity. The spine phantom was scanned by DEXXUM T bone densitometer in a constant scanning speed of 30 mm/s and resolution of 1.0 × 1.0 mm. BMD values were measured in a positive and negative lumbar lordosis and kyphosis tilt angles in the sagittal plane, from 0° to 35°, with 7° increments. Also BMD values were measured in axial and lateral rotations with 5° increments. Projectional dual-energy X-ray absorptiometry measurements are significantly affected by positioning of the lumbar spine, more severely affected by kyphotic curvature, but also by axial and lateral rotational scoliosis as well as lordotic curvature. Increasing the severity of lordosis and kyphosis curvatures leads to false reduction of BMD value up to 17.5% and 11.5%, respectively. Increasing the degree of lateral and axial rotational scolioses results in a false decrease in BMD measurements by up to 10.8% and 9.6%, respectively. To achieve the most accurate scanning results, error sources and abnormal positioning should be identified and minimized as much as possible. If not correctable, they should be taken into consideration while interpreting the results.

Validation of a Prototype Optical Computed Tomography System.

In radiation cancer treatments, the most of the side effects could be minimized using a proper dosimeter. Gel dosimeter is the only three-dimensional dosimeter and magnetic resonance imaging (MRI) is the gold standard method for gel dosimeter readout. Because of hard accessibility and high cost of sample reading by MRI systems, some other alternative methods were developed. The optical computed tomography (OCT) method could be considered as the most promising alternative method that has been studied widely. In the current study, gel dosimeter scanning using a prototype optical scanner and validation of this optical scanner was performed. Optical absorbance of the irradiated gel samples was determined by both of conventional spectrophotometer and the fabricated OCT system at 632 nm. Furthermore, these irradiated vials were scanned by a 1.5 T MRI. The slope of the curves was extracted as the dose-response sensitivity. The R2-dose sensitivity measured by MRI method was 0.1904 and 0.113 for NIPAM and PAGAT gels, respectively. The optical dose sensitivity obtained by conventional spectrophotometer and the fabricated optical scanner was 0.0453 and 0.0442 for NIPAM gels and 0.0244 and 0.0242 for PAGAT gels, respectively. The scanning results of the absorbed dose values showed that the new OCT and conventional spectrophotometer were in fair agreement. From the results, it could be concluded that the fabricated system is able to quantize the absorbed dose values in polymer gel samples with acceptable accuracy.

Low versus high radioiodine dose in postoperative ablation of residual thyroid tissue in patients with differentiated thyroid carcinoma: a large randomized clinical trial.

OBJECTIVES: Radioiodine ablation of thyroid tissue remains the cornerstone of treatment for patients with differentiated thyroid carcinoma after thyroidectomy. Selecting an optimal dose of radioiodine for successful ablation is a continuous challenge in these patients. METHODS: We compared the treatment response of 341 patients with thyroidectomy randomly allocated to the high-dose group, 3700 MBq (170 patients), versus the low-dose group, 1110 MBq (171 patients), for radioiodine ablation therapy in a double-blind randomized clinical trial. The response to treatment was defined as successful or unsuccessful according to post-therapy ultrasonography of the neck, serum thyroglobulin (Tg), anti-Tg, and functioning residual tissue after 6-month and 12-month intervals. The major criteria of successful ablation were Tg<2 ng/ml, anti-Tg<100 IU/ml, and absent remnant in the off-levothyroxine state. Additional radioiodine doses were administered in cases showing no significant response to the first therapy. Finally, the initial outcome, the total hospitalization time, and the cumulative I-131 doses during the 12-month course of the study were compared between the subgroups. RESULTS: The rate of initial successful ablation was 51.6% in all patients, 39.2% in the low-dose group, and 64.1% in the high-dose group. The corresponding success rates at the end of the 12-month follow-up without additional treatment were 55.1, 41.5, and 68.8%, respectively. The relative risk (RR) of unsuccessful ablation for the low-dose versus the high-dose group was 1.695 [95% confidence interval (CI), 1.34-2.14]. In the low-dose group, more patients needed a second dose of I-131, resulting in a higher cumulative activity (median, 4810 vs. 3700 MBq, P<0.0001) and more inpatient time (median 4 vs. 3 days) in comparison with the high-dose group. The covariate factors predicting the treatment response, in order of significance, were radioiodine dose, baseline Tg, baseline thyroid stimulating hormone (TSH) level, efficiency of TSH suppressive therapy, and sex. CONCLUSION: The higher dose of I-131 (3700 MBq) resulted in successful ablation more often than the low dose (1110 MBq).

Effects of crystal pixel size and collimator geometry on the performance of a pixelated crystal gamma-camera using Monte Carlo simulation.

Dedicated γ-cameras based on pixelated scintillators have long been used for breast tumor imaging. Intercrystal scattering (ICS) increases the background counting rate and degrades the image quality when small crystal pixels are used. Because of the small size of applied collimators, scattered radiation and septal penetration are high, and therefore collimator characteristics must be carefully considered. In our study, we investigated the influence of ICS events on position-detection accuracy (PDA) for pixelated crystals and the effects of different geometries of hexagonal-hole collimators on the performance of these cameras, using Monte Carlo simulation to optimize camera design. The arrays of thallium-doped cesium iodide detectors with different pixel dimensions that had been exposed to 140-keV photons of isotropic point source, 50 mm from the collimator surface, were simulated. Hexagonal-hole collimators were 10.5, 15, and 21 mm long. The septal thickness varied from 0.1 to 0.5 mm, with 3 different hole diameters. The results confirmed that by increasing the crystal pixel size, ICS was decreased and change of detection efficiency was negligible, but PDA, contrast-to-noise ratio, and spatial resolution (full width at half maximum) were increased. Our experiences confirmed that 2 × 2 mm was an optimum crystal pixel size, especially for a lower ICS fraction and an appropriate full width at half maximum. Because collimators are the limiting factor for spatial resolution and sensitivity, careful collimator design is of great importance.

The role of myocardial perfusion imaging in the evaluation of patients undergoing percutaneous transluminal coronary angioplasty.

INTRODUCTION: We studied the value of myocardial perfusion imaging (MPI) for the evaluation of improvement in myocardial perfusion in patients with successful percutaneous transluminal coronary angioplasty (PTCA). METHODS: Sixty patients (10 women, 50 men) aged 54.18 +/- 11.71 years were analyzed. MPI was performed before PTCA, 6-10 days (16 cases), 1-3 months (21 cases), and then 3-6 months (23 cases) after the procedure. In all patients repeated coronary angiography was done at least once after PTCA. Statistical analysis of the numbers of segments with various degrees of perfusion (normal, ischemia, fixed segment), before and after PTCA, was performed for three groups (6-10 days, 1-3 months and 3-6 months after PTCA) separately, using paired T and also ANOVA tests. A p-value <0.05 was considered to be statistically significant. RESULTS: Improvement, defined as a decrease in the number of ischemic or fixed segments, was observed in 13 of 16 patients at 6-10 days after PTCA, in 18 of 21 cases 1-3 months after PTCA, and in 20 of 23 patients 3-6 months after PTCA. The sensitivity and specificity of MPI calculated before PTCA and at the 3 subsequent time points, using angiography as the gold standard, were 80/81, 100/35, 90/100, and 76/100 percent, respectively. CONCLUSION: Our results confirm the necessity for an assessment of perfusion both before and shortly after angioplasty, since it provides the best documentation of the changes in myocardial perfusion.

Radioiodine treatment complications to the mother and child in patients with differentiated thyroid carcinoma.

Radioiodine ((131)I) has been widely used in the treatment of differentiated thyroid carcinoma (DTC). Since radiation can carry a known risk of mutagenic abnormalities, we decided to study the outcome of pregnancy in females with DTC and evaluate the genetic risks and health status of their offspring. We retrospectively studied the medical records of these patients in our Institute from 1999 to 2004. A total of 1110 women were hospitalized for treatment with high doses of (131)I, at least 3700MBq. During this period, 653 of these women were in their reproductive period. A hundred of them who had at least one pregnancy after (131)I treatment, were studied. These women had a total of 126 pregnancies (1-6 pregnancies each) after treatment and 101 pregnancies before treatment. We also reviewed the (131)I dose administered last, as well as the cumulative dose of (131)I. Our results show that the incidence of abortions before (131)I treatment was 16.83% (all were spontaneous abortions) and increased to 26.19% after (131)I treatment (15.87% induced and 10.3% spontaneous abortions). Spontaneous abortions were decreased. There was no significant difference between the mean last (131)I dose and the cumulative dose in patients with or without a history of abortions. Mean interval between the last dose of (131)I treatment and abortions versus the last dose and live child births showed a significant difference. All children had normal birth weight. Three congenital anomalies: Down's syndrome, cardiac abnormalities and macrocephaly were diagnosed. Three episodes of intrauterine death were also recorded. In conclusion, our findings indicate that in women with DTC, treated with high doses of(131)I: a) There was no evidence of increased spontaneous abortions, b) Increasing the interval between the last dose of (131)I treatment and time to pregnancy might be beneficial for decreasing the entire risk of abortions and c) It appears that (131)I treatment had no obvious adverse effects on the risk of congenital anomalies.

The long term effect of levothyroxine on bone mineral density in patients with well differentiated thyroid carcinoma after treatment.

To date a few studies have focused on the possible effects of subclinical hyperthyroidism on bone metabolism, showing conflicting results. This study was designed to evaluate this possibility. Sixty-six patients, 22 pre-menopausal women, 33 post-menopausal women and 11 men, who had received iodine-131 ((131)I) ablation postoperatively for well differentiated thyroid carcinoma (WDTC) and were treated for a long term with levothyroxine (T(4)), entered the study and were compared with sixty-six healthy controls individually matched to the patients for age, gender and menopausal status. The bone mineral density (BMD) of lumbar and hip regions of the patients was measured, while on the T(4) suppressive treatment, with average duration of 14.93+/-2.17 months after initiation of the T(4) suppressive treatment and was compared with the BMD of healthy controls. All patients were in the subclinical hyperthyroid state, while all controls were serologically and clinically euthyroid. Our results show that there was no significant difference in BMD measured at the lumbar spine of patients and controls in any subgroup (P>0.05). Analysis of the data of BMD from the hips in men, premenopausal women and controls, also revealed no difference. It was noted that the mean BMD of the femur in the postmenopausal women were at the statistical limit of significance as compared to the control group (P=0.05). In conclusion, our findings indicate that the replacement dose of T(4) in WDTC patients after (131)I ablation, does not have a significant effect on BMD in men, in pre and post-menopausal women and hence on the risk of osteoporosis. In post-menopausal women, the mean femoral BMD was at the limit of statistical significance.

Scatter correction for heart SPECT images using TEW method.

Radionuclide imaging has the potential to be used in quantitative analysis of the regional function of organs. However, quantification of SPECT images is degraded by many factors such as Compton photon scattering. This could have a destructive effect on clinical reports so it is important to do scatter correction to get better quality SPECT images. We intended to determine how scatter correction with the TEW method can help physicians who look at heart SPECT images, get better reports. This study used the TEW method for scatter correction, which was proposed by Ogawa et al.,(9) using the two narrow windows on either side of the photopeak (20% down and 20% up of the photopeak respectively). Injection of radiopharmaceutical 99mTc was used for medical imaging. In the Shariati Hospital, Tehran, we studied a total of 80 patients with heart disease indications (43 men and 37 women) over the ages of 30-80 years. Contrast and sharpness were considerably improved after scatter correction so physicians could look at defects better. In a few cases scatter correction changed heart defect reports to normal. Using TEW, sensitivity and specificity increased from 86% to 94% and from 61% to 84% respectively. This method was simple to use in clinics.

The effect of high-dose radioiodine treatment on lacrimal gland function in patients with differentiated thyroid carcinoma.

PURPOSE: There are a limited number of case reports confirming the radioiodine (I-131) presence in tears and only a few case reports of lacrimal gland dysfunction after I-131 therapy. This study was designed to clarify whether lacrimal gland function can be affected by I-131 therapy. MATERIALS AND METHODS: We studied 100 eyes of 50 patients who had received high doses of I-131 for treatment of differentiated thyroid carcinoma and 100 eyes of 50 age- and sex-matched control individuals without a history of interfering conditions. The exposed group was studied at least 3 months after their last I-131 therapy. Dry eye symptoms and Schirmer test values (wetting level in millimeters per 5 minutes) of an exposed group were compared with those of an unexposed group. RESULTS: Fifty-one percent of the exposed eyes and 50% of the unexposed ones revealed at least 1 of the dry eye symptoms. There was no significant difference in symptoms between 2 groups, except for burning sensation and eye redness, which were significantly higher in the exposed eyes. A lower Schirmer test value was noted in the exposed group, 14.5 +/- 10.8 mm, when compared with that in controls, 18.2 +/- 11.0 mm (P = 0.016), and the relative risk of an abnormal Schirmer test in exposed cases to control group was 1.78 +/- 0.62. Correlation coefficient analysis showed no significant relationship between Schirmer test values and cumulative doses of administered I-131. CONCLUSIONS: Reduction in the tear secretion from lacrimal glands is seen after high-dose I-131 therapy; however, their symptoms are no greater than an unexposed population.

Noninvasive temperature estimation using sonographic digital images.

OBJECTIVE: The purpose of this study was to develop and evaluate a speckle-tracking method for tissue temperature estimation due to heating fields using digital sonographic images. METHODS: The temperature change estimation method is based on the thermal dependence of the ultrasound speed and the thermal expansion of the medium. Local changes in the speed of sound due to changes in the temperature produce apparent displacement of the scatterers, and the expansion introduces physical displacement. In our study, a new technique has been introduced in which the axial physical displacements were obtained from digital sonographic images. The axial speckle pattern displacement was determined with a cross-correlation algorithm. The displacement data were then used for computing the temperature changes. To monitor the temperature in real time, the computational time was decreased by restricting the search region in the cross-correlation algorithm and carrying out the cross-correlation function in the frequency domain via a fast Fourier transform algorithm. RESULTS: Experiments were performed on tissue-mimicking phantoms. The imaging probe was a commercial linear array working at 10 MHz. In addition, the temperature changes during heating were measured invasively by negative temperature coefficient thermistors. There was good agreement between ultrasonic temperature estimations and invasive temperature measurements. CONCLUSIONS: The proposed method verifies the capability of the speckle-tracking algorithm for determining both the magnitude and direction of displacement. The average error was 0.2 degrees C; the maximum error was 0.53 degrees C; and the SD was 0.19 degrees C. Therefore, the proposed algorithm is capable of extracting the temperature information from sonographic digital images.

Efficacy of radioiodine therapy in the treatment of elevated serum thyroglobulin in patients with differentiated thyroid carcinoma and negative whole-body iodine scan.

INTRODUCTION: In the management of patients with differentiated thyroid carcinoma, serum thyroglobulin levels are often well correlated with whole-body radioiodine scanning (WBS) results. However, occasionally, a mismatched result - increased thyroglobulin with negative WBS - is observed. Radioiodine therapy has been suggested as a therapeutic choice with controversial results. METHOD: We studied 32 differentiated thyroid carcinoma patients with elevated thyroglobulin level and negative WBS who had been treated with high-dose radioiodine. With a mean follow-up of 25.6 months (all follow-ups >11 months), thyroglobulin and thyroid-stimulating hormone levels, WBS, clinical, radiographic and pathological findings following treatment were recorded. RESULTS: The mean pre-therapy off-treatment thyroglobulin was 152 +/- 119.0 ng.ml(-1). Although there was a mild trend towards an increase in thyroglobulin in the first post-treatment year, the difference was not significant. At the end of the follow-ups, 22 patients (68.7%) were categorized as non-responders to radioiodine therapy (any change or elevation of thyroglobulin or radiological and pathological evidences of progression), four patients (12.5%) as partial responders (transient reduction but not a normalization of thyroglobulin) and six patients (18.7%) as responders (normalization of thyroglobulin with no evidence of remnant disease). In nine of 10 partial and complete responders, reduction or normalization of thyroglobulin had occurred in the first post-treatment year. CONCLUSION: We recommend that in differentiated thyroid carcinoma patients with elevated thyroglobulin and negative WBS, at least one course of radioiodine therapy should be undertaken and if reduction or normalization of serum thyroglobulin is not achieved, repeated courses of radioiodine therapy are not logical and other therapeutic methods should be applied.

Frequency and severity of myocardial perfusion abnormalities using Tc-99m MIBI SPECT in cardiac syndrome X.

BACKGROUND: Cardiac syndrome X is defined by a typical angina pectoris with normal or near normal (stenosis <40%) coronary angiogram with or without electrocardiogram (ECG) change or atypical angina pectoris with normal or near normal coronary angiogram plus a positive none-invasive test (exercise tolerance test or myocardial perfusion scan) with or without ECG change. Studies with myocardial perfusion imaging on this syndrome have indicated some abnormal perfusion scan. We evaluated the role of myocardial perfusion imaging (MPI) and also the severity and extent of perfusion abnormality using Tc-99m MIBI Single Photon Emission Computed Tomography (SPECT) in these patients. METHODS: The study group consisted of 36 patients with cardiac syndrome X. The semiquantitative perfusion analysis was performed using exercise Tc-99m MIBI SPECT. The MPI results were analyzed by the number, location and severity of perfusion defects. RESULTS: Abnormal perfusion defects were detected in 13 (36.10%) cases, while the remaining 23 (63.90%) had normal cardiac imaging. Five of 13 (38.4%) abnormal studies showed multiple perfusion defects. The defects were localized in the apex in 3, apical segments in 4, midventricular segments in 12 and basal segments in 6 cases. Fourteen (56%) of all abnormal segments revealed mild, 7(28%) moderate and 4 (16%) severe reduction of tracer uptake. No fixed defects were identified. The vessel territories were approximately the same in all subjects. The Exercise treadmill test (ETT) was positive in 25(69%) and negative in 11(30%) patients. There was no consistent pattern as related to the extent of MPI defects or exercise test results. CONCLUSION: Our study suggests that multiple perfusion abnormalities with different levels of severity are common in cardiac syndrome X, with more than 30 % of these patients having at least one abnormal perfusion segment. Our findings suggest that in these patients microvascular angina is probably more common than is generally believed.

Comparative evaluation of two fixed doses of 185 and 370 MBq 131I, for the treatment of Graves' disease resistant to antithyroid drugs.

Radioiodine (131I) treatment is often applied for the treatment of Graves' disease (GD). The optimal dose of 131I for Graves' hyperthyroidism is debated. Various techniques suggest either fixed doses or varying doses based on elaborate calculations of the gland size, 131I uptake, and 131I turnover. Fixed dose regimens avoid dose calculations but there is no consensus on the actual dose to be administered. We compared two routinely recommended fixed 131I doses of 185 and 370 MBq for this purpose. Fifty nine patients with GD who had not been previously treated with 131I were randomized in two groups. Group A consisted of 33 patients who were treated with 185 MBq of 131I. Group B consisted of 26 patients who were treated with 370 MBq of 131I. Group A patients were 21% male and 78% female, mean age 38.1+/-14.4, range 15 to 77 y. Group B patients were 27% male and 73% female, mean age 40.7+/-11.7, range 27 to 72 y. All patients were reexamined every six months for two years. The following clinical outcomes were noticed: a) Persistent hyperthyroidism, which was considered as failure to treatment, requiring further 131I treatment. b) Hypothyroidism; requiring life-long replacement treatment. c) Euthyroid state. Euthyroid and hypothyroid states were considered as a response to treatment of hyperthyroidism. In Group A, 10 patients (30.3%) became euthyroid and 6 (18.2%) hypothyroid (an overall response of 48.5%), while 17 (51.5%) remained hyperthyroid by the end of the follow-up period. In Group B, 10 patients (38%) became euthyroid and 13 (50%) hypothyroid, an overall response of 88.5%. Non responders were 3 patients (11.5%). No correlation was noted between the outcome of treatment and age, sex, size of the thyroid gland or thyroid uptake in each Group of patients, while a significant correlation was noted between the disease outcome and the amount of administered 131I (P<0.003). The incidence of hypothyroidism by the end of two years of follow up was less in Group A than in Group B and the incidence of non responders to treatment was lower in Group A. In view of the higher cost of treatment, the longer time elapsing to treatment, the number of office visits by the patients and the higher number of patients with persistent hyperthyroidism in Group A, we conclude that a fixed dose of 131I of 370 MBq is more useful and effective for the treatment of GD as compared to 185 MBq of 131I.