Search

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: Percutaneous transluminal coronary angioplasty (PTCA) is an effective method for revascularizing of stenotic coronary vessels. Lack of response to this treatment, either in symptomatic or asymptomatic patients, is usually due to incomplete revascularization, restenosis, and/or irreversibility of myocardial perfusion. Introduction of a noninvasive method with high predictive value for diagnosis of reversibility in ischemic myocardium is of high importance to determine the patients who will benefit from PTCA. Methods: Sixty patients with one or two vessel disease, who were candidates for PTCA and had a successful PTCA (proved by post- revascularization angiography), enrolled the study. For all patients myocardial perfusion imaging (MPI) was performed before PTCA in stress and rest phases. MPI was repeated in stress and rest phases within 6 months after PTCA. The predictive values of pre-PTCA scan for the diagnosis of reversibility and prediction of perfusion improvement after PTCA were evaluated. Results: Perfusion improvement after PTCA was noted in 52 of 60 patients (86.7%). The positive predictive value of pre-intervention MPI for diagnosis of reversibility was 94.3% and the corresponding negative predictive value was 71.4%. Conclusion: Myocardial perfusion imaging may play an important role for accurate prediction of perfusion improvement after percutaneous transluminal coronary angioplasty. [ABSTRACT FROM AUTHOR]

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 ((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.

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.

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.