A study of the efficacy of radioiodine therapy with individualized dosimetry in Graves' disease: need to retarget the radiation committed dose to the thyroid.

Although Iodine-131 (131I) therapy is fully validated for Graves' disease (GD), there is debate about radioiodine amount to be administered (prescribed activity), as well as the use of individualized dosimetry vs fixed 131I activity. The clinical outcome of 119 GD patients treated with 131I from 2003 to 2008 has been evaluated. The prescribed activity was calculated according to a dosimetric protocol taking into account several variables, including thyroid volume reduction during treatment. In addition, we performed a simulation according to other dosimetric protocols, by calculating the corresponding prescribed activities. The patients were followed up for at least 12 months after treatment. In the first period of observation (2003), a 120-200 Gray (Gy) radiation dose to the thyroid was prescribed, according to the guidelines published by the Italian Societies of Endocrinology, Nuclear Medicine and Medical Physics: hyperthyroidism cure with a single radioiodine administration was obtained in 53% of patients. This outcome raised up to 89% when a higher radiation dose to the target (200- 250 Gy) was prescribed, although the administered activities were still lower, as a rule, than the most commonly employed fixed activities (400-600 Mega-Becquerel--MBq). Our method showed a high level of individual dose optimisation, particularly when compared to simplified methods. In conclusion, the protocol adopted in this study ensures a satisfactory rate of hyperthyroidism cure, while administering quite low 131I activities, provided that an adequate committed radiation dose to the thyroid is prescribed. In this context, the dose indication given by the aforementioned guidelines should probably be revised.

The determination of dose characteristics of ruthenium ophthalmic applicators using radiochromic film.

Ruthenium ophthalmic applicators are energetic beta ray sources, supplied in several shapes and dimensions, and used in intraocular tumor therapy. Because of their small dimensions, the determination of dosimetric characteristics represents a technical challenge. We developed a semiautomatic method to define surface dose, dose distribution, and percentage depth dose of such applicators using radiochromic dosimetric media. These detectors consist of a thin (7 microns) radiation sensitive layer on polyester base (100 microns total thickness) changing color as a function of radiation exposure. Transmission images of exposed films were then grabbed with a TV-digitizer system to obtain a gray-level image from which dosimetric characteristics such as isodose distribution, dose values, and homogeneity of nuclide distribution were derived. Good agreement between experimental results and Monte Carlo simulation performed using the GEANT 3 code, appear to be a confirmation of the validity of the method. Moreover while manufacturer specifications of absolute and relative dose rates present a standard deviation error of +/- 30% on dose rate and +/- 6% on accuracy of relative dose values, the proposed method reduces the errors to +/- 10% and +/- 4%, respectively.

Estimation of rectal radiodoses in gynecologic curietherapy by "small enema".

The Authors suggest a simple, inexpensive and accurate method to evaluate the sigmoid and rectal radiodoses delivered by brachitherapy in the treatment of cervical neoplasia.

[Use of common glass in radiation protection]. / Impiego di comuni cristalli in radioprotezione.

The X-ray absorption meter (Diagnostic energy between 20-60 Kev) of common place-glass has been studied. The possibility of replacing lead glass with a reinforced type, also very cheap, has been examined.

A personal dosimeter prototype for static magnetic fields.

A personal dosimeter prototype, for static magnetic fields with three Hall probes, has been designed and built to provide a reliable instrument for long-term analysis. The probe output signals, proportional to the magnetic flux density components of the vector B, are filtered, sampled, and stored in a buffer memory sufficient to cover a whole worker shift. The data sampling rate is high enough to record the operator movements within the fringes of the magnetic field. The content of the buffer memory is then transferred on a personal computer and registered on individual dosimetric cards. The data can be used for personal exposure monitoring.

Supervised automatic procedure to identify new lesions in brain MR longitudinal studies of patients with multiple sclerosis.

PURPOSE: Identification of new enhancing lesions is a major endpoint of longitudinal brain magnetic resonance (MR) studies of multiple sclerosis (MS). To date, this is a visual, time-consuming procedure. We present here a supervised automated procedure (SAP) aimed at reducing the time needed to identify new MS enhancing lesions. MATERIALS AND METHODS: The SAP uses an algorithm including Cartesian coordinates of the lesions to be compared, their area and a constant (k). The procedure was validated for enhancing lesions on T1-weighted spin-echo images after intravenous administration of 0.1 mmol/kg of paramagnetic contrast agent, randomly selected from a dataset of a longitudinal MR study on ten relapsing-remitting MS patients followed for 2-5 years. During the validation session, two readers decided by consensus whether two lesions, present on the same slice of two examinations performed on subsequent dates, were the same or not. In this way, k was calibrated to obtain the same result from both visual inspection and automatic algorithm output. RESULTS: After evaluating of 25+/-5 (mean+/-standard deviation) lesions in each of ten different sessions with correction of k value, the k value became a stable value (0.45+/-0.05). CONCLUSIONS: Once the suitable value of k was found, SAP was able to identify new enhancing lesions, avoiding visual inspection, which is usually a lengthy procedure.

[Development of a method for the quantitative evaluation of the regional kinetics of the left ventricle]. / Elaborazione di un metodo per la valutazione quantitativa della cenetica regionale del ventricolo sinistro.

Segmental wall motion abnormalities of the left ventricle frequently occur in ischemic heart disease. An objective, quantitative method is required to ensure the reproducibility of the assessment of left ventricular regional function, especially in evaluating the changes induced by diagnostic and therapeutic interventions. In 32 normal subjects we obtained 30 degrees right anterior oblique left ventriculograms and developed a method based on the following observations. The method should reflect the symmetric uniform motion of the left ventricular silhouette. Only actual contractile motion should be taken into account; therefore, rotatory and translational motion should be compensated for. Passive systolic movement of aortic and mitral valves accounts for the contraction of neighbouring myocardial segments. Left ventricular wall excursion is most often measured by a coordinate system: since the cavity of the left ventricle becomes relatively longer during systole, left ventricular walls contract neither toward a single central point nor toward the long axis; therefore the appropriate origin of the coordinate system will be a segment. Furthermore, as more elongated left ventricular end-diastolic silhouettes appear to show a greater extent of systolic lengthening (we show evidence of this), the length of the segment must be related to the end-diastolic shape. The basic steps of the method are: 1) identification of a symmetry line, from the aortic mid-point to the apex, by connecting the mid-point of 19 diameters perpendicular to the long axis; 2) roto-translation of the end-systolic silhouette so that the end-systolic apex and aortic mid-point lie on the symmetry line.(ABSTRACT TRUNCATED AT 250 WORDS)