ABSTRACT
PURPOSE: Brachytherapy with iodine-125 (125I) has been extensively used as a conservative treatment for uveal melanoma (UM). Surgical technique for correct placement of episcleral radioactive plaques (ERP) in UM cases with posterior choroidal location and/or small size can be difficult and inaccurate. In this study, the correct positioning of plaques was assessed by intra-operative ultrasound control. MATERIAL AND METHODS: This was a longitudinal, retrospective study of consecutive 20 patients with UM (small-medium size and/or posterior location) who received 125I brachytherapy. Location of plaques was adjusted by intra-operative ocular ultrasonography control. To perform ocular intra-operative ultrasonography, a 10 MHz probe was used to longitudinal and transverse bases in corresponding dummy plaques. RESULTS: The study included 8 males and 12 females, with a mean age of 66.3 years (SD = 14.53), 5 right eyes (RE) and 15 left eyes (LE). In ultrasound examination, 4 UMs were of mushroom morphology and the rest nodular. Means of the size of UM by ultrasound were (mm): Lb: 10.60 (SD = 2.24) × Tb: 9.88 (SD = 1.54) × H: 4.02 (SD = 1.44) (3 cases corresponding to small size of collaborative ocular melanoma study (COMS), and 17 cases to medium). The plaques used were between 14 and 20 mm in diameter, with an average distance between the edge of greater base of the tumor and the edge of plate of 2.44 mm (SD = 0.34). It was necessary to surgically reposition the plaque in 4 cases (20%). CONCLUSIONS: Intra-operative ultrasound control improves the accuracy of radioactive plaque placement for the treatment of medium-small UMs in posterior location. Probably, this technique should be applied in all cases of brachytherapy, regardless of the isotope chosen and the location of tumor mass, in order to perfectly adjust therapeutic position.
ABSTRACT
The last recommendations of the International Commission on Radiological Protection for eye lens dose suggest an important reduction on the radiation limits associated with early and late tissue reactions. The aim of this work is to quantify and optimize the eye lens dose associated to nurse staff during positron emission tomography (PET) procedures. PET is one of the most important diagnostic methods of oncological and neurological cancer disease involving an important number of workers exposed to the high energy isotope F-18. We characterize the relevant stages as preparation and administration of monodose syringes in terms of occupational dose. A direct reading silicon dosimeter was used to measure the lens dose to staff. The highest dose of radiation was observed during preparation of the fluorodesoxyglucose (FDG) syringes. By optimizing a suitable vials' distribution of FDG we find an important reduction in occupational doses. Extrapolation of our data to other clinical scenarios indicates that, depending on the work load and/or syringes activity, safety limits of the dose might be exceeded.
