The use of a thin guide-wire for urethral definition in prostate SBRT treatments with Cyberknife.

PURPOSE: To study and analyze the effect of the use of a thin guide-wire instead of a Foley catheter for urethral definition in prostate stereotactic body radiation therapy (SBRT) treatments and to compare treatment parameters in both situations. MATERIAL AND METHODS: Thirty-seven prostate SBRT patients were employed in this study. A Foley catheter was employed in nine of them, and a guide-wire was employed in the other 28 patients. For each of the 28 patients in which the guide-wire was employed, a comparison between urethral positions in both situations was performed, allowing for a margin definition of the urethra when a Foley catheter was employed. Displacements of the prostate during treatment were obtained, allowing for an analysis of prostate positions in both situations. Also, different treatment parameters such as the number of treatment interruptions, couch movements performed, and x-rays needed were gathered. RESULTS: Large differences between urethral positions can be found in the anterior-posterior (AP) directions compared to those in the lateral (LAT) direction. Differences are also larger in areas closer to the base of the prostate, where margins applied in the case of using a Foley catheter are 16 mm with a mean displacement of 6 mm in the posterior direction. No differences in the treatment parameters were found during treatment in both situations. The difference found in absolute prostate pitch rotations suggests that the Foley catheter provokes a shift of the prostate position, which does not occur when employing the guide-wire. CONCLUSIONS: Foley catheters shift the urethral position, making them a wrong surrogate of the urethra when no catheters are present. The margins needed to assess uncertainties introduced by the use of a Foley catheter are larger than those usually applied. The use of a Foley catheter did not present any additional difficulty during treatment delivery in terms of images employed or interruptions produced.

Dosimetric and Contrast Noise Ratio Comparison of Three Different Digital Imaging Technologies in Mammography.

PURPOSE: The purpose of the study was to compare the three most common technologies available in digital mammography based in the evaluation of average glandular dose and contrast noise ratio (CNR). METHOD: The average glandular dose was estimated with a direct digital detector (aSe) with a pixel size of 0.85 µm, a photon counter with a pixel size of 50 µm and a computerized radiography (CR) system. A semiconductor detector was used to measure the input kerma to the detector, and the average glandular dose was calculated from the conversion factors dependent on the anode filter combination, half value layer and breast glandularity. RESULTS: The average glandular dose obtained with polymethyl methacrylate and CNR of mean thickness 4.5 cm using direct digital equipment was 1.02 mGy and CNR = 7.4; using the photon counter it was 0.43 mGy and CNR = 4.7 in C100 mode, and 0.64 mGy and CNR = 5.7 in C120 mode; and using the photostimulable CR, the estimated value was 1.65 mGy and CNR = 5.1. CONCLUSIONS: The photon counter offers a lower average glandular dose than the other two devices with adequate image quality (CNR). The CR equipment offers a similar CNR value but delivers a higher dose than the new generations of available mammograms.

High-dose-rate (HDR) plesiotherapy with custom-made moulds for the treatment of non-melanoma skin cancer.

BACKGROUND: Non-melanoma skin tumours (NMSC) are one of the most frequent types of cancer, accounting for nearly one third of newly diagnosed tumours. NMSC are frequently diagnosed in elderly patients and while mortality rates are low, NMSC can be associated with significant morbidity in terms of cosmetic and functional impairment. OBJECTIVE: Surgical excision is nowadays considered the standard treatment for NMSC, although this approach might not be suitable for all the patients. Good rates of local control and cosmetic outcome are achieved by using high-dose-rate (HDR) plesiotherapy. METHODS: Nine consecutive patients with 11 NMSC were treated with custom-made moulds and HDR plesiotherapy reaching a fi nal dose of 44-48 Gy in 11-12 fractions of 4 Gy over 4 weeks. RESULTS: No local or distant relapses have been observed after a mean follow-up of 15 months (range 4-36 months). Acute toxicity was acceptable and cosmetic result was considered as excellent/good in 7 patients. CONCLUSIONS: This modality of treatment offers an alternative for those patients not candidates for surgical procedures because of medical contraindications or risk of disfigurement or functional impairment.