Vitamin D levels after UVB radiation: effects by UVA additions in a randomized controlled trial.

BACKGROUND: Ultraviolet B (UVB) radiation increases the serum level of 25-hydroxyvitamin D [25(OH)D]. However, the impact of UVA on vitamin D synthesis by UVB is poorly understood clinically. OBJECTIVE: To examine how different combinations of UVA and UVB radiation affect S-25(OH)D for the same vitamin D-weighted exposure. MATERIALS AND METHODS: Healthy participants were recruited and subsequently divided into four comparable groups regarding initial 25(OH)D value. The different radiations given were whole-body UVB (n = 23), UVAB (n = 23) and UVA (n = 10). The controls (n = 19) had no intervention. The exposure times were chosen to give the same calculated vitamin D effective dose (suberythemal exposures ≤1 standard erythema dose). Blood samples were collected before the first irradiation (t0), immediately after the last (fifth) irradiation (t1) and then after another 2 days after the last (fifth) irradiation (t2). RESULTS: UVB and UVAB radiation significantly increased 25(OH)D levels. In the UVA group the increase was less with the same vitamin D-weighted radiation dose. CONCLUSIONS: Short sessions of UVB or UVAB radiation with the same vitamin D-weighted exposure increased 25(OH)D levels. The UVA dose does not influence 25(OH)D levels under short exposure times. However, there was a significantly lower increase of 25(OH)D levels during longer UVA irradiation (≥9 min).

Experience from long-term monitoring of RAKR ratios in (192)Ir brachytherapy.

BACKGROUND: Ratios of values of brachytherapy source strengths, as measured by hospitals and vendors, comprise constant differences as, e.g., systematic errors in ion chamber calibration factors and measurement setup. Such ratios therefore have the potential to reveal the systematic changes in routines or calibration services at either the hospital or the vendor laboratory, which could otherwise be hidden by the uncertainty in the source strength values. METHODS: The RAKR of each new source in 13 afterloading units at five hospitals were measured by well-type ion chambers and compared to values for the same source stated on vendor certificates. RESULTS: Differences from unity in the ratios of RAKR values determined by hospitals and vendors are most often small and stable around their mean values to within +/- 1.5%. Larger deviations are rare but occur. A decreasing ratio, seen at two hospitals for the same source, was useful in detecting an erroneous pressure gauge at the vendor's site. CONCLUSIONS: Establishing a mean ratio of RAKR values, as measured at the hospital and supplied on the vendor certificate, and monitoring this as a function of time are an easy way for the early detection of problems with equipment or routines at either the hospital or the vendor site.

Dosimetry of anal radiation in high-dose-rate brachytherapy for prostate cancer.

PURPOSE: The objective of this study is to determine the radiation dose to the anus during brachytherapy using high-dose-rate Ir-192 sources. METHODS AND MATERIALS: Thermoluminescence dosimeters were used for measuring the dose to the distal part of the anus in 10 patients, and in a prostate phantom to measure the radiation dose during the transport of the radiation source. RESULTS: The measured dose to the anus in vivo was on average 0.85 Gy (range, 0.48-1.37 Gy) per treatment. The transport dose using 15 and 19 needles in the prostate phantom was 0.07 and 0.08 Gy, respectively. CONCLUSIONS: The dose delivered to the anus using high-dose-rate brachytherapy with Ir-192 sources is quite low. There is a contribution to the anal radiation dose during the transport of the Ir-192 source into the needles. However, in clinical practice when using 15-20 needles, the dose from transporting the Ir-192 source can be ignored.