A novel perineal shield for low-dose-rate prostate brachytherapy.

PURPOSE: To study the impact on radiation exposure to staff through the use of an original perineal shield during low-dose-rate prostate brachytherapy. MATERIAL AND METHODS: We designed a 1 mm thick stainless steel shield that duplicates and is able to slide directly over a standard commercialized prostate brachytherapy grid. We then analyzed the post-procedure exposure in 15 consecutive patients who underwent Iodine-125 seed placement. Measurements were performed with and without the shield in place at fixed locations relative to the grid template. Endpoints were analyzed using the paired two-sample t-test, with statistical significance defined as a p-value < 0.05. RESULTS: The exposure at the midline grid template ranged from 0.144-0.768 mSv/hr without the shield, and 0.038-0.144 mSv/hr with the shield (p < 0.0001). The exposure 10 cm left of the grid template was 0.134-0.576 mSv/hr without the shield, and 0.001-0.012 mSv/hr with the shield (p < 0.0001). The exposure 10 cm right of the grid template was 0.125-0.576 mSv/hr without the shield, and 0.001-0.012 mSv/hr with the shield (p < 0.0001). The median reduction of exposure at the grid was 76% midline, 98.5% left, and 99% right. Similarly, each individual dose rate was recorded at 25 cm from the perineum, both with and without shield. The median reduction of exposure 25 cm from the perineum was 73.7% midline, 77.7% left and 81.6% right (p < 0.0001). CONCLUSIONS: Our novel shield took seconds to install and was non-restrictive during the procedure, and provided at least a four-fold reduction in radiation exposure to the brachytherapist.

Assessment of risk of late rectal bleeding for patients with prostate cancer started on anticoagulation before or after radiation treatment.

AIM: To evaluate the risk of late rectal bleeding and its association with the timing and type of anticoagulation use in patients receiving dose-escalated radiation therapy (RT) (≥ 7,560 cGy) for prostate cancer. PATIENTS AND METHODS: Between 2003-2010, 465 patients were treated at our Institution with dose-escalated RT and included in this analysis. Patients were placed into the following categories: no anticoagulation use, aspirin during RT, clopidogrel/warfarin during RT, aspirin after completion of RT, clopidogrel/warfarin after completion of RT. RESULTS: The overall bleeding rate was 7.5%. For those on aspirin during RT, the 4-year freedom from rectal bleeding (FFBS) rate was 91%, compared to 94.7% for patients who were never on anticoagulation (p=0.16). For those on warfarin/clopidogrel during RT the 4-year FFBS rate was 78.2%, compared to 94.7% in those never on anticoagulation (p<0.001). On multivariate analysis, use of warfarin/clopidogrel during radiation treatment were strongly associated with an increased risk of rectal bleeding (multivariate HR=4.84, 95% CI=1.84-12.68, p=0.001). However, initiation of anticoagulation after completion of radiation treatment did not significantly increase the risk of rectal bleeding (multivariate HR=0.78, 95% CI=0.21-2.91, p=0.71). CONCLUSION: The use of clopidogrel or warfarin during radiation is associated with significantly increased risk of rectal bleeding. However, initiation of these medications after completion of radiation does not appear to impact such risk.

Evaluation of the eclipse electron Monte Carlo dose calculation for small fields.

Varian Medical Systems (Palo Alto, CA) has implemented the Monte Carlo electron dose calculation algorithm (eMC) in the Eclipse treatment planning system. Previous algorithms for electron treatment planning were limited in their calculation ability for small field depth doses and monitor units. An old rule of thumb to approximate the limiting cutout size for an electron field was determined by the lateral scatter equilibrium and approximated by E (MeV)/2.5 in centimeters of water. In this study we compared eMC calculations and measurements of depth doses, isodose distributions and monitor units for several different energy and small field cutout size combinations at different SSDs. Measurements were made using EBT film (International Specialty Products, Wayne, NJ) and a PinPoint Ion Chamber (PTW, Hicksville, NY). Our results indicate that the eMC algorithm can accurately predict depth doses, isodose distributions and monitor units (within 2.5%) for field sizes as small as 3.0 cm diameter for energies in the 6 to 20 MeV range at 100 cm SSD. Therefore, the previous energy dependent rule of thumb does not apply to the Eclipse electron Monte Carlo code. However, at extended SSDs (105-110 cm), the results show good agreement (within 4 %) only for higher energies (12, 16, and 20 MeV) for a field size of 3 cm.

Synchrotron-based infrared and X-ray imaging shows focalized accumulation of Cu and Zn co-localized with beta-amyloid deposits in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by the misfolding and plaque-like accumulation of a naturally occurring peptide in the brain called amyloid beta (Abeta). Recently, this process has been associated with the binding of metal ions such as iron (Fe), copper (Cu), and zinc (Zn). It is thought that metal dyshomeostasis is involved in protein misfolding and may lead to oxidative stress and neuronal damage. However, the exact role of the misfolded proteins and metal ions in the degenerative process of AD is not yet clear. In this study, we used synchrotron Fourier transform infrared micro-spectroscopy (FTIRM) to image the in situ secondary structure of the amyloid plaques in brain tissue of AD patients. These results were spatially correlated with metal ion accumulation in the same tissue sample using synchrotron X-ray fluorescence (SXRF) microprobe. For both techniques, a spatial resolution of 5-10 microm was achieved. FTIRM results showed that the amyloid plaques have elevated beta-sheet content, as demonstrated by a strong amide I absorbance at 1625cm(-1). Using SXRF microprobe, we find that AD tissue also contains "hot spots" of accumulated metal ions, specifically Cu and Zn, with a strong spatial correlation between these two ions. The "hot spots" of accumulated Zn and Cu were co-localized with beta-amyloid plaques. Thus for the first time, a strong spatial correlation has been observed between elevated beta-sheet content in Abeta plaques and accumulated Cu and Zn ions, emphasizing an association of metal ions with amyloid formation in AD.