Comparing radiation exposure between ablative therapies for small renal masses.

PURPOSE: The purpose of this study was to evaluate the amount of radiation exposure patients with small renal masses undergoing percutaneous cyroablation (PCA) or percutaneous radiofrequency ablation (PRFA) received during treatment and follow up. MATERIALS AND METHODS: A retrospective review was conducted on all patients with small renal masses <4 cm treated with PCA or PRFA over a 7-year period in a single academic center. Preoperative, operative, and post-operative variables were collected and compared. Radiation exposure received during treatment and 1 year of follow up were also determined for each modality. Statistical analysis was conducted using SPSS V.17 (SPSS, Chicago, IL). The groups were compared using the Mann-Whitney U and Pearson Chi-Square tests. Statistical significance was considered at p<0.05. RESULTS: There was no significant difference in pretreatment parameters or oncologic outcomes. The average PCA treatment radiation exposure was 39.7 mSv (15.5-133.4 mSv) compared with 22.2 mSv (8.1-67.7 mSv) for PRFA (p=0.001). During the initial year after treatment, the estimated mean treatment and follow-up radiation exposure for PCA was 134.5 mSv, compared with 117 mSv for RFA when routine computerized tomography imaging was employed. CONCLUSION: To our knowledge, this is the first published study that quantifies radiation exposure in PCA and PRFA treatment for small renal masses. These relatively high radiation exposures should be included in the informed consent for these procedures. In addition, caution should be employed when applying these technologies in young patients who are most susceptible to long-term radiation damage.

Radiation exposure during continuous and pulsed fluoroscopy.

UNLABELLED: Abstract Background and Purpose: Previous studies using pulsed fluoroscopy have shown variable effects on radiation exposure because of the ramp and trail effect in older C-arm systems. This study compares radiation delivered in pulsed and continuous modalities using a modern C-arm system. MATERIALS AND METHODS: Thermoluminescent dosimeters (TLDs) positioned in three body locations directly measured radiation dose during simulated ureteroscopy. Thirty pedal activations were administered using a pulsed or continuous mode to visualize an implanted guidewire and a radiopaque stone. TLD absorbed radiation and image quality were compared between imaging modes. RESULTS: Pulsed fluoroscopy delivered less radiation compared with continuous fluoroscopy at each site: Anterior skin (0.10 vs 0.26 mGy, P<0.001), kidney (0.15 vs 0.40 mGy, P<0.001), and posterior skin (0.92 vs 2.62 mGy, P<0.001). Mean fluoroscopy time differed between continuous and pulsed modes (12.5 vs 3.0 seconds; P<0.001). Fluoroscopy time positively correlated with radiation exposure at all sites: Anterior skin (0.017 mGy/s, R(2)=0.90), left kidney (0.026 mGy/s, R(2)=0.96), and posterior skin (0.18 mGy/sec, R(2)=0.98). When evaluated by blinded urologists, 100% of reviewers felt pulsed images were adequate to identify guidewire position and 90.5% felt pulsed images were adequate for stone localization. CONCLUSION: Pulsed fluoroscopy reduced fluoroscopy time by 76% and radiation dose by 64% compared with continuous fluoroscopy. Pulsed fluoroscopy images were adequate for most tasks of ureteroscopy and should be considered for reduction of radiation during ureteroscopy.

Ureteral calculi detection using low dose computerized tomography protocols is compromised in overweight and underweight patients.

PURPOSE: Low dose computerized tomography protocols have demonstrated a reduction in radiation exposure while maintaining excellent sensitivity and specificity in the detection of stones in patients of average size. Low dose computerized tomography protocols have not yet been evaluated in subjects in the extremes of weight. We evaluated the effect of body weight when using low dose protocols to detect ureteral calculi. MATERIALS AND METHODS: Three cadavers of increasing weight (55, 85 and 115 kg) were prepared by inserting 721 calcium oxalate stones (range 3 to 7 mm) in 33 random configurations into urinary tracts. Cadavers were then scanned using a GE LightSpeed® at 7 radiation settings. An independent, blinded review by a radiologist was conducted to generate ROC curves, with areas under the curve compared using a 1-way ANOVA (α = 0.05). RESULTS: Sensitivity and specificity were significantly lower in the low and high weight cadavers compared to the medium weight cadaver at 5 mAs (p <0.001) and 7.5 mAs (p = 0.048). Differences in sensitivity and specificity at radiation settings of 15 mAs or greater were not significant. CONCLUSIONS: The sensitivity and specificity for the detection of ureteral calculi on computerized tomography were decreased for underweight and overweight subjects when using extremely low dose radiation settings (less than 1 mSv). Low dose protocols of 15 mAs (2 mSv) can still be used for these subjects without jeopardizing the ability to identify ureteral stones.

Prostate specific antigen levels and prostate cancer detection rates in patients with end stage renal disease.

PURPOSE: Patients with end stage renal disease plus prostate cancer are ineligible to receive a renal transplant at most centers until an acceptable cancer-free period is demonstrated. To our knowledge previously established prostate specific antigen reference ranges have not been validated in patients with end stage renal disease. We determined age stratified 95th percentile prostate specific antigen reference ranges and the prostate cancer detection rate at specific prostate specific antigen intervals for patients with end stage renal disease. MATERIALS AND METHODS: We retrospectively reviewed the records of 775 male patients with end stage renal disease on the waiting list for a renal transplant who had undergone a serum prostate specific antigen test. Prostate specific antigen was stratified by age at the time of the blood test and 95th percentile reference ranges were calculated for each decade. A total of 80 patients underwent prostate biopsy for increased prostate specific antigen and/or abnormal digital rectal examination. The cancer detection rate was calculated for specific prostate specific antigen reference ranges. RESULTS: The age specific 95th percentile prostate specific antigen references ranges were 0 to 4.0 ng/ml for ages 40 to 49 in 137 patients, 0 to 5.3 ng/ml for ages 50 to 59 in 257, 0 to 10.5 ng/ml for ages 60 to 69 in 265 and 0 to 16.6 ng/ml for ages 70 to 79 years in 69. The cancer detection rate was 44%, 38% and 67% for prostate specific antigen 2.5 to 4.0, 4 to 10 and greater than 10 ng/ml, respectively. CONCLUSIONS: In our study population of patients with end stage renal disease age stratified prostate specific antigen was higher than in the general population. The cancer detection rate was increased in our patients with end stage renal disease compared to that in patients with normal renal function at specific prostate specific antigen intervals. Lower prostate specific antigen cutoffs may be appropriate to recommend prostate biopsy in patients with end stage renal disease.