Don Arnold

Reduced Fluoroscopy Protocol for Percutaneous Nephrostolithotomy: Feasibility, Outcomes and Effects on Fluoroscopy Time

PURPOSE Radiation exposure from fluoroscopy during percutaneous nephrostolithotomy contributes to patient overall exposure, which may be significant. We compared fluoroscopy times and treatment outcomes before and after implementing a reduced fluoroscopy protocol during percutaneous nephrostolithotomy. MATERIALS AND METHODS We retrospectively reviewed the charts of patients treated with percutaneous nephrostolithotomy at a single academic institution by a single surgeon. We compared 40 patients treated before implementation of a reduced fluoroscopy protocol to 40 post-protocol patients. The reduced protocol included visual and tactile cues, fixed lowered mAs and kVp, a laser guided C-arm and designated fluoroscopy technician, and single pulse per second fluoroscopy. Preoperative characteristics, fluoroscopy and operative time, complications and treatment success were examined using univariate and multivariate analysis. RESULTS There was no significant difference in body mass index, stone size, success rate, operative time or complications between the groups. After protocol implementation fluoroscopy time decreased from 175.6 to 33.7 seconds (p<0.001). A longer average hospital stay was seen in the pre-protocol group (3.9 vs 3.6 days, p=0.027). Stays greater than 2 days were associated with a body mass index of greater than 30 kg/m2 on multivariate analysis. No complication in either group was attributable to fluoroscopic technique. CONCLUSIONS Implementing a decreased fluoroscopy protocol during percutaneous nephrostolithotomy resulted in an 80.9% reduction in fluoroscopy time while maintaining success rates, operative times and complications similar to those of the conventional technique. Adopting this reduced fluoroscopy protocol safely decreased radiation exposure to patients, surgeons and operating room staff during percutaneous nephrostolithotomy.

Detection of Uric Acid Stones in the Ureter Using Low- and Conventional-dose Computed Tomography

OBJECTIVE To determine the ability of low- and conventional-dose computed tomography (CT) in identification of uric acid stones, which are of lower density than calcium oxalate stones. MATERIALS AND METHODS Uric acid stones (3, 5, and 7 mm) were randomly placed in human cadaveric ureters and scanned using conventional 140-mAs and low-dose 70-, 50-, 30-, 15-, 7.5-, and 5-mAs settings. A single-blinded radiologist reviewed a total of 523 scanned stone images. Sensitivity and specificity were compared among different settings and stone sizes. RESULTS Imaging using 140-, 70-, 50-, 30-, 15-, 7.5-, and 5-mAs settings resulted in 97%, 97%, 96%, 93%, 83%, 83%, and 69% sensitivity and 92%, 92%, 91%, 89%, 88%, 91%, and 94% specificity, respectively. There was a significant difference in sensitivity between 140 mAs and 15, 7.5, and 5 mAs (P = .011, P = .011, and P <.001, respectively). Sensitivity for 3-, 5-, and 7-mm stones was 83%, 90%, and 93%, respectively. At ≤ 15 mAs, 3-mm stones had a higher rate of false negatives (P <.001). CONCLUSION Both low- and conventional-dose CTs demonstrate excellent sensitivity and specificity for the detection of ureteral uric acid stones. However, low-dose CT at ≤ 15 mAs resulted in reduced detection of uric acid 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.

In automated fluoroscopy settings, does shielding affect radiation exposure to surrounding unshielded tissues?

BACKGROUND AND PURPOSE Automatic brightness control (ABC), a function of modern fluoroscopy machines, adjusts radiation intensity in real time to enhance image quality. While shielding reduces radiation exposure to protected areas, it is unknown how much radiation adjacent unshielded areas receive when using ABC settings. Our purpose was to assess radiation dosage to shielded and unshielded tissue when using fluoroscopic ABC mode compared with fixed exposure settings. MATERIALS AND METHODS In a simulated ureteroscopy, thermoluminescent dosimeters (TLDs) were placed at three sites in a female human cadaver, including the right renal hilum, right distal ureter adjacent to the uterus, and directly over the uterus. The cadaver received 60 seconds of radiation exposure using a C-arm fluoroscopy system under ABC and fixed settings (1.38 mAs, 66 kVp) with and without uterine shielding. Radiation dosage absorbed by the TLDs was compared using two-way analysis of variance and least-squares confidence intervals. RESULTS Shielding significantly reduced radiation dose to the uterus by 62% and 82% (P<0.05 for both) in ABC and fixed settings, respectively. Shielding of the uterus in ABC, however, resulted in an approximately twofold increase in radiation dosage to the ureter and ipsilateral kidney (P<0.05 for both) and a decrease in image quality. Using fixed settings, shielding of the uterus did not increase radiation dose to the ipsilateral ureter and kidney. CONCLUSION There is a significant increase in radiation dosage to surrounding tissues when shielding is used with ABC mode during fluoroscopy. Radiation can be reduced and image quality improved by using fixed settings when shielding is indicated.