Jason C. Smith

Effect of Low Dose Radiation Computerized Tomography Protocols on Distal Ureteral Calculus Detection

PURPOSE Unenhanced multidetector computerized tomography is the imaging modality of choice for urinary calculi but exposes patients to substantial radiation doses with a subsequent risk of radiation induced secondary malignancy. We compared ultra low dose and conventional computerized tomography protocols for detecting distal ureteral calculi in a cadaveric model. MATERIALS AND METHODS A total of 85 calcium oxalate stones 3 to 7 mm long were prospectively placed in 14 human cadaveric distal ureters in 56 random configurations. The intact kidneys, ureters and bladders were placed in a human cadaveric vehicle and computerized tomography was performed at 140, 100, 60, 30, 15 and 7.5 mA seconds while keeping other imaging parameters constant. Images were independently reviewed in random order by 2 blinded radiologists to determine the sensitivity and specificity of each mA second setting. RESULTS Overall sensitivity and specificity were 98% and 83%, respectively. Imaging using 140, 100, 60, 30, 15 and 7.5 mA second settings resulted in 98%, 97%, 97%, 96%, 98% and 97% sensitivity, and 83%, 83%, 83%, 86%, 80% and 84% specificity, respectively. Interobserver agreement was excellent (kappa >0.87). There was no significant difference in sensitivity or specificity at any mA second settings. All false-negative results were noted for 3 mm calculi at a similar frequency at each mA second setting. CONCLUSIONS Ultra low dose computerized tomography protocols detected distal ureteral calculi in a fashion similar to that of conventional computerized tomography protocols in a cadaveric model. These protocols may decrease the radiation dose up to 95%, reducing the risk of secondary malignancies.

Randomized Clinical Trial Comparing Proton Beam Radiation Therapy with Transarterial Chemoembolization for Hepatocellular Carcinoma: Results of an Interim Analysis.

PURPOSE To describe results of a planned interim analysis of a prospective, randomized clinical trial developed to compare treatment outcomes among patients with newly diagnosed hepatocellular carcinoma (HCC). METHODS AND MATERIALS Eligible subjects had either clinical or pathologic diagnosis of HCC and met either Milan or San Francisco transplant criteria. Patients were randomly assigned to transarterial chemoembolization (TACE) or to proton beam radiation therapy. Patients randomized to TACE received at least 1 TACE with additional TACE for persistent disease. Proton beam radiation therapy was delivered to all areas of gross disease to a total dose of 70.2 Gy in 15 daily fractions over 3 weeks. The primary endpoint was progression-free survival, with secondary endpoints of overall survival, local tumor control, and treatment-related toxicities as represented by posttreatment days of hospitalization. RESULTS At the time of this analysis 69 subjects were available for analysis. Of these, 36 were randomized to TACE and 33 to proton. Total days of hospitalization within 30 days of TACE/proton was 166 and 24 days, respectively (P<.001). Ten TACE and 12 proton patients underwent liver transplantation after treatment. Viable tumor identified in the explanted livers after TACE/proton averaged 2.4 and 0.9 cm, respectively. Pathologic complete response after TACE/proton was 10%/25% (P=.38). The 2-year overall survival for all patients was 59%, with no difference between treatment groups. Median survival time was 30 months (95% confidence interval 20.7-39.3 months). There was a trend toward improved 2-year local tumor control (88% vs 45%, P=.06) and progression-free survival (48% vs 31%, P=.06) favoring the proton beam treatment group. CONCLUSIONS This interim analysis indicates similar overall survival rates for proton beam radiation therapy and TACE. There is a trend toward improved local tumor control and progression-free survival with proton beam. There are significantly fewer hospitalization days after proton treatment, which may indicate reduced toxicity with proton beam therapy.

Fluoroscopic Organ and Tissue-Specific Radiation Exposure by Sex and Body Mass Index During Ureteroscopy

INTRODUCTION Although radiation exposure from CT and plain film imaging has been characterized, the radiation received by patients during modern-era fluoroscopy has not been well described. The purposes of this study were to measure absolute organ and tissue-specific radiation doses during ureteroscopy and to determine the influence of body mass index (BMI) and sex on these doses. MATERIALS AND METHODS Eight cadavers underwent a simulated left ureteroscopy. Using a modern C-arm with automatic exposure control settings, thermoluminescent dosimeters were exposed for a fluoroscopy time of 145 seconds (mean time of clinical ureteroscopies from 2006 to 2008). Total tissue exposures were compared by BMI and between sexes using the Wilcoxon signed ranks test and the Mann-Whitney test with p < 0.05 considered significant. RESULTS Among all cadavers, radiation doses were significantly lower in all contralateral organs excluding the gonad (p < 0.012). Doses were similar bilaterally in the gonad in cadavers with BMI <30, and in all organs in cadavers with BMI >30 (p > 0.05). There were significantly higher mean bilateral gonadal doses in female cadavers (3.4 mGy left and 1.9 mGy right) compared with male cadavers (0.36 mGy left and 0.39 mGy right). The highest cancer risk increase was seen at the posterior skin equivalent to 104 additional cancers per 100,000 patients. CONCLUSION Contralateral doses were lower for all organs except the gonad when the BMI was <30. In contrast, when the BMI was >30, there was no difference in radiation dose delivered to the ipsilateral and contralateral organs. Gonadal doses were significantly higher in female cadavers. Modern-era fluoroscopy remains a significant source of radiation exposure and steps should be taken to minimize exposure during ureteroscopy.

Increased plasma nitric oxide, L-arginine, and arginase-1 in cirrhotic patients with progressive renal dysfunction

Background and Aims:  Increased levels of nitric oxide (NO) are hypothesized to contribute to renal dysfunction in patients with decompensated cirrhosis. In this study, we examined whether splanchnic and/or peripheral NO levels and L‐arginine (L‐Arg) correlate with progressive renal dysfunction in cirrhotics.

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.

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.

Angioplasty or Stent Placement in the Proximal Common Iliac Artery: Is Protection of the Contralateral Side Necessary?

PURPOSE To determine if protection of the contralateral common iliac artery is necessary when performing angioplasty or stent placement in a proximal common iliac artery. MATERIALS AND METHODS A retrospective review of all patients undergoing endovascular treatment for unilateral common iliac artery stenosis or occlusion from 1979 to 2000 was performed. All angiograms were reviewed independently by three experienced vascular interventional radiologists who evaluated both common iliac arteries before and after angioplasty or stent placement. RESULTS The medical records or angiograms of 514 patients were located. Of these, complete records and angiograms were found for 175 patients who underwent proximal (within 2 cm of its origin) common iliac artery angioplasty or stent placement without treatment or protection of the contralateral common iliac artery. Treatment of proximal common iliac stenosis in 160 patients resulted in luminal compromise of the contralateral common iliac in two patients (17% and 24% reduction in luminal diameter). No contralateral compromise was noted in 15 patients treated for iliac occlusion. CONCLUSION The data reported herein suggest that protection of the contralateral common iliac artery during angioplasty or stent placement in a proximal common iliac artery is not mandatory.

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.

Postprocedural Aspiration Test to Predict Adequacy of Dialysis Following Tunneled Catheter Placement

The objective of the study was to determine if a timed aspiration technique with a 20-ml syringe can be used to predict adequacy of blood flow in tunneled dialysis catheters. Sixteen patients referred for de novo placement or manipulation of failing tunneled hemodialysis catheters had the time it takes to fill a 20-ml syringe with the plunger fully withdrawn measured to the nearest tenth of a second. These measurements were correlated with flow rates recorded in dialysis just prior to (if failed catheter) and in the following dialysis session with adequacy determined as at least 300 ml/min. Syringe-filling time (22 catheters in 16 patients) was plotted against adequacy of dialysis. The mean time to fill a 20-ml syringe was 2.2 sec, with a range of 1.0–4.7 sec. The mean time to fill syringes for catheters with adequate dialysis was 1.7 ± 0.5 sec, and for inadequate catheters, it was 2.8 ± 0.8 sec. These differences are statistically significant (p < 0.001). Using a filling time of greater than or equal to 2 sec as a threshold gives the highest sensitivity (100%) for predicting inadequate dialysis while maintaining high specificity (75%). To achieve a specificity of 100%, a 3-sec cutoff would be necessary, but would lead to a sensitivity of only 20%. A simple and objective aspiration technique can be performed at the time of tunneled dialysis catheter placement/manipulation to reasonably predict adequacy of subsequent dialysis.

Accuracy of digital subtraction angiography, computed tomography angiography, and magnetic resonance angiography in grading of carotid artery stenosis in comparison with actual measurement in an in vitro model.

BACKGROUND The aim of this study was to investigate the accuracy of digital subtraction angiography (DSA), computed tomography angiography (CTA), and magnetic resonance angiography (MRA) in grading of carotid stenosis compared with actual measurement in an in vitro model. METHODS Various grades of stenosis were created by adhering different amounts of silicone rubber sealant onto the inner wall of clear, radiolucent tubes. After DSA, CTA, and MRA, the tubes were transected with 1-mm interval through the plaques. The cross-sectional areas were digitally photographed, and the percentage of area reduction of every single slide was measured with ImageJ planimetric software. The maximum actual area reduction (AAR) stenosis of each tube was recorded. The differences among DSA, CTA, MRA, and AAR were compared statistically using paired Student t test. RESULTS Overall, CTA and MRA significantly underestimated the degrees of stenosis compared with AAR (P = 0.001 and P = 0.0009, respectively), and no significant difference was found between DSA and AAR (P = 0.40). In the subgroup with stenosis of <70%, there was no significant difference between DSA, CTA, and MRA versus AAR (P = 0.18, P = 0.16, and P = 0.08, respectively). In the subgroup with severe stenosis of >70%, CTA and MRA significantly underestimated the stenosis versus AAR (P = 0.004, and P = 0.007 respectively), and DSA significantly overestimated the stenosis (P = 0.0007). CONCLUSIONS This in vitro model study demonstrated that CTA and MRA underestimate the lesions in severe stenosis of >70%. DSA tends to overestimate the disease. The accuracy of DSA is affected by plaque morphology, such as mountain-shaped lesions.