2076 SPECIFIC ORGAN DOSES UTILIZING A NEW TECHNIQUE FOR IMAGING NEPHROLITHIASIS: DIGITAL TOMOSYNTHESIS

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THE JOURNAL OF UROLOGY姞

Vol. 189, No. 4S, Supplement, Wednesday, May 8, 2013

that collagen is 14% Hyp and all of the body flux of Hyp is derived from the breakdown of endogenous collagen, total body flux of collagen is approximately twice that previously estimated. Source of Funding: NIH grants R01DK83527 and U54DK83908

2076 SPECIFIC ORGAN DOSES UTILIZING A NEW TECHNIQUE FOR IMAGING NEPHROLITHIASIS: DIGITAL TOMOSYNTHESIS Andreas Neisius, Gaston M. Astroza, Nicholas J. Kuntz*, Agnes J. Wang, Giao Nguyen, Chu Wang, Natalie Januzis, Amy M. Neville, Greta Toncheva, Ramy Youssef, Muhammad W. Iqbal, Michael N. Ferrandino, Terry T. Yoshizumi, Glenn M. Preminger, Michael E. Lipkin, Durham, NC INTRODUCTION AND OBJECTIVES: Digital tomosynthesis (DT) is a novel imaging technique for the evaluation of patients of with nephrolithiasis. It consists of a plain abdominal radiograph (KUB) and one tomographic sweep. Software is used to recreate a series of coronal images from the tomographic sweep. We determined organ specific dose and effective dose (ED) for DT and compared it to our institutional “low dose” non contrast computed tomography (NCCT). METHODS: A validated anthropomorphic male phantom was placed supine on a GE Definium 8000 CT scanner. High sensitivity metal oxide semiconductor field effect transistors (MOSFET) dosimeters were placed at 20 organ locations and used to measure organ doses (OD). A routine DT study was performed consisting of two KUB (scout) images and one tomographic sweep in a 60 degree arc over the phantom. OD were determined as the sum of the doses for the study. Equivalent doses were calculated by multiplying OD and the appropriate tissue weighting factor. ED was calculated by the summation of the equivalent doses. OD and ED were determined in a similar fashion for a renal stone protocol NCCT and the doses were compared. RESULTS: Specific organ doses for DT (2 scouts and 1 tomographic sweep) and NCCT are shown in the table. The ED for NCCT is 3.04 (⫾0.34) mSv. The calculated ED for digital tomosynthesis is 0.54 (⫾0.07) mSv (2 scouts at 0.10mSv and 0.08mSv ⫹ 1 sweep at 0.36mSv), p⫽0.0002. CONCLUSIONS: Digital tomosynthesis exposes patients to substantially less radiation than NCCT. This is particularly true for radiation sensitive organs. Further studies are needed to compare the sensitivity and specificity of DT as compared to NCCT. However, its low overall radiation dose make it an ideal study for the follow up of the recurrent stone former in the office setting.

Table: Exemplary organ doses (OD) from NCCT (stone protocol) compared to DT Digital tomosynthesis Organs NCCT (⫹/⫺ SD) (⫹/⫺ SD) p value Skin entrance 7.23 (⫹/⫺0.51) mGy 9.69 (⫹/⫺0.43) mGy 0.0031 Lungs Red bone marrow

3.05 (⫹/⫺1.26) mGy

6.40 (⫹/⫺0.61) mGy

0.0143

3.2 (⫹/⫺0.1) mGy

0.81 (⫹/⫺0.15) mGy

⬍ 0.0001

Testes

5.17 (⫹/⫺3.73) mGy

0.12 (⫹/⫺0.21) mGy

0.0793

Liver

4.28 (⫹/⫺0.24) mGy

4.26 (⫹/⫺4.07) mGy

0.9960

Kidney

5.18 (⫹/⫺0.47) mGy

2.10 (⫹/⫺1.16) mGy

0.0130

Source of Funding: This work has been supported in part by a Ferdinand Eisenberger grant of the Deutsche Gesellschaft für Urologie (German Society of Urology), grant ID NeA1/FE-11 (Andreas Neisius)

2077 NON-CONTRAST CT ATTENUATION VALUE OF RENAL PAPILLA PREDICTS THE SEVERITY AND RECURRENCE OF KIDNEY STONE DISEASE Yasuo Kohjimoto*, Akinori Iba, Satoshi Nishizawa, Nagahide Matsumura, Isao Hara, Wakayama, Japan INTRODUCTION AND OBJECTIVES: In idiopathic calcium stone formers (ICSFs), most stones are known to grow attached to Randall’s plaque, which can be identified by measuring computed tomography (CT) attenuation value of renal papilla. The purpose of the present study was to test the hypothesis that CT attenuation value of renal papilla can predict the severity and recurrence of the stone disease. METHODS: We retrospectively reviewed the charts of ICSFs who underwent non-contrast CT scan from May 2010 to April 2011. Two observers independently measured the Hounsfield unit (HU) of the renal papilla from the upper pole, middle region and lower pole in both kidneys. Patients were classified into high- and low-HU value groups based on the mean HU values of all papillae. The median value was used for differentiation. Proportions of patients with severe disease (recurrent and/or multiple stones), urine chemistries and recurrence rates were compared between the groups. RESULTS: A total of 80 patients, 50 men and 30 women, were included in the analysis. Median HU value of all papillae was 50.5. The proportion of patients with recurrent and/or multiple stones was significantly higher in high-HU group compared to low-HU group (p⬍0.01). No significant differences were noted in urine parameters except for urinary uric acid. Recurrence rate in high-HU value group (0.40 personyear) was higher than that of low-HU value group (0.23, p⫽0.11). CONCLUSIONS: These results demonstrated that the HU value of renal papilla was correlated with disease severity and recurrence in ICSFs. This may allow us to identify patients with a higher risk of recurrent stone formations and change the clinical management of these patients if necessary. Low-HU (⬍ 50.5) group Recurrent and/or multiple stones, %

High-HU (ⱖ 50.5) group

p⫽

40

90

⬍ 0.01

U-Volume, mL/day

1694 ⫾ 548

1428 ⫾ 650

0.25

U-oxalate, mg/day

32 ⫾ 19

38 ⫾ 23

0.42

U-calcium, mg/day

190 ⫾ 111

197 ⫾ 108

0.86

U-uric acid, mg/day

621 ⫾ 220

424 ⫾ 141

⬍ 0.01

79 ⫾ 30

79 ⫾ 32

0.94

U-citrate, mg/day

453 ⫾ 314

566 ⫾ 843

0.65

AP(CaOx)

0.80 ⫾ 0.49

1.13 ⫾ 0.71

0.17

0.23 (0.12 - 0.39)

0.40 (0.24 - 0.63)

0.11

U-magnesium, mg/day

Recurrence rate, person-year (95% confidence interval)

Source of Funding: None

2078 IS TOTAL ABDOMINAL EXPOSURE DURING NON-CONTRAST COMUTERIZED TOMOGRAPHY (NCCT) NECESSARY AS FOLLOW -UP(F-U) OF PATIENTS WITH URETERAL STONES?! Avi Stein, Yuval Freifeld*, ofir Avitan, Roni Molnar, Yoel Mecz, Dmitri Goldin, Tal May, Ilan Klein, Hashul Sharbal, Moad Yichie, Mati Shnap, Nathan Peled, Yoram Dekel, Haifa, Israel INTRODUCTION AND OBJECTIVES: Ureteral calculi are a common and recurrent clinical emergency in younger patients. The calculi are frequently progressing downstream and some get expelled spontaneously. Repeated NCCT involving radiation exposures are therefore often needed in the course of the same and in recurrent episodes. The issue of X-ray potential accumulated risk has been widely described. We conducted a prospective study in which a batch was formed from the f-u NCCT including only “slices” distal to the