Category: Clinical Stones: Outcomes

MP8-9 - Standard vs Low-dose CT following Nephrolithiasis Treatment: A Head to Head Comparison

Fri, Sep 21
10:00 AM - 12:00 PM

Introduction & Objective :

Standard dose CT scan (SCT) provides the most accurate imaging following nephrolithiasis treatment. However, due to the high radiation dose associated with SCT ultrasound or x-ray has been often utilized in its place despite inferior imaging quality. Low dose CT (LCT) presents a promising compromise of improved imaging detail at a significantly lower radiation dose. As such, we sought to compare the accuracy of LCT to SCT using a prospective within-subject experimental design.


 


Methods :

After IRB approval, clinical and imaging data were prospectively collected from twenty patients over age 40, who underwent nephrolithiasis treatment between October 2017 and March 2018. Each patient underwent SCT immediately followed by LCT. Both sets of images from each patient were then anonymized and randomized prior to review by a board certified radiologist. Stone size was measured using the largest dimension on axial images of each stone and site-specific (upper pole, mid pole, lower pole, ureter) stone measurements were calculated by adding the sizes of all stones at that site. Effective doses of radiation were estimated using the dose-length-product. Differences in radiation dose, site-specific stone measurements and total stone measured, were compared across CT type.  Site-specific stone measurements were considered to be concordant if the difference in measurements between CT types was less than 3mm. All-site concordance rates and the concordance correlation coefficient (CCC) were then calculated.  


Results :

40% of patients were male, with a median age of 54.7 (IQR 43.3, 66.5) and a median BMI of 30 (IQR 27.6, 33.1). The mean effective dose of radiation for LCT was significantly lower than that of SCT (3.2mSv vs 10.2mSv, p<0.01).The average total stone measurements were noted to be 19.6mm on SCT and 21.1mm on LCT (p=0.67). No significant differences were noted between site-specific mean stone measurements (Table). The mean difference between total stone measurements on SCT vs LCT was found to be 8.4mm (SD 13.0mm). The all-site concordance rate was noted to be 78.6% between SCT and LCT with a CCC of 0.81 (p<0.01).


Conclusions :

LCT provides axial imaging using a significantly lower radiation dose than SCT with no statistically significant difference in site-specific and total mean stone volume measurements noted between CT types. Measurements were concordant within 3mm at all-sites in 78.6% of exams and excellent concordance between modalities was demonstrated by the all-site CCC of 0.81. Given these results, LCT may prove to be a viable alternative for postoperative imaging with excellent imaging quality and a significantly lower radiation dose than SCT.

Jorge Pereira

Minimally Invasive Urology Fellow
Minimally Invasive Urology Institute, Alpert Medical School at Brown University
Providence, Rhode Island

David Grand

Associate Professor of Diagnostic Imaging and Director of Body Imaging
Department of Radiology, Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Ohad Kott

Research Fellow
Minimally Invasive Urology Institute, The Miriam Hospital; The Warren Alpert Medical School at Brown University, Division of Urology
Providence, Rhode Island

Ohad Kott, MD, MHA. Research Fellow, Minimally Invasive Urology Institute, The Miriam Hospital; The Warren Alpert Medical School at Brown University, Providence, RI USA. Dr. Kott earned his undergraduate and graduate degrees in medical science from Sackler Medical School at Tel-Aviv University where he later completed his medical education. Prior to getting his MD, he earned his MBA and graduated cum laude with his Masters in Health Administration from Tel-Aviv University. His main fields of interest are endourology and urologic oncology.

Eric Jung

Resident
Department of Urology, Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Timothy Wright

Medical Student
Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Meredith Wasserman

Resident
Department of Urology, Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Alejandra Balen

Resident
Department of Urology, Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Paul Bower

Resident
Department of Urology, Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Christopher Tucci

Program Manager
Minimally Invasive Urology Institute, The Miriam Hospital
Providence, Rhode Island

Simone Thavaseelan

Assistant Professor of Surgery (Urology)
Department of Urology, Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

Gyan Pareek

Associate Professor of Surgery (Urology), Director of Minimally Invasive Urologic Surgery
Minimally Invasive Urology Institute, Alpert Medical School at Brown University
Providence, Rhode Island