Comparative Evaluation of Diagnostic Quality in Native Low-dose CT without and with Spectral Shaping employing a Tin Filter in Urolithiasis with implanted Ureteral Stent

Abstract

Purpose Spectral shaping employing a tin filter can be used for dose reduction in CT of the abdomen in patients with urolithiasis. As ureteral stents may be in direct contact with the calculus, a good image quality is mandatory. The goal of this study was to obtain data of the effect of tin filtering on image quality and dose in patients with urolithiasis in direct contact with ureteral stents.

Materials and Methods 84 examinations (conventional low dose vs. modified low dose protocol with tin filtering, randomized) were performed in 65 patients (48 men, 17 women, age 55.0 ± 15.2 years (18–90 years), maximum of one examination per protocol). Image quality and visibility of the calculus was rated on a 5-point-Likert scale by 2 experienced radiologists. Quantitative indicators of image quality were signal-to-noise-(SNR) and contrast-to-noise-ratios (CNR) as well as a figure-of-merit (FOM).

Results With a non-inferiority margin of 0.5 points of the 5-point Likert scale, there was non-inferiority of the examinations with tin filter regarding image quality (95 % CI 4.1–4.3, rejection limit 3.5). Non-inferiority regarding visibility of the calculus could be shown (calculus size: 1–2.4 mm: 95 % CI 3.39–4.12; limit 2.73; 2.4–3.8mm: 95 % CI 4.09–4.47; limit 3.65; > 3.8mm: all maximal ratings). Average values of CNR were significantly higher using tin filters (17.0 vs. 10.6). Doses were significantly reduced in the modified protocol (effective dose 1.2 mSv vs. 1.5 mSv; size-specific dose estimate 2.33 mGy vs. 3.09 mGy) with non-significant effect in the subgroup of patients with BMI ≥ 35.

Conclusion Even with direct contact between a calculus and ureteral stent, radiation reduced examinations by spectral shaping by tin filters are non-inferior to examinations without tin filtering at a concurrent significant dose reduction.

Key points: 

• Spectral shaping by tin filter is suitable for dose reduction.

• The image quality in patients with ureteral stents with tin filtering is non-inferior to that in a conventional low-dose protocol.

Citation Format

• Axer B, Garbe S, Hadizadeh DR. Comparative Evaluation of Diagnostic Quality in Native Low-dose CT without and with Spectral Shaping employing a Tin Filter in Urolithiasis with implanted Ureteral Stent. Fortschr Röntgenstr 2022; 194: 1358 – 1366

Key words

urolithiasis - dose-reduction - CT - ureteral stent - tin-filter

Publication History

Received: 11 February 2022

Accepted: 04 May 2022

Article published online:
18 July 2022

• References

• 1 Robert Koch Institut. Gesundheitsberichterstattung des Bundes. Diagnosedaten der Krankenhäuser ab 2000. Im Internet (Stand: 20.06.2021): https://www.gbe-bund.de/gbe/pkg_isgbe5.prc_menu_olap?p_uid=gast&p_aid=10932625&p_sprache=D&p_help=3&p_indnr=550&p_indsp=&p_ityp=H&p_fid=
• 2 Deutsche Gesellschaft für Urologie. 043-025l_S2k_Diagnostik_Therapie_Metaphylaxe_Urolithiasis_2019-07_1.
• 3 Tang VCY, Attwell-Heap A. Computed tomography versus ureteroscopy in identification of renal tract stone with ureteral stent in situ. Ann R Coll Surg Engl 2011; 93: 639-641 DOI: 10.1308/003588411X13165261993996.
• 4 Chen TT, Wang C, Ferrandino MN. et al. Radiation Exposure during the Evaluation and Management of Nephrolithiasis. J Urol 2015; 194: 878-885 DOI: 10.1016/j.juro.2015.04.118.
• 5 Bodelle B, Fischbach C, Booz C. et al. Single-energy pediatric chest computed tomography with spectral filtration at 100 kVp: effects on radiation parameters and image quality. Pediatr Radiol 2017; 47: 831-837 DOI: 10.1007/s00247-017-3813-1.
• 6 Braun FM, Johnson TRC, Sommer WH. et al. Chest CT using spectral filtration: radiation dose, image quality, and spectrum of clinical utility. Eur Radiol 2015; 25: 1598-1606 DOI: 10.1007/s00330-014-3559-1.
• 7 Leyendecker P, Faucher V, Labani A. et al. Prospective evaluation of ultra-low-dose contrast-enhanced 100-kV abdominal computed tomography with tin filter: effect on radiation dose reduction and image quality with a third-generation dual-source CT system. Eur Radiol 2019; 29: 2107-2116 DOI: 10.1007/s00330-018-5750-2.
• 8 Saltybaeva N, Krauss A, Alkadhi H. Technical Note: Radiation dose reduction from computed tomography localizer radiographs using a tin spectral shaping filter. Med Phys 2019; 46: 544-549 DOI: 10.1002/mp.13353.
• 9 Dewes P, Frellesen C, Scholtz J-E. et al. Low-dose abdominal computed tomography for detection of urinary stone disease – Impact of additional spectral shaping of the X-ray beam on image quality and dose parameters. Eur J Radiol 2016; 85: 1058-1062 DOI: 10.1016/j.ejrad.2016.03.016.
• 10 Mozaffary A, Trabzonlu TA, Kim D. et al. Comparison of Tin Filter-Based Spectral Shaping CT and Low-Dose Protocol for Detection of Urinary Calculi. Am J Roentgenol 2019; 212: 808-814 DOI: 10.2214/Am J Roentgenol.18.20154.
• 11 Zhang G-M-Y, Shi B, Sun H. et al. High-pitch low-dose abdominopelvic CT with tin-filtration technique for detecting urinary stones. Abdom Radiol (NY) 2017; 42: 2127-2134 DOI: 10.1007/s00261-017-1103-x.
• 12 Likert R. A technique for the measurement of attitudes. Arch Psychol 1932; 140: 1-55
• 13 Bright DS, Newbury DE, Steel EB. Visibility of objects in computer simulations of noisy micrographs. J Microsc 1998; 189: 25-42 DOI: 10.1046/j.1365-2818.1998.00249.x.
• 14 [Anonym]. AAPM Report No. 96: The Measurement, Reporting, and Management of Radiation Dose in CT.
• 15 [Anonym]. AAPM Report No. 204: Size-Specific Dose Estimates (SSDE) in Pediatric and Adult Body CT Examinations.
• 16 Ahn S, Park SH, Lee KH. How to demonstrate similarity by using noninferiority and equivalence statistical testing in radiology research. Radiology 2013; 267: 328-338 DOI: 10.1148/radiol.12120725.
• 17 Head SJ, Kaul S, Bogers AJJC. et al. NI study design: lessons to be learned from cardiovascular trials. Eur Heart J 2012; 33: 1318-1324 DOI: 10.1093/eurheartj/ehs099.
• 18 Schumi J, Wittes JT. Through the looking glass: understanding NI. Trials 2011; 12: 106 DOI: 10.1186/1745-6215-12-106.
• 19 Wang. Confidence interval for the mean of non‐normal data.
• 20 Schubert G. Stone analysis. Urol Res 2006; 34: 146-150 DOI: 10.1007/s00240-005-0028-y.
• 21 van Straten M, Schaap M, Dijkshoorn ML. et al. Automated bone removal in CT angiography: comparison of methods based on single energy and dual energy scans. Med Phys 2011; 38: 6128-6137 DOI: 10.1118/1.3651475.
• 22 Mayer C, Meyer M, Fink C. et al. Potenzial for radiation dose savings in abdominal and chest CT using automatic tube voltage selection in combination with automatic tube current modulation. Am J Roentgenol 2014; 203: 292-299 DOI: 10.2214/Am J Roentgenol.13.11628.