1511Vol. 11 | No. 02 | March- April 2014 |U R O LO G Y J O U R N A L Digital Tomosynthesis: An Innovative Tool for Challenging Diagnoses in Urology Alexis Lacout,1 Pierre Yves Marcy2 Corresponding Author: Alexis Lacout, MD Centre d’imagerie Médicale 47, Boulevard du Pont Rouge, 15000 Aurillac, France. Tel: +33 471 480050 Fax: +33 471 485348 E-mail: lacout.alexis@wanadoo.fr Received December 2012 Accepted November 2012 1 Centre d’imagerie Médicale 47, Boulevard du Pont Rouge, 15000 Aurillac, France. 2 Polyclinique Les Fleurs, Service Imagerie Médicale, 332 Avenue Frederic Mistral, 83190 Ollioule, France. CASE REPORT Keywords:‎nephrolithiasis;‎radiography;‎tomography,‎x-ray‎computed;‎methods;‎radiographic‎ image‎enhancement INTRODUCTION Digital‎tomosynthesis‎(DTS)‎allows‎the‎visualization‎of‎dilated‎renal‎cavities‎with-out‎need‎of‎contrast‎medium‎injection‎and‎better‎shows‎ureteral‎and‎kidney‎stones‎than‎standard‎abdominal‎X-ray.‎From‎now‎on,‎digital‎tomosynthesis‎is‎indeed‎re- vival‎of‎the‎old‎‘conventional’’‎tomography‎technique‎that‎progressively‎has‎become‎obso- lete.‎The‎strong‎growth‎and‎development‎of‎digital‎radiology‎and‎plane‎sensors‎has‎led‎to‎ give‎birth‎to‎this‎innovative‎imaging‎technique,‎which‎may‎soon‎be‎part‎of‎the‎standard‎initial‎ work‎up‎and‎follow-up‎of‎patients‎with‎ureteral‎and‎kidney‎stone. CASE REPORT A‎60‎year-old‎man‎was‎referred‎to‎our‎institution‎for‎left‎flank‎pain‎assessment‎occurring‎after‎ a‎left‎renal‎stone‎lithotripsy‎(Figure‎1).‎Ultrasonography‎(US)‎examination‎revealed‎the‎pres- ence‎of‎bilateral‎intra-renal‎stones‎as‎well‎as‎a‎dilation‎of‎the‎left‎renal‎pyelocalyceal‎cavities.‎ However,‎no‎obstacle‎was‎shown‎on‎the‎urinary‎tract.‎Conventional‎X-ray‎examination‎(Figure‎ 1512 | 2)‎suggested‎the‎presence‎of‎kidney‎stones.‎DTS‎(SonialVi- sion‎Safire;‎Shimadzu‎Co.,‎Kyoto,‎Japan)‎(Figure‎3)‎exami- nation‎of‎the‎abdomen‎confirmed‎the‎intra-renal‎location‎of‎ the‎stones‎that‎were‎already‎shown‎on‎US‎and‎also‎formally‎ disclosed‎the‎presence‎of‎three‎other‎obstructive‎stones‎into‎ the‎ left‎ ureter‎ lumen.‎Although‎ DTS‎ has‎ been‎ performed‎ without‎contrast‎medium‎injection,‎this‎innovative‎technique‎ was‎prone‎to‎demonstrate‎the‎dilation‎of‎the‎left‎pyelocal- yceal‎cavities.‎ DISCUSSION DTS‎is‎a‎technical‎evolution‎of‎conventional‎geometric‎to- mography.‎It‎allows‎the‎production‎of‎as‎many‎high‎spatial‎ resolution‎slice-images‎(200‎μm‎in‎the‎acquisition‎plane)‎as‎ necessary‎ following‎ a‎ single‎ low-dose‎ acquisition.(1)‎ This‎ technique‎ uses‎ a‎ flat-panel‎ detector‎ and‎ a‎ computer-con- trolled‎moving‎X-ray‎tube.‎The‎patient‎is‎laying‎on‎the‎table,‎ in‎the‎desired‎position‎(supine‎or‎prone‎position‎when‎frontal‎ views‎are‎required,‎lateral‎position‎if‎sagittal‎views‎are‎need- ed).‎Breath‎hold‎is‎required‎to‎avoid‎motion‎artifacts‎of‎the‎ patient.‎During‎acquisition,‎the‎X-ray‎tube‎moves‎through‎a‎ 40-degree‎(-20‎to‎+20‎degrees)‎circular‎arc‎symmetric‎over‎ the‎patient.‎At‎the‎same‎time,‎the‎plane‎sensor‎synchronously‎ moves‎inside‎the‎table.‎Several‎parameters‎can‎be‎modified:‎ kV,‎mA,‎the‎number‎of‎pulses‎per‎second‎(X-ray‎emission‎is‎ discontinuous‎or‎‘‘pulsed’’),‎the‎duration‎(2.5‎to‎5‎s),‎center‎ and‎total‎thickness‎of‎the‎volume‎acquisition.‎Median‎slice‎ thickness‎is‎not‎precisely‎quantifiable‎(about‎ten‎millimeter)‎ but‎can‎be‎roughly‎modified‎(++,‎+,‎±,‎-,‎--).‎Interestingly,‎ specific‎algorithms‎allow‎reconstruction‎of‎slice-images‎par- allel‎to‎the‎central‎projection‎throughout‎the‎entire‎volume‎of‎ the‎patient.‎A‎posteriori‎post-processing‎reformations‎can‎be‎ produced‎at‎different‎places‎in‎the‎acquisition‎volume,‎de- creasing‎or‎increasing‎the‎number‎of‎slices‎at‎will. ‎DTS‎allows‎an‎accurate‎exploration‎with‎low‎radiation‎dose‎ exposure‎i.e.‎ lower‎than‎with‎computed‎tomography‎(CT)‎ scan,(2)‎equivalent‎to‎two‎standard‎X-ray‎procedures.(3) Ac- cording‎to‎the‎literature‎data,‎an‎effective‎dose‎is‎in‎the‎order‎ of‎0.85‎millisieverts‎(mSv),‎to‎be‎compared‎to‎0.5‎mSv‎with‎ digital‎radiography,‎and‎2.5‎mSv‎with‎low-dose‎CT‎scan,‎and‎ 12.6‎mSv‎with‎high-dose‎CT‎scan.(4) However,‎major‎drawbacks‎include‎low‎resolution‎in‎density‎ of‎tomosynthesis‎compared‎to‎CT‎scan,‎and‎inability‎to‎pro- duce‎multiplanar‎(plane‎to‎plane)‎reformations.‎Indeed,‎the‎ Case Report Figure 1. Computed tomography scan, frontal 11 mm thick maximum intensity projection reformation performed before lithotripsy, showing bilateral renal stones (arrows). Figure 2. Supine abdominal radiograph performed after litho- tripsy of the left renal stone showing renal stones (arrows). Note the anatomical superimpositions of colonic gas and faces. 1513Vol. 11 | No. 02 | March- April 2014 |U R O LO G Y J O U R N A L Digital Tomosynthesis in Urology | Lacout et al higher‎performances‎of‎DTS‎compared‎to‎standard‎X-‎ray‎ in‎the‎evaluation‎of‎renal‎stones‎include‎its‎very‎high‎spatial‎ resolution‎and‎the‎absence‎of‎anatomical‎superimpositions‎ of‎feces.(3)‎In‎the‎near‎future,‎DTS‎may‎thus‎replace‎conven- tional‎X-ray,‎at‎initial‎work‎up‎and‎in‎some‎cases‎at‎follow- up,‎thus‎limiting‎excessive‎irradiation‎exposure.‎In‎addition,‎ DTS‎may‎be‎more‎advantageous‎than‎CT‎scan‎examination‎ from‎a‎medico-economic‎point‎of‎view.‎ CONFLICT OF INTEREST None declared. Figure 3. Abdominal digital tomosynthesis performed after left renal stone lithotripsy; (A) showing intra- renal stones (arrows) and the dilation of the left pyelocalyceal cavities (double arrow), (B) magnification shows three persistent obstructive ureteral stones despite previous left renal stone lithotripsy fragmentation (arrows). REFERENCES 1. Dobbins JT 3rd, McAdams HP. Chest tomosynthesis: technical prin- ciples and clinical update. Eur J Radiol. 2009;72 :244-51. 2. Koyama S, Aoyama T, Oda N, Yamauchi-Kawaura C. Radiation dose evaluation in tomosynthesis and C-arm cone-beam CT examina- tions with an anthropomorphic phantom. Med Phys. 2010;37:4298- 306. 3. Mermuys K, De Geeter F, Bacher K, et al. Digital tomosynthesis in the detection of urolithiasis: Diagnostic performance and dosime- try compared with digital radiography with MDCT as the reference standard. AJR Am J Roentgenol. 2010;195:161-7. 4. Mermuys K, De Geeter F, Bacher K, et al. 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