A STUDY OF URINARY TRACT ABNORMALITIES: ROLE OF LOW DOSE MDCT UROGRAPHY

Introduction: Computed Tomography (CT) urography is more accurate in detection of renal masses, urinary tract tumors, inflammatory lesion, calculi and other causes of urinary tract obstruction compared with intravenous urography. The standard single bolus MDCT Urography protocol comprises three to four phases, consists of non-contrast, corticomedullary, nephrographic and excretory phases. A major disadvantage is a high radiation dose, which is 8-10 times higher than an IVP examination. In comparison, an split-bolus, dual-phase technique scans the urinary system in the non-contrast and combined nephrographic-excretory phases. This study aimed to compare the total CT radiation dose of patient and image quality in standard MDCTU protocol and low dose MDCTU protocol. Methodology: In this hospital based prospective study total 100 patients (50 tests and 50 controls) were compared for radiation dose and subjective image quality assessment between standard dose MDCTU protocol [non contrast scan at 120kvp , followed by contrast enhanced corticomedullary phase and excretory phase] and low dose MDCTU protocol (non contrast scan (at 80 kvp), followed by contrast enhanced synchronus corticomedullary phase and excretory phase acquisition by using split bolus contrast administration technique) . Result: In the standard dose MDCTU protocol in unenhanced and enhanced phase, patients received mean net effective dose of 18.83 mSv and in the low dose protocol, patients received mean net effective dose of 9.06 mSv with significant 52% dose reduction (P value <0.001). In Standard dose protocol in unenhanced phase, optimal resolution in 82% patients, moderately grainy/poor resolution in 14% and significantly grainy/very poor resolution in 4% patients. In low dose protocol, optimal resolution in 64% patients, mild to moderately grainy/poor resolution in 22% and significantly grainy/very poor resolution in 14% patients with no significant difference in image quality in both protocol (P value>0.05). In low dose protocol, mild to moderately grainy/poor resolution images (22%) of unenhanced phase reviewed together with normal dose good qualitysynchronus corticomedullary and excretory phase images to diagnosis the almost same spectrum of pathology like standard dose protocol. Conclusion: In low dose MDCT Urography radiation dose reduction of approx 50% is possible with no significant difference in image quality in line to ALARA principle (As low as reasonably achievable), facilitating diagnosis of urological pathologies.