This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Radiation exposure is the least in the following procedure: 
Select and explain. 
A. Micturating cystourethrogram, B. IVP, C. bilateral nephrostomogram, D. Spiral CT for stones
A: Micturating cystourethrogram
Answer: A: Micturating cystourethrogram 
Explanation: Micturating cystourethrogram [Ref: website of 'International atomic energy agency' at address: rpop.iaea.org/RPOP/RPoP/Content/InfonnationFor/HealthProfessionals/623therClinicalSpecialities/Urology/index.h un; Revised radiation doses for typical x-ray examinations, Br. J. Radiol. 70 (1997) 437-4391 Typical radiation doses in urolo ical procedures Procedure Mean effective dose (mSv) values Abdomen radiography (AP) 0.7 Intravenous Urogram (6 films) 2.5 Micturating cysto urethrogram 1.2 Cystography 1.8 Lithotripsy 1.3 Nephrostomy 3.4 Percutaneous nephrolithotomy (PCNL) 4.5 Ureteric stenting 4.7 CT abdomen 10 Renal angiogram 2 to 30 Kidney stent inseion 12.7 About Bilateral Nephrostogram: Nephrostogram is done in patients who have a nephrostonny tube in place. Dye is injected into the tube and flow of contrast is noted into the ureters and bladder. It is almost similar to IVP except that here the dye is directly pushed into the renal pelvis rather than being excreted by the kidneys. So we assume that the radiation dose would be somewhat lower than that for IVP, but since its bilateral, it is most likely to be higher then that for MCU.