David Knipp MD, Abstract Co-Author: Nothing to Disclose

Jason Wayne Mitchell MD, Abstract Co-Author: Nothing to Disclose

Barton Frederick Lane MD, Abstract Co-Author: Nothing to Disclose

Barry David Daly MD, Presenter: Research Grant, Koninklijke Philips NV

Reduction of iodinated contrast load for CTA is of importance in azotemic patients, especially those who are not dialysis dependent, and may be achieved with the improved iodine absorption of lower kVp techniques. We compared quantitative and qualitative scan data in two abdominopelvic CT Angiography (AP-CTA) protocols, one with a 50% reduced dose of iodinated contrast @ 80 kVp, the other with a standard dose @ 120 kVp. Radiation dose was also compared between the two techniques.

A chart review was performed yielding 103 patients who underwent AP-CTA on 64 or 256 channel CT scanners with 320-350 mg I/mL contrast: 49 with 30-60 mL (mean 48) at 80 kVp, and 54 controls with 90-100 mL (mean 98) at 120 kVp. Objective image quality parameters included arterial attenuation, noise, and contrast to noise ratio (CNR) measured at 6 levels in the aorta and iliac arteries. Subjective assessment of image quality (IQ), enhancement intensity (EI) and image noise (IN) was scored blindly at the same levels by three attending radiologists on a 3 point scale. Iterative reconstruction (iDose, Philips Healthcare, Cleveland, OH) was utilized in 18 and 49 of the 120 and 80 kVp groups respectively. Radiation dose (CTDIvol & DLP) was recorded in each case.

The aggregate of 6 level CNR for the 120 kVp group was 12.4 ± 4.6, compared to 11.8 ± 7.0 for the 80 kVp group (p =0.60).  The 120 kVp technique scored better for subjective IQ (p=0.042) and IN (p=0.004) but not for EI (p=0.205). No study had to be repeated. Radiation dose was significantly higher in the 120 kVp than 80 kVp group [DLP 863 ± 344 and 482 ± 206 (mGy*cm) respectively (p<0.0001)]. In the 80 kVp group, serum creatinine pre-and post AP-CTA (means 3.7 & 3.4 mg/dl respectively) showed no significant change (p=0.172).    

Based upon objective CNR and subjective EI scores, the 80 kVp technique with 50% lower iodine contrast dose allowed satisfactory AP-CTA studies without neprotoxicity in azotemic patients. Use of iterative reconstruction in all 80 kVp group cases contributed to a 43% mean radiation dose reduction. Negative but potentially reversible sequelae of this major drop in radiation dose included increased IN and reduced subjective IQ.

In azotemic patients, 80 kVp technique using 50% lower iodinated contrast dose and iterative reconstruction allows safe and satisfactory AP-CTA studies with major radiation dose reduction.

Knipp, D, Mitchell, J, Lane, B, Daly, B, CT Angiography of the Abdomen and Pelvis in Azotemic Patients utilizing 80 kVp Technique and Low Dose Iodinated Contrast—Comparison with Routine 120 KvP Technique.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005351.html