Atul Padole MD, Presenter: Nothing to Disclose

Sarabjeet Singh MD, Abstract Co-Author: Research Grant, Siemens AG Research Grant, Toshiba Corporation Research Grant, General Electric Company Research Grant, Koninklijke Philips NV

Ranish Deedar Ali Khawaja MD, Abstract Co-Author: Nothing to Disclose

Alexi Otrakji MD, Abstract Co-Author: Nothing to Disclose

Diego Alfonso Lira MD, Abstract Co-Author: Nothing to Disclose

Mannudeep K. S. Kalra MD, Abstract Co-Author: Nothing to Disclose

Da Zhang PhD, Abstract Co-Author: Nothing to Disclose

Bob Liu PhD, Abstract Co-Author: Nothing to Disclose

Andrew Primak PhD, Abstract Co-Author: Employee, Siemens AG

George Xu PhD, Abstract Co-Author: Nothing to Disclose

To assess effect of fixed and modulated tube current on organ doses measured with surgically implanted dosimeters in a human cadaver and compare measured organ doses with the estimated organ doses obtained from radiation dose tracking software (RDT).

With the regulatory approval, ionization chambers (Radcal) were surgically implanted in cadaver (age: 88 years, male, weight: 68 kg, BMI: 20 kg/m2) in six locations including liver, stomach, colon, left kidney, para-vertebral area, and urinary bladder. The cadaver was scanned with routine abdomen pelvis protocol on a 128-slice dual-source MDCT scanner (Siemens Definition FLASH) using both fixed mAs and automatic exposure control (AEC) technique. Effective mAs of 100, 200, and 300 were used for fixed mAs scanning and reference quality mAs (Care Dose 4D) of 100, 200, and 300 were used for AEC. Scanning was repeated three times for each setting and organ doses were recorded for each acquisition (total series = 3*3*2=18). All other scanning parameter were held constant including tube potential of 120 kV. CTDIvol, and DLP, and image noise were recorded. All CT image series were exported to the web-based dose-monitoring RDT software (eXposure) to obtain estimated organ doses.  

The mean CTDIvol for fixed mAs of 100, 200, and 300 were 7, 14, and 21 mGy and for AEC were 4, 8, 13 mGy, respectively. There was a strong positive correlation between measured organ doses and CTDIvol for both AEC and fixed mAs (r= +0.99). The measured organ doses for liver, stomach, colon, left kidney, para-vertebral area, and urinary bladder at fixed mAs of 100, 200 and 300 were 28-54% higher than AEC at corresponding reference quality mAs of 100, 200 and 300 mAs (p<0.001). There was a linear increase in the organ doses from 100 mAs to 200 mAs for both fixed mAs and AEC (p=0.3). Similarly, the organ doses increased linearly from 200 mAs to 300 mAs for fixed and AEC (p=0.3). There was no significant difference in the correlation coefficients of estimated and measured organ doses for fixed mAs (r=+0.58) compared to AEC technique (r=+0.53) (p=0.9).

AEC technique allows the organ doses reduction compared to fixed tube current for routine abdomen CT in a human cadaver. Measured and estimated organ doses are not substantially different. 

AEC technique results in substantial reduction in overall dose (CTDIvol) as well as measured and estimated organ doses.

Padole, A, Singh, S, Khawaja, R, Otrakji, A, Lira, D, Kalra, M, Zhang, D, Liu, B, Primak, A, Xu, G, Effect of Tube Current on CT Radiation Organ Dose: Organ Dosimetry in a Human Cadaver Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14046030.html