Federica Zanca PhD, Presenter: Nothing to Disclose

Martine Demeter MD, Abstract Co-Author: Nothing to Disclose

Jurgen Jacobs MSc, Abstract Co-Author: Nothing to Disclose

Jhony Verschakelen MD,PHD, Abstract Co-Author: Nothing to Disclose

Dirk Vanbeckevoort MD, Abstract Co-Author: Nothing to Disclose

Raymond H Oyen MD, Abstract Co-Author: Nothing to Disclose

Hilde Bosmans PhD, Abstract Co-Author: Research grant, Siemens AG

Determine extra patient and organ doses associated with z-axis coverage beyond anatomic limits in chest and abdomen CT.

One-hundred-sixty-seven (167) routine chest and/or abdomen CT examinations (83 men, 84 women; age range 18-92 years) were collected and analyzed to assess the degree of extra scan length using dedicated software. Top and bottom limits for chest CT were lung apices and costodiaphragmatic sinus; for abdominal CT diaphragm dome and inferior pubic margin. Extra z-axis coverage was quantified on coronal reconstructions by one resident, supervised by two senior radiologists. Effective and organ doses (thyroid, liver, breasts, testes) were calculated, using CT-expo v2.0 and ICRP 103 recommendations. Paired t-test was applied to evaluate statistically significant difference between doses associated with ideal and real scan length.

One-hundred-thirty-three (80%) examinations had extra coverage (mean 4.6 cm, range 1-19.5 cm), resulting in excess total scan dose (mean 10%, range 1%-41%). Mean extra scan length was 3.4 cm, for both thorax and abdomen CT; 5.4 cm for combined thorax–abdomen. For thorax CT, a significant difference (p<0.05) was found between extra scan length at the top (mean 1.8 cm) and at the bottom (mean 2.9 cm), while for abdomen, no significant difference was found (mean 2.3 cm). Significantly higher effective doses for chest (p<0.05, mean 4.8 mSv vs 4.1 mSv for correct scan length), abdomen (p<0.05, 8.4 mSv vs 7.9 mSv) or thorax-abdomen CT (p< 0.05, 12.7 mSv vs 11.8 mSv) were found. Significantly more organ dose was estimated for thyroid (p<0.001, extra dose 99%, 4.9 mSv), testes (p<0.001, extra dose 115%, 7.6 mSv), liver (p<0.001, extra dose 56%, 2.3 mSv) and breasts (p<0.001, extra dose 163%, 1.5 mSv).

A large number of patients are scanned beyond anatomic limits during routine chest and abdomen CT, resulting in substantially higher organ and effective doses.

While many advanced techniques are studied for their dose reducing capabilities, present study demonstrates that a proper basic radiographic technique remains important for clinical dose optimization.

Zanca, F, Demeter, M, Jacobs, J, Verschakelen, J, Vanbeckevoort, D, Oyen, R, Bosmans, H, Z-axis Coverage beyond Anatomic Boundaries in Chest and Abdomen CT: Frequency and Effect on Organ Doses.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034371.html