Vangipuram Shankar MD, Presenter: Nothing to Disclose

Chiramana Haritha MD, DM, Abstract Co-Author: Nothing to Disclose

Hasmukh Prajapathi, Abstract Co-Author: Nothing to Disclose

To study the impact of the radiographic parameters and 3-Dimensional planning technique on the volumetric dose of the lung and heart, thus deduce analytic equations for quick volume estimation,for patients undergoing postmastectomy radiation therapy (PMRT).

Between Aug.2003-Mar.2007, 182 postmastectomy patients underwent a course of postoperative tangential breast irradiation ± Axillary / Supraclavicular radiation. After adequate immobilization on the CT compatable breast board, CT scans of the chest are performed with patient in the treatment position with 1cm slice intervals, covering lung apex to lung base. Following final tangential beam planning, the ipsilateral total lung area and the lung area included within the treatment port are contoured for each CT slice.It is multiplied by slice thickness, and then integrated in all CT slices to give respective volumes.Similarly, for left sided tumors, volume of entire heart and the portion of heart included in the tangential fields was calculated. Parameters related to lung (n=121) studied from the DRR's included: Central lung distance(CLD), Maximum perpendicular distance (MPD), Length of the lung (L). Parameters related to heart (n=61)included: Maximum heart distance - (MHD), Maximum heart length (MHL). Linear regression analysis is applied to test relationship between the percentage of ipsilateral lung volume involved and the CLD / MPD / L and similarly between MHD / MHL and the cardiac volume in irradiation.

Equation Predicting percentage irradiated volume(PIV) for: Right Lung = 4.0118+6.6474(CLD) OR -5.965 + 6.827(MLD) Left Lung = 6.6395(CLD) OR 5.431(MLD) Heart = 7.325(MHD) OR 6.742(CLD)

The conclusion of the present study, to the best of our knowledge, is the largest series reported so far in literature. CLD and MLD deduced from the DRR, are the direct measures of the lung volumes irradiated in tang. breast RT (r2=0.91 & 0.79). While MHD and CLD appear to be direct measure of the irraidiated heart volume (r2 =0.98 & 0.91).

CT Based simulation helps in minimising the normal strutures irradiated volume and thus complications resulting from such treatments.

Shankar, V, Haritha, C, Prajapathi, H, Three-dimensional Irradiated Lung and Heart Volume Prediction from 2D Datasets: Value of CT-based Treatment Planning in Postmastectomy Tangential Beam Radiation Therapy.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5015404.html