Arvind Kumar, Bhatt CP and Rishabh Dobhal
Aim: The purpose of this dosimetric study was to find a suitable treatment & planning technique which can serve as an optimized technique with respect of PTV coverage and better sparing of concerned OAR’s.
Introduction: DIBH technique for left sided breast cancer is popular now-a-days, because as in DIBH the heart gets separated from the chest wall and left lung volume increases significantly resulting in reduced heart and left lung doses as compared to FB technique. Referring to previous available literature of DIBH studies, it is clearly showed that DIBH has advantage over FB in case of left sided breast cancer radiotherapy treatment in terms of reduced risk of cardiovascular related morbidity and mortality. DIBH is now a well-established technique in case of left sided breast cancer radiotherapy treatment. This dosimetric study explores the benefit of using a suitable treatment & planning technique in case of left sided breast cancer radiotherapy treatment.
Material and methods: In this study we have taken 10 patients of left sided breast cancer (7 MRM + 3 BCS) treated with DIBH technique at our Centre. The Varian’s RPM respiratory gating system (Varian Medical System, Palo Alto, CA) was used for respiratory motion monitoring. All patients were coached for three to four days for obtaining the desired respiratory breathing cycle. Once the patient was coached successfully, CT scans were acquired, one with conventional free breath (FB) and also three random scans with deep inspiration breath hold (DIBH) i.e., gated CT scans on SOMATOM Sensation Open CT simulator machine (Siemens Medical System’s).
On importing the acquired CT images in TPS, it showed that left lung volume increment in DIBH technique as compared to FB was significant. Patient contouring and treatment planning performed on Eclipse V13.5 and a dosimetric comparison was made between two treatment & planning techniques i.e., ((DIBH vs. FB) for (3DCRT vs. IMRT) and it is for PTV coverage, left lung, heart, left anterior descending coronary artery (LAD), left ventricle and contralateral breast.
Results: Left lung volume increment in DIBH technique as compared to FB was 69.375% showed that there was a significant increment in left lung volume, which results a larger separation of heart and the PTV chest wall. DIBH showed a significant reduction in doses of associated organ at risk.
Conclusion: This dosimetric study showed that in FB and DIBH techniques, DIBH is showing drastically dose reduction for left lung, heart C/L breast, LAD and left ventricle. From the data of DIBH and FB, we can conclude that DIBH technique in many respect has advantage over FB, which is solving the purpose of reducing cardiac and pulmonary doses without compromising the PTV coverage.
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