Dosimetric impact from cardiac motion to heart substructures in thoracic cancer patients treated with a magnetic resonance guided radiotherapy system

Abstract

Few studies have examined the cardiac volume and radiation dose differences among cardiac phases during radiation therapy (RT). Such information is crucial to dose reconstruction and understanding of RT related cardiac toxicity. In a cohort of nine patients, we studied the changes in the volume and doses of several cardiac substructures between the end-diastolic and end-systolic phases based on the clinical magnetic resonance-guided RT (MRgRT) treatment plans. Significant differences in the volume and dose between the two phases were observed. Onboard cardiac cine MRI holds promise for patient-specific cardiac sparing treatment designs.

Effects of respiratory and cardiac motion on estimating radiation dose to the left ventricle during radiotherapy for lung cancer

“…The largest cardiac‐induced LV displacement occurring in the AP and SI directions, along with the observation of a smooth variation of maximum and mean dose during the cardiac cycle, support this interpretation (Figure 4). Consistent with these findings, previous studies have reported variations in dose to the LV/LVM during systole and diastole that depend on the patient population and tumour's location 26–28 . Despite this difference between doses at systole and diastole, no significant dose differences were noted between the non‐cardiac gated 50% 4DCT and systole or diastole at expiration since the cLV volume on 4D‐CT remains roughly between systolic and diastolic LV volumes (due to the lack of cardiac gating).…”

“…Consistent with these findings, previous studies have reported variations in dose to the LV/LVM during systole and diastole that depend on the patient population and tumour's location. [26][27][28] Despite this difference between doses at systole and diastole, no significant dose differences were noted between the non-cardiac gated 50% 4DCT and systole or diastole at expiration since the cLV volume on 4D-CT remains roughly between systolic and diastolic LV volumes (due to the lack of cardiac gating). Also, relative maximum and mean LV/LVM doses over the cardiac cycle were all positive, over the population, since the cardiac cycle was monitored during expiration breath-hold when the dose is already higher than the AIP dose.…”