Respiratory Motion of The Heart and Positional Reproducibility Under Active Breathing Control

Abstract

Purpose-To reduce cardiotoxicity from breast radiotherapy (RT), innovative techniques are under investigation. Information about cardiac motion with respiration and positional reproducibility under active breathing control (ABC) is necessary to evaluate these techniques.Methods-Patients requiring loco-regional RT for breast cancer were CT-scanned using an ABC device at various breath-hold states, before and during treatment. Ten patients were studied. For each patient, 12 datasets were analyzed. Mutual information-based regional rigid alignment was used to determine the magnitude and reproducibility of cardiac motion as a function of breathing state. For each scan session, motion was quantified by evaluating the displacement of a point along the left anterior descending artery (LAD) with respect to its position at end expiration. Long-term positional reproducibility was also assessed.Results-Displacement of the LAD was greatest in the inferior direction, moderate in the anterior direction, and lowest in the left-right direction. At shallow breathing states, the average displacement of LAD position was up to 6mm in the inferior direction. The maximum displacement in any patient was 2.8cm in the inferior direction, between expiration and deep-inspiration breath hold (DIBH). At end expiration, the long-term reproducibility (SD) of the LAD position was 3mm in the A-P, 6mm in the S-I, and 4mm in the L-R directions. At DIBH, long-term reproducibility was 3mm in the A-P, 7mm in the S-I, and 3mm in the L-R directions.Conclusions-These data demonstrate the extent of LAD displacement that occurs with shallow breathing and with DIBH. This information may guide optimization studies considering the effects of respiratory motion and reproducibility of cardiac position on cardiac dose, both with and without ABC.

Dosimetric effect due to the motion during deep inspiration breath hold for left‐sided breast cancer radiotherapy

“…The reported discrepancy was $0.2\pm 0.19 \text{cm}$, which was fairly reproducible. On the other hand, it was reported that the interfraction DIBH motion of the heart had reproducibility of 3 mm in the anterior–posterior (AP), 7 mm in the superior–inferior (SI), and 3 mm in the left–right (LR) directions (24) . Moderate correlation was found between surface and heart setup errors in Alderliesten et al: (13) ${\mathrm{normalR}}^2=0.53$, 0.37, 0.64 in AP, SI, and LR directions, respectively.…”

Clinical experience using a video‐guided spirometry system for deep inhalation breath‐hold radiotherapy of left‐sided breast cancer

“…These are valid measures to analyze interfraction motion; however, they cannot provide residual intrafraction motion during beam‐on. Jagsi et al (15) reported displacements (3 mm in AP and 6 mm in SI) of LAD position under shallow breathing states using active breathing control and the images were acquired at the time of the CT simulation. Moran et al (5) also used CT‐simulation images to study the short‐term displacement and reproducibility of the breast or chest wall and nodal regions at different breath‐hold states using ABC, in which $-4$ of reproducibility was observed.…”

Does radiotherapy planning without breath control compensate intra-fraction heart and its compartments’ movement?

“…The RP technology requires execution of radiotherapy in certain parts of the breathing cycle to exclude OAR and target displacement [19,21,22]. RP is used to tailor treatment plan, considering breath cycle-related movement and anatomic changes in target and neighboring tissues; planning and treatment that were done based on I images contributes heart protection in breast carcinoma [19,21,22].…”

“…The ventricles and atria volumes differ correspondingly to circulation causing intrinsic heart motion. It was shown that, although there was a large displacement, heart shape changed slightly during breath cycle [22]. Since heart is a relatively flexible organ and has intrinsic motion, it constitutes images like oscillations on MR and CT images.…”

“…Radiation dose and irradiated volume changes for both target and OAR, during normal breathing cycle in patients with breast carcinoma were previously reported [19][20][21][22]. This study investigates whether cardiac volume changes and related dose differences during breath cycle are exceeding tolerance limits.…”