Cardiac magnetic resonance imaging and Echocardiogram to investigate myocardial structural and functional changes in patients undergoing irradiation for left sided breast cancer with or without Deep Inspiration Breath Hold

A Cardiac MRI using T1 mapping sequences to assess myocardial structural changes and a Echocardiogram using global strain imaging to assess myocardial functional changes will be performed in women undergoing radiation therapy to the left breast, or left chest wall +/- regional nodal areas with or without deep inspiration breath hold following surgery for left sided breast cancer. The MRI and echocardiogram will be performed between one to three weeks prior to commencement of radiation therapy (baseline) and at six months post completion of radiation therapy. The cardiac MRI will take between 45 and 60 minutes and will be performed by a cardiac MRI technician. The images will be reviewed by a Cardiologist with a special interest in cardiac MRI. Deep inspiration breath hold (DIBH) is the process whereby the patient's breathing is monitored and, at a preset lung volume during inspiration, airflow is stopped for a short period of time, during which the radiation therapy is delivered. The duration of the breath hold and volume held is determined individually depending on what is comfortable for each patient. At the Princess Alexandra Hospital, the Elekta active breathing control (ABC) device has been used successfully for eighteen months. By holding the patient in deep inspiration, the lung expands, moving the heart away from the chest wall while the radiation beam is delivered, thus decreasing heart exposure to radiation. DIBH is monitored by the radiation therapists who are delivering the radiation treatment. The DIBH technique is offered to all women undergoing radiation therapy for left sided breast cancer. However, some women (less than 5%) are not able to comply with this technique and therefore do not undergo DIBH. These women are being offered participation in the cardiac MRI/Echocardiogram trial to determine if there is any difference between women who are able to undergo DIBH and those who do not in the incidence of cardiac structural and functional changes as a secondary enpoint. Patients undergoing cardiac MRI will not be asked to do the DIBH technique. However, all patients will be asked to hold their breath for short periods as part of standard protocol for cardiac MRI. Therefore, participants may or may not undergo DIBH during radiation therapy depending on individual tolerance. Patients will not undergo DIBH during cardiac MRI but will be asked to hold their breath for short periods only as part of standard protocol for MRI.