The investigators will identify 10 patients in the department of radiation oncology who will receive standard of-care radiation therapy, and the treating radiation oncologist anticipates a mean left ventricular dose of at least 5 Gy. Patients will be evaluated by CMRI before and within one week of the completion of RT. We will compare the pre- and post-RT CMRI scans to identify changes related to radiation exposure. Our primary endpoint will be changes in myocardial strain. Secondary endpoints will include other CMRI parameters.

Cardiac toxicity is a significant cause of morbidity and mortality in cancer survivors after radiation therapy (RT) to the chest. Typically, cardiotoxicity is identified years after radiation exposure. Emerging clinical data show that subclinical injury can be identified immediately after treatment. Early identification of subclinical injury may enable intervention to reduce the risk of progression to clinically significant toxicity. The investigators hypothesize that cardiac magnetic resonance imaging (CMRI) will detect early cardiac injury after RT and that imaging changes will be associated regionally with cardiac radiation dose.

Inclusion Criteria:

1. Provision to sign and date the consent form.
2. Stated willingness to comply with all study procedures and be available for the duration of the study.
3. 18 - 100 years of age
4. KPS ≥ 70 or ECOG ≥ 1
5. Will receive RT using computed tomography (CT)-based treatment planning that will involve delivery of dose to the heart
6. Estimated by the treating radiation oncologist at the time of simulation to have a mean left ventricular dose of at least 5 Gy

Exclusion Criteria:

1. Previous history of RT to the thorax or breast
2. Implanted device that is non-MRI compatible or any implanted device in chest
3. Known gadolinium contrast allergy or other contraindication to CMRI scan. Patients needing sedation or medication for claustrophobia or anxiety will not be excluded from participating.
4. Found to be pregnant or breast-feeding
5. Known history of atrial fibrillation or frequent ventricular or atrial premature beats
6. Known history of chronic kidney disease (such as, but not limited, to a glomerular filtration rate < 60mL/min)
7. History of coronary artery disease or myocardial disease
8. History of hypertension, requiring >1 antihypertensive agent to maintain blood pressure <140/90
9. Known history of valvular stenosis or regurgitation of > moderate severity
10. Known history of heart failure (defined as baseline New York Heart Association Class III or IV (see Appendix A)
11. Systolic blood pressure < 90mmGy
12. Pulse < 50/minute
13. Known history of pulmonary hypertension or elevated right ventricular systolic pressures.
14. Suspicion or diagnosis of amyloidosis
15. Suspicion or diagnosis of hemochromatosis