Recently had an imaging study at a Radiology clinic in Massachusetts. 
After the study the would provide me with the images, but refused to
give me the Radiology report indicating it was their policy to only
provide the report to a referring physician.
Does the patient not "own" this data (specifically, the Radiology
report) and have the right for direct access upon request?

The patient does indeed own the report, but you must request a copy of
the report from the primary care physician that ordered it.

Allied health services such as lab and imaging (X-rays, CT scans,
etc.) report results to the doctor who ordered them, and do not give
reports directly to the patient. This is so the doctor can explain the
results in accordance with your case. Not many patients are able to
interpret imaging results themselves. Not only that, a result that may
be abnormal for one patient, may, in your case, be the desired reault.
The doctor will determine the results and how they fit your particular
case.

After your doctor receives the report from imaging, ask her/him for a
copy of the report. This you are entitled to.

Regards, Crabcakes