Clinical evaluation of the computed tomography attenuation correction map for myocardial perfusion imaging: The potential for incidental pathology detection

The benefits of hybrid imaging in nuclear medicine have been proven to increase the diagnostic accuracy and sensitivity of many procedures by localizing or characterizing lesions or by correcting emission data to more accurately represent radiopharmaceutical distribution. Single-photon emission computed tomography/computed tomography (SPECT/CT) has a significant role in the diagnosis and follow-up of ischaemic heart disease with attenuation correction data being obtained on an integrated CT scanner. Initially, the CT component of hybrid SPECT/CT systems was what could be described as low specification utilizing fixed output parameters. As technology has progressed, the CT component of newer systems has specifications that are identical to that of stand-alone diagnostic systems. Irrespective of the type of scanner used, the computed tomography attenuation correction (CTAC) for myocardial perfusion imaging produces low-quality, limited-range CT images of the chest that include the mediastinum, lung fields and surrounding soft tissues. The diagnostic potential of this data set is unclear; yet, examples exist whereby significant pathology can be identified and investigated further. Despite guidance from a number of professional bodies suggesting that evaluation of the resulting images for every medical exposure be carried out, there is no indication as to whether this should include the evaluation of CTAC images. This review aims to initiate discussion by examining the ethical, legal, financial and practical issues (e.g. CT specification and image quality) surrounding the clinical evaluation of the CTAC for myocardial perfusion imaging images. Reference to discussions that have taken place, and continue to take place, in other modalities, current European and UK legislations, and guidelines and research in the field will be made.