While some areas of clinical medicine have for some time been using dual information from anatomical imaging of CT/MRI with functional data from SPECT/PET, cardiology has lagged behind in utilising the dual imaging of SPECT/CTCA.

Cardiac SPECT retains a cornerstone position in providing functional detail about cardiac perfusion and function. Its predictive potential for clinical cardiac events is useful as a preoperative cardiac risk tool and to guide cardiac interventional directions.

CTCA is a relatively new cardiac imaging tool with the ability to provide precise anatomical coronary arterial details. It can define plaque burden well and differentiate this according to plaque morphology. It can also localise plaque to high and low risk areas, whether they are proximal or more distally located or complex involving branch points. This type of detail greatly assists the interventional cardiologist triage best management options.

CTCA in patients with moderate to heavy coronary calcification can provide an overwhelming degree of abnormality such that it leaves uncertainty about the clinical significance of the underlying coronary plaque. This is where cardiac SPECT fused with the CTCA images allow interpretation of what is clinically significant.

Fusion of cardiac SPECT and CTCA images is particularly valuable in cases of established disease, pre and post coronary grafting or multiple PTCA's and those with moderate to high calcification in which one is trying to establish clinical relevance.

A tool to "sort out the wood from the trees".

(This paper won the John Orr Memorial award (NZ Branch ANSNM October 2008)