Coronary CT angiography (CCTA) provides an accurate evaluation of coronary-artery disease and coronary-artery anomalies, and it gives us the ability to evaluate the cardiac chambers, myocardium, and valves. Effective deployment of CCTA service requires optimization of workflow to make this procedure cost effective and practical.
After more than six years of experience doing all interpretation in volumetric mode, we applied similar workflow-enhancement principles to optimize our CCTA workflow.
Baltimore VA Medical Center was the first completely filmless department when it opened its doors in June 1993. Over the past 15 years of being filmless, extensive work has been done in the department to optimize every aspect of the digital imaging chain, from physician order entry to scheduling, acquisition, interpretation, andresults delivery.
Similarly, in 2002, the department made another transition to volumetric interpretation, with every CT examination acquired in thin collimation (less than1 mm) and interpretation done in volumetric/multiplanar mode for every study, irrespective of clinical indication. During this transition, volumetric interpretation tools were also deployed enterprise wide to give physicians access to the same tools that radiologists use for diagnosis. In short, we made volumetric interpretation part of routine workflow for radiologists and clinicians.
This transition converted what is commonly referred to as postprocessing and brought it into the interpretation process; instead of relying on technologists to create pretty pictures for clinicians and radiologists, the radiologists took control of the data and began interpreting the data as needed. Because clinicians also had access to the same interpretation tools, they could interact with data in their offices, operating rooms, patient rooms, and even homes. This transition also optimized technologists' workflow, so that now they were able to concentrate more on image acquisition and the patient, rather than on creating reconstructions for others.
The success of CCTA depends on team effort, and that team includes the ordering physician, nursing staff, technologists, and radiologists. Many of the steps that ensure acquisition of a good dataset take place even before scanning begins. Appropriate discussion with the ordering physician regarding the indication for the examination, patient preparation, and patient education are crucial. Screening patients for potential contraindications can save time and prevent patient dissatisfaction. A patient who is aware and educated is more interested and readily participates in making the examination successful.
At the Baltimore VA Medical Center, friendly and competent staff set the tone. Patients are brought into a separate room where there is low ambient light and soothing music to relax them. They also are provided with warm blankets to prevent shivering during the examination. Patients are given explicit breathing instructions, and they practice several times before starting the scan. Patients are also made aware of the possible effects of contrast material, including warmth, a metallic taste in the mouth, and pelvic tingling. The ultimate goal is to convey a feeling of reassurance to the patient.
The CT scan begins with obtaining a calcium score, scanning from the level of the tracheal bifurcation to the bottom of the heart. The calcium score not only provides independent prognostic information, but also helps in determining whether a patient is a good candidate for CCTA. In a patient with very dense coronary calcifications along the length of the coronary vessels and at multiple branch points, it is extremely difficult to interpret CTA images.
Table 1 highlights the protocol currently used in performing 64-slice CCTA at our institution. Just as for coronary calcium scoring, the scan range is from the tracheal bifurcation to the bottom of the heart; however, in patients who have undergone coronary-artery bypass grafting, the range is extended to include the top of the chest, in order to identify the origin of the bypass grafts.
Table 1. Sixty-four–slice Coronary CT Angiography Protocol
Coronary Calcium Scoring
Scanning range: tracheal bifurcation to the bottom of the heart
Energy: 120 kVp
Effective mA: 190 (with dose modulation enabled)
Detector collimation: 1.2 mm
Slice thickness: 3 mm with 50% overlap
Coronary CT Angiography
Scanning range: Tracheal