The rapid advances in CT technology over the last decade have been amazing. This is especially true in the field of cardiac CT, which pushes computed tomography technologic innovation to its limits. The introduction of the 320-detector row dynamic volume CT scanner (Toshiba America Medical Systems) in 2007 promised to improve patient outcomes and cost-effectiveness by providing more accurate, comprehensive results in shorter periods of time. Our experiences to date lend support to these promises.
The biggest advantage of 320-detector CT is its 16-cm anatomic coverage that can scan an entire organ, such as the heart, in a single gantry rotation. For cardiac imaging, this means we can obtain the entire image in a single heartbeat rather than multiple heartbeats, thus minimizing artifacts and allowing lower-dose imaging. We also are seeing the potential to open up completely new fields of study with this technology in terms of brain and other organ perfusion.
I have been involved in more than 400 cardiac CT angiograms, 300 peripheral vascular studies and more than 50 neurovascular perfusion studies on the 320-detector CT. This article will discuss my experiences over the past year using 320-detector row dynamic volume CT and explore dynamic volume CT’s impact on streamlining clinical pathways and workflow, as well as improving the bottom line.
New vs. ‘old’
Using traditional multidetector CT to image the heart requires five to seven heartbeats and images are “stitched” together, potentially creating clinical inaccuracies and artifacts (misregistration). Furthermore, if the patient’s heart rate is irregular, the heart may be in different locations from beat to beat throughout the scan, resulting in the data not lining up.
Using 320-detector CT, the entire heart is imaged in less than a heartbeat and using a single gantry rotation that takes less than a second. This results in unparalleled temporal uniformity by imaging the whole heart at one point in time, and capturing the contrast and data acquisition from a single heartbeat. In addition, there is no need to stitch together images from multiple gantry rotations, so issues with artifacts, misregistration and contrast non-uniformity associated with traditional multidetector CT are eliminated. Furthermore, this makes heart rate irregularities (arrhythmias) easier to manage.
Benefits of dynamic volume CT
Besides the advantages noted above, we have seen the following dramatic improvements over multidetector CT:
- Better Image Quality. For cardiac-specific work, 320-detector CT eliminates contrast non-homogeneity, artifacts, misregistration and many other problems we see with traditional multidetector cardiac CT. We have observed less blooming around calcium and stents, allowing for faster interpretation of studies and improved workflow.
- Reduced Contrast and Radiation Dose. Radiation dose associated with CT has always been a concern and 320-detector dynamic volume CT offers a dramatic improvement. Since the system’s x-ray tube is on for such a short period and there is no overlap scanning (as there is in 64-slice imaging), radiation dose is significantly reduced. In many cases, we see radiation dose as low as 2 to 3 mSv per study–about half the dose of an invasive diagnostic cardiac catheterization and a fraction of the dose seen with multidetector CT. Thus far, the average dose is 4 mSv. The speed of the system also reduces the amount of contrast needed. A typical dynamic volume CT scan uses 50 cc to 60 cc of contrast, which is down from 80 cc to 100 cc on previous CT systems.
- Greater Coverage. As noted earlier, the 16 cm coverage and the ability to take multiple acquisitions to obtain real-time organ perfusion is unprecedented in CT.
- Lower Costs, Improved Workflow. In the workup of certain types of chest pain patients, the dynamic volume CT scan can lower costs through faster, more accurate diagnosis and help replace several diagnostic tests with a single exam. When used correctly, we have seen this advanced technology reduce exam time and hospital stays for patients, and reduce contrast and radiation dose, all of which can help lower costs and improve workflow.
In step with healthcare policy changes
This technology is ideal for inpatient