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What is SPECT imaging and how does it work?

Posted on: 03.07.19

SPECT stands for single-photon emission computerized tomography. In layman’s terms, it’s a type of non-invasive nuclear imaging test that allows your doctor to see how well your internal organs are functioning. It uses a radioactive substance and a special gamma camera to create 3-D pictures of your organs at different angles.

Gamma cameras like the Digirad Cardius® 3 XPO and the X-ACT+ employ advanced solid-state technology that uses a silicon-based photodiode, coupled with cesium iodide (CsI). The technology not only offers better sensitivity and high energy resolution, but it also makes the camera smaller in size than a traditional MRI machine. And, with their open and upright design, they’re much more ergonomic and patient-friendly.

While an x-ray takes a picture of what your organs look like at a given point in time, a SPECT image shows blood flowing to and from the heart or blood flow restrictions due to narrow or blocked arteries. It can also be used to evaluate brain and neurological conditions and bone disorders.

In what cases is SPECT imaging ordered?

Not only can SPECT imaging capture how well your heart is performing, but it can also help diagnose disease processes that may be underway, including narrowing of the arteries, clogged arteries, identifying scar tissue due to heart attacks, or evaluating the success of surgeries like bypass surgery.

How does SPECT imaging work?

SPECT scans use a radioactive material called a tracer. The tracer is injected intravenously and mixes with your blood. As your blood moves through your body, it’s “taken up” or absorbed by your living heart muscle.

The Digirad Cardius® 3 XPO and the X-ACT+ allow for patients to be imaged in a comfortable seated position but other gamma cameras require you to lie down on a table. During the scan, the SPECT camera rotates around you. It picks up signals from the radioactive tracer, which are then converted to 3-D images by a computer.

When you undergo a nuclear stress test, a SPECT scan will be taken while you’re exercising and again when you’re at rest. The comparison of the images will allow your physician to evaluate blood flow under different levels of exertion.

Your images may show different shades of color that will indicate which areas of your heart absorbed more of the radioactive tracer and which areas absorbed less. A normal test result indicates there is sufficient and unrestricted blood flow to your heart, while an abnormal result means your heart’s blood flow is insufficient. Once your physician reviews your images, you’ll meet to discuss the results and any necessary treatment plan.

Example of SPECT imaging heart scan

What are the risks of SPECT imaging?

SPECT imaging is generally safe and most patients can go back to their normal activity right away. The amount of radioactive material injected into your bloodstream is small and your body will expel it through your kidneys in 24 to 72 hours. Be sure to drink plenty of water for a few days following the procedure.

If you are pregnant, think you may be pregnant, or are a nursing mother, be sure to notify your doctor prior to the scan. The test uses a low-dose of radiation, which is contraindicated for pregnant women. Nursing mothers may be advised to wait additional time before nursing again so that your body can excrete the tracer.

Patients may also have an allergic reaction to the radioactive tracer, although it’s uncommon.

SPECT imaging is a popular, cost-effective, and safe method of evaluating your heart and diagnosing disease. While you may be a little anxious, be assured that the scan is painless and it provides important clinical value to your physician.



What’s next for SPECT with Kathy Flood

Posted on: 02.14.19

After several years of reduced reimbursements and decreasing volumes, SPECT imaging has stabilized and is primed for growth. Digirad recently spoke with Kathy Flood, CEO of the American Society of Nuclear Cardiology, to get her viewpoint on SPECT imaging and where the modality is headed.

“Volumes are not dropping as dramatically as they were in the past,” she said, “one factor in this is that people are recognizing the value of nuclear cardiology, and secondly we’re seeing increases due to the implementation of appropriate use criteria.” ASNC has supported their members with increased education on appropriate use, which is helping. But, looking down the road, the applications for SPECT nuclear are beginning to grow.

SPECT Applications for Cardiac Amyloidosis

One of those new applications involves cardiac amyloidosis. In the past, a cardiac amyloidosis diagnosis could only be confirmed with a cardiac biopsy. And still, there was no available treatment. Now, a nuclear scan using technetium-99m pyrophosphate (Tc 99m PYP) is almost as effective as a cardiac biopsy.

With treatment drugs in the pipeline, there’s an exciting opportunity for nuclear imaging to play a significant role in both the diagnosis and management of the disease.

The availability of new treatments has heightened the importance of awareness, early diagnosis, and accurate typing of cardiac amyloidosis. In response, ASNC is working on an educational campaign that focuses on PYP imaging for patients with suspected cardiac amyloidosis.

New Educational Initiatives

ASNC’s annual Nuclear Cardiology Today Event, scheduled for April 12-14, 2019, will include a practical workshop on cardiac amyloidosis where not only nuclear cardiologists, but also referring physicians can learn about the disease.

The half-day, case-based program will address the diagnosis and management, tackle the challenges of disease presentation, discuss the role of various imaging modalities in the diagnosis, and give an overview of current and emerging treatments.

Cardiac amyloidosis is considered a rare and potentially under-diagnosed disease. One of the contributing factors is that its symptoms closely resemble heart failure. As statistics say that about 30% of heart failure patients have been misdiagnosed and that heart failure is the number one disease state where Medicare spends money, that equates to a lot of patients.

“Our goal is to make our members and referring physicians aware of cardiac amyloidosis, about the role of nuclear cardiology, and how to provide high-quality imaging around that for decision making and treatment,” said Flood.

ASNC also plans to offer more hands-on simulation opportunities at their meetings so that members can network with experts in their field, better understand how they’re performing nuclear cardiology, and learn how they can improve. Taking those experiences back to their labs will help them provide the best images for their patients.

Investing in the Next Generation

Looking ahead, ASNC is intent on making sure their members have what they need, but they’re also making investments in the new generation. “We’re working to put together programs specifically for the cardiology fellowship training programs. We want to be able to either help supplement some of the nuclear education they receive, or if they don’t receive any, be able to direct them to ASNC,” said Flood.

SPECT remains the most common procedure in nuclear cardiology, but the younger generation tends to focus on the newer modalities, like Cardiac CT. Once they graduate, they’re often unable to use this knowledge in practice because the new modalities are not as widespread in the field. That’s when they look back and wish they would have spent more time on SPECT imaging.

“We’re trying to fill that void as we move forward over the next couple of years so we have more programs and touch points with fellows in training so they can get just as excited about nuclear, too,” said Flood.



2018 ASNC SPECT MPI Imaging Guidelines Issued

Posted on: 07.19.18

Recent advancements in SPECT Myocardial Perfusion Imaging prompted ASNC to issue updated SPECT guidelines, which were published on May 25, 2018.

The highly anticipated new guidelines, ASNC Imaging Guidelines: Single Photon Emission Computed Tomography (SPECT) Myocardial Perfusion Imaging—Instrumentation, Acquisition, Processing, and Interpretation, incorporate the most up-to-date information and advancements in SPECT technology since the previous 2010 ASNC SPECT guidelines were published.

Today’s SPECT technology effectively allows for exceedingly low radiation dose imaging, myocardial blood flow quantitation, and personalized imaging protocols. By leveraging the new advancements, the revised guidelines promote a more patient-centric and personalized approach that contributes to higher-quality imaging and more meaningful results.

The medical community considers the update a significant move toward the standardization of SPECT MPI and one that will ultimately allow them to provide patients with the highest level of customized care.

The new guideline features updates on novel hardware, collimators, and CZT scanners, as well as newly added sections on reduced count density reconstruction techniques, SPECT myocardial blood flow quantification, stress-first/stress-only imaging, and patient-centered myocardial perfusion imaging.

The guidelines were endorsed by the Society of Nuclear Medicine and Molecular Imaging and published in the Journal of Nuclear Cardiology. You can view and download the new guidelines from ASNC’s website and read the official press release here.



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