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What Is the Difference Between SPECT and PET Imaging for Cardiology?

Posted on: 02.07.20

Difference between SPECT and PET Imaging for Cardiology

Cardiac imaging is a critical technology, particularly as cardiovascular disease is the leading cause of mortality for most developed nations.

While SPECT remains the leading modality for cardiac imaging, PET has continued to see growing interest. Naturally, patients and physicians want to know if one is better than the other and what the benefits and limitations are. In this article, we’re examining PET vs. SPECT in terms of utility for cardiology. Here is our comparison:

The technology

Both PET and SPECT imaging use cameras that detect injected radiotracers. However, each type of imaging works differently:


Single-Photon Emission Computed Tomography (SPECT) imaging provides metabolic and functional information about the heart. It is a non-invasive technique that involves injecting radioactive tracers into the bloodstream to get pictures which indicate whether or not a patient has cardiovascular disease.

The SPECT gamma camera picks up signals from the radioactive tracers as they move around the patient’s chest, then these signals are transformed into computer images. SPECT can be used to examine the heart while the patient is at rest, or during a nuclear stress test.

Perfusion imaging is generally performed twice – once at rest, then again after cardiac stress. It measures the blood flow to the heart.

The half-life of technetium-99m, the radiotracer used for SPECT is around six hours, which means technologists have plenty of time to perform the imaging that is required. This is how they are able to perform nuclear stress tests.

If we look at the decay of the radiotracer, it is quite straightforward. Each decay provides one gamma ray which is detected by the camera. Combining thousands of these gamma ray detections assist in the image creation that the physician uses for diagnosis.

Get the bonus content: FDA-Approved Radiotracers for Cardiac PET


Positron Emission Tomography (PET) is also non-invasive and uses injections of radiopharmaceuticals to assist a camera to create images of the heart. PET can be used to examine blood flow to the heart and will also show any damage, such as scar tissue from a heart attack.

A PET image can help physicians to identify areas of the heart that are damaged, but can be saved if blood flow is restored. They can identify whether a percutaneous coronary intervention (PCI) or coronary artery bypass is appropriate.

PET imaging mainly uses rubidium-82 as the radiotracer, which has a relatively short half-life of just 75 seconds. This means that technicians need to work very quickly to get the images required.

Looking at the decay of the PET radiotracer, it is slightly more complex than SPECT in that a positron emission occurs with each decay. Each positron decay site produces two gamma rays that are detected by the camera.

SPECT vs PET: Pros and cons

How do the two types of technology compare in terms of costs and benefits for cardiac imaging? Each modality has its own pros and cons:


SPECT is much more widely available than PET. It’s also much more affordable, with the average camera costing between $400,000 and $600,000. Due to its widespread use, there are more trained technologists available too.

The longer half-life of the SPECT radiotracer makes it more widely available and is ideal for cardiac stress testing. Improvements in radiotracer and camera technology are expected to boost image quality, helping to overcome a common SPECT complaint.

Image quality is the most common comparison point between SPECT and PET cardiac imaging. It is reported that SPECT resolution is at 12mm to 15mm and images can be prone to attenuation on older cameras. SPECT also does not provide a quantifiable estimate of the blood flow.


PET is less widely available and much more costly to implement, with cameras running into the millions of dollars. Cardiac stress testing can be performed with existing radiopharmaceuticals but can be challenging due to their short half-life, although this is potentially going to be solved in the future as new radiotracers are being developed.

One of the biggest pluses for PET scanning is the superiority of its image quality. For example, it tends to have fewer artifacts in images than SPECT. PET provides high spatial resolution and the capability to provide quantitative estimates of blood flow.

Get the bonus content: FDA-Approved Radiotracers for Cardiac PET

Final thoughts

SPECT and PET are both used for cardiac imaging, although SPECT is more broadly available. Each has its own strengths and challenges, but each can provide quality images that allow for accurate diagnosis.

Is one better than the other? That very much depends on the technology involved. New developments are being made for both SPECT and PET, improving image quality, attenuation and other issues associated with imaging.

While there are studies that lean toward PET as a more accurate option for cardiology, there’s no denying that SPECT is still the go-to choice for most cardiologists .

Is offering coronary flow reserve studies right for your practice?

Posted on: 04.25.19

Coronary flow reserve (CFR) is the ratio of resting coronary blood flow to maximum coronary blood flow. As a descriptor of myocardial blood supply, CFR suggests the ability of the coronaries to increase blood flow under stress. It’s a non-invasive test that could help rule out or measure multi-vessel ischemic Coronary Artery Disease (CAD).

Physicians primarily consider coronary flow reserve studies for cardiac patients who continue to be symptomatic after standard imaging and studies. Two factors that cardiologists often weigh when considering offering CFR are the frequency of which you’ll require the study and the overall clinical value of the data. In this post, we’ll take a look at these two dynamics and explore the benefits and limitations of offering coronary flow reserve studies.

Diagnostic Alternatives

The current approaches to evaluate myocardial blood flow include Intracoronary Doppler Ultrasound, echocardiography transesophageal sampling or transthoracic sampling with doppler, Cardiac SPECT, Cardiac PET, and pressure tipped catheters that can be used during diagnostic cardiac catheterization.

Frequency of CFR studies and diagnostic confidence

Coronary flow reserve studies are generally reserved for more unique cases that require greater clarification rather than ordered on a routine basis. It’s estimated that less than 10% of patients would benefit from CFR and the study provides a marginal amount of information which rarely cements a clinical diagnosis.

Typically, CFR is considered an additional data point that can confirm suspicions of triple vessel disease or poor dilation during stress, for example. However, many variables can affect the quality of the results.

When the images appear normal but the CFR result is contradictory or inconclusive, the coronary flow reserve results are often in question. Many cardiologists are more apt to lean towards what they can see or place more trust in other tests. CFR can be valuable, especially when it’s consistent with other findings, but when the results are called into question, a coronary flow reserve study may not create the diagnostic confidence to override other tests.

Evaluating the full picture

Although Cardiac PET is getting a lot of buzz for Coronary Flow Reserve studies, many cardiology practices have to step back and consider the full spectrum of their imaging needs. Given the small subset of cardiology patients who might qualify for CFR—especially under the stricter appropriate use guidelines— and given that several other diagnostic approaches are available, the ability to obtain CFR is not the determining factor in whether or not to invest in a Cardiac PET program in your office.

A substantial patient panel would be necessary to justify the purchase of a Cardiac PET imager for the ability to obtain CFR, and while the current reimbursement landscape is favorable to PET, changes could be on the horizon that greatly affect the rates and red tape associated with the studies.

The coronary flow reserve calculation can be an important component in certain diagnoses, but it’s critical to weight the full picture before making an investment that will affect your practice.

Where does Cardiac PET fit in your current imaging offerings?

Posted on: 12.20.18

Offering in-house Cardiac PET imaging to your patients adds a new modality to your imaging toolbox. This modality can expand your services by offering another option for diagnostic imaging while potentially providing an additional revenue stream.

If you’re thinking of adding Cardiac PET, it’s important to consider how the new modality will fit with your current imaging offerings. Think about how it could affect the level of service you provide and what its impact might be on your bottom line. Let’s take a look at where Cardiac PET fits in your current imaging offerings:

Top-Level and Bottom-Line Considerations

The addition of Cardiac PET imaging may not provide a clear net gain for your facility. Most practices will end up replacing some of their current SPECT imaging volume with PET because it may be a more appropriate choice. With the addition of PET, you can expect the volume to decline in one modality and rise in the other, at least in the short term.

If your practice is currently overbooked or your staff is overworked, Cardiac PET could offer relief and if your monthly volumes are sustainably high enough, this modality may positively affect your bottom line. However, if your current imaging is underutilized, it could worsen your situation.

As you make your decision, you’ll need to account for the new capabilities that Cardiac PET can offer. Think through when and why you would offer PET vs. SPECT and the additional flexibility it can provide you with patient care. You must also fully understand the reimbursement criteria of all of your payers and plans.

Establishing clear guidelines prior to the arrival of the camera is the best way to eliminate confusion. It will also help you utilize the imager in the most effective and efficient manner.

Key Considerations

On the positive side, a Cardiac PET imager can provide you with the capability to offer additional tests and enter into new markets. Many of the cameras come with the option of CT, so you might consider adding calcium scoring or coronary vessel imaging to your offerings.

Like Attenuation Correction SPECT, PET imaging has the ability to reduce the number of false positives and can ultimately lower the number of unnecessary cardiac catheterizations. It will, however, impact the activity of your cath lab, which needs to be factored into your plan.

With the addition of Cardiac PET, payers may also view your practice differently. PET MPI scans have a high reimbursement, which means your facility will be submitting a higher claim. This may result in greater scrutiny across all of your tests.

Lastly, when looking at PET MPI, it’s important to determine where it’s going to physically fit in your practice. PET imagers are larger than Echo, EKGs or even SPECT cameras and the radiopharmaceuticals have specific space requirements. You’ll need to identify a 15’x20’ – 20’x30’ room to accommodate a PET camera.

Aiming for Balance

The ultimate goal for any physician is to be able to order the right test, for the right patient, at the right time. Cardiac PET is a valuable tool that can help you provide the best care for your patients and help you achieve that goal.

As you evaluate the camera, it’s important to look at the entire picture. The camera price and its ongoing costs are major drivers, but those alone can’t determine your decision. It’s critical to evaluate how all of your diagnostic imaging services will work together after the initial purchase.

How much does it cost to offer Cardiac PET?

Posted on: 09.13.18

As imaging technology continues to advance, Cardiac PET MPI is gaining more awareness in today’s clinical market. In recent years, the modality has seen growth and is generating interest among cardiologists.

While the diagnostic benefits of Cardiac PET are clear, it’s important to understand the financials and investments needed to offer the service before making a commitment. In this post we’ll explore five aspects to consider as you evaluate Cardiac PET.

1. Equipment Requirements

If you decide to offer PET imaging, you’ll need to choose between the purchase of a new imaging system, or refurbished. It’s common for pre-owned options to be 8-10 year-old traditional PET cameras that have been refurbished to factory standards for technology and performance.

Many of these older cameras use line sources to perform attenuation correction. Generally, the camera and attenuation correction sources are considered the acquisition component. It’s often bundled with a new processing workstation that employs some of the latest cardiac processing features, including coronary flow information.

Depending upon the manufacturer, a refurbished system can cost between $350,000 and $450,000, but because there is limited availability in the secondary market, they’re also subject to the law of supply and demand.

An additional factor in the equipment equation should be your maintenance and repair costs, which, for a pre-owned system, will typically range from $80,000 -$85,000 annually.

If you’re considering a refurbished model, it’s important to do business with a reputable company. Keeping quality and service in mind, a trustworthy organization will help you find the best fit for your investment.

The alternative option is to purchase a new PET MPI camera. Most modern PET imagers include a CT component that provides attenuation correction. Most new PET/CT imagers cost over $1,500,000 and are a significantly higher investment than the cost of a refurbished model.

New cameras come with various levels of CT sophistication, some of which can perform calcium scoring and coronary vessel imaging. If you’re contemplating the larger investment, you might want to consider purchasing the most sophisticated camera your budget can afford, and offset the cost by the additional tests you can offer your patients.

It’s important to remember that regardless of which new PET/CT model you choose, you’ll need to spend 10-12% of the purchase price for annual repair and maintenance costs.

Many cardiology practices choose the refurbished route. When you do the math, depreciating $350,000 over 72 months is a lot easier to digest than $1,500,000 over the same time period. The sticker shock alone prevents some practices from considering the more sophisticated tests.

2. Radiopharmaceutical Expenses

The radiopharmaceuticals used with PET MPI are a significant component of the monthly cost in offering the modality. If you’re using the Rubidium-82 radiotracer, you can expect to pay between $40,000 and $45,000 each month, depending upon your study volume, the size of your generator, and the length of your contract. Supply contracts are generally a minimum of 1 year but are typically negotiated for 3-year terms.

13n-ammonia is an alternative radiotracer, but its practicality and cost make it prohibitive. A unit dose solution, however, is known to be in clinical trials, which may or may not lead to commercial availability within 3-5 years.

3. Staffing Considerations

If your practice is offering SPECT imaging in-house, your current nuclear technologist should have the educational background and licensing required to perform PET studies as well. While they may not have direct PET/CT expertise, your technologists can easily be trained. The only procedural difference between SPECT and PET MPI is the type of stress imposed on the patient. SPECT imaging includes both chemical and mechanical while PET includes only chemical stress. It does not require the use of a treadmill.

When you purchase a PET camera, the manufacturer will include applications training, as will the generator or cyclotron company.

Depending upon your volume, one technologist may be able to manage the workflow. You might also consider adding an assistant if an additional technologist isn’t warranted. Generally, adding PET MPI to your services should not affect your staffing, unless, of course, your volume is such that both your SPECT and PET imaging are significant enough to require an additional team member.

4. Facility Requirements

Adding a PET camera to your office may require some site planning considerations. The PET camera is significantly larger than the typical SPECT camera. Since you’ll be keeping your SPECT camera, you’ll not only need additional space, it will also have to be larger than what you have allotted for your SPECT camera. A 15’x20’ – 20’x30’ room could accommodate a PET camera, depending on the manufacturer. The space will also need to be lead-lined for radiation shielding. If your office square footage is tight, consider building an addition or even acquiring other real estate either in your current building or at another location.

5. Regulatory Expenses

Some states in the U.S. require physicians to apply for a Certificate of Need (CON)to install a PET camera. The goal of the CONprogram is to control health care facility costs and facilitate the coordinated planning of new services. Approval is not guaranteed as they reserve the right to determine the necessity of an additional PET camera in a particular area. If you live in one of these states, be sure to factor in the cost and time of submitting your application.

There may also be additional taxes or fees assessed by some states for high-end imaging. In that case, a percentage of the revenue from your PET studies may be payable to the state government.

Four important ways Cardiac PET Perfusion Imaging can affect your profitability

Posted on: 08.02.18

In today’s economic climate, practices are looking for additional services that will benefit their patients while also positively affecting their bottom line. Some cardiologists are exploring the idea of offering PET imaging at their facility. While convenient, in-house PET scans may not be the right fit for every practice. The smartest and most informed decision should take into account these four important factors.

1. Radiopharmaceuticals

Consumables for cardiac PET are unlike those used for SPECT imaging. The two commonly available radiopharmaceuticals for the modality include a 13N ammonia based product and 82Rubidium.

The exceptionally short half-life of the advanced ammonia-based radioactive tracers used for PET imaging, 15O water and 13N ammonia, is a significant challenge that in almost all cases, requires an on-site cyclotron.

Most providers offering PET use a 82Rubidium tracer, which can be produced by an on-site generator. While it delivers similar results and is less costly than the ammonia-based tracer, it’s still a considerable investment, often costing more than $40,000 a month for the rental of the generator.

2. Preauthorization Considerations

An often cited dynamic of Cardiac PET is that it does not require Medicare preauthorization. While this makes the ordering process more manageable, it’s important to remember that there is a critical distinction between pre-authorization and pre-approval.

Pre-authorization is not necessarily a green light for payment approval. All the existing rules still apply and, once evaluated, Medicare has to agree with the clinical validity of the decision. As the procedure becomes more popular, Medicare and payers will continue to increase their scrutiny and regulations surrounding reimbursement.

3. Patient Volume

Patient volume is a critical factor when evaluating Cardiac PET. Statistically, 20-30% of SPECT patients receive inconclusive results and clinically qualify for a PET scan for future follow ups. In order to cover the overhead, a set number of scans will need to take place each month.

If your volume is in the gray area after factoring in the 20% referral rate, it’s worth carefully looking at the numbers. Given their higher patient population, large organizations, universities, and hospitals are typically a good fit. But again, the total reimbursement must also be considered.

If the organization is not a free-standing clinic, the Medicare reimbursement code is written so that only the cost of the study is reimbursed. Expenses related to the 82Rubidium generator are excluded from hospitals, and they are only allowed to bill for the procedure.

In this ever-changing regulatory environment, rules and reimbursement rates will be modified over time. In calculating your expectations, whether it’s patient volume, cost, or reimbursement rates, you also assume the risk of change…for better or for worse.

4. Exchanging SPECT for PET

Remember, too, that your estimated PET studies per month will ultimately reduce your SPECT study volume. It’s essential that you accurately forecast your SPECT and PET revenue since an increase in one will inversely affect the other. Double counting the number of scans is a mistake some Pro Forma’s make and ultimately leads to unmet expectations after the financial commitment has been made.

The Bottom Line

While financials are a critical consideration, the value of a PET scan in a patient’s diagnosis and the outcome is also significant. While SPECT is a vital part of any cardiology practice, the ability to offer a PET scan could confirm or deny the need for invasive surgery. For the right cases, it saves money, time, and unnecessary risk for patients, surgeons, and insurers across the board.

It’s not an easy decision, by any means. There’s no denying that PET adds clinical value, but the financial aspect is also a practical consideration in any business. If it’s not financially feasible in your practice, and your recommended course of action is a PET scan, referring a patient to the local hospital is still the smart option. It could be a simple solution to a complex problem, and one that ultimately supports the highest level of care for your patients.

How to know if Cardiac PET makes sense for your practice

Posted on: 03.22.18

Cardiac PET has been used as a diagnostic imaging tool for a number of years, but has recently seen an increase in interest among cardiologists. When evaluating a considerable investment, such as Cardiac PET, it’s critical to look beyond the buzz and know for sure if it’s the right choice for your practice. Let’s take a look at Cardiac PET and some ways to see if it makes sense for you and your practice.

The Basics of Cardiac PET

Although most commonly used when imaging certain Oncology patients, PET cameras can potentially be of benefit to cardiologists for a segment of patients needing myocardial perfusion imaging. Supporters of PET MPI suggest higher diagnostic accuracy when compared to SPECT MPI, especially when Attenuation Correction is not available on the SPECT system.

Cardiac PET imaging must be performed on a PET or PET/CT system as SPECT imaging systems cannot image these higher energy agents. Instead of using readily available unit doses of Thallium or Technetium based MPI agents, Cardiac PET utilizes a Rubidium (Rb 82) Generator or an Ammonia (N-13) cyclotron for onsite production of the patient doses. Rubidium generators and Ammonia cyclotrons require a significant and ongoing investment, so a considerable volume of patients is necessary to support the overhead.

The working assumption is that PET MPI can reduce downstream costs by creating less false positives. While reducing false positives can lower costs, the total expense of providing PET MPI testing is considerable to both the practice and the patient.

Benefits of Cardiac PET

Cardiac PET is an excellent tool to diagnose patients who may have CAD. PET MPI benefits patients with a high likelihood of interventional needs because of its ability to calculate estimated blood flow and flow reserve. For patients who fit this profile, data from a PET MPI scan can be used to gauge the potential success of intervention (angioplasty, CABG, etc).

Images from Cardiac PET cameras typically offer excellent clarity and resolution due to the high-count rates and high Kev level of the PET MPI agents. Additionally, PET systems all have Attenuation Correction (either source based or CT based), further increasing reader confidence when interpreting images.

Though Cardiac PET is a useful tool in diagnosing coronary artery disease, a very small percentage of cardiac practices own a PET imaging system. The most recent estimates suggest less than 200 dedicated Cardiac PET facilities are operational in the U.S.

Drawbacks and Risks of Cardiac PET

One of the limiting factors in the growth of Cardiac PET is the cost of offering the modality. PET systems, whether refurbished, used, or new, are significantly more expensive than SPECT systems in terms of purchase price and in terms of ongoing repair, maintenance, and upkeep.

Outside of the known camera costs, the ongoing expenses and consumables are a considerable jump from SPECT. The nature of the radiotracers requires costly, long-term contracts that must be committed to before the first scan is provided.

For practices and hospital systems with the right panel size, Cardiac PET can be a profit center that offers a real benefit to patients. However, for groups that have clinical volume in the gray area, it can be a financial burden.

Because of this dynamic, it’s essential to know what imaging volume is needed to cover your overhead. While vendors may provide a pro forma, they often minimize cost factors, so the decision requires more due diligence as compared to other modalities.

Additionally, there is growing uncertainty about the future of reimbursement for Cardiac PET scans. Today, Medicare does not require prior authorization or pre-certification in order to be reimbursed for performing PET MPI. This stance on PET reimbursement has driven very modest growth over the last 18 months. Most Medicare Advantage plans currently require the same prior authorization or pre-certification for payment as is mandated by private insurance payers. The scrutiny will undoubtedly increase as study volumes grow. Even a slight change in reimbursements could move the camera from being a profit producer to a financial loss.

The Bottom Line

There is no question that Cardiac PET imaging offers high-quality images, may increase reading confidence for interpreting physicians, and provides information that may prove invaluable for some patients. Current estimates are that between 15% and 25% of MPI studies may be more appropriately performed as PET MPI rather than SPECT MPI (if PET MPI is available).

Even considering possible reimbursement instability, with the right panel size it’s a beneficial modality to add to your diagnostic imaging department. That said, it should be explored with a mindful approach that takes the full cost into account.

Ultimately, you want to perform the right test, for the right patient, at the right time, and for the right reason. Gaining a thorough understanding of the required investment, technology, and reimbursement dynamics is the first step in the process to determine if and how a Cardiologist might add PET MPI to their diagnostic toolkit.

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