Positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) may be considered medically necessary for Initial Treatment Strategy Planning and Subsequent Treatment Strategy Planning for known or suspected malignancy (but not for Screening or Surveillance) when the following criteria are met:
Initial Treatment Strategy Planning
One PET or PET/CT study may be considered medically necessary for Initial Treatment Strategy Planning for patients who have solid tumors that are biopsy proven, or suspected based on other diagnostic testing, when a PET or PET/CT study is needed to determine the location and/or extent of the tumor for the following therapeutic purposes related to the initial treatment strategy:
- to determine whether or not the patient is an appropriate candidate for an invasive diagnostic or therapeutic procedure; OR
- to determine the optimal anatomic location for an invasive procedure; OR
- to determine the anatomic extent of tumor when the recommended anti-tumor treatment reasonably depends on the extent of the tumor.
NOTE: BREAST CANCER, MELANOMA, AND PROSTATE CANCER HAVE SPECIFIC EXCLUSIONS FOR PET OR PET/CT, AS NOTED BELOW
PET or PET/CT is considered experimental, investigational and unproven
- for diagnosis of breast cancer; OR
- to evaluate a suspicious breast mass; OR
- for initial staging of axillary lymph nodes in patients with breast cancer.
PET or PET/CT is considered experimental, investigational and unproven for the evaluation of regional lymph nodes in melanoma.
PET or PET/CT is considered experimental, investigational and unproven to determine initial anti-tumor treatment in patients with adenocarcinoma of the prostate.
Subsequent Treatment Strategy Planning
PET or PET/CT imaging for subsequent treatment strategy planning may be considered medically necessary when the initial diagnostic PET criteria were met and PET is needed:
- for the purpose of detecting residual disease within six months after completion of any surgical, chemotherapy, or radiation therapy treatment has completed; OR
- during the course of chemotherapy or radiation treatment when clinical signs and symptoms are significant and suggestive of disease progression or worsening despite treatment and the results are necessary to plan a new course of treatment; OR
- to determine the extent of a known recurrence established by other diagnostic modalities; OR
- to monitor tumor response to treatment during the planned course of therapy when a change in therapy is anticipated.
Surveillance of Asymptomatic Patients After Completion of Therapy for Malignancy
PET or PET/CT is considered not medically necessary for patients ≥12 months after completion of therapy for lymphoma, or ≥6 months after completion of therapy for all other malignancies, unless the patient demonstrates signs, symptoms, laboratory or other objective findings suggestive of recurrence or spread of the original malignancy.
Screening of Asymptomatic Patients
PET or PET/CT is considered not medically necessary as a screening test (i.e., for evaluation of patients without specific signs and symptoms of disease).
A. Myocardial Perfusion
Cardiac PET scanning may be considered medically necessary as a technique to assess myocardial perfusion defects when the patient has at least intermediate risk* for coronary artery disease AND the following criteria are met:
- Indeterminate noninvasive imaging tests (e.g., SPECT scan, myocardial perfusion imaging, stress echocardiogram); OR
- Patients for whom SPECT could be reasonably expected to be suboptimal in quality due to body habitus (such as, but not limited to: moderate to severe obesity, i.e., BMI > 35 kg/m2; large breasts and/or implants; left mastectomy; chest wall deformity; etc.) or other technical problems (e.g., indeterminant prior SPECT, extensive prior MI, etc)
* Intermediate risk is discussed in the Description section.
B. Myocardial Viability
Cardiac PET scanning may be considered medically necessary to assess the myocardial viability in patients with severe left ventricular dysfunction as a technique to determine candidacy for a revascularization procedure
C. Cardiac Sarcoidosis
Cardiac PET scanning may be considered medically necessary for the diagnosis of cardiac sarcoidosis in patients who are unable to undergo magnetic resonance imaging (MRI) scanning. Examples of patients who are unable to undergo MRI include, but are not limited to, patients with pacemakers, automatic implanted cardioverter-defibrillators (AICDs), or other metal implants.
Positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) may be considered medically necessary for the following:
- Diagnosis of chronic osteomyelitis;
- Assessment of selected patients with epileptic seizures who are candidates for surgery. NOTE: Appropriate candidates are those patients who have complex partial seizures that have failed to respond to medical therapy and who have been advised to have a resection of a suspected epileptogenic focus located in a region of the brain accessible to surgery. Conventional techniques for seizure localization must have been tried and provided data that suggested a seizure focus, but were not sufficiently conclusive to permit surgery.
EEG's AND PET EXAMINATION: The purpose of the PET examination should be to avoid subjecting the patient to extended pre-operative electroencephalographic recording with implanted electrodes.
Positron Emission Mammography (PEM)
Positron emission mammography (PEM) is considered experimental, investigational and unproven for breast cancer screening, diagnosis or management.
Positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) is considered experimental, investigational and unproven for all other indications.
Sodium 18F-Fluoride (NaF-18) Radiotracer for Positron Emission Tomography (PET) Bone Scans
Sodium 18F-Fluoride (NaF-18) radiotracer for positron emission tomography (PET) bone scans is considered experimental, investigational and unproven for non-oncologic indications, including but not limited to osteomyelitis.
This policy is based on multiple evaluations of PET, including Blue Cross Blue Shield Association (BCBSA) Technology Evaluation Center (TEC) Assessments. In the TEC Assessments, PET scanning was considered an adjunct to other imaging methods (i.e., CT, MRI, ultrasonography), often used when previous imaging studies are inconclusive or provide discordant results. In this setting, the clinical value of PET scans is the rate of discordance among imaging techniques and the percentage of time that PET scanning results in the correct diagnosis, as confirmed by tissue biopsy. Development of this medical policy also included consideration of other systematic reviews, meta-analyses, decision analyses, and cost-effectiveness analyses, including those conducted by Centers for Medicare and Medicaid Services (CMS) and the National Comprehensive Cancer Network (NCCN), as well as guidelines from the American College of Radiology, the Society for Nuclear Medicine, and others.
The NCCN Clinical Practice Guidelines Panel recommends against use of PET or PET/CT in the staging of breast cancer for patients with Stage I, IIA, IIB, or T3N1MO invasive breast cancer because of the high false negative rate in the detection of lesions that are small (<1cm) or low grade, the relatively low sensitivity for detection of axillary nodal metastases, the low prior probability of the patients having detectable metastatic disease, and the high rate of false positive scans. The NCCN Panel discourages the use of PET or PET/CT for the evaluation of Stage III and IV invasive breast cancer, except in situations where other staging studies are equivocal or suspicious; the Panel considers biopsy of suspicious sites to be more likely than PET to provide useful staging information.
In their review of management of malignant melanoma, Kumar et al. concluded that FDG-PET is of limited use in patients with early-stage disease and cannot replace sentinel node biopsy, which is more sensitive in detecting microscopic lymph node metastases. Wagner et al. compared FDG PET to conventional imaging studies and concluded that FDG PET is an insensitive indicator of occult melanoma lymph node metastases in patients with melanoma because of minute tumor volumes in this population, and does not have a primary role for staging regional lymph nodes in patients with clinically localized melanoma.
FDG PET is not highly effective for primary diagnosis of prostate cancer, and has a limited role in staging and recurrence detection. The National Cancer Institute has an ongoing phase II/III clinical trial (NCT00002981) that is studying how well PET scans work in detecting cancerous changes in patients with metastatic prostate cancer. The American College of Radiology Appropriateness Criteria recommends the use of CT, MRI, Prostascint Scan, and Tc-99m Bone Scan for diagnosis and management of prostate cancer. Although research is promising, a search of peer-reviewed literature did not locate any studies that would support the use of PET for diagnosis or management of prostate cancer.
Surveillance and Screening
Prevalence of PET Used for Surveillance
It is unknown how frequently and for which cancers PET is used for surveillance. An unsystematic attempt to find studies in which PET was apparently used for surveillance reveals some literature. Unger et al. (2004) reports the findings of 26 asymptomatic patients after treatment for cervical cancer among a larger series of patients who underwent PET in order to detect recurrence. The scans were done at a mean of 7.8 months after treatment, but the range was 2-40 months. Chung et al. (2006) reports the findings of 30 women undergoing surveillance PET among a larger series of other patients with clinical indications of recurrence of cervical cancer.
The only study that was found through unsystematic searches, and that solely examined use of surveillance PET, was by Ryu et al. (2003). In this study from Korea, 249 patients with no evidence of recurrent cervical cancer at least six months after treatment received PET scans at a variable time after treatment. Thirty-two percent of patients had positive scans, and 11.2% were clinically or histologically confirmed as having recurrences. The calculated sensitivity and specificity were 90.3% and 76.1%, respectively. Subsequent treatment and survival are not reported in this study.
Registries of PET utilization and analyses of claims data do not report, and do not appear to be capable of counting, PET scans used for surveillance. The National Oncologic PET Registry, a data collection effort commissioned by the Centers for Medicare and Medicaid Services (CMS) to develop evidence to consider CMS coverage for various indications for PET, did not collect information on surveillance PET (Hillner et al. 2008). The data collection forms noted specifically that PET is not covered by Medicare for surveillance purposes, and surveillance was not offered as one of the possible indications for the PET scan.
A study by Zafar et al. (2010), using merged Medicare and the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Program data on patients undergoing resection for colorectal cancer, measured the use of PET in the 2-year period following surgery. Ten percent of patients underwent at least one PET scan following surgery. However, the study does not report which scans were done for surveillance, nor does it appear that such a calculation could be made using the data elements available from either Medicare or SEER.
Principles of Surveillance
Surveillance has also been called “tertiary prevention” or “monitoring.” Tertiary preventive services are those that are provided to persons who clearly have or have had a disease in order to prevent further complications. Although some might not consider surveillance for recurrent disease to be prevention, the principles of surveillance are actually similar, if not identical to, those of traditional screening tests used for initial early detection of disease.
The purpose of a regimen of surveillance is to detect recurrence or progression earlier than would have otherwise. The diagnostic characteristics of the surveillance test for patients without suspected recurrence should be consistent with a reasonable degree of accuracy for both accurate and efficient identification of recurrence. In addition, recognizing the recurrence or progression earlier than it would have without the surveillance regimen should result in clinical interventions that produce a better outcome than would have if the recurrence had been detected clinically. Thus, the cancer must be biologically more responsive to treatment at the time that it is detected with the surveillance test than it is when it is detected clinically. For example, if PET detects the recurrence at a point in time in which distant metastasis is less likely, then it is possible that a treatment of the local recurrence may be more likely to benefit the patient. This implies that the surveillance test must be able to detect the cancer at a meaningful, rather than trivially earlier, interval in time than clinical detection.
As in screening, evaluating surveillance is complicated by several potential biases when trying to determine its efficacy. Analyses of outcomes from observational data can be misleading. Lead-time bias can result in apparent longer survival in surveillance-detected cases simply due to the additional increment of time between asymptomatic detection and clinical detection of recurrence. Lead-time effects could be particularly harmful for cancer recurrence due to adverse effects of treatment.
Length-time bias and overdiagnosis bias result from the preferential detection of slow-growing recurrences by surveillance tests, again resulting in an apparent, but not real, improvement in survival when comparing the outcomes of surveillance-detected cases to historical controls or to clinically detected cases. If treatments for recurrence are started simply based on the results of surveillance tests without some kind of confirmation of recurrence, an extreme form of over-diagnosis bias can occur if the surveillance tests are falsely positive. Thus, it is difficult to determine the efficacy of surveillance regimens using most kinds of observational data, such as case series data. These biases have long been recognized for traditional screening tests, leading to the recognition that randomized, clinical trials are often necessary to demonstrate the efficacy of screening tests.
However, the evidence supporting any surveillance regimen after cancer treatment is scant. Most recommended surveillance strategies appear to be recommended based on consensus, rather than rigorous trials. However, for colorectal cancer at least, recommended surveillance guidelines have some support from randomized, clinical trials. The American Society of Clinical Oncology (ASCO) guidelines recommending abdominal CT after treatment for colon cancer cite randomized, clinical trials as providing some support for this particular surveillance test (Desch et al. 2005). However, the evidence is less than definitive, as the guidelines acknowledge that several other organizations do not recommend any routine imaging studies.
Several clinical trials were completed comparing clinical visits and mammography to more intensive surveillance regimens that included bone scans, chest x-rays, and laboratory tests for women after treatment for breast cancer. The separate results of the trials and a systematic review of all trials concluded that the more intensive regimens did not improve survival (Rojas et al. 2009). Thus, for at least a few diseases, surveillance regimens have been evaluated with randomized, clinical trials leading to guidelines which in one case (colon cancer) support a particular surveillance test (CT) while in another case (breast cancer) do not recommend a particular test (bone scan).
Use of PET for surveillance may be thought to be effective without rigorous proof because it may be believed that PET is a sensitive and specific diagnostic test for cancer. In the absence of clinical trials or a rigorous trail of evidence supporting the full chain of logic that supports the utility of surveillance, and the desire to do some sort of surveillance, physicians may opt to perform what they believe is the most sensitive test. Certain literature reviews may reinforce this emphasis on the diagnostic characteristics of the test rather than evidence of improved health outcome. For example, an Agency for Healthcare Research and Quality (AHRQ) technology assessment on PET appears to focus almost solely on the calculation of diagnostic characteristics of PET for various cancers (University of Alberta Evidence-based Practice Center 2008).
A recently published guideline statement on the use of PET for colorectal cancer cites numerous systematic reviews and meta-analyses that seem to suggest that PET has superior sensitivity and specificity to CT in detecting colorectal hepatic metastases (Fletcher et al. 2007). A cursory look at some of the studies included in these meta-analyses reveals that these conclusions may, in fact, be flawed. In one of these studies by Valk et al. (1999), patients were included in the study for suspicion of recurrence, of which one of the indications for suspicion was an abnormal CT scan. If having a positive test on one of the tests being analyzed is one of the referral criteria for being in the study, then its performance cannot be estimated in an unbiased fashion. In fact, the authors state themselves “…an unbiased determination of the accuracy of PET and CT cannot be obtained from studies of this type, in which many patients are selected for PET imaging because of positive CT findings.” However, the conclusion of the authors is that PET is more sensitive and specific than CT for detection of recurrent colorectal cancer. Another reason for viewing these results with caution is that the PET diagnostic characteristics were determined in the setting of suspected recurrence, not routine surveillance. In addition to the probability of recurrence being higher in this situation than in the surveillance setting, differences in the detectability of the recurrence, so-called “spectrum biases,” may mean that the results are not generalizable to the surveillance setting.
The justification of the use of PET for detection of suspected recurrence as stated in many guidelines tends not to be because of the additional identification of more curable or treatable recurrence (early detection), but in more accurate staging of suspected recurrence (restaging), which then often changes the treatment plan when the recurrence is discovered to be more extensive than originally thought. In this scenario, then, the improved outcome of the patients is generally not because of the overall superior outcomes of treating the recurrence (although the subset of patients that are more accurately identified as having only local recurrence will appear to have superior survival), but in the avoidance of the morbidity of radical attempts at cure. This is clearly a different scenario than that of disease surveillance; the probability of recurrent disease is high or close to one, negating for the most part the problem of false positive results. The avoidance of futile radical curative treatments is an unambiguous benefit for patients who have more extensive disease found by using PET.
In summary, several biases inherent in the evaluation of surveillance as a type of screening make it difficult to assess the efficacy of PET used in this situation. Rigorous trials evaluating PET as a method of cancer surveillance to improve patient outcomes have not been carried out. Lacking such evidence, belief that PET scan is a sensitive and specific test may drive its use. However, the sensitivity and specificity of PET scan in the surveillance setting is probably unknown, and the scientific literature may very well be flawed in comparisons of PET to other imaging techniques. Use of PET to make treatment decisions may result in the appearance of superior outcomes for certain subsets of patients, but aggregate outcomes for all patients subjected to PET scanning should be accounted for.
Potential Harms of PET Surveillance
While there is potential benefit of early detection of recurrence that ideally should be demonstrated in a rigorous trial, these would need to be greater than the potential harms of such surveillance. Such harms would include any adverse effects from further testing, treatments, or procedures resulting from false-positive tests.
The test itself has substantial radiation exposure and potential for inducing cancer. A study by Huang et al. (2009) estimated that radiation doses ranged from 13.5 mSv to 32.3 mSv for a whole-body PET/CT scan depending on the particular scanning protocol and the gender of the patient. A lifetime attributable risk for cancer of up to 0.514% for a scan in a 20-year old woman was estimated, very similar to an estimate from another study analyzing the potential risk from coronary CT angiography (Einstein et al 2007). Another study by Brix et al. (2005) estimated a radiation dose from a whole-body PET/CT scan to be about 25 mSv, consistent with the estimates from Huang et al. (2009). These estimates were based on the risk of a single scan. The potential harms mentioned above are multiplied over time when surveillance tests are repeated.
Guideline Statements and Systematic Reviews Regarding PET for Surveillance in Oncology
Guideline statements regarding the use of PET for cancer surveillance were reviewed. Statements or evidence reviews supporting the use of PET for surveillance were rarely found for any cancer. The following Guidelines and Reviews were included:
· National Comprehensive Cancer Network Task Force Reports regarding use of PET;
· NCCN guidelines on treatment of selected specific cancers;
· AHRQ Technology Assessment on PET;
· Technology Assessment by the National Health Service Research & Development Health Technology Assessment Programme;
· CMS Technology Assessment in support of proposed coverage decision;
· American Society of Clinical Oncology (ASCO)—Convened Panel Recommendation Statement;
· Canadian Agency for Drugs and Technologies in Health (CADTH) Health Technology Assessment;
· The American College of Chest Physicians.
Conclusions and Recommendations for Further Research
There is simply inadequate direct and indirect evidence supporting the efficacy of PET scanning for the purpose of surveillance. Reflecting this lack of evidence, current practice guidelines appear unanimously to recommend against the use of PET for surveillance. No strong support of the use of PET for surveillance was found in editorials, case reports, or other studies. Given such problems as lead-time bias, length-time bias, and the uncertain diagnostic characteristics of PET in the surveillance setting, it would be difficult to determine whether the efficacy of PET for surveillance could be determined with observational data. Clinical trials may be necessary to determine whether PET surveillance is effective in improving health outcomes.
Positron Emission Mammography (PEM)
PEM has shown promising results in detecting primary ductal carcinoma in situ and recurrent breast disease, as well as for directing biopsy of suspicious lesions.
Raylman et al. found initial testing of the PEM/PET scanner revealed that the imaging capabilities of the system are excellent; more advanced testing is ongoing.
Berg et al. prospectively assessed the diagnostic performance of PEM scanning at four centers on 94 consecutive women with known breast cancer or suspicious breast lesions. Readers were provided clinical histories and x-ray mammograms (when available). After excluding inevaluable cases and two cases of lymphoma, PEM lesions were correlated with histopathology for 92 lesions in 77 women. Overall, PEM sensitivity for detecting cancer was 90%, specificity 86%, positive predictive value (PPV) 88%, negative predictive value (NPV) 88%, accuracy 88%, and area under the receiver-operating characteristic curve (Az) 0.918. In three patients, cancer foci were identified only on PEM, significantly changing patient management. Excluding eight diabetic subjects and eight subjects whose lesions were characterized as clearly benign with conventional imaging, PEM sensitivity was 91%, specificity 93%, PPV 95%, NPV 88%, accuracy 92%, and Az 0.949 when interpreted with mammographic and clinical findings. The study concluded that FDG PEM has high diagnostic accuracy for breast lesions, including DCIS (ductal carcinoma in situ).
The National Institutes of Health (NIH) have several studies underway for PEM. An ongoing phase IV study (identified as NCT00484614) is a prospective multi-center clinical trial to evaluate the role of high resolution PEM, used in combination with the radiotracer FDG, for pre-surgical planning in women with newly diagnosed breast cancer who are considered candidates for breast conserving surgery (i.e., lumpectomy) after full routine workup (including mammography, clinical breast exam, and additional ultrasound). Participants undergo both contrast enhanced MRI and PEM imaging. In order to control for potential bias in interpretation of the second examination (i.e., PEM or MRI), the order of interpretation of these examinations is randomly assigned at study entry. The primary objective of the study is to determine changes in surgical management resulting from PEM or MRI or both, separately and in conjunction with conventional imaging, and to determine whether these changes were appropriate (i.e., to excise malignancy) or inappropriate (e.g., wider excision or mastectomy for what proved to be benign disease).
A phase III trial (NCT00896649) is studying PEM to see how well it works compared with standard mammography in women with dense breast tissue or who are at high risk of breast cancer. This study is currently accepting participants.
Another study (NCT00981812) is not yet open for participant recruitment. The purpose of this research study is to evaluate the ability to perform breast biopsies using PEM and the Stereo Navigator software and to see whether PEM and Stereo Navigator help the doctors obtain results sooner (in fewer clinical visits) than if they use MRI, mammography and/or ultrasound.
In September 2009, the National Cancer Institute et al. of the NIH made a presentation titled “Diagnosis and Management of Ductal Carcinoma In Situ (DCIS)” at the NIH State-of-the-Science Conference. In their summary of future research directions they stated, “…Work must be continued with attention to newer imaging technologies, such as tomosynthesis, breast computed tomography, breast positron emission mammography, breast-specific gamma imaging, and others still in earlier phases of development.”
In 2003, the American College of Cardiology (ACC) and the American Heart Association (AHA) published updated guidelines for cardiac radionuclide imaging. Cardiac applications of PET scanning were included in these guidelines. The ACC/AHA guidelines categorize specific indications for PET scanning:
· Class I is defined as conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.
· Class IIa is defined as conditions for which there is conflicting evidence or a divergence of opinion but the weight of evidence/opinion is in favor of usefulness/efficacy.
· Class IIb is similar to Class IIa except that the usefulness/efficacy is less well established by evidence/opinion.
The medically necessary indications for PET myocardial perfusion studies in this policy are consistent with Class I and Class IIa indications in the ACC guidelines.
PET has perhaps been most thoroughly researched as a technique to assess myocardial viability to determine candidacy for a coronary revascularization procedure. For example, a patient with a severe stenosis identified by coronary angiography may not benefit from revascularization if the surrounding myocardium is non-viable. A fixed perfusion defect, as imaged on SPECT scanning or stress thallium echocardiography, may suggest non-viable myocardium. However a PET scan may reveal metabolically active myocardium, suggesting areas of hibernating myocardium that would indeed benefit from revascularization. The most common PET technique for this application consists of N-13 ammonia as a perfusion tracer and FDG as a metabolic marker of glucose utilization. A pattern FDG uptake in areas of hypoperfusion (referred to as FDG/blood flow mismatch) suggests viable, but hibernating myocardium. The ultimate clinical validation of this diagnostic test is the percentage of patients who experience improvement in left ventricular dysfunction after revascularization of hibernating myocardium, as identified by PET scanning.
SPECT scanning may also be used to assess myocardial viability. For example, while initial myocardial uptake of thallium-201 reflects myocardial perfusion, redistribution after prolonged periods can be used as a marker of myocardial viability. Initial protocols required redistribution imaging after 24 to 72 hours. While this technique was associated with a strong positive predictive value, there was a low negative predictive value, i.e., 40% of patients without redistribution nevertheless showed clinical improvement after revascularization. The negative predictive value has improved with the practice of thallium reinjection. Twenty-four to 72 hours after initial imaging, patients receive a reinjection of thallium and undergo redistribution imaging.
The ACC/AHA guidelines conclude that PET imaging “appears to have slightly better overall accuracy for predicting recovery of regional function after revascularization in patients with left ventricular (LV) dysfunction than single photon techniques (i.e., SPECT scans).” However, the ACC guidelines indicate that either PET or SPECT scans are Class I indications for predicting improvement in regional and global LV function and natural history after revascularization, and thus do not indicate a clear preference for either PET or SPECT scans in this situation.
Further supporting the equivalency of these two testing modalities, Siebelink and colleagues performed a prospective randomized study comparing management decisions and outcomes based on either PET imaging or SPECT imaging in 103 patients with chronic coronary artery disease and left ventricular dysfunction who were being evaluated for myocardial viability. Management decisions included drug therapy or revascularization with either angioplasty or coronary artery bypass grafting. This study is unique in that the diagnostic performance of the two studies was tied to the actual patient outcomes. No difference in patient management or cardiac event-free survival was demonstrated between management based on the two imaging techniques. The authors concluded that either technique could be used for management of patients considered for revascularization with suspicion of jeopardized myocardium.
In patients with symptoms suggestive of CAD, a central clinical issue is to determine whether a coronary angiogram is necessary for further work-up. A variety of non-invasive imaging tests, including PET (using rubidium-82) and SPECT scans, have been investigated as a means of identifying reversible perfusion defects, which may reflect coronary artery disease, and thus identify patients who may benefit from further work-up with an angiogram. The following table summarizes the ACC guidelines for myocardial reperfusion for both SPECT and PET scans in patients with an intermediate risk of coronary artery disease
Identify extent, severity, and location of ischemia (SPECT protocols vary according to whether patient can exercise).
Repeat test after 3–5 years after revascularization in selected high-risk asymptomatic patients (SPECT protocols vary according to whether patients can exercise).
As initial test in patients who are considered to be at high risk (i.e., patients with diabetes or those with a more than 20% 10-year risk of a coronary disease event) (SPECT protocols vary according to whether patients can exercise).
Myocardial perfusion PET when prior SPECT study has been found to be equivocal for diagnostic or risk stratification purposes.