Description 

Positron Emission Tomography (PET) scanning can be used to assesses brain metabolism and perfusion. Uses include identifying epileptic foci prior to surgery, differentiation of residual tumor versus scar, helping differentiate inconclusive findings on Brain MRI and identifying causes of cognitive decline. ⁽¹⁴⁾

Current agents that show promise in assessing plaques of the protein beta-amyloid include: florbetapir F 18, florbetaben F 18, and flutemetamol F 18 with PET. PET/MR is also being studied. Some other new agents look at the tau protein and microglial activation.

GENERAL INFORMATION

It is an expectation that all patients receive care/services from a licensed clinician. All appropriate supporting documentation, including recent pertinent office visit notes, laboratory data, and results of any special testing must be provided. If applicable: All prior relevant imaging results and the reason that alternative imaging cannot be performed must be included in the documentation submitted.

Where a specific clinical indication is not directly addressed in this guideline, medical necessity determination will be made based on widely accepted standard of care criteria. These criteria are supported by evidence-based or peer-reviewed sources such as medical literature, societal guidelines and state/national recommendations.

Policy
INDICATIONS FOR BRAIN PET SCAN

Brain PET scans are considered MEDICALLY NECESSARY for the following indications:

Known Brain Tumor or Cancer (1,2)
FDG-PET indications for brain tumor imaging after brain MRI is indeterminant or insufficient to:

• Differentiate radiation necrosis or post-treatment change from residual/recurrent tumor
• Differentiate low from high grade glioma
• Evaluation of primary brain lymphoma
• To guide intervention/biopsy

Refractory Seizures

• To determine operability of refractory seizures^(3,4,5)

Post-Treatment/Procedural Evaluation

• A follow-up study may be needed to help evaluate a patient's progress after treatment, procedure, intervention, or surgery. Documentation requires a medical reason that clearly indicates why additional imaging is needed

Mild Cognitive Impairment or Dementia (6,7,8,9,10,11,12)

• FDG PET for either:
  • Detection of early Alzheimer’s disease OR
  • Differentiation between Alzheimer's, dementia with Lewy body disease (DLB) and frontotemporal lobal degeneration (FTD)

AND ALL of the following criteria are met (criteria apply to both of the above indications):

• • • Brain MRI is insufficient or indeterminant AND
    • Objective measures demonstrate objective impairment (MMSE/MoCA < 26 or mild cognitive impairment on neuropsychological testing) AND
    • Full lab evaluation (thyroid function tests, CBC, CMP including LFTs and B12) has been completed and if abnormal, have been treated and cognitive difficulty persists AND
    • Medication side effect ⁽⁹⁾ and medical causes, such as vascular or traumatic or inflammatory etiologies have been excluded

NOTE: Brain CT is acceptable if brain MRI is contraindicated

Further Evaluation of Indeterminate Findings
On prior imaging (unless follow-up is otherwise specified within the guideline):

• For initial evaluation of an inconclusive finding on a prior imaging report that requires further clarification
• One follow-up exam of a prior indeterminate MR/CT finding to ensure no suspicious interval change has occurred. (No further surveillance unless specified as highly suspicious or change was found on last follow-up exam.)

Rationale
Background

Positron Emission Tomography (PET) scanning can be used to assesses brain metabolism and perfusion. Uses include identifying epileptic foci prior to surgery, differentiation of residual tumor versus scar, helping differentiate inconclusive findings on Brain MRI and identifying causes of cognitive decline. (14)

Contraindication and Preferred Studies

• Contraindications and reasons why a CT/CTA cannot be performed may include: impaired renal function, significant allergy to IV contrast, pregnancy (depending on trimester).
• Contraindications and reasons why an MRI/MRA cannot be performed may include: impaired renal function, claustrophobia, non-MRI compatible devices (such as non- compatible defibrillator or pacemaker), metallic fragments in a high-risk location, patient exceeds wight limit/dimensions of MRI machine.

References

1. Galldiks N, Albert N, Sommerauer M, Grosu A, Ganswindt U et al. PET imaging in patients with meningioma-report of the RANO/PET Group. Neuro Oncol. Nov 29 2017; 19: 1576-1587. 10.1093/neuonc/nox112.
2. NCCN. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) Central Nervous System Cancers. March 24, 2023; 2023: Version 1.2023.
3. Govil-Dalela T, Kumar A, Behen M, Chugani H, Juhász C. Evolution of lobar abnormalities of cerebral glucose metabolism in 41 children with drug-resistant epilepsy. Epilepsia. Jul 2018; 59: 1307- 1315. 10.1111/epi.14404.
4. Jones A, Cascino G. Evidence on Use of Neuroimaging for Surgical Treatment of Temporal Lobe Epilepsy: A Systematic Review. JAMA Neurol. Apr 2016; 73: 464-70. 10.1001/jamaneurol.2015.4996.
5. Tang Y, Liow J, Zhang Z, Li J, Long T et al. The Evaluation of Dynamic FDG-PET for Detecting Epileptic Foci and Analyzing Reduced Glucose Phosphorylation in Refractory Epilepsy. Front Neurosci. 2018; 12: 993. 10.3389/fnins.2018.00993.
6. Albert M S, DeKosky S T, Dickson D, Dubois B, Feldman H H et al. The diagnosis of mild cognitive impairment due to Alzheimer’s disease: recommendations from the National Institute on Aging- Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimer’s Dement. 2011; 7: 270-9. 10.1016/j.jalz.2011.03.008.
7. Bohnen N, Djang D, Herholz K, Anzai Y, Minoshima S. Effectiveness and safety of 18F-FDG PET in the evaluation of dementia: a review of the recent literature. J Nucl Med. Jan 2012; 53: 59-71. 10.2967/jnumed.111.096578.
8. Caminiti S, Ballarini T, Sala A, Cerami C, Presotto L et al. FDG-PET and CSF biomarker accuracy in prediction of conversion to different dementias in a large multicentre MCI cohort. Neuroimage Clin. 2018; 18: 167-177. 10.1016/j.nicl.2018.01.019.
9. Campbell N, Boustani M, Lane K, Gao S, Hendrie H et al. Use of anticholinergics and the risk of cognitive impairment in an African American population. Neurology. Jul 13 2010; 75: 152-9. 10.1212/WNL.0b013e3181e7f2ab.
10. Davis D, Creavin S, Yip J, Noel-Storr A, Brayne C. Montreal Cognitive Assessment for the diagnosis of Alzheimer’s disease and other dementias. Cochrane Database Syst Rev. Oct 29 2015; 2015: Cd010775. 10.1002/14651858.CD010775.pub2.
11. Frey K, Lodge M, Meltzer C, Peller P, Wong T et al. ACR-ASNR Practice Parameter for Brain PET/CT Imaging Dementia. Clin Nucl Med. Feb 2016; 41: 118-25. 10.1097/rlu.0000000000001037.
12. Motara H, Olusoga T, Russell G, Jamieson S, Ahmed S et al. Clinical impact and diagnostic accuracy of 2-[(18)F]-fluoro-2-deoxy-d-glucose positron-emission tomography/computed tomography (PET/CT) brain imaging in patients with cognitive impairment: a tertiary centre experience in the UK. Clin Radiol. Jan 2017; 72: 63-73. 10.1016/j.crad.2016.08.003.
13. Washington State Health Care Authority. WSHCA 20150116A Functional Neuroimaging for Primary Degenerative Dementia or Mild Cognitive Impairment. 2015; https://www.hca.wa.gov/about-hca/programs-and-initiatives/health-technology-assessment/functional-neuroimaging-primary- degenerative-dementia-or-mild-cognitive-impairment.
14. Wippold F 2, Brown D, Broderick D, Burns J, Corey A et al. ACR Appropriateness Criteria Dementia and Movement Disorders. J Am Coll Radiol. Jan 2015; 12: 19-28. 10.1016/j.jacr.2014.09.025.

Coding Section

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive. 

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other nonaffiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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