Description
This document addresses the medical imaging technique in which the results obtained from a single photon emission computed tomography (SPECT) scan are merged with those obtained from a computed tomography (CT) scan (also known as hybrid imaging). This fusion may occur by the combining of images from two separate devices, or by the use of specialized equipment designed to perform both SPECT scanning and CT scanning simultaneously.

Background
Although there are some SPECT procedures that utilize whole body scanning (such as bone scans), SPECT studies typically focus on the function of specific organs, such as the thyroid, heart, lungs, gallbladder, liver and kidneys. SPECT agents (radiopharmaceuticals) incorporate antibody and peptide formulations that can be targeted to specific tissue receptors, allowing one to discriminate healthy from diseased tissue. For instance, the octreotide series of single photon-emitting peptide tracers is far more specific for identifying the neuroendocrine tumors, iodine-131 for thyroid tumors, technetium-99m methoxyisobutylisonitrile (MIBI) for parathyroid imaging and In-131 ProstaScint^™ for prostate cancer. SPECT agents can also be monitored for tissue changes over time, allowing physicians to narrow down the characteristics of a specific disease process. Because SPECT tracers have very specific characteristics, more than one agent, each emitting a particular energy level, can be injected to track related processes simultaneously. The goal is to be able to pinpoint both the disease process and its ongoing response to treatments. However, because there are fewer landmarks using SPECT, the more specific the targeting agent is, the more difficult it is to interpret its anatomical position. This may make it difficult for physicians to accurately interpret certain SPECT images.

A CT scan is a painless, noninvasive diagnostic procedure that uses X-ray equipment to obtain cross-sectional images of the body. With the aid of a computer, each cross-sectional image of the body is added together to create a tomogram (a 3-D image of the internal structures and organs in the body). On occasion, a contrast material, or X-ray dye, may be administered to enhance the image. CT scans are performed to analyze the internal structures of various parts of the body. For example, in the event of traumatic injuries, CT scans may be taken to identify blood clots or fractures. CT scans of the abdomen are extremely helpful in defining body organ anatomy, including visualizing the liver, gallbladder, pancreas, spleen, aorta, kidneys, uterus and ovaries. CT scans in this area are used to verify the presence or absence of tumors, infection and abnormal anatomy. CT scans are also used to aid radiologists in performing procedures such as the biopsy of suspected cancers, the removal of internal body fluids for testing and the draining of abscesses located deep within the body. With regard to cancer, CT scans are used to detect or confirm the presence of a tumor, its size, location, whether it has metastasized (spread) and to monitor the body's response to treatment.

CT scans are not without limitations. CT scans do not show muscles or ligaments clearly. Also, with regard to the spinal region, the administration of contrast agents or dye is necessary to show the discs and nerves of the spine. CT scans are also very sensitive to body movement. For instance, the simple act of the individual breathing or the normal inflating and deflating of the bowel can distort the position of neighboring organs.

By fusing SPECT and CT scans into a single procedure, researchers hope to obtain the superior metabolic information provided by SPECT studies with the clear anatomical information gained from CT scans. Performing the two exams while the individual remains on the table increases the likelihood of good image registration.

Policy 
The use of SPECT/CT fusion imaging is considered MEDICALLY NECESSARY in the evaluation of parathyroid glands in individuals with hyperparathyroidism when used for anatomic localization prior to parathyroid surgery. 

The use of SPECT/CT fusion imaging is investigational and/or unproven and is therefore considered NOT MEDICALLY NECESSARY for all other indications. 

Rationale
SPECT/CT fusion refers to the imaging technique that combines the functional information from SPECT with the anatomical information from CT into one set of images. The SPECT and CT images are either "fused" by a software package that superimposes two digital images together or are processed simultaneously by combined SPECT/CT scanners. In either case, SPECT/CT fusion has been purported to allow for more accurate diagnosis and, thus, improved outcomes and treatment.

Parathyroid Imaging
The parathyroid glands are four small glands in the neck that control the body's calcium level. Keeping a proper balance of calcium is essential to the normal functioning of other organs in the body, including the heart, kidneys, bones and the nervous system. Due to the size and location of the parathyroid glands, localization is important preoperatively. In a 2007 study by Lavely and colleagues, 98 participants had a diagnosis of primary hyperparathyroidism and single adenoma. Each participant had planar imaging, SPECT scanning and SPECT/CT fusion imaging and comparisons were made to compare the accuracy of parathyroid SPECT/CT imaging to SPECT and planar imaging for localization of parathyroid adenomas. The overall sensitivity for localization for all modalities was 60%, specificity was 99%, positive predictive value (PPV) was 80%, negative predictive value (NPV) was 97% and area under the curve (AUC) was 80%. When SPECT/CT was compared to planar imaging, the single-phase SPECT/CT was not significantly superior to dual-phase imaging for sensitivity, AUC or PPV of localization. The dual-phase SPECT/CT did have a higher sensitivity, AUC and PPV than the dual-phase planar imaging. When SPECT/CT was compared to SPECT scan, the dual-phase SPECT/CT was superior to dual-phase SPECT sensitivity and AUC for localization. The most superior method found was early SPECT/CT in combination with any delayed imaging when compared to a single- or dual-phase planar or SPECT scan for localization of parathyroid adenoma.

A study by Prommegger and colleagues (2009) looked at 116 participants with primary hyperparathyroidism who had a SPECT scan and CT scan compared to SPECT/CT scan to determine whether the SPECT/CT fusion scan was superior in detecting abnormal parathyroid glands. The CT scan alone predicted the position of the abnormal gland in 75 participants, the SPECT scan alone predicted the position in 64 participants and the SPECT/CT fusion scan predicted the position of the abnormal gland in 102 participants. The sensitivity for CT scan was 70% and specificity was 94%. Sensitivity for SPECT scan was 59% with a specificity of 95%, SPECT/CT scan showed sensitivity of 80% with a specificity of 99%. A total of 62 participants underwent surgery. The authors concluded that the use of SPECT/CT fusion imaging had a higher sensitivity and specificity than CT or SPECT imaging alone when used for preoperative localization of parathyroid glands in those individuals with hyperparathyroidism.

In a 2015 meta-analysis by Wong and colleagues, the authors sought to determine the diagnostic utility of parathyroid scintigraphy with SPECT/CT fusion imaging for localization of parathyroid adenoma when compared to older planar and SPECT scans. A total of 24 articles were included in their analysis. Sensitivity of SPECT/CT was found to be 0.86 (confidence interval [CI] 0.81 – 0.90) compared to sensitivity of SPECT at (0.74; CI 0.66 – 0.82) and planar imaging at (0.70; CI 0.61 – 0.80). Using SPECT/CT imaging with parathyroid scintigraphy improves performance when compared to older planar and SPECT imaging.

Another meta-analysis by Treglia and colleagues (2016) reported on 23 articles in which participants with primary hyperparathyroidism had SPECT/CT fusion imaging prior to surgery. The pooled detection rate of SPECT/CT in preoperative planning of individuals with primary hyperparathyroidism was 88% (95% CI = 84% to 92%) on a per participant-based analysis and 88% (95% CI = 82% to 92%) on a per lesion-based analysis.

Based on expert opinion and guidance, SPECT/CT is found to be medically necessary for certain parathyroid indications, especially when compared with other imaging modalities. In a 2006 study by Sharma and colleagues, the authors compared the accuracy of four types of sestamibi-based scans for preoperative parathyroid localization. A total of 138 participants underwent planar imaging, 165 participants underwent SPECT scanning, 350 participants underwent SPECT with thyroid I-subtraction phase and 180 participants underwent SPECT/CT imaging. False negative scans were noted in 38% of planar scans, 27% of SPECT scans, 4% of SPECT with thyroid I-subtraction phase and 17% in SPECT/CT. The accuracy of each scan was determined based on intraoperative parathyroid pathology. When a single focus of uptake was noted on scan, a single adenoma was found at that location in 77% of planar imaging, 85% of SPECT imaging, 68% SPECT with thyroid I-subtraction and 87% with SPECT/CT. A 2009 European Association of Nuclear Medicine parathyroid guideline notes that, "Use of integrated SPECT/CT with a high spatial resolution, spiral CT used for anatomical localization, improves accuracy and reporter confidence in clinical practice."

Other Clinical Conditions
The use of SPECT/CT fusion has been studied for other clinical conditions. A 2011 guideline by the European Association of Nuclear Medicine (Flotats), reported on hybrid imaging for individuals with known or suspected coronary artery disease. In terms of cardiac imaging, the hybrid systems are not routinely used because of the difficulty in determining which individuals would benefit from the dual scanning and radiation exposure is reported as a concern.

References 

1. Centers for Medicare & Medicaid Services. National Coverage Determination: Computerized Tomography. NCD #220.1. Effective March 12, 2008. http://www.cms.hhs.gov/mcd/index_list.asp?list_type=ncd. Accessed on July 8, 2016.
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3. Damgaard M, Nimb L, Madsen JL. The role of bone SPECT/CT in the evaluation of lumbar spinal fusion with metallic fixation devices. Clin Nucl Med. 2010; 35(4):234-236.
4. Flotats A, Knuuti J, Gutberlet M, et al. Hybrid cardiac imaging: SPECT/CT and PET/CT. A joint position statement by the European Association of Nuclear Medicine (EANM), the European Society of Cardiac Radiology (ESCR) and the European Council of Nuclear Cardiology (ECNC). Eur J Nucl Med Mol Imaging. 2011; 38(1):201-212.
5. Gabriel M, Hausler F, Bale R, et al. Image fusion analysis of (99m) Tc-HYNIC-Tyr(3)-octreotide SPECT and diagnostic CT using an immobilisation device with external markers in patients with endocrine tumours. Eur J Nucl Med Mol Imaging. 2005; 32(12):1440-1451.
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11. Meyer-Rochow GY, Schembri GP, Benn DE, et al. The utility of metaiodobenzylguanidine single photon emission computed tomography/computed tomography (MIBG SPECT/CT) for the diagnosis of pheochromocytoma. Ann Surg Oncol. 2010; 17(2):392-400.
12. Prommegger R, Wimmer G, Profanter C, et al. Virtual neck exploration: a new method for localizing abnormal parathyroid glands. Ann Surg. 2009; 250(5):761-765.
13. Schillaci O, Danieli R, Manni C, et al. Technetium-99m-labelled red blood cell imaging in the diagnosis of hepatic haemangiomas: the role of SPECT/CT with a hybrid camera. Eur J Nucl Med Mol Imaging. 2004; 31(7):1011-1015.
14. Shafiei B, Hoseinzadeh S, Fotouhi F, et al. Preoperative 99mTc-sestamibi scintigraphy in patients with primary hyperparathyroidism and concomitant nodular goiter: comparison of SPECT-CT, SPECT, and planar imaging. Nucl Med Commun. 2012; 33(10):1070-1076.
15. Sharma J, Mazzaglia P, Milas M, et al. Radionuclide imaging for hyperparathyroidism (HPT): which is the best technetium-99m sestamibi modality? Surgery. 2006; 140(6):856-863.
16. Stoffels I, Boy C, Pöppel T, et al. Association between sentinel lymph node excision with or without preoperative SPECT/CT and metastatic node detection and disease-free survival in melanoma. JAMA. 2012; 308(10):1007-1014.
17. Suga K, Iwanaga H, Tokuda O, et al. Steal phenomenon-induced lung perfusion defects in pulmonary arteriovenous fistulas: assessment with automated perfusion SPECT-CT fusion images. Nucl Med Commun. 2010; 31(9):821-829.
18. Suga K, Kawakami Y, Iwanaga H, et al. Comprehensive assessment of lung CT attenuation alteration at perfusion defects of acute pulmonary thromboembolism with breath-hold SPECT-CT fusion images. J Comput Assist Tomogr. 2006; 30(1):83-91.
19. Suga K, Kawakami Y, Zaki M, et al. Clinical utility of co-registered respiratory-gated (99m)Tc-Technegas/MAA SPECT-CT images in the assessment of regional lung functional impairment in patients with lung cancer. Eur J Nucl Med Mol Imaging. 2004; 31(9):1280-1290.
20. Sumer J, Schmidt D, Ritt P, et al. SPECT/CT in patients with lower back pain after lumbar fusion surgery. Nucl Med Commun. 2013; 34(10):964-970.
21. Tharp K, Israel O, Hausmann J, et al. Impact of 131I-SPECT/CT images obtained with an integrated system in the follow-up of patients with thyroid carcinoma. Eur J Nucl Med Mol Imaging. 2004; 31(10):1435-1442.
22. Treglia G, Sadeghi R, Schalin-Jäntti C, et al. Detection rate of 99m Tc-MIBI single photon emission computed tomography (SPECT)/CT in preoperative planning for patients with primary hyperparathyroidism: A meta-analysis. Head Neck. 2016; 38 Suppl 1:E2159-E2172.
23. Utsunomiya D, Shiraishi S, Imuta M, et al. Added value of SPECT/CT fusion in assessing suspected bone metastasis: comparison with scintigraphy alone and nonfused scintigraphy and CT. Radiology. 2006; 238(1):264-271.
24. Wong KK, Fig LM, Gross MD, Dwamena BA. Parathyroid adenoma localization with 99mTc-sestamibi SPECT/CT: a meta-analysis. Nucl Med Commun. 2015; 36(4):363-375.
25. Yamamoto Y, Nishiyama Y, Monden T, et al. Clinical usefulness of fusion of 131I SPECT and CT images in patients with differentiated thyroid carcinoma. J Nucl Med. 2003; 44(12):1905-1910.
26. Zheng JG, Yao ZM, Shu CY, et al. Role of SPECT/CT in diagnosis of hepatic hemangiomas. World J Gastroenterol. 2005; 11(34):5336-5341.
27. Lavely WC, Goetze S, Friedman KP, et al. Comparison of SPECT/CT, SPECT, and planar imaging with single- and dual-phase (99m)Tc-sestamibi parathyroid scintigraphy. J Nucl Med. 2007; 48(7):1084-1089
28. Liddy S, Worsley D, Torreggiani W, Feeney J. Preoperative imaging in primary hyperparathyroidism: literature review and recommendations. Can Assoc Radiol J. 2017; 68(1):47-55.
29. Prommegger R, Wimmer G, Profanter C, et al. Virtual neck exploration: a new method for localizing abnormal parathyroid glands. Ann Surg. 2009; 250(5):761-765.
30. Sandqvist P, Nilsson IL, Grybäck P, et al. SPECT/CT's advantage for preoperative localization of small parathyroid adenomas in primary hyperparathyroidism. Clin Nucl Med. 2017; 42(2):e109-e114.
31. Shafiei B, Hoseinzadeh S, Fotouhi F, et al. Preoperative 99mTc-sestamibi scintigraphy in patients with primary hyperparathyroidism and concomitant nodular goiter: comparison of SPECT-CT, SPECT, and planar imaging. Nuc Med Commun. 2012; 33(10):1070-1076.
32. Sharma J, Mazzaglia P, Milas M, et al. Radionuclide imaging for hyperparathyroidism (HPT): which is the best technetium-99m sestamibi modality? Surgery. 2006; 140(6):856-863.
33. Treglia G, Sadeghi R, Schalin-Jäntti C, et al. Detection rate of 99m Tc-MIBI single photon emission computed tomography (SPECT)/CT in preoperative planning for patients with primary hyperparathyroidism: A meta-analysis. Head Neck. 2016; 38 Suppl 1:E2159-E2172
34. Wong KK, Fig LM, Gross MD, Dwamena BA. Parathyroid adenoma localization with 99mTc-sestamibi SPECT/CT: a meta-analysis. Nucl Med Commun. 2015; 36(4):363-375.
35. Centers for Medicare & Medicaid Services. National Coverage Determination: Computerized Tomography. NCD #220.1. Effective March 12, 2008. http://www.cms.hhs.gov/mcd/index_list.asp?list_type=ncd. Accessed on July 7, 2017.
36. Flotats A, Knuuti J, Gutberlet M, et al. Hybrid cardiac imaging: SPECT/CT and PET/CT. A joint position statement by the European Association of Nuclear Medicine (EANM), the European Society of Cardiac Radiology (ESCR) and the European Council of Nuclear Cardiology (ECNC). Eur J Nucl Med Mol Imaging. 2011; 38(1):201-212
37. Hindié E, Ugur O, Fuster D, et al. 2009 EANM parathyroid guidelines. Eur J Nucl Med Mol Imaging. 2009; 36(7):1201-1216..

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 non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies and accredited national guidelines.

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