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Monitoring of Regional Cerebral Blood Flow Using an Implanted Cerebral Thermal Perfusion Probe

Policy Number: MP-214

Latest Review Date: September 2023

Category: Medicine                                                               


Monitoring of regional cerebral blood flow using an implanted cerebral thermal perfusion probe is considered investigational.


Cerebral blood flow (CBF) is essential for normal metabolism of the brain.  Ischemic brain injury occurs when CBF is insufficient to meet metabolic demand, which can occur in acute neurological disorders (e.g. head injury, subarachnoid hemorrhage, or following neurosurgery).

Various imaging techniques have been attempted to identify individuals at risk for secondary ischemic brain injury and manage response to therapies.  Some of these techniques are still evolving (e.g., stable-xenon-enhanced computed tomography (XeCT), perfusion computed tomography, perfusion magnetic resonance imaging, single photon emission computed tomography (SPECT) and positron emission tomography (PET)).  While these techniques can provide regional information about CBF, the data provided is a single snap shot in time.  Methods for the continuous measurement of CBF have been investigated and are now commercially available.  One such method is a thermal perfusion probe, which is placed intra-cerebrally via a burr hole in the vascular area of interest in the brain.  The probe is connected to a monitor that displays CBF data. 

The QFlow 500 probe (Hemedex, Inc, Cambridge, MA) is an example of a commercially available thermal perfusion probe that has received 510(k) marketing clearance from the Food and Drug Administration (FDA).  It is used along with the Bowman Perfusion Monitor, Model 500 (Hemedex, Inc, Cambridge, MA).  According to the manufactures website, one potential application of the device is for monitoring CBF in patients with traumatic brain injury to help identify secondary ischemic injury to the brain.  The manufacturer states that, by measuring continuous, real-time CBF, clinicians may identify cerebral edema and measure tissue blood flow response to therapies.  Another potential neurological application is monitoring CBF following neurosurgery (e.g., aneurysm and subarachnoid hemorrhage procedures).


The most recent literature search was performed through September 14, 2023.

Summary of Evidence

Current literature on thermal perfusion probes has focused on their feasibility and technical capabilities.  Prospective clinical outcome studies are needed to determine their clinical value over other standard methods of identifying individuals at risk for secondary ischemic brain injury (e.g., head injury, subarachnoid hemorrhage, or following neurosurgery) and in monitoring response to therapies.


Cerebral perfusion, cerebral thermal perfusion probe, Qflow 500™ Perfusion Monitoring System, subarachnoid hemorrhage, transcranial doppler (TCD)


The Qflow 500™ Perfusion Monitoring System is a cerebral thermal perfusion probe that received FDA clearance through the 510(k) process in 2000. The labeled indication for the device is as follows:

“The QFlow™ is intended for extravascular monitoring of microcirculation blood flow in buried tissues. Examples of this application include (but are not limited to) 1) the monitoring of buried muscle or esophagus following free muscle transfer or esophageal free muscle transfer or esophageal reconstruction, 2) monitoring soft tissue microcirculation following reconstructive surgery, such as oral and facial reconstruction, and 3) monitoring cerebral blood flow during and following neurosurgery for head trauma.”


Coverage is subject to member’s specific benefits.  Group-specific policy will supersede this policy when applicable.

ITS: Home Policy provisions apply

FEP: Special benefit consideration may apply.  Refer to member’s benefit plan.


CPT Codes:

There are no specific CPT codes for cerebral thermal perfusion probes. It is likely they are reported with:


Twist drill hole(s) for subdural, intracerebral, or ventricular puncture; for implanting ventricular catheter, pressure recording device, or other intracerebral monitoring device


Burr hole(s); for implanting ventricular catheter, reservoir, EEG electrode(s), pressure recording device, or other cerebral monitoring device (separate procedure)


  1. Barth M, Capelle HH, et al. Effects of the selective endothelin A (ER(A)) receptor antagonist Clazosentan on cerebral perfusion and cerebral oxygenation following severe subarachnoid hemorrhage – preliminary results from a randomized clinical series. Acta Neurochir 2007; 149(9): 911-918.
  2. Blue Cross Blue Shield Association. Monitoring of regional cerebral blood flow using an implanted cerebral thermal perfusion probe. Medical Policy Reference Manual, March 2008.
  3. De Georgia MA, Deogaonkar A. Multimodal monitoring in the neurological intensive care unit. Neurologist. 2005;11(1):45-54.
  4. Hemedex, Inc. Bowman Perfusion Monitor [website]. Cambridge, MA: Hemedex; 2002. Available at:
  5. IOM (Institute of Medicine). 2011. Clinical Practice Guidelines We Can Trust. Washington, DC: The National Academies Press.
  6. Jaeger M, Soehle M and Meixensberger J. Brain tissue oxygen (PtiO2): A clinical comparison of two monitoring devices. Acta Neurochir Suppl 2005; 95: 79-81. (Abstract)
  7. Rosenthal G, Sanchez-Mejia RO, et al. Incorporating a parenchymal thermal diffusion cerebral blood flow probe in bedside assessment of cerebral autoregulation and vasoreactivity in patients with severe traumatic brain injury. J Neurosurg. 2011;114(1):62-70.
  8. Steiner LA, Czosnyka M. Should we measure cerebral blood flow in head-injured patients? Br J Neurosurg. 2002;16(5):429-439.
  9. Tasneem N, Samaniego EA, Pieper C, et al. Brain multimodality monitoring: A new tool in neurocritical care of comatose patients. Crit Care Res Pract. 2017;2017:6097265.
  10. Thome, C., Vajkoczy, P., Horn, P., & et al. Continuous monitoring of regional cerebral blood flow during temporary arterial occlusion in aneurysm surgery. J Neurosurg 2001; 95:402-11.
  11. U.S. Food and Drug Administration. 510(k) Summary of Safety and Effectiveness: QFlow™ 500 Perfusion Monitoring System, May 2002. //
  12. U.S. Food and Drug Administration. 510(k) Summary for CMA Cerebral Tissue Monitoring System. October 2002, //
  13. Vajkoczy, P., Horn, P., Thome, C., & et al. Regional cerebral blood flow monitoring in the diagnosis of delayed ischemia following aneurismal subarachnoid hemorrhage. J Neurosurg 2003; 98:1227-1234.
  14. Vajkoczy, R., Roth, H., Horn, P., & et al. Continuous monitoring of regional cerebral blood flow; experimental and clinical validation of a novel thermal diffusion microprobe. J Neurosurg 2000; 93:265-74.


Medical Policy Group, December 2005 (4)

Medical Policy Administration Committee, December 2005

Available for comment December 23, 2005-February 6, 2006

Medical Policy Group, December 2006 (1)

Medical Policy Group, December 2007 (1)

Medical Policy Group, February 2009 (1)

Medical Policy Group, June 29, 2011; Active Policy but no longer scheduled for regular literature reviews and updates.

Medical Policy Group, March 2016 (4): Key Points and Coding section updates. No change to policy statement.

Medical Policy Group (3): 2019 Updates to Key Points. A peer reviewed literature analysis was completed and no new information was identified that would alter the coverage statement of this policy.

Medical Policy Group, August 2021(6): Updates to Description, Key Points, Governing Bodies and References.

Medical Policy Group, September 2022 (3): 2022 Updates to Key Points. Reviewed by consensus. No new published peer-reviewed literature available that would alter the coverage statement in this policy.

Medical Policy Group, September 2023 (3): 2023 Updates to Key Points, Benefit Applications, and References. Reviewed by consensus. No new published peer-reviewed literature available that would alter the coverage statement in this policy.  

This medical policy is not an authorization, certification, explanation of benefits, or a contract. Eligibility and benefits are determined on a case-by-case basis according to the terms of the member’s plan in effect as of the date services are rendered. All medical policies are based on (i) research of current medical literature and (ii) review of common medical practices in the treatment and diagnosis of disease as of the date hereof. Physicians and other providers are solely responsible for all aspects of medical care and treatment, including the type, quality, and levels of care and treatment.

This policy is intended to be used for adjudication of claims (including pre-admission certification, pre-determinations, and pre-procedure review) in Blue Cross and Blue Shield’s administration of plan contracts.

The plan does not approve or deny procedures, services, testing, or equipment for our members. Our decisions concern coverage only. The decision of whether or not to have a certain test, treatment or procedure is one made between the physician and his/her patient. The plan administers benefits based on the member’s contract and corporate medical policies. Physicians should always exercise their best medical judgment in providing the care they feel is most appropriate for their patients. Needed care should not be delayed or refused because of a coverage determination.

As a general rule, benefits are payable under health plans only in cases of medical necessity and only if services or supplies are not investigational, provided the customer group contracts have such coverage.

The following Association Technology Evaluation Criteria must be met for a service/supply to be considered for coverage:

1. The technology must have final approval from the appropriate government regulatory bodies;

2. The scientific evidence must permit conclusions concerning the effect of the technology on health outcomes;

3. The technology must improve the net health outcome;

4. The technology must be as beneficial as any established alternatives;

5. The improvement must be attainable outside the investigational setting.

Medical Necessity means that health care services (e.g., procedures, treatments, supplies, devices, equipment, facilities or drugs) that a physician, exercising prudent clinical judgment, would provide to a patient for the purpose of preventing, evaluating, diagnosing or treating an illness, injury or disease or its symptoms, and that are:

1. In accordance with generally accepted standards of medical practice; and

2. Clinically appropriate in terms of type, frequency, extent, site and duration and considered effective for the patient’s illness, injury or disease; and

3. Not primarily for the convenience of the patient, physician or other health care provider; and

4. Not more costly than an alternative service or sequence of services at least as likely to produce equivalent therapeutic or diagnostic results as to the diagnosis or treatment of that patient’s illness, injury or disease.