(February 2, 2026): Neurologists, radiologists, and vascular surgeons around the country who perform Transcranial Doppler Ultrasound procedures are currently under the government’s regulatory microscope. Therefore, it is more important than ever that you review your business practices to confirm your transcranial doppler procedures fully meet applicable medical necessity, documentation, coding, and billing requirements. As discussed in more detail below, transcranial Doppler[1] ultrasound studies may be billed under various CPT[2] Codes, depending on the specific nature of the study performed. Transcranial Doppler ultrasound procedures are one of the latest risk areas being examined by Medicare Administrative Contractors (MACs) and various program integrity and medical review contractors working for the Centers for Medicare and Medicaid Services (CMS). In this article, we examine the current enforcement environment and outline how to respond if your transcranial Doppler ultrasound studies are audited.
I. Overview of Transcranial Doppler Ultrasound Studies and Their Role in Evaluating Specific Clinical Conditions:
A. Early Development of Transcranial Doppler Ultrasound Studies.
Transcranial Doppler ultrasound was first invented in 1981 by Rune Aaslid, PhD., a Norwegian researcher specializing in neuroscience and medical engineering. Dr. Aaslid’s novel approach allowed for the non-invasive assessment of blood flow velocity in the brain’s major arteries. This advancement enabled healthcare professionals to monitor cerebral circulation at the patient’s bedside, greatly enhancing the ability to diagnose and manage neurological conditions such as stroke and cerebral vasospasm after subarachnoid hemorrhage. The initial detailed account of the transcranial Doppler ultrasound technique developed by Dr. Aaslid first appeared in a 1982 article in the Journal of Neurosurgery.[3] This seminal article described how ultrasound waves, applied through the temporal bone, could yield real-time measurements of blood flow within the brain without requiring invasive procedures. Dr. Aaslid’s innovation established transcranial Doppler ultrasound as a valuable diagnostic tool in both neurology and critical care settings.
B. What is the Purpose of Transcranial Doppler Ultrasound Testing?
Transcranial Doppler ultrasound procedures are a non-invasive and painless imaging technique that uses sound waves to assess how blood moves through the main arteries in the brain. The main purposes of this procedure include the following:
- To detect conditions that can disrupt normal blood flow. These conditions may include stroke (caused by blockages from clots), stenosis (the narrowing of blood vessels), and vasospasm that may occur after bleeding in the brain.[4]
- To provide a quick, immediate look at a patient’s cerebrovascular function. Transcranial doppler ultrasound procedures provide clinicians with a rapid, contemporaneous look at how well blood is circulating in the brain’s arteries. It allows them to measure the speed and direction of blood flow, helping detect issues such as vessel narrowing or small clots traveling through the bloodstream.[5]
- To assist in diagnosing and monitoring a range of cerebrovascular conditions. For example, transcranial Doppler ultrasound procedures can be essential in diagnosing a number of conditions, such as sickle cell disease, emboli, and ischemic cerebrovascular disease.
In summary, transcranial Doppler ultrasound serves as a non-invasive way to monitor and assess blood flow in the brain, supporting the diagnosis, management, and follow-up of conditions that could threaten the brain’s blood supply.
C. How are Transcranial Doppler Ultrasound Studies Conducted?
Transcranial Doppler ultrasound studies are conducted using a specialized pulsed-wave Doppler ultrasound machine. Unlike standard ultrasound tests, these machines use a low-frequency (2 MHz transducer) probe to penetrate the dense bone of the skull and measure the velocity and direction of blood flow in the brain's major arteries. To conduct the procedure, a clinician or trained technician places a small ultrasound transducer on specific areas of the patient’s head, such as the temples, the base of the skull, or over closed eyelids. A gel is applied to help transmit the sound waves effectively. The probe is positioned at certain “acoustic windows” in the skull where the bone is thinner, allowing ultrasound waves to pass through and reach the brain’s blood vessels. The device emits sound waves that bounce off moving blood cells within the cerebral arteries. The returning echoes are analyzed by a computer to create visual and audio representations of blood flow. The Doppler effect allows clinicians to measure the speed and direction of blood flow in real time. Since a transcranial Doppler ultrasound machine is portable and non-invasive, it can be performed at the bedside in critical care settings or in outpatient clinics. Although there are a variety of Doppler ultrasound machines currently in use, most utilize the following basic components:
- 2 MHz Transducer: This transducer serves as the primary hand-held tool used to send sound waves through the skull. High-frequency probes used for other parts of the body cannot penetrate the skull effectively.
- Main Unit: Often a portable system or a laptop-based setup that processes sound wave echoes into visual and audible data.
- Spectral Display Monitor: A screen that shows waveforms representing blood flow patterns, velocities (peak systolic and end-diastolic), and “pulsatility indices.”[6]
- Head Frame (Optional): A dedicated headset or headband that can hold probes in a fixed position for continuous, long-term monitoring without a technician holding them.
II. Medicare Coverage of Transcranial Doppler Ultrasound Procedures:
A. LCD Guidance Addressing Transcranial Doppler Ultrasound Studies.
Two MACs have published Local Coverage Determination (LCD) guidance addressing transcranial Doppler ultrasound procedures, either specifically or as part of a broader LCD. Each of these LCDs outline the clinical indications, limitations, CPT codes, and coverage criteria for each of the transcranial Doppler ultrasound studies discussed in the guidance. Additionally, one MAC has a Billing and Coding Article that further elaborates on the utilization, coding, and billing of transcranial Doppler ultrasound procedures. The guidance issued by these MACs is set out in the two charts below.
| LCD Specifically Targeting Transcranial Doppler Ultrasound Studies | ||||
|---|---|---|---|---|
| MAC Name | LCD and / or LCA Number | LCD / LCA Title |
States/Territories Covered (Part B Only) |
LCD / LCA Effective Date |
| First Coast Service Options |
Jurisdiction J-N
LCD -- L33977[7] Jurisdiction J-N
Article -- A57633[8] |
LCD – Transcranial Doppler Studies
Article – Billing and Coding: Transcranial Doppler Studies |
Jurisdiction J-N Florida, Virgin Islands, Puerto Rico |
LCD – Revision Effective Date: For services performed on or after 10/29/2019.
Article – Revision Effective Date: 01/01/25. |
Currently, only First Coast Service Options has issued an LCD that is dedicated to transcranial Doppler ultrasound studies. However, National Government Solutions has issued broader LCD guidance covering “Non-Invasive Vascular Studies” which includes a section dedicated to transcranial Doppler ultrasound procedures. Please see below:
| Broader LCD With Section Covering Transcranial Doppler Ultrasound Studies | ||||
|---|---|---|---|---|
| MAC Name | LCD and / or LCA Number | LCD / LCA Title |
States/Territories Covered (Part B Only) |
LCD / LCA Effective Date |
| National Government Services (NGS) | Jurisdiction J-6 LCD -- L33627[9] |
LCD – Non-Invasive Vascular Studies | Jurisdiction J-6 Illinois, Minnesota, Wisconsin |
LCD – Revision Effective Date: For services performed on or after 10/01/2019. |
B. Transcranial Doppler Ultrasound Studies – Related CPT Codes.
The CPT Codes used to bill Medicare for transcranial Doppler ultrasound studies were updated in 2025. The primary codes are for the complete or limited study, with additional add-on codes for specialized procedures. For example, additional codes can be reported with a complete transcranial Doppler study (CPT Code 93886) on the same date. Add-on codes must be listed separately when also studies on vasoreactivity (93896), emboli detection (93897), and venous-arterial shunt detection (93898).
| CPT Codes Outlined in Billing and Coding Article A57633 | |
|---|---|
| CPT Code | Description |
| 93886 | Transcranial Doppler study of the intracranial arteries, complete study. |
| 93888 | Transcranial Doppler study of the intracranial arteries; limited study.
Notes:
|
| 93892 | Transcranial Doppler study of the intracranial arteries; emboli detection without intravenous microbubble injection. |
| 93893 | Transcranial Doppler study of the intracranial arteries; venous-arterial shunt detection with intravenous microbubble injection. |
| 93896 | Vasoreactivity study performed with transcranial Doppler study of intracranial arteries, complete.
Notes:
|
| 93897 | Emboli detection without intravenous microbubble injection performed with transcranial Doppler study of intracranial arteries, complete.
Notes:
|
| 93898 | Venous-arterial shunt detection with intravenous microbubble injection performed with transcranial Doppler study of intracranial arteries, complete.
Notes:
|
C. Covered Diagnosis Codes When Conducting Transcranial Doppler Ultrasound Studies.
Providers must review a patient’s ICD-10 diagnosis codes and ensure that the patient’s medical condition and diagnosis support medical necessity BEFORE performing a transcranial Doppler ultrasound study. Accurate coding not only justifies the clinical need for the procedure but also ensures compliance with insurance requirements and regulatory standards. For example, First Coast Service Options has issued a billing and coding article (A57633)[10] that set out 160 ICD-10 diagnosis codes, ranging from “Aneurysm of Vertebral Artery” (ICD-10 Code 172.6) to “Brain Death” (ICD-10 Code G93.82). If a patient’s ICD-10 diagnosis code(s) does not support medical necessity, transcranial Doppler ultrasound study claims will likely be denied. It may also trigger an audit of a provider’s claims. Please note, the fact that a patient’s diagnosis supports the medical necessity of ordering a transcranial Doppler ultrasound study does not necessarily mean that the procedure will automatically qualify for coverage and payment. Providers must review applicable LCD and other applicable guidance to ensure that all coverage and payment requirements have been met.
III. Overview of Government Enforcement of Improper Billing of Transcranial Doppler Ultrasound Studies:
From an enforcement standpoint, health care providers ordering and billing for transcranial Doppler ultrasound studies may be subject to both administrative audit and law enforcement review. The audit and enforcement risks faced by providers when billing Medicare for these procedures are discussed in more detail below.
A. Administrative Audits of Transcranial Doppler Ultrasound Claims.
Health care providers billing Medicare for transcranial Doppler ultrasound studies may have their claims audited by various CMS contractors. Unified Program Integrity Contractors (UPICs), Recovery Audit Contractors (RACs) and / or the current Supplemental Medical Review Contractor (SMRC) working for CMS are the primary contractors likely to audit a provider’s transcranial Doppler ultrasound claims. The primary denial reasons likely to be cited by these and other CMS contractors have included the following:
- Lack of Medical Necessity. Providers performing transcranial Doppler ultrasound studies need to fully document the clinical reasons why this procedure is medically necessary. As earlier indicated, it is not sufficient to merely list a covered diagnosis ICD-10 code on the CMS Form 1500. The patient’s medical records need to substantiate that the diagnosis is supported by the clinical findings in the records. Moreover, merely having a covered diagnosis is not determinative of coverage. For example, if a patient has suffered a subarachnoid hemorrhage, the provider should document why a transcranial Doppler ultrasound study is needed to further assess vasoconstriction of the patient’s cerebral vessels.
- Improper Coding and Billing Practices. There are countless ways that transcranial Doppler ultrasound studies can be improperly coded or billed. The improper use of modifiers and / or the billing of procedures performed in ineligible settings are examples of improper coding and billing practices that have been identified by CMS audit contractors. Several examples of improper coding and / or billing practices are set out below:
Modifier 26. Modifier 26 is used to reflect that a qualified medical provider performed the professional component of a service / diagnostic procedure. Modifier 26 cannot be used if the technical component of a service or procedure was provided. In the context of a transcranial Doppler ultrasound study, appending Modifier 26 to the code billed indicates that the professional component (Interpretation[11] and Report[12]) was completed by a qualified physician.
Modifier 50. Modifier 50 is used to reflect that a service / diagnostic procedure was conducted bilaterally. In the case of transcranial Doppler ultrasound studies, the test to assess blood flow in the major arteries of the brain may be performed on one or both sides of the brain. Unfortunately, over the years, some MACs have issued guidance regarding this issue that has been confusing and / or contradictory. In fact, a number of transcranial Doppler ultrasound related CPT Codes have been assigned a bilateral indicator of “0” in the Medicare Physician Fee Schedule. Therefore, even if both sides of the brain are studied with the use of a transcranial Doppler ultrasound machine, providers should research whether it is appropriate to use Modifier 50.
Moreover, billing separately for the technical and professional components of a transcranial Doppler ultrasound study on the same date of service, when this is not allowed by a specific payor, would be improper billing. Transcranial Doppler ultrasound studies performed during certain surgical procedures, such as carotid endarterectomy, may be included in the reimbursement for the surgery itself and cannot always be billed separately.
Ineligible Facility Settings. Setting aside medical necessity and a variety of other billing concerns, providers need to keep in mind that Medicare does not allow for transcranial Doppler ultrasound studies to be billed to the payor if the procedure is performed in an ineligible facility setting (for example, in a mobile ultrasound setting that does not meet IDTF requirements). - Unsupported or False Diagnosis Code. When auditing transcranial Doppler ultrasound claims, one of the first steps that will be taken by a CMS contractor is to review the patient’s medical records to verify that the covered diagnosis listed by the provider is documented and supported in the medical records. In the past, some providers have allegedly attempted to bypass payor edits by listing a covered, false diagnosis code, even though the patient's actual medical history did not support that code.
B. Civil Liability Under the False Claims Act.
To be clear, most instances of improper billing involving transcranial Doppler ultrasound procedures are addressed administratively through the assessment of an overpayment. Nevertheless, depending on the facts, the conduct at issue may be pursued by the government as a violation of the civil False Claims. Under the False Claims Act, if a person “knowingly” [13] submits, or causes to be submitted, a false claim to be submitted to the government for payment, that person may be liable for treble damages and significant penalties. It is important to keep in mind that mere errors, mistakes, and accidents are not a violation of the False Claims Act. For false claims or statements made on or after July 3, 2025, the penalties that may be assessed vary from a minimum of $14,308, to a maximum penalty of $28,619, per false claim, plus treble damages.[14]
In January 2026, the U.S. Attorney’s Office for the Middle District of Florida announced that it had reached a civil settlement with several ophthalmology practices that agreed to pay nearly $6 million to resolve alleged violations of the False Claims Act that arose out of a kickback arrangement with a third-party testing company. The tests at issue were transcranial doppler studies. The government further alleged that nearly all the patients who received transcranial doppler procedures were diagnosed as having a covered diagnosis that was not reflected in the patients’ medical records. Notably, this case arose out of a whistleblower complaint.
C. Criminal Liability Associated with Transcranial Doppler Ultrasound Studies.
Significant criminal cases pursued by federal prosecutors involving transcranial Doppler ultrasound procedures have typically involved violations of the Anti-Kickback Statute (sometimes coupled with various other improper coding or billing conduct). Examples of cases prosecuted include the following:
Massachusetts. Federal prosecutors charged the Sales / Operations Director (Director) of a mobile medical diagnostics company with conspiracy to violate the Anti-Kickback Statute. More specifically, the government alleged that the Director conspired with others to enter to offer and pay kickbacks to a number of physicians based on the number of transcranial Doppler ultrasound studies they ordered to be conducted by the defendant’s mobile medical diagnostics company. Notably, the Director and his co-conspirators were further alleged to have created sham rental and administrative services agreements to hide the true nature of the kickback payments made to the physicians. As a result of this scheme, the government claimed that approximately $70 million was wrongfully billed to the Medicare program. Of this total, approximately $27 million was paid to the mobile medical diagnostics company.
Connecticut. A Connecticut-based physician pleaded guilty to receiving kickbacks from a medical diagnostics company in exchange for ordering transcranial Doppler ultrasound procedures to be performed by their company. The government alleged that the defendant physician and his co-conspirator at the medical diagnostics company falsified patient diagnosis codes when submitting medically unnecessary orders for transcranial Doppler ultrasound procedures to Medicare. The government further alleged that this scheme resulted in more than $3 million of fraudulent claims submitted to Medicare and private payors.
Massachusetts. In this case, a New York physician pleaded guilty to one count of conspiracy to commit healthcare fraud. The government alleged that the defendant physician received kickbacks in exchange for ordering medically unnecessary transcranial Doppler ultrasound procedures. When ordering the procedures, the defendant physician was alleged to have assigned false diagnoses codes to patients in support of the transcranial Doppler ultrasound claims. The fraudulent conduct resulted in more than $800,000 being improperly billed to Medicare and other payors.
Although each of the kickback cases above were criminally prosecuted, it is important to keep in mind that violations of the Anti-Kickback Statute could have also been pursued by the government as violations of the civil False Claims Act. When the Affordable Care Act was passed by Congress and subsequently signed into law by President Obama, specific language was added to the Anti-Kickback Statute to permit the government to pursue kickback violations civilly under the False Claims Act.[15] It is also increasingly common to see both civil and criminal cases brought against parties allegedly in violation of the False Claims Act, Anti-Kickback Statute, and Stark Law.
IV. Responding to an Audit or Investigation of Your Transcranial Doppler Ultrasound Claims:
As discussed above, providers performing and billing for transcranial Doppler ultrasound studies need to ensure that these procedures meet applicable medical necessity requirements. Additionally, it is essential that the patient’s clinical condition is fully documented and that the diagnosis that qualifies for coverage of this procedure can be reviewed and verified by CMS contractors in the event of an audit. Providers must also confirm that their coding and billing practices are compliant with the payor’s requirements. Finally, providers must exercise caution when entering any business arrangement. The Anti-Kickback Statute is quite broad, and violations can lead to significant criminal liability. Are your transcranial Doppler ultrasound procedures under audit or investigation? If so, we recommend that you engage experienced health law counsel to represent you. Please schedule a free initial consultaion with Liles Parker.
Matthew Catoe is a health care regulatory attorney at Liles Parker. In addition to being an experienced health law attorney, Matthew is also a Certified Professional Coder (CPC). Matthew’s practice is focused on the defense of health care providers and suppliers in connection with UPIC audits, the appeal of Part B claim denials, and the defense of False Claims Act matters. Are your transcranial Doppler ultrasound claims being audited? Click here to schedule a complimentary consultaion with Liles Parker.
- [1] The word “Doppler” (capitalized) is an eponym, named after the physicist, Christian Doppler, who first described wave frequency change phenomenon.
- [2] The American Medical Association (AMA) has developed a set of “Current Procedural Terminology” (CPT) codes used to describe medical, surgical, and diagnostic services. The codes are used when coding and billing for medical services and procedures.
- [3] Dr. Aaslid’s 1982 paper in the Journal of Neurosurgery, "Noninvasive Transcranial Doppler Ultrasound Recording of Flow Velocities in Basal Cerebral Arteries," is considered to be a foundational work in the field of clinical neuroscience. Aaslid R, Markwalder TM, Nornes H. Noninvasive transcranial Doppler ultrasound recording of flow velocity in basal cerebral arteries. J Neurosurg. 1982 Dec; 57(6): 769-74
- [4] A more comprehensive list of cerebrovascular diseases that may be detected through the use of transcranial doppler ultrasound testing is listed on Cleveland Clinic’s website.
- [5] See article in Seminars in Neurology, “Transcranial Doppler Ultrasound: Technique and Application.” Semin Neurol 2012; 32(04): 411-420.; See also generally: Carrizosa, J. (2022). Transcranial Doppler (TCD/TCCS) Approaches: Acoustic Windows. In: Rodríguez, C.N., et al. Neurosonology in Critical Care. Springer, Cham. https://doi.org/10.1007/978-3-030-81419-9_10.
- [6] A “Pulsatility Index” is defined as the “calculated flow parameter in ultrasound, derived from the maximum, minimum, and mean Doppler frequency shifts during a defined cardiac cycle.” Simply put, it is a non-invasive way of assessing a patient’s vascular resistance using Doppler ultrasound testing.
- [7] First Coast Service Options, Inc., LCD L33977, “Transcranial Doppler Studies.” (Revision Effective Date – For services performed on or after 10/29/2019).
- [8] First Coast Service Options, Inc., A57633, “Billing and Coding: Transcranial Doppler Studies.” Revision Effective Date – 01/01/2025).
- [9] National Government Services, Inc., LCD L33627, “Non-Invasive Vascular Studies.” (Revision Effective Date – 10/01/2019).
- [10] 10 First Coast Service Options, Inc., A57633, “Billing and Coding: Transcranial Doppler Studies.” Revision Effective Date – 01/01/2025).
- [11] The term “Interpretation” means that the physician must interpret the images or data produced by the study and apply his / her expertise to determine what these images mean in terms of the patient’s diagnosis or treatment plan.
- [12] The term “Report” means that the physician must generate a formal, written report documenting the physician’s findings, impressions, and recommendations. Importantly, the interpreting physician must sign the report.
- [13] Under 31 U.S.C. § 3729(b)(1), "knowledge" is defined as (1) actual knowledge, (2) deliberate ignorance of the truth or falsity of the information, or (3) reckless disregard of the truth or falsity of the information.
- [14] The U.S. Department of Justice publishes the updated penalty amounts in the Code of Federal Regulations at 28 C.F.R. § 85.5.
- [15] As 42 U.S.C. §1320(a)-7b(g) provides:
“(f) HEALTH CARE FRAUD.—
(1) KICKBACKS.—Section 1128B of the Social Security Act
(42 U.S.C. 1320a–7b) is amended by adding at the end the following new subsection:
. . .
(g) In addition to the penalties provided for in this section or section 1128A, a claim that includes items or services resulting from a violation of this section constitutes a false or fraudulent claim for purposes of subchapter III of chapter 37 of title 31, United States Code."