Assessment Of Flow In Cerebrospinal Fluid Shunts With A Wireless Thermal Anisotropy Measurement Device: Phase A
Conditions: Hydrocephalus
Sponsor: Rhaeos, Inc.

NCT05015751 
 
 
 
 
 
Protocol: 2020-01 
Title: Assessment of Flow in Cerebrospinal Fluid Shunts with a Wireless Thermal 
Anisotropy Measurement Device: Phase A 
Version Date (Last IRB Approval): February 18, 2023 
 
 

Study Purpose and Rationale: 
Cerebrospinal ﬂuid (CSF) shunts fail often, but diagnosis is difficult as symptoms are non-
speciﬁc. Existing non-invasive tests are not able to assess ﬂow directly but rely on 
secondary measures of shunt function. Conversely, invasive tests can be painful and risk 
contamination and infection of the shunt system.  
This trial will evaluate the performance of FlowSense, a device for non-invasively assessing 
CSF shunt ﬂow using thermal anisotropy measurements, in a prospective study setting. 
The results of this study will be used to establish baseline device performance. 
 
Study Design: 
This is a prospective, open-label, blinded, multi-center, single-arm observational study of 
up to 31 main study subjects at a minimum of 2 trial sites. Subjects with an existing CSF 
shunt and symptoms of a shunt failure will be recruited by the clinical investigators based 
on the inclusion and exclusion criteria. Subjects will undergo evaluation with the 
FlowSense device and standard-of-care testing and will be followed for 14 days to 
determine if a revision was performed to repair or replace the existing shunt. In subjects 
undergoing a revision, intraoperative assessment of shunt functionality will establish the 
presence or absence of a complete shunt obstruction. FlowSense device data will be used 
to categorize shunt function as “ﬂow conﬁrmed” or “ﬂow not conﬁrmed.” The results of this 
study will be used to establish baseline device performance. 
Clinical staff will be required to complete training on the protocol and device measurement 
procedures as well as complete a roll-in study device measurement prior to enrolling main 
study subjects. 
 
Statistical Procedures: 
Data from this study will be used to determine baseline study device measurement 
characteristics and performance. The device sensitivity and speciﬁcity are the primary 
endpoints. Performance measures (sensitivity, speciﬁcity, accuracy, positive predictive 
value (PPV), and negative predictive value (NPV)) will be estimated along with 95% two-
sided conﬁdence intervals (CI).  
To calculate the performance measures, the study device output of either “ﬂow conﬁrmed” 
or “ﬂow not conﬁrmed” and the standard-of-care clinical treatment will place each subject 
into one of the following categories: 

 
True Positive (TP): 
Device outputs “ﬂow not conﬁrmed” AND a shunt revision surgery 
with conﬁrmed shunt failure is performed 
False Positive (FP):  
Device outputs “ﬂow not conﬁrmed” AND either no shunt revision 
surgery is performed for 14 days or a shunt revision surgery without 
a conﬁrmed shunt failure is performed 
True Negative (TN): 
Device outputs “ﬂow conﬁrmed” AND either no shunt revision 
surgery is performed for 14 days or a shunt revision surgery without 
a conﬁrmed shunt failure is performed 
False Negative (FN):  Device outputs “ﬂow conﬁrmed” AND a shunt revision surgery with 
conﬁrmed shunt failure is performed 
 
If a subject does not fall within one of these categories (e.g., if shunt patency was not 
assessed during revision surgery), data for that subject was not included in the endpoint 
calculation. Study device sensitivity will be calculated as TP / (TP + FN) and study device 
speciﬁcity will be calculated as TN / (TN + FP). 
This study is intended to generate preliminary performance data and is not designed for 
statistical signiﬁcance. 
 
Enrollment Criteria: 
Inclusion criteria 
1. Existing ventriculoperitoneal CSF shunt on which the patient is dependent 
2. At least one symptom of shunt malfunction as determined by the investigator, 
including seizure, fever, headache, vision problems, dizziness, disorientation, 
confusion, vomiting, lethargy, irritability, difficulty waking or staying awake, swelling 
along shunt tract, enlargement of head, loss of balance, gait disturbance, and loss of 
sensory or motor function 
3. Suspicion of shunt obstruction warrants the performance of a test for this condition in 
4. Region of intact skin overlying an unambiguously identiﬁable chronically indwelling 
ventricular shunt which crosses the clavicle and is appropriate in size for application 
of the study device 

5. Available for follow-up for up to fourteen days 
6. Signed informed consent by patient or a parent, legal guardian, health care agent, or 
surrogate decision maker (according to local statutes, and collectively referred to as 
"surrogates" in this protocol) 
7. Verbal assent by minors four years of age and older who are able to understand the 
study and communicate their decision 
 
Exclusion criteria 
1. Presence of multiple shunts, or presence of more than one distal shunt catheter 
(regardless of function) crossing the clavicle ipsilateral to the shunt with suspected 
obstruction 
2. Use of the study device would interfere with standard patient care, or emergency 
surgery that cannot be delayed 
3. Presence of an interfering open wound or edema over any portion of the shunt 
4. Patient-reported history of adverse skin reactions to adhesives 
5. Investigator judges that the subject is likely to be lost to follow-up due to unavailability 
or clinical outcome being unobtainable 
6. Participation in the study will interfere with, or be detrimental to, administration of 
optimal health-care to the subject 
7. Prior enrollment in this study (multiple enrollments of the same patient are disallowed) 
8. Participation in any other investigational procedural, pharmaceutical, and/or device 
study that may inﬂuence the collection of valid data under this study 
 
Study Procedures: 
Pediatric and adult shunt-dependent hydrocephalus patients with an existing CSF shunt 
and shunt failure symptoms will be screened and enrolled based on the inclusion and 
exclusion criteria. Written informed consent will be obtained from all subjects or their legal 
representative before enrollment into the trial.  

To use the study device, the subject will be oriented in an upright, seated position. The 
location of the CSF catheter near the clavicle will be marked and the device will be 
adhered. The study staff will press down on the device to ensure good contact, and the 
device measurement will be initiated through a mobile application that has been preloaded 
onto an iPad. The measurement result will be displayed on the iPad as an encoded 
alphanumeric string. 
The study device temperature data and device photos will be stored directly onto the iPad. 
Radiology, medical oncology, surgery, and pathology records may also be collected. 
 
Study Device: 
Device name: FlowSense® 
Device description: FlowSense (Rhaeos, Inc.; Model Alpha), the study device, is designed to 
provide non-invasive wireless measurement of ﬂow in implanted CSF shunts via thermal 
anisotropy measurements. The single-use device, which includes a low-power heating 
element, a set of temperature sensors, a Bluetooth low energy (BLE) wireless chip, and a 
coin cell battery enclosed in a ﬂexible housing, is similar in size to a conventional adhesive 
bandage and communicates with an iPad application to perform measurements and report 
the results. 
 
Research Questions(s)/Hypothesis(es): 
Primary objective: The primary objective of this study is to establish baseline study device 
performance. 
Secondary objectives: The secondary objectives of this study are to determine the 
accuracy, positive predictive value (PPV), and negative predictive value (NPV) of the study 
device in this population. Additional objectives include collecting and describing clinical, 
demographic, and hydrocephalus (e.g., etiology, shunt system type, shunt system brand, 
shunt valve settings) characteristics of the study population, device user feedback, and 
shunt testing data (e.g., imaging studies). Additional study device diagnostic and 
performance data (e.g., temperature data and error codes) will be collected for 
adjudication and review purposes. 
 
Scientiﬁc Abstract: 

Diagnosing cerebrospinal ﬂuid (CSF) shunt failure can be difficult and currently relies on a 
combination of indirect and/or invasive methods. This study will evaluate the performance 
of the non-invasive FlowSense wireless device to rapidly assess shunt ﬂow. The primary 
objective of this study is to establish baseline device performance (sensitivity and 
speciﬁcity). 
This is a prospective, blinded, observational multi-center study. Subjects will undergo 
evaluation with the FlowSense device and standard-of-care imaging and will be followed 
for 14 days to determine if a revision was performed to repair or replace the existing shunt. 
In subjects undergoing a revision, intraoperative assessment of shunt functionality 
established the presence or absence of a complete failure. FlowSense device data will be 
used to categorize shunt function as “ﬂow conﬁrmed” or “ﬂow not conﬁrmed.”  
 
Lay Abstract: 
Cerebrospinal ﬂuid (CSF) shunts often fail.  However, it can be difficult to know when the 
device has failed because the symptoms patients experience are common (such as 
headache, nausea, and tiredness) and can have many causes that are unrelated to the CSF 
shunt. In addition, the current tests used to determine if a CSF shunt has failed are not 
always correct. When a CSF shunt does fail, patients typically have a shunt revision 
surgery. During the surgery, the entire shunt or some of its components are repaired or 
replaced. 
This trial will gather data to improve how the study device distinguishes between 
functioning (ﬂowing) and non-functioning (non-ﬂowing) shunts. The study will use the 
device on patients who have a CSF shunt and are experiencing symptoms of possible shunt 
failure. The patients and clinical staff will not see the device results, and the patients will 
receive their normal care. The patients will be followed for 14 days to see if they have a 
shunt revision surgery. If a patient has surgery, the doctor will check the shunt to see if ﬂuid 
can ﬂow through it. The device data will then be compared to the patient outcome (no 
revision surgery/revision surgery with a ﬂowing shunt or revision surgery with a non-ﬂowing 
shunt).