Assessment of Flow in Cerebrospinal Fluid Shunts With a Wireless Thermal Anisotropy Measurement Device, Phase B
Conditions: Hydrocephalus
Sponsor: Rhaeos, Inc.

NCT05432986 
 
 
 
 
 
 
Protocol: 2021-01 
Title: Assessment of Flow in Cerebrospinal Fluid Shunts with a Wireless Thermal 
Anisotropy Measurement Device, Phase B 
Version Date (Last IRB Approval): September 7, 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 objective of this study is to establish the performance of the device in subjects 
presenting with a possible shunt failure. 
 
Study Design: 
This is a prospective, open-label, blinded, multi-center, single-arm observational study of 
up to 150 (roll-in and main study) subjects at up to 10 trial sites. Patients 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 7 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.” This trial will evaluate the ability of the study device to accurately 
distinguish between functioning (ﬂowing) and non-functioning (non-ﬂowing) shunts.  
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 patients. 
 
Statistical Procedures: 
The co-primary endpoints for this study are sensitivity and speciﬁcity. 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 patient 
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 7 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 7 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 patient does not fall within one of these categories (e.g., if shunt patency was not 
assessed during revision surgery), data for that patient will not be 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). 
A minimum of 30 “positive” patients (those who undergo shunt revision surgery with a 
conﬁrmed shunt failure) will be enrolled. 
Secondary subgroup analyses will be performed to report on any variation between 
pediatric and adult patients. Additional subgroup analyses will be performed to identify any 
patient characteristics that may impact device performance.  
 
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, such as 
but not limited to 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 
the investigator’s judgement 
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 seven 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) 
 
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 main study 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 patient 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 
to the skin. 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 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 Number FS01), 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 objectives: The primary objectives of this study are to determine the sensitivity and 
speciﬁcity of the study device for identifying the presence or absence of complete shunt 
failure in symptomatic hydrocephalus patients with CSF shunts. 
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. The diagnostic performance of an additional ﬂow 

assessment algorithm will also be assessed using the data acquired in this study by the 
study device. 
 
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 objective of this study is to establish performance of the study device in subjects 
presenting with symptoms of a possible shunt failure. 
This is a prospective, blinded, observational multi-center study. Patients will undergo 
evaluation with the FlowSense device and standard-of-care imaging and will be followed 
for 7 days to determine if a revision was performed to repair or replace the existing shunt. In 
patients undergoing a revision, intraoperative assessment of shunt functionality 
established the presence or absence of a complete obstruction. 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 determine if the study device can accurately distinguish between functioning 
(ﬂowing) and non-functioning (non-ﬂowing) shunts. The study will enroll patients who have 
a CSF shunt and are experiencing symptoms of possible shunt failure. The patients and 
clinical staff will not see the study device results, and the patients will receive their normal 
care. The patients will be followed for 7 days to see if they have a shunt revision surgery. In 
patients who do have surgery, the doctors will check the shunt to see if ﬂuid can ﬂow 
through it. The study device results of “ﬂow conﬁrmed” or “ﬂow not conﬁrmed” 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).