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CT-guided indirect percutaneous facet synovial cyst rupture combined with
direct fenestration: 10-year review at a single institution
Allison Y. Yang
a,*
, Troy A. Hutchins
b
, Lubdha M. Shah
b
, Lacey Woods
c
, Ghazaleh Safazadeh
b
,
Blair A. Winegar
b
, Anna Hudson
b
, Miriam E. Peckham
b
a
Department of Radiology and Imaging Sciences, Indiana University, United States
b
Departments of Radiology and Imaging Sciences University of Utah Health Sciences Center, United States
c
University of Utah School of Medicine, United States
ABSTRACT
Background: Facet synovial cysts (FSCs) are benign, extradural outpouchings arising from the facet joint that can cause radiculopathy. Effectiveness of CT-guided
indirect percutaneous cyst rupture (IPCR) alone and direct fenestration (DF) treatment alone have previously been reported in large cohorts. We performed a
retrospective review of all FSCs treated under CT-guidance at a single institution where patients underwent IPCR, and IPCR followed by DF if necessary. We hy-
pothesized that CT-guided FSC rupture would demonstrate similar effectiveness to previously reported uoroscopic-guided methods, with potential improvement due
to the opportunity to employ the DF technique in cases of IPCR failure.
Methods: A search was conducted of all CT-guided FSC rupture procedures over 10 years. Data included demographics, needle gauge used for IPCR and DF, rupture
success, cyst size and T2 intensity, presence of spinal hardware, and cyst location. Subsequent surgery at the level of the cyst was documented.
Results: 90 FSC rupture attempts were performed on 75 patients (28 M/47 F). FSC rupture using IPCR had a 70.0% success rate. In 22 FSC rupture attempts, IPCR
failed and was followed by DF, with a success rate of combined IPCR +DF of 90.6 %. Subsequent surgery was required for 36.0% of patients involving the same level
as the cyst or cysts.
Conclusion: Rates of successful FSC rupture under CT-guidance increased when the indirect rupture technique could be followed by direct fenestration in cases of
failure. Our ndings emphasize the benets of exibility afforded to the operator with CT-guidance.
1. Introduction
Facet synovial cysts (FSCs) are benign, extradural, uid-lled out-
pouchings that arise from synovium in the setting of chronic spinal facet
motion and degenerative facet arthropathy, most commonly at the L4/5
level [1,2]. When present, FSCs can impinge upon the intradural neural
elements, as well as exiting and transiting nerve roots, which may
manifest as intractable back pain, radiculopathies, neurogenic claudi-
cation, and, in rare cases, cauda equina syndrome [1].
Treatment options for patients with FSCs generally include non-
operative medical management, surgical excision, indirect percuta-
neous cyst rupture (IPCR) via the facet joint itself (Fig. 1), or direct
fenestration (DF) (Fig. 2) [2,3]. IPCR has been found to achieve statis-
tically and clinically signicant pain relief in patients [4]. Some imaging
markers, specically inherent T2 signal intensity of FSCs, have been
found to directly correlate with success of percutaneous rupture, i.e.
high and intermediate signal intensity cysts are signicantly easier to
rupture than low signal intensity cysts, although the reason for this is not
entirely clear [5].
Access of the facet joint under image guidance may be performed
using either uoroscopy or computed tomography (CT). Use of uo-
roscopy provides real-time assessment of needle trajectory in the ante-
roposterior and lateral planes and can also minimize the radiation dose
to the patient relative to CT [6]. Fluoroscopically-guided procedures use
the IPCR method to treat FSCs, accessing the facet joint from a posterior
approach, conrming intra-articular needle placement by contrast in-
jection, and using high pressure to indirectly rupture the cyst [4,7]. FSCs
treated with IPCR under uoroscopic guidance have been reported to be
successful in up to 81% of cases [8], with an overall success rate of
55.8% as shown in a meta-analysis of 29 studies [9]. A potential
downside of using uoroscopic technique, however, is that it only shows
a two-dimensional evaluation of contrast spread into the epidural space
to conrm rupture [10,11], which can be difcult to differentiate from
the retrodural space of Okada [12]. On the other hand, intervention with
* Corresponding author.
E-mail addresses: yangay@iu.edu (A.Y. Yang), Troy.Hutchins@hsc.utah.edu (T.A. Hutchins), Lubdha.Shah@hsc.utah.edu (L.M. Shah), Lacey.Woods@hci.utah.
edu (L. Woods), Ghazaleh.Safazadeh@hci.utah.edu (G. Safazadeh), Blair.Winegar@hsc.utah.edu (B.A. Winegar), Aewillis10@gmail.com (A. Hudson), Miriam.
Peckham@hsc.utah.edu (M.E. Peckham).
Contents lists available at ScienceDirect
Interventional Pain Medicine
journal homepage: www.journals.elsevier.com/interventional-pain-medicine
https://doi.org/10.1016/j.inpm.2024.100447
Received 30 September 2024; Received in revised form 29 October 2024; Accepted 3 November 2024
Interventional Pain Medicine 3 (2024) 100447
2772-5944/Published by Elsevier Inc. on behalf of International Pain & Spine Intervention Society. This is an open access article under the CC BY-NC-ND license
( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).
CT, albeit a more limited procedural resource, can be instrumental for
accessing joints in patients who may have anatomical variations or large
osteophytes which complicate facet joint access [6]. Under CT-guidance,
FSCs can be treated using the less invasive IPCR method as in uoros-
copy, as well as the more invasive DF technique via an interlaminar
approach to directly aspirate and/or rupture the cyst [2]. The advan-
tages of CT include [1]: accurate visualization of contrast extravasation
into the epidural space to conrm successful cyst rupture (Fig. 1) [13],
and [2] the ability to use a DF technique in the case of IPCR failure
(Fig. 2).
The effectiveness of CT-guided IPCR FSC treatment alone and DF FSC
treatment alone have previously been reported in large cohorts. In our
study, we performed a retrospective review of all FSCs treated under CT-
guidance at a single institution where patients underwent IPCR, DF, or a
combination of techniques over the last ten years. We hypothesized that
CT-guided IPCR would be similarly effective when compared to previ-
ously reported uoroscopic-guided methods in the literature, with
potentially improved effectiveness due to the opportunity to employ the
DF technique in cases of IPCR failure. We investigated the patient de-
mographics, pre-procedure FSC imaging features, and procedure tech-
niques in order to determine if any of these were associated with
successful cyst rupture or the need for subsequent surgical intervention.
2. Materials and methods
This exploratory retrospective, single-arm cohort/case series was
conducted under an institutional review board-approved protocol, and
informed consent was waived.
2.1. Subjects
We conducted a search in the Nuance mPower (Montage, Burlington,
Massachusetts) database for all CT-guided facet synovial cyst rupture
procedures performed within the last ten years, August 2012 - August
2022. Search terms included ‘facet AND synovial AND cyst AND needle
AND rupture.’ Results were ltered by Exam description, including ‘CT
guidance needle placement’ and ‘CT guided cyst aspiration’ and ‘CT
guided needle biopsy’. Data for each case, including accession number,
patient sex, patient age, and report text, were exported into Microsoft
Excel Spreadsheet (Microsoft Corporation, Redmond, Washington).
Next, a search was conducted in the Picture Archiving and
Communication System (PACS) using the accession numbers to record
corresponding medical record numbers, demographic information, level
of intervention, presence of spinal hardware, needle gauge used, suc-
cessful indirect rupture (which was determined by contrast
extravasating into the ventral or dorsal epidural fat pad or into the
foramina), and follow-up direct fenestration and rupture attempt, as
applicable. Additionally, pre- and post-procedure pain scores by
numeric rating system were recorded as available. For each patient, the
most recent pre-intervention lumbar MR images were accessed to record
cyst size in greatest biaxial dimension, cyst location, and cyst T2 in-
tensity. Chart review was performed on each patient to assess rates of
subsequent surgery at the same level of prior intervention during the
study period.
2.2. Procedural technique
All cases were performed by one of three operators with a range of
2–15 years of procedural experience during the 10-year search period
and used techniques established by the practice. Pre-procedure MR
imaging was reviewed for each patient to determine precise location of
each FSC. Potential risks of the procedure were discussed with the pa-
tient, including but not limited to bleeding, infection, or injury to sur-
rounding blood vessels, nerves, or the spinal cord. Each patient was
positioned prone on the table, and the overlying skin was prepped and
draped in the usual sterile fashion and anesthetized locally with 1–2%
lidocaine. Conscious sedation was achieved with IV Versed and Fentanyl
and titrated to effect under continuous physiologic monitoring.
All FSC ruptures were rst attempted using the less invasive IPCR
approach prior to consideration of using the more invasive DF approach.
Under CT-guidance, either a 17-, 18-, 20-, or 22-gauge needle (as
deemed by physician by patient anatomic factors) was placed with its tip
in the posterior aspect of the facet joint ipsilateral to the FSC. Contrast
was injected into the facet joint in order to visualize the lling of the
synovial cyst under CT. Once visualized, a mixture of 80 mg Depo-
Medrol, 1 cc of 0.5 % Bupivacaine, and 1 cc of normal saline was
forcefully injected into the facet joint to attempt indirect rupture of the
synovial cyst and bathe the epidural space at this level. Cyst rupture via
this indirect technique was conrmed by visualization of contrast
extravasating into the epidural space, after previously being contained
within the cyst. Upon procedure completion, the needle was removed,
and a sterile dressing applied to the area. If no contrast was seen
extravasating into the epidural space, additional indirect attempts were
performed using preservative-free normal saline to achieve FSC rupture.
If multiple (i.e. at least 3) subsequent IPCR attempts with normal
saline failed, the more invasive DF technique was performed as feasible
via an interlaminar approach. Under CT-guidance, a 17-, 18-, 20-, or 22-
gauge spinal needle was placed using either [1] an ipsilateral inter-
laminar approach or [2] a contralateral interlaminar approach in order
to access the FSC. Direct fenestration of the cyst was performed, and
Fig. 1. The indirect percutaneous cyst rupture technique as shown in three sequential procedural CT axial images. Image A demonstrates placement of a spinal
needle into the posterior aspect of the right facet joint, with injection of contrast to ll the joint space (arrow). Image B demonstrates contrast extending from the
joint and lling the FSC (arrow). Image C demonstrates extravasation of contrast into the right lateral and ventral aspects of the epidural space after successful FSC
rupture (arrows).
A.Y. Yang et al.
Interventional Pain Medicine 3 (2024) 100447
2
preservative-free normal saline was injected into the cyst to induce a
direct rupture. Subsequent CT images through the intervention site were
attained in order to conrm contrast extending from the cyst into the
epidural space, demonstrating a successful cyst rupture.
2.3. Statistical analysis
Analyses were performed to evaluate imaging and procedural vari-
ables and their effect on the following outcomes: success of IPCR, suc-
cess of IPCR followed by DF, and necessity for subsequent surgery at the
level of FSC. Successful IPCR or rupture via DF was dened by visuali-
zation of contrast extravasation through the epidural space. Statistical
analysis was performed using the Mann-Whitney test for non-parametric
variables, Student t-test for parametric continuous variables, and Fisher
Exact test for categorical variables. The variables analyzed were as fol-
lows: sex, age, hardware, needle gauge, cyst size in greatest bi-axial
dimension, and cyst T2 intensity, all of which were chosen to replicate
studies that have preceded ours, in order to determine the relationship
between each of these variables and successful cyst rupture at our
institution. The change in numeric rating scale between pre- and post-
procedure was correlated with procedure success, both in the IPCR
and IPCR +DF groups.
The T2 intensity of FSCs was evaluated by a neuroradiology
attending with 9 years of experience (BW) and neuroradiology fellow
with one year of experience (AH). They assigned categories of T2 signal
per the methods originally developed by Cambron et al. [5]. Weighted
Cohen’s Kappa Coefcient was used to report the reliability of the two
radiologists [14].
For analyses of predictor variables and their association with out-
comes, a total of 75 patients consisting of 90 FSC rupture attempts/90
cases were analyzed. Three procedures involved bilateral synovial cyst
ruptures. Patients’ sex and hardware status did not change between
procedures (n =75). Patients’ age, needle gauge, cyst size, and cyst
intensity changed between total cases (n =90). Three procedures used
the same MR ndings, and as such, T2 cyst intensity and size were
excluded from outcome calculations for these procedures (n =87). Data
Analyses were generated using STATA version 17 statistical software
[StataCorp. College Station, TX].
3. Results
3.1. Subjects
Ninety cases were yielded from our search. Three cases had no
intervention performed due to no cyst lling with contrast during the
procedure (one cyst previously seen on MRI not found to communicate
with the facet joint, one case found to represent facet hypertrophy on the
CT planning scan prior to intervention instead of a cyst, and one case
demonstrating a vascular structure rather than a cyst). However, we
included these cases as they would have likely undergone intervention
in the uoroscopic setting. The 90 FSC attempted ruptures remaining for
review were performed on 75 patients (28 males with an average 62.3
years of age; 47 females with an average 61.1 years of age) under CT-
guidance. Three cases involved bilateral FSCs (3.2%), with the
remainder being unilateral (96.8%). Eleven patients required repeated
FSC interventions [1]: 9 were treated twice [2], 1 was treated 3 times,
and [3] 1 treated 4 times in total. This resulted in a total of 90 FSCs being
treated in 90 cases involving 75 patients (Supplemental Table). There
were no procedural complications.
3.2. Inter-rater reliability
An inter-rater reliability analysis of cyst T2 signal intensity showed
Kw =0.65, which falls in the substantial level of agreement [15]. The
agreement values were dened as follows: ≤0 poor, 0.01–0.20 slight,
0.21–0.40 fair, 0.41–0.60 moderate, 0.61–0.80 substantial, and
0.81–1.00 almost perfect.
3.3. Overall rates of successful cyst rupture
63/90 (70.0%) FSCs were successfully treated using the IPCR
method alone. In 27 FSCs the IPCR method did not result in cyst rupture.
In 22 of these FSCs the failed rupture was subsequently followed by DF,
which was successful in 14/22 FSCs (63.6%). In 5 of these FSCs, DF was
not attempted due to anatomy barriers (no interlaminar window). The
overall success rate for FSC rupture using IPCR alone was 70.0% (63/90
FSCs), and the success rate of combined IPCR +DF was 90.6% in FSCs
where both techniques were attempted (77/85 FSCs, as 5 FSCs never had
a DF attempted).
Twenty-seven out of 75 patients required subsequent surgery
involving the same level as the cyst or cysts (36.0%). The average
amount of time after the attempted percutaneous cyst rupture to sub-
sequent surgery was 10.21 (standard deviation±15.23) months.
3.4. Association of age, sex, and presence of surgical hardware with
treatment outcomes
Neither age nor sex were found to be associated with success of IPCR
alone, IPCR +DF, or subsequent need for surgery (Table 1, Table 2).
Fourteen patients had surgical hardware, and of these, 13 (92.9%)
had the hardware present either directly adjacent to or at the same level
as the FSC. The presence of surgical hardware was also not found to be
Fig. 2. Failure of indirect percutaneous cyst rupture followed by successful rupture by direct fenestration. Image A demonstrates indirect lling of the FSC via lling
of the right facet joint (arrow). There was failure of rupture after multiple attempts at pressurizing the cyst indirectly. Image B demonstrates direct fenestration of the
cyst. This caused subsequent spillage of contrast into the epidural space (early extravasation noted by arrow).
A.Y. Yang et al.
Interventional Pain Medicine 3 (2024) 100447
3
associated with treatment success or subsequent need for surgery
(Table 1).
3.5. Association of procedural technique and treatment outcomes
An 18-gauge Quincke needle was most used in the IPCR technique
(82/90 FSCs, 91.1 %). Four FSC ruptures were attempted with a 20-
gauge Quincke needle, three with a 22-gauge Quincke needle, and one
used a 17-gauge needle. Needle gauge was not found to be associated
with treatment success of IPCR alone, IPCR +DF, or subsequent need for
surgery (Table 2).
3.6. Association of procedural outcomes and pain relief
Pre- and post-procedure pain scores were available in both the IPCR
+DF and IPCR alone groups. There were only 46 paired pain scores in
the IPCR +DF and 45 paired pain scores in IPCR alone group.
In IPCR +DF group, the mean change in pain scores was the same
between successful and unsuccessful procedures (−3.8 vs. −3.3, p =
.83). In the IPCR alone group, those with unsuccessful rupture had a
slightly greater reduction in pain (−4.3) compared to those with suc-
cessful rupture (−3.5); however, it was not statistically signicant (p =
.45), (Table 3).
Given the similar levels of pain reduction across the success rates, it
suggests that procedural success of rupture did not immediately impact
the amount of pain relief, or that the sample sizes might be too small to
detect a signicant effect. There were not enough observations for
analysis in the group that subsequently underwent surgery.
3.7. Association of imaging features and treatment outcomes
Cyst size in greatest bi-axial dimension had a mean size of 46.4 mm.
Size was not found to be associated with treatment success of IPCR or
IPCR +DF. However, small cysts were more often found to require
subsequent surgery (mean of 44.2 mm vs 50.0 mm, p =.012) (Table 2).
Forty-two of the 87 FSCs with corresponding MRI demonstrated a bright
T2 signal, forty demonstrated an intermediate signal, and ve demon-
strated a dark signal on T2-weighted imaging. Intrinsic cyst intensity
was not found to be associated with success of IPCR, IPCR +DF, or
subsequent surgery.
4. Discussion
Our study is, to our knowledge, one of the rst to evaluate the
effectiveness of FSC rupture using a combination of IPCR, followed by
the DF technique in cases of IPCR failure, by employing CT-guidance.
We found a lower rate of rupture using IPCR under CT-guidance
Table 1
Patient-level characteristics and outcomes. (n =75).
Overall Success Success IPCR alone Subsequent surgery
No Yes p-value No Yes p-value No Yes p-value
Age mean (SD), y 61.52 (10.7)
Female 61.06 (10.7)
Male 62.28 (10.8)
Sex no. (%)
Female 47 (62.6) 10 (71.4) 37 (60.6) .45 19 (731) 28 (57.2) .17 32 (66.6) 15 (55.5) .34
Male 28 (37.3) 4 (28.5) 24 (39.3) 7 (27) 21 (42.8) 16 (33.3) 12 (44.4)
Hardware no. (%)
No 64 (85.3) 12 (85.7) 52 (85.2) .96 24 (92.3) 40 (81.6) .21 41 (85.4) 23 (85.2) .97
Yes 11 (14.7) 2 (14.3) 9 (14.8) 2 (7.7) 9 (18.4) 7 (14.6) 4 (14.8)
-Student t-test for parametric continuous variables and Fisher Exact or chi-squared test for categorical variables where appropriate.
Table 2
FSC rupture attempt characteristics and outcome.
Overall Success Success IPCR alone Subsequent surgery
No Yes p-
value
No Yes p-
value
No Yes p-
value
Age mean (SD), y (n =90) 66 (9.5) 61.7 (10.5) .15 62.7 (10.5) 62.1 (10.5) .78 62 (11.5) 63 (8.5) .67
Needle Gauge no. (%) (n =90)
Any 18 13 (100) 69 (89.6) .22 26 (96.3) 56 (88.9) .25 51 (89.572) 31 (94) .47
Other 0 8 (10.4) 1 (3.7) 7 (11.1) 6 (10.5) 2 (6)
Cyst size median [IQR], mm (n =
87)
a
46 [32.2,
52.5]
46.7 [35.7,
91.5]
.44 47.6 [32.8,
66]
45.8 [35.7,
80.2]
.92 50 [37.2,
100.7]
44.2 [30,
57.6]
.012
T2 Signal no. (%) (n =87)
a
Hyper-intense (H) 3 (23) 39 (52.7) .10 9 (33.3) 33 (55) .15 24 (43.5) 18 (56.3) .41
Intermediate (I) 9 (69.3) 31 (41.9) 16 (59.3) 24 (40) 28 (51) 12 (37.5)
Hypo-intense (L) 1 (7.7) 4 (5.4) 2 (7.4) 3 (5) 3 (5.5) 2 (6.1)
-Student t-test used for parametric continuous variables (Age),-Mann-Whitney test for non-parametric variable (Cyst Size), and Fisher Exact or chi-squared test for
categorical variableswhere appropriate.
-Cyst size: L x W (mm), calculated by multiplying the two greatest biaxial dimensions in millimeters.
a
In three FSC rupture attempts same MR was used and were excluded.
Table 3
Absolute pain score change from pre-to post-procedure.
obs mean change (SD) p-value
IPCR þDF Success (n =46)
Yes 43 −3.8 (3.1) 0.83
No 3 −3.3 (3.5)
IPCR Alone Success (n =45)
Yes 33 −3.5 (3.3) 0.45
No 12 −4.3 (2.7)
- Student t-test.
- Pain scores were documented on a scale of 0–10 (0: no pain, 10: the worst
pain).
A.Y. Yang et al.
Interventional Pain Medicine 3 (2024) 100447
4
compared to what has been previously reported using uoroscopy in a
large cohort (70.0% vs 81% [8]). However, we found a higher rate of
successful FSC rupture when IPCR was followed by DF (90.6%), and
combining the IPCR and DF techniques resulted in a higher rate of
success than uoroscopically guided IPCR alone rates, which has been
described in prior meta-analyses (55.8%) [9].
Rates of success with IPCR combined with DF in our study were
overall similar to a previously reported IPCR alone CT-guided study,
which reported an 87% success rate [5]. Though our study utilized
slightly different techniques (e.g. needles used in the Cambron et al.
study included a 14-gauge to penetrate covering facet osteophytes), our
high rate of success emphasizes the value of CT-guided intervention to
not only allow for repeated attempts until unequivocal rupture with the
less invasive initial IPCR approach, but also the exibility to transition
to the more invasive DF technique, which we have shown increases the
likelihood of FSC rupture.
Prior studies have examined radiologic FSC features, and association
with subsequent surgical conversion in one study of 45 patients found no
correlation between cyst signal intensity, size, facet effusion, spondy-
lolisthesis, canal stenosis, or facet edema with eventual surgery [7]. In
comparison, our study, with a larger cohort, interestingly found an as-
sociation between smaller cyst size and the need for subsequent surgery.
This result was somewhat surprising, and we surmise that smaller cysts
may perhaps have an easier time reforming than larger cysts, which in
turn, results in persistent symptoms for the patient. However, it is not
certain from these ndings that the symptoms requiring FSC treatment
and subsequent surgery were caused by these small cysts, and our as-
sumptions based on this correlation are therefore limited. Cambron et al.
found in their study of 110 patients that cysts with higher intrinsic T2
intensity were more likely to rupture using the IPCR technique, and they
hypothesized that the higher proportion of uid within the cyst im-
proves ease of IPCR compared to lower intensity cysts, which may be
more characteristically gelatinous or calcied. They also discussed that
increased T2 intensity led to fewer subsequent surgeries compared to the
cohort with more hypointense cysts. Our study, however, did not nd
these same associations, potentially limited by our lower sampling
power with a smaller patient cohort.
Rates of surgical intervention following IPCR +DF were found to be
lower in our CT-guided cohort than previously reported in a large IPCR
by uoroscopy study in 101 patients (36.0% vs 54% [8]), and more
similar to other uoroscopically-guided studies demonstrating a con-
version rate of 20–38.7% [7,9,16].
Strengths of our study include the ability to unequivocally conrm
FSC rupture with CT-guidance. Single and bi-planar views with uo-
roscopy may not be as denitive, as we suspect there may be a
component of false positive ruptures when assessing rupture under
uoroscopic guidance versus CT. This may partially account for the
discrepancy between CT conrmed success, and previously reported
uoroscopic success.
One limitation of our study includes the retrospective nature of our
investigation with absence of patient-reported outcomes, and inconsis-
tent collection of pre and post pain scores, which limited our analyses.
There is also a lack of repeat MR imaging in some patients that went
underwent repeat rupture, as clinicians might order a repeat interven-
tion upon return of symptomatology with the assumption of recurrence
instead of obtaining post-procedural MR imaging, which partially limits
our determination of associated imaging variables. Additionally, we
could only track subsequent surgery in this patient cohort if it occurred
at our institution which may under-represent this percentage.
5. Conclusion
Conrmed FSC rupture via indirect technique under CT-guidance
was lower compared to previously reported uoroscopic-guided
studies in the literature, but the rates of successful rupture increased
with the addition of the direct fenestration technique. Our ndings
emphasize the benets of exibility afforded to the operator with a CT-
guided approach. CT guided direct fenestration may be indicated to treat
FSCs that fail uoroscopic or CT-controlled indirect rupture.
Declaration of competing interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
the work reported in this paper.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.inpm.2024.100447.
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