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Radiation exposure in the endovascular therapy of cranial and spinal dural arteriovenous fistula in the last decade: a retrospective, single-center observational study

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Purpose This study aims to determine local diagnostic reference levels (DRLs) in the endovascular therapy (EVT) of patients with cranial and spinal dural arteriovenous fistula (dAVF). Methods In a retrospective study design, DRLs and achievable dose (AD) were assessed for all patients with cranial and spinal dAVF undergoing EVT (I) or diagnostic angiography (II). All procedures were performed at the flat-panel angiography-system Allura Xper (Philips Healthcare). Interventional procedures were differentiated according to the region of fistula and the type of procedure. Results In total, 264 neurointerventional procedures of 131 patients with dAVF (94 cranial, 37 spinal) were executed between 02/2010 and 12/2020. The following DRLs, AD, and mean values could be determined: for cranial dAVF (I) DRL 507.33 Gy cm ² , AD 369.79 Gy cm ² , mean 396.51 Gy cm ² ; (II) DRL 256.65 Gy cm ² , AD 214.19 Gy cm ² , mean 211.80 Gy cm ² ; for spinal dAVF (I) DRL 482.72 Gy cm ² , AD 275.98 Gy cm ² , mean 347.12 Gy cm ² ; (II) DRL 396.39 Gy cm ² , AD 210.57 Gy cm ² , mean 299.55 Gy cm ² . Dose levels of EVT were significantly higher compared to diagnostic angiographies ( p < 0.001). No statistical difference in dose levels regarding the localization of dAVF was found. Conclusion Our results could be used for establishing DRLs in the EVT of cranial and spinal dAVF. Because radiation exposure to comparably complex interventions such as AVM embolization is similar, it may be useful to determine general DRLs for both entities together.
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Neuroradiology (2022) 64:587–595
https://doi.org/10.1007/s00234-021-02816-6
INTERVENTIONAL NEURORADIOLOGY
Radiation exposure intheendovascular therapy ofcranial andspinal
dural arteriovenous fistula inthelast decade: aretrospective,
single‑center observational study
MarcelOpitz1· SebastianZensen1· DeniseBos1· YanLi1· HannaStyczen1· AxelWetter1,2· NikaGuberina3·
RamazanJabbarli4· UlrichSure4· MichaelForsting1· IsabelWanke1,5· CorneliusDeuschl1
Received: 4 July 2021 / Accepted: 8 September 2021 / Published online: 27 September 2021
© The Author(s) 2021
Abstract
Purpose This study aims to determine local diagnostic reference levels (DRLs) in the endovascular therapy (EVT) of patients
with cranial and spinal dural arteriovenous fistula (dAVF).
Methods In a retrospective study design, DRLs and achievable dose (AD) were assessed for all patients with cranial and
spinal dAVF undergoing EVT (I) or diagnostic angiography (II). All procedures were performed at the flat-panel angiography-
system Allura Xper (Philips Healthcare). Interventional procedures were differentiated according to the region of fistula and
the type of procedure.
Results In total, 264 neurointerventional procedures of 131 patients with dAVF (94 cranial, 37 spinal) were executed between
02/2010 and 12/2020. The following DRLs, AD, and mean values could be determined: for cranial dAVF (I) DRL 507.33Gy
cm2, AD 369.79Gy cm2, mean 396.51Gy cm2; (II) DRL 256.65Gy cm2, AD 214.19Gy cm2, mean 211.80Gy cm2; for
spinal dAVF (I) DRL 482.72Gy cm2, AD 275.98Gy cm2, mean 347.12Gy cm2; (II) DRL 396.39Gy cm2, AD 210.57Gy
cm2, mean 299.55Gy cm2. Dose levels of EVT were significantly higher compared to diagnostic angiographies (p < 0.001).
No statistical difference in dose levels regarding the localization of dAVF was found.
Conclusion Our results could be used for establishing DRLs in the EVT of cranial and spinal dAVF. Because radiation
exposure to comparably complex interventions such as AVM embolization is similar, it may be useful to determine general
DRLs for both entities together.
Keywords Radiation exposure· Arteriovenous fistula· Embolization· Interventional neuroradiology
Abbreviations
AD Achievable dose
AVM Arteriovenous malformation
CCF Carotid-cavernous fistula
DAP Dose area product
dAVF Dural arteriovenous fistula
DRLs Diagnostic reference levels
EVT Endovascular therapy
FOV Field of view
FT Fluoroscopy time
ICRP International Commission on Radiological
Protection
* Marcel Opitz
marcel.opitz@uk-essen.de
1 Institute ofDiagnostic andInterventional Radiology
andNeuroradiology, Faculty ofMedicine University
Hospital Essen, University Hospital Essen, Hufelandstrasse
55, 45147Essen, Germany
2 Department ofDiagnostic andInterventional Radiology,
Neuroradiology, Asklepios Klinikum Harburg, Hamburg,
Germany
3 Department ofRadiotion Therapy, University Hospital Essen,
West German Cancer Center, Essen, Germany
4 Department ofNeurosurgery, University Hospital Essen,
Essen, Germany
5 Department ofNeuroradiology, Clinic Hirslanden, Zurich,
Switzerland
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Neuroradiology (2022) 64:587–595
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Introduction
Cranial dural arteriovenous fistulas (dAVFs) represent 10–15%
of all intracranial vascular malformations with arteriovenous
shunting and belong to the most frequently acquired vascular
lesions of the central nervous system [1, 2]. The indication for
treatment depends on the morphology of the cranial dAVF,
the resulting probability of bleeding, and clinical presenta-
tion. High-grade fistulas type 2b-5 with cortical reflux clas-
sified by Cognard/Merland have a significantly higher risk of
intracranial hemorrhage [3, 4]. In low-grade fistulas, type 1-2a
by Cognard/Merland, a therapy refractory pulse-synchronous
tinnitus is a typical treatment indication [5, 6]. Over the past
decade, endovascular therapy (EVT) of patients with cranial
dAVF evolved as the first-line treatment with high occlusion
rates, low risk profile, and very low recurrence rates [79].
However, microsurgery, stereotactic radiosurgery, or combined
therapy approaches remain as alternative treatment options.
Spinal dAVF represents the most common subset of spinal
vascular malformations, accounting for approximately 70%.
Nevertheless, it is a rare, probably underdiagnosed pathology
with an incidence of only 5–10 new cases per million inhabit-
ants per year [10]. In contrast to cranial dAVF, hemorrhage in
spinal dAVF is very rare [11]. Nevertheless, a causal therapy
is required in all patients because only the occlusion of the
fistulous point will prevent progressive myelopathy caused by
venous hypertension [12, 13]. Microneurosurgical occlusion of
the fistula was the method of choice for many years, but more
recently, endovascular techniques have augmented the thera-
peutic spectrum. Up to date, both endovascular and surgical
treatment have been proven to be safe and effective [14, 15].
The role of DRLs in interventional neuroradiology has
significantly increased over the last years as the guidelines
for radiation protection have been updated recently [16,
17]. These minimally invasive fluoroscopically guided pro-
cedures are a highly effective treatment option for various
neurovascular conditions. However, because of the complex-
ity of the pathologies, some procedures may comprise high
radiation exposure to patients and staff members [18, 19],
leading to an increased potential deterministic and stochastic
risk of developing radiation-induced cancer [20]. In order to
raise dose awareness and in the long term optimize the modi-
fication of equipment, technique, and imaging parameters,
several professional and regulatory organizations, such as
the International Commission on Radiological Protection
(ICRP), are proclaiming the necessity for diagnostic refer-
ence levels (DRLs), especially in interventional neuroradiol-
ogy [2123].
Data on radiation exposure of EVT in patients with cra-
nial and spinal dAVF remain scarce. Hence, the goal of this
study was to establish local DRLs at our department utilizing
contemporary digital equipment.
Methods
Patient cohort
This retrospective study was approved by the ethical com-
mittee of our institution (20–9758-BO) and is conducted
in accordance with the principles of the Declaration of
Helsinki. All procedures were performed after written
informed consent. The internal database was searched with
an in-house-developed software for all consecutive diag-
nostic angiographies and endovascular treatments of cranial
and spinal dAVF in the period between February 2010 to
December 2020 (Table1). All cranial dAVF were classified
by Cognard/Merland type 1–5 (Table2) [4].
Procedure
All patients of this study cohort underwent diagnostic digi-
tal subtraction angiography (DSA) in house or external
prior to EVT. DSA was performed to confirm the suspected
diagnosis and classify the fistula for further tailoring the
appropriate treatment. The decision to perform endovascular
intervention was based on a case-by-case evaluation in an
interdisciplinary decision-making process between neuro-
surgeons and interventional neuroradiologists. In the case
of primary surgery in patients with spinal dAVF, DSA was
Table 1 Demographic data and classification of dAVF
dAVF dural arteriovenous fistula, EVT endovascular therapy
Parameter Number (%)
Number of patients 131 (100%)
Cranial dAVF 94 (72%)
Male/female 60 (64%)/34 (36%)
Age (mean, range) 57, 23–83
Total number of EVT sessions 111
EVT with Onyx/EASYX 109 (98%)/2 (2%)
Frustrated EVT 5 (4%)
Additional platinum coils 24 (22%)
Additional ballon protection 29 (26%)
Additional surgery 6 (6%)
Spinal dAVF 37 (28%)
Male/female 26 (70%)/11 (30%)
Age (mean, range) 70, 30–79
Total number of EVT sessions/number of
patients
24/ 22 (59%)
EVT with Glubran/Onyx 22 (92%)/2 (8%)
Frustrated EVT 3 (12%)
Additional platinum coils 2 (8%)
Additional surgery 4 (17%)
Exclusively surgery 15 (41%)
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Neuroradiology (2022) 64:587–595
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performed subsequently for control purposes. All EVTs were
performed under general anesthesia.
The standard EVT procedure of cranial dAVFs at our
department is described in detail by Moenninghoff etal.
[24]. A transfemoral access was gained via a 6-F sheath,
and fluoroscopic guided superselective catheterization
was performed to reach a wedge position with the micro-
catheter tip close to the fistula point. Almost all dAVFs
were treated as the primary treatment by ethylene vinyl
alcohol (EVOH) copolymer (Onyx®, Medtronic, Inc.,
Irvine, USA); only two patients received Easyx (Antia
Therapeutics AG, Berne, Switzerland) alternatively.
Superselective transarterial embolization technique and
a detailed description of the EVOH liquid embolic system
are stated in a precursor study of our department [9]. In
some cases, an additional coil embolization or balloon
protection of the venous sinus via venous transfemoral
access was performed.
The standard EVT procedure of spinal dAVFs at our
department is described in detail by Özkan etal. [25]. A
transfemoral arterial approach was obtained, and under
fluoroscopy, a guiding catheter was placed in the seg-
mental artery. A microcatheter was introduced coaxi-
ally through the feeding pedicle and advanced into the
distal aspect of a feeding artery close to the fistula in
the ideal case in wedge-position so that a liquid embolic
agent could be pushed up to the proximal venous side. In
20 patients, a mixture of Glubran® (cyanoacrylate glue,
GEM s.r.l., Italy) and iodized oil (Lipiodol®, Guerbet,
Aulnay-sous-Bois, France) in case-dependently variable
concentrations (ranging from 1:3 up to 1:5) for appro-
priate flow characteristics and in two patients Onyx was
injected. Ideally, a continuous injection embolized the
feeding pedicle, including the terminal feeders up to
the fistulous point, as well as the beginning of the early
draining vein. A final spinal angiogram of the initially
feeding segmental artery and of the adjacent and con-
tralateral segmental arteries was performed.
The intervention was considered successful if embo-
lization of the dAVF was possible. In a few cases, an
endovascular embolization attempt was made, but failed
and was considered frustrating.
Biplanar angiography system
All procedures were performed at the Allura Xper FD20/10
system (Philips Healthcare, Eindhoven, The Netherlands)
by an experienced team of neuroradiologists. As we are a
university hospital, young neuroradiologists were regularly
involved in the interventions in addition to a neuroradiolo-
gist with many years of angiography experience. The X-ray
unit is equipped with automatic control dose rate system.
The frame rate frequently used at pulsed fluoroscopy mode
was 1 pulse/s. The focus-to-skin distance varied from 60 to
70cm. The Allura Xper system has one detector 20-inch
with a maximum field of view (FOV) of 48cm and one
10-inch detector with a max. FOV of 25cm. The deposited
protocol for the treatment of dAVF was set at a characteristic
tube voltage of 80kV. An anti-scatter grid and an aluminum
filter with 1-mm thickness were used. To test system perfor-
mance and stability over time, periodic quality controls were
performed during maintenance visits.
Dose calculation
Radiation exposure for diagnostic DSA and EVT was deter-
mined in terms of dose area product (DAP). To achieve dose
optimization in the clinical routine, DRLs are a globally
accepted parameter for dose monitoring, in the interven-
tional setting typically defined in terms of the DAP. DRLs
represent the 75th percentile of a dose distribution of a spe-
cific radiological procedure and may indicate whether the
radiation dose lies within the normal range of a dose distri-
bution at radiological departments [26, 27]. The achievable
dose (AD) is another important parameter for dose optimi-
zation representing the median of a dose distribution [28].
Statistical analysis
The interventions were analyzed according to the type of
procedure and the type of fistula. The mean, median, and
75th percentile of the DAP, as well as the mean fluoroscopy
time, were calculated. A p-value lower than 0.05 was con-
sidered as statistically significant. Statistical analysis was
performed with the Statistical Package for Social Sciences
v. 27.0. (SPSS Inc., New York, USA).
Table 2 Classification of the 94 patients with cranial dural arterio-
venous fistula (dAVF) according to Merland-Cognard Classification
Fistula type Drainage pattern n (%)
1 Drainage into dural venous sinus, antegrade
flow
11 (11.7)
2a Drainage into dural venous sinus, retrograde
flow
24 (25.5)
2b Drainage into dural venous sinus, antegrade
flow, and cortical venous reflux
1 (1.0)
2a + b Drainage into dural venous sinus, retrograde
flow, and cortical venous reflux
14 (14.8)
3 Cortical venous reflux, no venous ectasia 8 (8.5)
4 Cortical venous reflux, venous ectasia 35 (37.2)
5 Drainage into spinal veins 1 (1.0)
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Neuroradiology (2022) 64:587–595
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Results
Patient cohort
Between February 2010 and December 2020, 264 con-
secutive neurointerventional procedures in 131 patients
with dAVF (94 cranial, 37 spinal) were performed in our
department. The median age of patients with cranial and
spinal dAVF was 60years (range 23–87years) and 70years
(range 30–79years), respectively. The gender distribution in
both cohorts was in favor of the male gender (cranial dAVF
60/94; spinal dAVF 26/37). Out of 94 patients with cranial
dAVF, 111 EVTs were performed using Onyx/EASYX
(109/ 2). A successful embolization was achieved in 106
out of 111 interventions (95.5%). Out of 37 patients with
spinal dAVF, 22 received EVT with Glubran/ Onyx and 15
patients underwent primary surgery. Embolization was in
21/24 (87.5%) procedures successful (Table1).
Radiation exposure andDRLs
The following DRLs, AD, and mean values could be deter-
mined for all patients with dAVF undergoing EVT (I) or
diagnostic cerebral angiography (II): for cranial dAVF (I)
DRL 507.33Gy cm2, AD 369.79Gy cm2, mean 396.51Gy
cm2; (II) DRL 256.65Gy cm2, AD 214.19Gy cm2, mean
211.80Gy cm2; for spinal dAVF (I) DRL 482.72 Gy
cm2, AD 275.98Gy cm2, mean 347.12Gy cm2; (II) DRL
396.39Gy cm2, AD 210.57Gy cm2, mean 299.55Gy cm2
(Table3).
Comparison ofradiation exposure
regardingthetype offistula andprocedure
The Kruskal–Wallis test with Dunn-Bonferroni post hoc
test revealed for both cranial and spinal dAVF a significant
dose difference regarding the type of procedure (p < 0.001)
(Fig.1). No statistical dose difference was found between
the different region of fistula (cranial vs. spinal) according
to DSA (p = 0.380) and EVT (p = 0.472). As normal dis-
tribution was fulfilled and the Levene´s test confirmed the
equality of variance between the subgroups Cognard 4 and
2a in patients with cranial dAVF (p = 0.685), the t-test was
applied. No significant differences of DAP between the two
subgroups (p = 0.548) were observed. The one-way ANOVA
confirmed a significant dose difference between initial
DSA and postsurgery DSA in patients with spinal dAVF
(p < 0.001) (Fig.2). Excluding the frustrated therapy ses-
sions, no significant difference of DAP was observed for cra-
nial dAVF (p = 0.932) or spinal dAVF (p = 0.076). Likewise,
no significant difference of DAP was found for cranial dAVF
(p = 0.151) or spinal dAVF (p = 0.873) by excluding all the
patients who underwent more than one therapy session.
The mean fluoroscopy times (FT) are listed in Table3.
Spearman correlations were run to assess the linear relation-
ship between DAP and FT for DSA and EVT (Fig.3).
Discussion
Our study analyzes radiation exposure of fluoroscopy-guided
angiographies of patients with dAVF and reveals useful
dose data differentiated by the type of fistula, anatomical
region of fistula, and procedure. The results may be used as a
benchmark for the national radiation protection authorities to
implement DRLs in the EVT of cranial and spinal dAVF as
proposed by the European Directive 2013/59/Euratom [23].
With regard to interventional neuroradiology, until now,
the German Federal Office for Radiation Protection only
published DRLs for thrombus aspiration (DRL 180.0Gy
cm2) and aneurysm coiling (DRL 250.0Gy cm2) [29]. For
dAVF embolization, only few authors addressed the issue
of radiation exposure at all. Forbig etal. provided detailed
dosimetry data for the endovascular treatment of intracranial
lateral dAVF differentiated by the Cognard grade and endo-
vascular technique [30]. The proposed DRLs are slightly
lower compared to our study (DRL 414.0Gy cm2). This is
probably related to the strict selection criteria. In our study,
we also excluded other intracranial fistulae, such as CCF.
However, in their study, anterior crainal fossa dAVF were
also excluded. Other studies neither yielded information
Table 3 Distribution of total
DAP as a function of procedure
type and dural arteriovenous
fistula site
DCA diagnostic cerebral angiography, DAP dose area product in gray per square centimeter, dAVF dural
arteriovenous fistula, EVT endovascular treatment, FT fluoroscopic time in minutes, n number of studies
Location of dAVF Type of
proce-
dure
Total DAP (Gy cm2) FT
n 25th percentile Median 75th percentile Mean Mean
Cranial DCA 71 129.57 214.19 256.65 211.80 17min 18s
EVT 111 264.65 369.79 507.33 396.51 58min 57s
Spinal DCA 58 125.57 210.57 396.39 299.55 25min 33s
EVT 24 169.37 275.98 482.72 347.12 35min 45s
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Neuroradiology (2022) 64:587–595
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concerning the dedicated type of dAVF nor the applied
endovascular approach [31, 32].
The local DRLs determined in our study (dAVF cranial
507.3Gy cm2 and spinal 482.7Gy cm2) are higher, but in
the range of the published data of other studies describing
the radiation exposure of AVM embolization only, e.g.,
Miller etal. (479,2Gy cm2 cranial AVM, 476,3Gy cm2
spinal AVM) and Kien etal. (440Gy cm2 cranial AVM)
[33, 34]. Since EVT of both cerebrovascular malforma-
tions are complex neurointerventional procedures with a
similar therapeutic approach, it may not surprise that our
DRLs are in a similar range.
As shown in previous studies, the amount of radiation
for interventional procedures is much more affected by
procedure complexity than by patient size and weight [35].
Therefore, DRLs for interventional procedures should be
ideally established according to the type and complexity
level of the procedure. Although the EVT of cranial and
spinal dAVF is performed in different anatomical regions,
the therapeutic approach is similar, and both are complex
interventional procedures. This may explain why we could
not find any significant dose differences in the EVT of
both fistula types in our cohort. Since our DRLs are in a
similar range to the published local DRLs for embolization
of AVM, it is worth discussing whether DRLs should be
defined under the umbrella term EVT of cerebrovascular
malformations.
The failure of a dAVF embolization only becomes appar-
ent in the course of the procedure and frustrated fluoroscopy-
guided therapy sessions can involve a similarly high radia-
tion dose as successful procedures. This may explain why
in our study no significant difference of DAP was found by
excluding the frustrated therapy sessions.
Excluding all the patients who underwent more than one
therapy session did not affect the total DAP in the EVT of
cranial and spinal dAVF. However, most patients received
only one therapy session, so conclusions about dose differ-
ences are obsolete.
As shown in Figs.2 and 3, there is a linear correlation
between the DAP and the FT, but the FT is a poor predictor
of dose to the patient, because it does not account for the
effects of image acquisition modes. To estimate stochas-
tic risks of radiation exposure, the effective dose is a more
straightforward value [36]. However, to compare radiation
Fig. 1 Histogram of dose area product (Gy cm2) for diagnostic DSA and endovascular therapy (EVT) of cranial and spinal dAVF; blue curve
highlighting distribution graph
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Neuroradiology (2022) 64:587–595
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exposure of different devices at different sites in the clini-
cal routine, DRLs are a practical and a globally accepted
parameter for dose monitoring.
Patients with spinal dAVF received an initial DSA and
in some cases also a postoperative control DSA to ascertain
successful elimination of the fistula. The initial DSAs are
more time-consuming in clinical routine and usually require
more sequences due to the complexity of the disease. For
this reason, it is not surprising that a significantly higher
dose was determined for the initial DSA compared to the
post-surgery DSA (Fig.2).
Cranial dAVF type 2a are confined to sinus, and con-
sequently, the fistula point is easier to reach than in type 4
fistula, which drains directly into cortical veins. However,
with regard to radiation exposure, no significant difference
was found in our study. Consequently, it does not seem to
be useful to distinguish DRLs between the different fistula
types according to Cognard.
It is striking that the gender distribution in our study
clearly favors the male gender. This finding is consistent
with studies that have shown that men are more prone to
cranial and spinal dAVF than women [24, 37].
The most important limitation of our study is the retro-
spective and unicenter design with different cohort sizes.
Our determined dose levels may differ from those of other
sites and angiography devices. Therefore, the examination
of radiation exposure at different sites and devices are the
next necessary steps for the determination of national and
European DRLs. An experienced team of neuroradiologists
performed all procedures, but on a university hospital, young
neuroradiologists are also trained. In terms of radiation dose,
our results therefore may indicate higher doses than can pos-
sibly be achieved.
Strengths of our study include the large number of data-
sets collected on the same biplanar angiography system ena-
bling specific dose assessment. To determine local DRLs for
a single center, it is recommend by Vano etal. to collect the
radiation data of more than 50 examinations within the same
type of procedure because of the high individual variability
of interventional procedures [38]. In this study, the number
of procedures was greater than 50 for the EVT of cranial
dAVFs. In rare interventional procedures, DRLs may also be
determined for more than 20 examinations, as in our study
for the EVT of spinal dAVF.
Fig. 2 Histogram of dose area product (Gy cm2) and scatter plot with adjustment line between dose area product (DAP) and fluoroscopy time for
initial and postsurgery diagnostic DSA in patients with spinal dAVF
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Neuroradiology (2022) 64:587–595
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Conclusion
Increasing regulatory requirements necessitate dose moni-
toring of patients and staff members, and justification of
aberrant exposures. This is the first comprehensive data
acquisition of radiation exposure during dAVF therapy in a
neuroradiology referral centre, which explicitly distinguishes
between EVT of cranial and spinal dAVF. Although EVT
was performed in two different anatomical regions, no sig-
nificant dose difference was found between the two entities.
Because radiation exposure to comparably complex inter-
ventions such as AVM embolization is similar, it may be
useful to determine general DRLs for both entities together.
Funding Open Access funding enabled and organized by Projekt DEAL.
No funding was received for this study. D. Bos was supported as a Clini-
cian Scientist within the University Medicine Essen Academy (UMEA)
program, funded by the German Research Foundation (DFG; grant
FU356/12–1) and the Faculty of Medicine, University of Duisburg-Essen.
Declarations
Ethical approval All procedures performed in the studies involving
human participants were in accordance with the ethical standards of
the institutional and/or national research committee and with the 1964
Helsinki Declaration and its later amendments or comparable ethical
standards.
Informed consent For this type of retrospective study, formal consent
is not required and all patient data was anonymized.
Conflict of interest The authors declare no competing interests.
Open Access This article is licensed under a Creative Commons Attri-
bution 4.0 International License, which permits use, sharing, adapta-
tion, distribution and reproduction in any medium or format, as long
as you give appropriate credit to the original author(s) and the source,
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need to obtain permission directly from the copyright holder. To view a
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... The reported results in terms of local DRLs were quite various (414 Gy cm 2 , 507.33 Gy cm 2 and 730 Gy cm 2 ). However, Forbrig et al. [14] and Opitz et al. [21] ...
... Only in a few dosimetry studies, have intracranial DAFVs been represented as a subcategory [14,21,22]. The reported results in terms of local DRLs were quite various (414 Gy cm 2 , 507.33 Gy cm 2 and 730 Gy cm 2 ). ...
... The reported results in terms of local DRLs were quite various (414 Gy cm 2 , 507.33 Gy cm 2 and 730 Gy cm 2 ). However, Forbrig et al. [14] and Opitz et al. [21] excluded CCFs, and Kien et al. [22] did not describe the inclusion criteria in detail. Regarding Intracranial DAFVs represent a heterogenous group of vascular pathologies handled in different ways using various embolic materials. ...
Article
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Carotid cavernous fistulas (CCFs) are abnormal connections between the cavernous sinus and the internal and/or external carotid artery. Endovascular therapy is the gold standard treatment. In the current retrospective single-center study we report detailed dosimetrics of all patients with CCFs treated by endovascular coil embolization between January 2012 and August 2021. Procedural and dosimetric data were compared between direct and indirect fistulas according to Barrow et al., and different DSA protocol groups. The local diagnostic reference level (DRL) was defined as the 3rd quartile of the dose distribution. In total, thirty patients met the study criteria. The local DRL was 376.2 Gy cm2. The procedural dose area product (DAP) (p = 0.03) and the number of implanted coils (p = 0.02) were significantly lower in direct fistulas. The median values for fluoroscopy time (FT) (p = 0.08) and number of DSA acquisitions (p = 0.84) were not significantly different between groups. There was a significantly positive correlation between DAP and FT (p = 0.003). The application of a dedicated low-dose protocol yielded a 32.6% DAP reduction. In conclusion, this study provides novel DRLs for endovascular CCF treatment using detachable coils. The data presented in this work might be used to establish new specific DRLs.
... Recently, Opitz et al. suggested a DRL for spinal angiographies performed in patients presenting with SDAVF. They presented dosimetric data for SDAVFs from 58 diagnostic spinal angiographies, revealing a DRL of 396.39 Gy cm 2 [18], which is in line with our calculated values. Furthermore, two multicenter studies from France done by Etard et al. and Kien et al. reported DRLs for spinal angiographies [19,20]. ...
Article
Full-text available
Purpose Spinal dural arteriovenous fistulas (SDAVFs) represent the most common indication for a spinal angiography. The diagnostic reference level (DRL) for this specific endovascular procedure is still to be determined. This single-center study provides detailed dosimetrics of diagnostic spinal angiography performed in patients with SDAVFs. Methods Retrospective analysis of all diagnostic spinal angiographies between December 2011 and January 2021. Only patients with an SDAVF who had baseline magnetic resonance angiography (MRA), diagnostic digital subtraction angiography (DSA), treatment and follow-up at this institution were included. Dose area product (DAP, Gy cm ² ) and fluoroscopy time were compared between preoperative and postoperative angiographies, according to SDAVF locations (common versus uncommon), MRA results at baseline (positive versus negative) and DSA protocols (low-dose, mixed-dose, normal-dose). The 75th percentile of the DAP distribution was used to define the local DRL. Results A total of 62 spinal angiographies were performed in 25 patients with SDAVF. Preoperative angiographies (30/62, 48%) yielded a significantly higher DAP and longer fluoroscopy time when compared to postoperative angiographies (32/62, 53%) ( p < 0.01). The local DRL was 329.41 Gy cm ² for a nonspecific ( n = 62), 395.59 Gy cm ² for a preoperative and 138.6 Gy cm ² for a postoperative spinal angiography. Preoperative angiography of uncommonly located SDAVFs yielded a significantly longer fluoroscopy time ( p = 0.02). The MRA-based fistula detection had no significant impact on dosimetrics ( p > 0.05). A low-dose protocol yielded a 61% reduction of DAP. Conclusion The results of the present study suggest novel DRLs for spinal angiography in patients with SDAVF. Dedicated low-dose protocols enable radiation dose optimization in these procedures.
Article
Full-text available
Purpose Intracranial lateral dural arteriovenous fistula (LDAVF) represents a specific subtype of cerebrovascular fistulae, harboring a potentially life-threatening risk of brain hemorrhage. Fluoroscopically guided endovascular embolization is the therapeutic gold standard. We provide detailed dosimetry data to suggest novel diagnostic reference levels (DRL). Methods Retrospective single-center study of LDAVFs treated between January 2014 and December 2019. Regarding dosimetry, the dose area product (DAP) and fluoroscopy time were analyzed for the following variables: Cognard scale grade, endovascular technique, angiographic outcome, and digital subtraction angiography (DSA) protocol. Results A total of 70 patients (19 female, median age 65 years) were included. Total median values for DAP and fluoroscopy time were 325 Gy cm2 (25%/75% percentile: 245/414 Gy cm2) and 110 min (68/142min), respectively. Neither median DAP nor fluoroscopy time were significantly different when comparing low-grade with high-grade LDAVF (Cognard I + IIa versus IIb–V; p > 0.05, each). Transvenous coil embolization yielded the lowest dosimetry values, with significantly lower median values when compared to a combined transarterial/transvenous technique (DAP 290 Gy cm2 versus 388 Gy cm2, p = 0.031; fluoroscopy time 85 min versus 170 min, p = 0.016). A significant positive correlation was found between number of arterial feeders treated by liquid embolization and both DAP (rs = 0.367; p = 0.010) and fluoroscopy time (rs = 0.295; p = 0.040). Complete LDAVF occlusion was associated with transvenous coiling (p = 0.001). A low-dose DSA protocol yielded a 20% reduction of DAP (p = 0.021). Conclusion This LDAVF study suggests several local DRLs which varied substantially dependent on the endovascular technique and DSA protocol.
Article
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Objective: The purpose of this study was to examine risks of cancer incidence and mortality among U.S. radiation technologists performing or assisting with fluoroscopically guided interventional procedures. Subjects and methods: A nationwide prospective cohort of 90,957 radiologic technologists, who responded to a 1994-1998 survey that collected information on whether they had ever worked with fluoroscopically guided interventional procedures, was followed through completion of a subsequent cohort survey during 2003-2005 (for cancer incidence) or December 31, 2008 (for cancer mortality). Sex-adjusted hazard ratios (HRs) and 95% CIs were calculated by use of Cox proportional hazards models for incidence and mortality from all cancers other than nonmelanoma skin cancer and for specific cancer outcomes in participants who reported ever performing fluoroscopically guided interventional procedures compared with technologists who never performed these procedures. Results: The analysis showed an approximately twofold increased risk of brain cancer mortality (HR, 2.55; 95% CI, 1.48-4.40) and modest elevations in incidence of melanoma (HR, 1.30; 95% CI, 1.05-1.61) and in breast cancer incidence (HR, 1.16; 95% CI, 1.02-1.32) but not mortality (HR, 1.07; 95% CI, 0.69-1.66) or among technologists who performed fluoroscopically guided interventional procedures compared with those who never performed these procedures. Although there was a small suggestive increase in incidence of all cancers combined, excluding nonmelanoma skin cancers (HR, 1.08; 95% CI, 1.00-1.17), mortality from all cancers combined, including nonmelanoma skin cancers, was not elevated (HR, 1.00; 95% CI, 0.88-1.14). We similarly observed no elevated risk of cancers of the thyroid, skin other than melanoma, prostate, lung, or colon and rectum or of leukemia that was not chronic lymphocytic leukemia among workers who performed fluoroscopically guided interventional procedures. Conclusion: We observed elevated risks of brain cancer, breast cancer, and melanoma among technologists who performed fluoroscopically guided interventional procedures. Although exposure to low-dose radiation is one possible explanation for these increased risks, these results may also be due to chance or unmeasured confounding by nonradiation risk factors. Our results must be confirmed in other studies, preferably with individual radiation dose data.
Article
Rationale and objectives: This retrospective single-center study aims to evaluate endovascular therapy (EVT) of cranial dural arteriovenous fistulas (dAVF) with ethylene vinyl alcohol (EVOH) copolymer (Onyx) regarding occlusion rates, complications, and recurrences. Material and methods: From January 2008 to April 2018, 75 patients with dAVF (41 men, 34 women; mean age 56 years) underwent EVT with the nonadhesive liquid embolic agent as primary treatment. Patient records and angiograms were reviewed for demographic data, symptoms, fistula type and size, number of EVTs, amount of embolic material, occlusion rates, and recurrences. Results: Seventy-five patients with dAVFs were primarily embolized with EVOH in 96 EVTs. According to the Merland-Cognard classification the majority of dAVFs treated were type 4 (42.7%), followed by type 2a (18.7%), type 2a+b (17.3%), type 1 (8%), type 2b (5.3%), type 3 (5.3%), and type 5 (2.7%). Complete occlusion (CO) of the dAVF was achieved in 45/75 (60%) of cases after a single EVT and in 58 (77%) patients after one or several EVTs. Seven patients (9%) required additional surgical therapy for CO. Successful treatment was achieved for 70/75 (93%) patients including 10 (13%) patients with residual dAVFs type 1-2a. Recurrence after CO occurred in one (1.3%) patient and four (5.3%) patients remained refractory to therapy with dAVFs type > 2a. Procedure-related permanent morbidity occurred in 4/75 (5.3%) patients. Conclusion: For more than a decade transarterial EVOH embolization has established as the first-line treatment for cranial dAVFs with high cure rates and low rates of complications and recurrences. Additional neurosurgical therapy is rarely required for curative treatment.
Article
Purpose Recent developments in medical technology have broadened the spectrum of X-ray procedures and changed exposure practice in X-ray facilities. For this reason, diagnostic reference levels (DRLs) for diagnostic and interventional X-ray procedures were updated in 2016 and 2018, respectively. It is the aim of this paper to present the procedure for the update of the DRLs and to give advice on their practical application. Materials and Methods For the determination of DRLs, data from different independent sources that collect dose-relevant data from different facilities in Germany were considered. Seven different weight intervals were specified for classifying pediatric X-ray procedures. For each X-ray procedure considered, the 25th, 50th, and 75th percentile of the respective national distribution of the dose-relevant parameters were determined. Additionally, effective doses that correspond to the DRLs were estimated. Results In procedures with already existing DRLs before 2016, the values were lowered by circa 20 % on average. Numerous DRLs were established for the first time (9 for interventional procedures, 10 for CT examinations). Conclusion For dose optimizations even below the new national DRLs, the BfS recommends establishing local reference levels, using dose management software (particularly in CT and interventional radiology), adapting dose-relevant parameters of X-ray protocols to the individual patient size, and establishing internal radiation protection teams responsible for optimizing X-ray procedures in clinical practice. When applying good medical practice and using modern equipment, the median dose values of the nationwide dose distributions can not only be easily achieved but can even be undercut. Key Points: Citation Format
Article
Objectives: Finding the underlying cause for pulsatile tinnitus can be challenging. We aimed to determine the incidence of arteriovenous shunts, i.e., arteriovenous malformations (AVMs) or dural arteriovenous fistulas (dAVFs), in patients referred for catheter angiography (digital subtraction angiography [DSA]). Furthermore, we assessed which clinical features were predictive for the presence of such a lesion. Study design and methods: Fifty-one patients with pulsatile tinnitus, who were referred to us for DSA to exclude an arteriovenous shunt, were enrolled, prospectively. Main outcome measures: DSA determined the presence of a dAVF or AVM. Clinical characteristics were recorded systematically and all patients underwent a physical examination. Results: Fifty patients were included in the final analyses. While no AVMs were found, a dAVF was found in 12 cases (24%). Three of these demonstrated cortical venous reflux, thus requiring treatment due to the risk of hemorrhage. In three cases (6%), DSA demonstrated a non-arteriovenous-shunt abnormality, likely causing the tinnitus. The odds of having a dAVF were significantly raised by unilaterality, objective bruit, and the ability to influence the tinnitus with compression. Unilaterality even had a negative predictive value of 1 and, if used as selection criterion, would have raised dAVF prevalence from 24 to 32%. Conclusion: In a tertiary care setting, the prevalence of dAVFs in patients with pulsatile tinnitus is not negligible. Thus, patients with unilateral pulsatile tinnitus should be offered dynamic vascular imaging to rule out a dAVF. Especially, since some of these patients are at risk of intracranial hemorrhage and treatment options exist.
Article
Background and purpose: Per the ALARA principle, reducing the dose delivered to both patients and staff must be a priority for endovascular therapists, who should monitor their own practice. We evaluated patient exposure to radiation during common neurointerventions performed with a recent flat-panel detector angiographic system and compared our results with those of recently published studies. Methods: All consecutive patients who underwent a diagnostic cerebral angiography or intervention on 2 modern flat-panel detector angiographic biplane systems (Innova IGS 630, GE Healthcare, Chalfont St Giles, UK) from February to November 2015 were retrospectively analyzed. Dose-area product (DAP), cumulative air kerma (CAK) per plane, fluoroscopy time (FT), and total number of digital subtraction angiography (DSA) frames were collected, reported as median (interquartile range), and compared with the previously published literature. Results: A total of 755 consecutive cases were assessed in our institution during the study period, including 398 diagnostic cerebral angiographies and 357 interventions. The DAP (Gy × cm(2)), fontal and lateral CAK (Gy), FT (min), and total number of DSA frames were as follows: 43 (33-60), 0.26 (0.19-0.33), 0.09 (0.07-0.13), 5.6 (4.2-7.5), and 245 (193-314) for diagnostic cerebral angiographies, and 66 (41-110), 0.46 (0.25-0.80), 0.18 (0.10-0.30), 18.3 (9.1-30.2), and 281 (184-427) for interventions. Conclusion: Our diagnostic cerebral angiography group had a lower median and was in the 75th percentile of DAP and FT when compared with the published literature. For interventions, both DAP and number of DSA frames were significantly lower than the values reported in the literature, despite a higher FT. Subgroup analysis by procedure type also revealed a lower or comparable DAP.
Article
Background and purpose: Advancements in medical device and imaging technology as well as accruing clinical evidence have accelerated the growth of the endovascular treatment of cerebrovascular diseases. However, the augmented role of these procedures raises concerns about the radiation dose to patients and operators. We evaluated patient doses from an x-ray imaging platform with radiation dose-reduction technology, which combined image noise reduction, motion correction, and contrast-dependent temporal averaging with optimized x-ray exposure settings. Materials and methods: In this single-center, retrospective study, cumulative dose-area product inclusive of fluoroscopy, angiography, and 3D acquisitions for all neurovascular procedures performed during a 2-year period on the dose-reduction platform were compared with a reference platform. Key study features were the following: The neurointerventional radiologist could select the targeted dose reduction for each patient with the dose-reduction platform, and the statistical analyses included patient characteristics and the neurointerventional radiologist as covariates. The analyzed outcome measures were cumulative dose (kerma)-area product, fluoroscopy duration, and administered contrast volume. Results: A total of 1238 neurointerventional cases were included, of which 914 and 324 were performed on the reference and dose-reduction platforms, respectively. Over all diagnostic and neurointerventional procedures, the cumulative dose-area product was significantly reduced by 53.2% (mean reduction, 160.3 Gy × cm(2); P < .0001), fluoroscopy duration was marginally significantly increased (mean increase, 5.2 minutes; P = .0491), and contrast volume was nonsignificantly increased (mean increase, 15.3 mL; P = .1616) with the dose-reduction platform. Conclusions: A significant reduction in patient radiation dose is achievable during neurovascular procedures by using dose-reduction technology with a minimal impact on workflow.
Article
Here we describe the first clinical experiences regarding the use of an automated radiation dose management software to monitor the radiation dose of patients during routine examinations. Many software solutions for monitoring radiation dose have emerged in the last decade. The continuous progress in radiological techniques, new scan features, scanner generations and protocols are the primary challenge for radiation dose monitoring software systems. To simulate valid dose calculations, radiation dose monitoring systems have to follow current trends and stay constantly up-to-date. The dose management software is connected to all devices at our institute and conducts automatic data acquisition and radiation dose calculation. The system incorporates 18 virtual phantoms based on the Cristy phantom family, estimating doses in newborns to adults. Dose calculation relies on a Monte Carlo simulation engine. Our first practical experiences demonstrate that the software is capable of dose estimation in the clinical routine. Its implementation and use have some limitations that can be overcome. The software is promising and allows assessment of radiation doses, like organ and effective doses according to ICRP 60 and ICRP 103, patient radiation dose history and cumulative radiation doses. Furthermore, we are able to determine local diagnostic reference doses. The radiation dose monitoring software systems can facilitate networking between hospitals and radiological departments, thus refining radiation doses and implementing reference doses at substantially lower levels.
Article
Background: In interventional neuroradiology, few operators routinely use radiation protection glasses. Moreover, in most centers, radiation dose data only accounts for whole body dose without specific information on lens dose. In 2012, the International Commission on Radiological Protection advised that the threshold limit value for the lens should be 20 mSv/year instead of the previous 150 mSv/year limit. The purpose of this study was to compare the radiation dose in the operator's lens during real diagnostic and interventional neuroangiographies, either using or without lead protection glasses. Methods: Using the Educational Direct Dosimeter (EDD30 dosimeter), accumulated radiation dose in the lens was measured in 13 neuroangiographies: seven diagnostic and six interventional. Operators with and without radiation protection glasses were included and the sensor was placed near their left eye, closest to the radiation beam. Results: Without glasses, the corrected mean dose of radiation in the lens was 8.02 µSv for diagnostic procedures and 168.57 µSv for interventional procedures. Using glasses, these values were reduced to 1.74 µSv and 33.24 µSv, respectively. Conclusion: Considering 20 mSv as the suggested annual limit of equivalent dose in the lens, neuroradiologists may perform up to 2,494 diagnostic procedures per year without protecting glasses, a number that increases to 11,494 when glasses are used consistently. Regarding intervention, a maximum of 119 procedures per year is advised if glasses are not used, whereas up to 602 procedures/year may be performed using this protection. Therefore, neuroradiologists should always wear radiation protection glasses.