Fast 3-T MR-guided transrectal prostate biopsy using an in-room tablet device for needle guide alignment: a feasibility study
Fast 3-T MR-guided transrectal prostate biopsy using an in-room tablet device for needle guide alignment: a feasibility study
Christiaan G. Overduin 0 1 2 3
Jan Heidkamp 0 1 2 3
Eva Rothgang 0 1 2 3
Jelle O. Barentsz 0 1 2 3
Frank de Lange 0 1 2 3
Jurgen J. Fütterer 0 1 2 3
MRI PCa PI-RADS 0 1 2 3
0 Magnetic resonance imaging Prostate cancer Prostate Imaging Reporting Archiving and Data System Prostate-specific antigen Transrectal ultrasound Turbo spin echo
1 Department of Radiology and Nuclear Medicine, Radboud University Medical Center , P.O. Box 9101 (767), 6500 HB Nijmegen , The Netherlands
2 Christiaan G. Overduin
3 MIRA Institute for Biomedical Engineering and Technical Medicine, University of Twente , Enschede , The Netherlands
Objectives To assess the feasibility of adding a tablet device inside the scanner room to assist needle-guide alignment during magnetic resonance (MR)-guided transrectal prostate biopsy. Methods Twenty patients with one cancer-suspicious region (CSR) with PI-RADS score ≥ 4 on diagnostic multiparametric MRI were prospectively enrolled. Two orthogonal scan planes of an MR fluoroscopy sequence (~3 images/s) were aligned to the CSR and needle-guide pivoting point. Targeting was achieved by manipulating the needle-guide under MR fluoroscopy feedback on the in-room tablet device. Technical feasibility and targeting success were assessed. Complications and biopsy procedure times were also recorded. Results Needle-guide alignment with the in-room tablet device was technically successful in all patients and allowed sampling after a single alignment step in 19/20 (95%) CSRs (median size 14 mm, range: 4-45). Biopsy cores contained cancer in 18/20 patients. There were no per-procedural or post-biopsy complications. Using the tablet device, the mean time to first biopsy was 5.8 ± 1.0 min and the mean total procedure time was 23.7 ± 4.1 min. Conclusions Use of an in-room tablet device to assist needle-guide alignment was feasible and safe during MR-guided transrectal prostate biopsy. Initial experience indicates potential for procedure time reduction. Key Points Performing MR-guided prostate biopsy using an in-room tablet device is feasible. CSRs could be sampled after a single alignment step in 19/20 patients. The mean procedure time for biopsy with the tablet device was 23.7 min.
Magnetic resonance imaging; Prostate cancer; Image-guided biopsy; Tablet computers; Operative time
ASTM American Society for Testing of Materials
bSSFP Balanced steady-state free precession
CSR Cancer-suspicious region
DWI Diffusion-weighted imaging
IFE Interactive front end
mpMRI Multiparametric MRI
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00330-018-5497-9) contains supplementary
material, which is available to authorized users.
Siemens Healthcare GmbH, Erlangen, Germany
Patient age (years)
PSA level (ng/ml)
Previous negative TRUS-guided biopsy sessions
Prostate volume (ml)
Lesion suspicion score
Lesion size (mm)
Lesion size distribution
≤ 10 mm
> 10 mm
Fig. 1 a Schematic diagram of
the setup for prostate biopsy using
an in-room tablet device. b
Photograph shows the setup of the
tablet device in the MR room
Median or mean
(range) or n (%)
Prostate cancer (PCa) is the most common non-cutaneous
cancer diagnosed in men in developed countries, with an estimated
180,000 new cases in the US in 2016 . Transrectal ultrasound
(TRUS)-guided biopsy is the current standard technique to
detect PCa. However, this technique has limited sensitivity, and
false-negative rates up to 32% have been reported for initial
6to 12-core systematic biopsy [2, 3]. Repeated biopsy sessions
have shown little impact on cancer detection [4, 5].
In recent years, multiparametric magnetic resonance (MR)
imaging has evolved toward a mature imaging modality to
detect PCa with high localization a ccuracy [6, 7].
Consequently, MR imaging (MRI) has been proposed in
targeting biopsies toward cancer-suspicious regions (CSRs)
, and several studies have demonstrated high diagnostic
performance using in-bore MR-guided transrectal prostate
biopsy in patients with initial negative TRUS biopsy [9–11].
Nevertheless, an important concern for in-bore biopsy is that
the repeated needle guide adjustments requiring the physician
to walk in and out of the MRI room are time consuming ,
and typical procedure times have been considerably longer
than those of TRUS-guided biopsy .
To improve the current workflow, we propose a method for
needle guide alignment using dedicated software integrated
with MR fluoroscopy feedback, visualized on a tablet device
inside the scanner room. This approach may eliminate the
need for repeated needle guide repositioning and could
potentially accelerate in-bore prostate biopsy procedures.
Therefore, the purpose of this study was to assess the
feasibility of adding a tablet device inside the MR room to assist
needle guide alignment during 3-T MR-guided transrectal
Materials and Methods
For this institutional review board (IRB)-approved feasibility
study, 20 males scheduled for MR-guided prostate biopsy
with a single CSR with a PI-RADS v2  score ≥ 4 on
diagnostic multiparametric prostate MRI (mpMRI) were
prospectively enrolled between June and October 2016.
Indications for diagnostic prostate mpMRI and subsequent
biopsy were either elevated PSA (> 4.0 ng/ml) and clinical
suspicion of primary PCa (n = 12) or follow-up in patients
under active surveillance for minimal low-risk PCa (Gleason
score ≤ 6) diagnosed on previous TRUS-biopsy (n = 8). None
of the patients had received previous prostate treatment.
Informed consent was obtained from all patients. A summary
of patient and lesion characteristics is given in Table 1.
MRI safety assessment
Prior to IRB application for this study, an MR safety
assessment was conducted to determine safe operation conditions
for the tablet device (iPad 2, Apple, Cupertino, CA, USA) in a
3-T MRI suite. The magnetically induced displacement force
on the tablet device was determined according to American
Society for Testing of Materials (ASTM) standard test method
F2052-06 . The tablet device was attached to a
nonmagnetic fixture using a nylon string such that it hung free
in space. Using a protractor with 1° graduated markings, the
deflection angle due to magnetic attraction of the tablet device
was recorded at multiple locations in the scanner room and
varying distances from the bore entry. Additional ASTM
safety tests  were conducted to establish whether the tablet
device or wireless network connection affected MR image
In-room tablet device setup
For the proposed method, the tablet device was installed in the
MR room. The tablet device was connected to a stand-alone
computer outside the scanner room via a remote desktop
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application (VNC Viewer, RealVNC, Cambridge, UK) on a
secured wireless network connection (Fig. 1a). To prevent an
accidental approach to the scanner bore during operation, the
device was incorporated into a Perspex holder mounted to a
non-magnetic fixture secured to the MR scanner table
MR-guided biopsy procedure
All patients received antibiotic prophylaxis (oral
ciprofloxacin, 2dd 500 mg) for 3 days, starting on the day before
biopsy. All biopsy procedures were performed on a 3-T
clinical MR system (MAGNETOM Skyra, Siemens,
Erlangen, Germany) by one prostate interventionalist
(C.O., 4-year experience). Patients were positioned in a
prone position on the MR table. A commercially available
transrectal biopsy device (DynaTrim, Invivo, Gainesville,
FL, US) was used. Axial T2-weighted turbo spin echo
(T2TSE) and diffusion-weighted imaging (DWI) were acquired
to reproduce pre-biopsy MRI findings. An additional
extended axial T2-TSE data set incorporating the entire needle
guide was acquired for planning purposes. On the
standalone computer, two points were identified in the extended
T2-TSE set using interventional planning software
[Interactive Front End (IFE), Siemens Healthcare GmbH,
Erlangen, Germany]: (
) the biopsy target, defined as the
center of the lesion, and (2) the needle guide pivoting point,
which had been previously determined at 9.2 cm from the
proximal edge of the contrast-filled compartment of the
needle guide in in-house experiments. The software then
calculates the planned trajectory between these two points,
representing the desired needle guide position to target the
CSR (Supplemental Figure 1). Two orthogonal MR scan
planes were aligned to this trajectory in axial and sagittal
orientation and returned to the scanner console, providing
the slice positions for an interactive real-time balanced
steady-state free precession (BEAT) MR fluoroscopy
sequence (temporal resolution ~3 imagings/s). The
interventionalist then entered the MR room and manipulated the
needle guide into both scan planes under MR fluoroscopy
feedback visualized on the in-room tablet device while the
patient was inside the scanner bore (Supplemental Video 1).
Upon completion, short balanced steady-state free
precession (bSSFP) scans were performed in axial and sagittal
orientation to confirm correct alignment with the CSR. In
case of correct alignment, subsequent biopsy was
performed using an 18-gauge fully automatic MR-compatible
biopsy gun (Invivo, Gainesville, FL, US). In case of
incorrect alignment, additional routine manual adjustment steps
were performed for correction. Axial and sagittal bSSFP
confirmation scans were obtained to map each biopsy
location. Detailed imaging parameters are summarized in
Table 2. An overview of the biopsy procedure is shown in
Per- and post-procedural complications were recorded with
rates and description of adverse events. Complications were
scored according to the Clavien grading system .
Targeting success and procedure times
Technical feasibility and single-step targeting success of
needle guide alignment were assessed. Single-step targeting
success was defined as obtainment of a representative biopsy core
directly after a single alignment step under MR fluoroscopy
feedback on the in-room tablet device without requiring
further needle guide repositioning. Representativity of each
biopsy core was indicated on a five-point scale (i.e., 1 = not
representative to 5 = representative) by a prostate radiologist
reviewing each biopsy confirmation scan, where a score of ≥ 4
was considered a representative sample.
Biopsy procedure times were also recorded. The time to
first biopsy was defined as the time from acquisition of the
DWI sequence until the confirmation scan of the first biopsy
Fig. 3 Images in a 63-year-old male with elevated PSA. (a) Axial b
diagnostic T2-weighted and (b) DW imaging (calculated high b-value
image; 1400 s/mm2) shows a focal hypointense lesion with diffusion
restriction (white outline) suspicious for PCa in the left peripheral zone.
(c) Axial and (d) sagittal view of the needle guide trajectory planning. (e)
Axial and (f) sagittal BEAT images aligned to the planned trajectory show
the final needle guide position after alignment under MR fluoroscopy
feedback displayed on the in-room tablet device. (g) Axial and (h)
sagittal fast bSSFP scans confirm correct alignment of the needle guide
to the CSR in both orientations (yellow dotted lines). Subsequent biopsy
showed a Gleason 3 + 4 = 7 prostate cancer
of the CSR (Fig. 2). The total procedure time was defined as
the time between localizer acquisition and the last scan of the
biopsy procedure. Finally, the MR fluoroscopy time was
defined as the duration the physician required to align the needle
guide under MR fluoroscopy feedback. The setup time of the
required hardware was not recorded as multiple subsequent
biopsy procedures only required a single installation of ± 5-10
After the biopsy procedures, core samples underwent
histopathological workup with hematoxylin-eosin staining and
were subsequently evaluated for the presence of PCa or
benign findings. When applicable, a Gleason score was
In the 3-T suite, it was found that the specified unfixed tablet
device could be safely operated at ≥ 50 cm from the bore entry
without significant magnetic attraction according to ASTM
tolerance levels. No noticeable interferences or artifacts
affecting MR image quality were observed because of the presence
of the tablet device or wireless network connection.
A total of 20 CSRs was successfully sampled in 20 patients (1
per patient). A median of two biopsy cores (range: 2-3) was
taken per CSR resulting in 46 biopsy samples. There were no
per-procedural or post-biopsy complications.
Needle guide alignment using the in-room tablet device
was technically feasible in all patients (Fig. 3). Single-step
targeting was successful in all but one patient (19/20 lesions;
95%). In the latter patient, an additional routine repositioning
step was needed because the lesion was located anteriorly
outside of the maximum range of the biopsy device. After
forward adjustment of the needle guide, biopsy was performed
successfully. The median radiological score of biopsy
representativity was 5 out of 5 (range: 4-5).
With use of the in-room tablet device, mean time to first
biopsy was 5.8 ± 1.0 min and mean total procedure time was
23.7 ± 4.1 min. There was a downward trend in total
procedure time with increasing procedure number, with the last ten
procedures being performed in less than 25 min (Fig. 4). The
mean MR fluoroscopy time was 1.1 ± 0.3 min.
Histopathology revealed prostate cancer in 18/20 (90%)
patients. Gleason scores were 3+3 (3), 3+4 (
), 3+5 (
(2), 4+4 (
) and 4+5 (
). In total, 42 of 46 (91%) biopsy
samples contained cancer. In two pati
ents (10%), biopsy samples contained prostatitis.
This work described a method for needle guide alignment
using an in-room tablet device during MR-guided transrectal
prostate biopsy and demonstrated its feasibility in patients.
Biopsy samples could be successfully obtained from each
CSR after a single alignment step using the in-room tablet
device in all but one patient.
In an effort to reduce procedure times of in-bore
MR-guided prostate biopsy, alternative solutions have previously been
proposed. Several groups have developed MR-compatible
robotics to aid in in-bore prostate biopsy [18–20]. Another
report has described an algorithm for automated phase-only
cross correlation (POCC)-based needle-guide tracking .
Also, an MR-compatible display screen could be used instead
of the proposed tablet device to visualize MR fluoroscopy
images inside the MR room. An advantage however of the
method proposed here is its relative simplicity, requiring
minimal additional equipment costs (i.e., a tablet device and
wireless network connection).
Disadvantages of the tablet device are that the screen is
relatively small and MRI safety needs to be concerned. MRI
safety assessment showed that the tablet device could be
safely operated in a 3-T MRI suite at distances ≥ 50 cm from the
bore entry. This is in line with previous results in a 1.5-T MR
environment . Nevertheless, when a tablet device is
applied for different applications and MRI suites caution should
be taken and device safety assessed in each individual setting
by local MR safety authorities.
The mean total procedure time for biopsy using the
inroom approach was 23.7 min, with the last ten procedures
all performed in < 25 min including ~2 min additional
scanning time required to obtain the extended T2-TSE data set for
trajectory planning. Compared with the median procedure
times of transrectal in-bore MR-guided prostate biopsy
reported in the literature (30-68 min) , this presents a
considerable time improvement. Another study described initial results
using a robotic manipulator and reported biopsy of one CSR
per patient in a median of 37 min (range: 23-61) . Another
study used a needle-guide tracking sequence enabling biopsy
of a median of two CSRs (range: 1-4) per patient in a median
of 32 min (range: 14-48), without diagnostic scans at the
beginning of the biopsy procedure. In our preliminary cohort,
needle guide alignment using the in-room tablet device
allowed biopsy of the CSR after a single adjustment step in
almost all patients. With the manipulation under MR
fluoroscopy being performed in ~1 min and the physician only
needing to walk between the MR and control room once, this is the
main area where the time improvement was achieved in this
Some aspects of the in-room targeting process may still be
optimized. Scanning time could be saved by incorporating a
T2-TSE sequence that can be used for CSR-reidentification
and planning of the needle guide trajectory. Also, optimization
of the planning software or integration with the scanner
platform could improve the slice positioning workflow and allow
further acceleration of the biopsy procedure.
One issue with the presented method is that MR
fluoroscopy guidance comes with the prerequisite of manipulating the
needle guide in the center of the bore while the patient is on
the scanner table. Potentially, some performing physicians
may be unable to reach the needle guide inside the magnet.
Also, the in-room method is presently only compatible with
transrectal biopsy using a specific commercial biopsy device
in combination with interventional planning software of one
The most important limitations to this feasibility study are
the relatively small population and investigation of biopsy of
only one CSR per patient with a PI-RADS score ≥ 4. Finally,
we acknowledge that the future of in-bore biopsy is unclear as
recently interest in MRI-TRUS fusion biopsy has been
increasing as a targeted biopsy alternative. Some initial studies
have shown promising results using fusion biopsy [24, 25].
One disadvantage is that MRI-TRUS fusion systems often
require pre-segmentation of tumors on the diagnostic MRI,
which can also be a time-consuming process. Ultimately,
validation in larger cohorts is needed to determine which lesions
are best amenable to each biopsy technique. In cases of
discrepancies between imaging and fusion biopsy findings, an
important role could remain for in-bore biopsy. Moreover,
physician preference of technique and site experience may
also play a part.
In conclusion, use of an in-room tablet device to assist
needle guide alignment was feasible and safe during 3-T
MR-guided transrectal prostate biopsy. Our initial clinical
experience indicates potential for procedure time reduction,
which could be of value to increase the clinical applicability
of this biopsy technique.
Acknowledgements The authors would like to thank E. van der Wielen
for providing technical assistance in setting up the network and system
Funding The authors state that this work has not received any funding.
Compliance with ethical standards
Guarantor The scientific guarantor of this publication is Prof. Dr. J.J.
Conflict of interest The authors of this manuscript declare no
relationships with any companies, whose products or services may be related to
the subject matter of the article.
Statistics and biometry
for this paper.
No complex statistical methods were necessary
Informed consent Written informed consent was obtained from all
subjects (patients) in this study.
Ethical approval Institutional Review Board approval was obtained.
performed at one institution
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