DOI:10.2214/AJR.07.3711
AJR 2008; 191:1182-1185
© American Roentgen Ray Society
A Technique for MRI-Guided Transrectal Deep Pelvic Abscess Drainage
Sherif Gamal Nour1,2,3,
Jamal J. Derakhshan1,2,
Nila J. Akhtar1,
Martin A. Ayres1,
Mark E. Clampitt1,
Thomas A. Stellato4 and
Jeffrey L. Duerk1,2,5
1 Department of Radiology, University Hospitals of Cleveland, Case Western
Reserve University School of Medicine, 11100 Euclid Ave., Cleveland, OH
44106.
2 Department of Biomedical Engineering, Case Western Reserve University,
Cleveland, OH.
3 Department of Diagnostic Radiology, Cairo University Hospitals, Cairo,
Egypt.
4 Department of Surgery, University Hospitals of Cleveland, Case Western Reserve
University School of Medicine, Cleveland, OH.
5 Department of Oncology, University Hospitals of Cleveland, Case Western
Reserve University School of Medicine, Cleveland, OH.
Received January 22, 2008;
accepted after revision April 29, 2008.
Address correspondence to S. G. Nour
(sherif.nour{at}uhhospitals.org).
S. G. Nour received research funding from Siemens Medical Solutions.
Abstract
OBJECTIVE. The purpose of this article is to introduce a technique
for transrectal drainage of deep pelvic abscesses performed under interactive
MRI guidance.
CONCLUSION. A new method for triorthogonal image plane MRI guidance
was developed and used to interactively monitor the puncture needle on
continuously updated sets of adjustable three-plane images. The merits and
limitations of the technique are highlighted and the patient population that
is likely to benefit from this approach is suggested.
Keywords: interventional MRI • MRI-guided pelvic abscess drainage
Introduction
Transrectal access is an alternative route for draining deep pelvic
abscesses when establishing a safe percutaneous trajectory is technically
challenging. Although the technique has been described under both sonographic
[1,
2] and CT
[3] guidance, the former is
more commonly used because of its cost and time effectiveness and its ability
to image along the needle path. Sonographic guidance, however, entails the
insertion of a transrectal imaging probe coupled with the biopsy device, which
can be difficult to tolerate in certain patient populations. In addition,
sonographic imaging can be compromised by the presence of large amounts of air
within the abscess cavity. CT guidance is restricted to the axial
(xy) plane, requiring significant mental triangulation by the
interventionist while introducing the needle or catheter along the
craniocaudal (z) plane direction. In addition, in the younger age
groups, CT guidance entails unnecessary radiation exposure to the pelvis.
In this report, we introduce the first use of interventional MRI technology
to guide transrectal drainage of a deep pelvic abscess, highlight the merits
and limitations of the technique, and suggest the patient population that is
likely to benefit from this approach.
Materials and Methods
Approval was obtained from the institutional review board, and written
informed consent was obtained from the patient. The study was HIPAA compliant.
A 62-year-old man with presacral abscess secondary to anastomotic leakage
after resection of invasive rectal adenocarcinoma was referred for abscess
drainage. The procedure was performed entirely on a high-field (1.5 T),
open-configuration (bore diameter, 70 cm; bore length, 125 cm) interventional
MRI scanner (Magnetom Espree, Siemens Medical Solutions) equipped with an
electronically shielded in-room high-resolution liquid crystal display (LCD)
monitor. Mild IV conscious sedation was administered (0.25 mg of midazolam, 1
mg/mL, and 50 µg of fentanyl citrate, 0.05 mg/mL). No local anesthesia was
administered. The patient was placed on the MRI table in the supine lithotomy
position and was introduced feet-first into the short-bore (125-cm) gantry. A
20-cm, 18-gauge MRI-compatible needle (E-Z-EM) was placed inside the plastic
sheath provided by the manufacturer. The latter was cut to expose the needle
tip. The needle tip was then retracted within this plastic sheath, the sheath
was lubricated with sterile gel, and the needle–sheath combination was
advanced through the rectum directed at the fluid component of the abscess
under real-time MR "fluoroscopic" guid ance using the in-room
monitor.
A new method for triorthogonal image plane MR guidance was developed and
used to interactively monitor the puncture needle on continuously updated sets
of adjustable sagittal, coronal, and axial true fast imaging with steady-state
free precession (true-FISP) images (TR/TE, 4.35/2.18; field of view, 250
x 250 mm; matrix, 192 x 192; slice thickness, 5 mm; flip angle,
60°; number of signals averaged, 3; bandwidth, 554 Hz per pixel;
acquisition time, 3.11 seconds per slice). The three orthogonal planes could
be acquired relative to the needle axis, relative to the target abscess
itself, or in any three arbitrary planes relative to each other and to the
patient's body (Figs. 1A and
1B). The reconstruction and
display program was modified to simultaneously project the three planes
immediately as they were acquired. The interventionist first determined the
"ideal" trajectory and placed the localizing planes along this
trajectory (Figs. 1A and
1B). The interventionist then
introduced the needle under interactive three-plane imaging. Typically, the
needle is initially seen on only one or two of the three planes. The
interventionist would then use the in-room monitor and controller to
co-localize the missing plane or planes on the planes where the needle is
already visualized. This process can be repeated whenever the needle is
deflected out-of-plane on any of the three planes.
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Fig. 1A —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Preprocedural sagittal (A) and axial
(B) true fast imaging with steady-state free precession (true-FISP)
images (TR/TE, 4.35/2.18; field of view, 250 x 250 mm, matrix, 192
x 192; slice thickness, 5 mm; flip angle, 60°; number of signals
averaged, 3) show typical setup for triorthogonal image plane guidance.
Desired trajectory is planned so that fluid component of presacral abscess
(arrowheads) cavity resides along sagittal (1), oblique coronal (2),
and axial (3) planes of guidance. Trajectory can subsequently be modified to
any combination of three planes during needle navigation in time-efficient
manner.
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Fig. 1B —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Preprocedural sagittal (A) and axial
(B) true fast imaging with steady-state free precession (true-FISP)
images (TR/TE, 4.35/2.18; field of view, 250 x 250 mm, matrix, 192
x 192; slice thickness, 5 mm; flip angle, 60°; number of signals
averaged, 3) show typical setup for triorthogonal image plane guidance.
Desired trajectory is planned so that fluid component of presacral abscess
(arrowheads) cavity resides along sagittal (1), oblique coronal (2),
and axial (3) planes of guidance. Trajectory can subsequently be modified to
any combination of three planes during needle navigation in time-efficient
manner.
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Fig. 1C —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Under real-time MR "fluoroscopy"
using true FISP images (C, sagittal; D, coronal oblique;
E, axial), puncture needle (arrowheads) has been advanced
through rectum. Needle tip (arrows) is seen within fluid component of
abscess cavity. Ability to observe continuous update of needle tip location on
simultaneously displayed three planes allows fast and confident puncture of
abscess cavity.
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Fig. 1D —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Under real-time MR "fluoroscopy"
using true FISP images (C, sagittal; D, coronal oblique;
E, axial), puncture needle (arrowheads) has been advanced
through rectum. Needle tip (arrows) is seen within fluid component of
abscess cavity. Ability to observe continuous update of needle tip location on
simultaneously displayed three planes allows fast and confident puncture of
abscess cavity.
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Fig. 1E —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Under real-time MR "fluoroscopy"
using true FISP images (C, sagittal; D, coronal oblique;
E, axial), puncture needle (arrowheads) has been advanced
through rectum. Needle tip (arrows) is seen within fluid component of
abscess cavity. Ability to observe continuous update of needle tip location on
simultaneously displayed three planes allows fast and confident puncture of
abscess cavity.
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Once the tip of the puncture needle was identified within the fluid
component of the abscess (Figs.
1C,
1D,
1E; for video, see Fig. S1H in
supplemental data online at
www.ajronline.org),
the stylet was removed and 10 mL of pus was aspirated and sent for a
bacteriological culture. A 0.035-inch standard Rosen guidewire was advanced
under MRI guidance through the needle into the collection. The needle was then
removed over the wire and an 8-French pigtail catheter (Skater, Angiotech) was
advanced into the abscess. The pigtail was formed, the strings were locked,
and the tip location within the abscess was confirmed on sagittal and axial
true-FISP (4.58/2.29; field of view, 280 x 280 mm; matrix, 320 x
320; slice thickness, 5 mm, flip angle, 65°; number of signals averaged,
1; bandwidth, 558 Hz per pixel; acquisition time, 39.4 seconds) (Figs.
1F and
1G) and turbo spin-echo
T2-weighted (4,840/67; field of view, 360 x 360 mm; matrix, 205 x
256; slice thickness, 4 mm; flip angle, 150°; number of signals averaged,
2; fat-saturation pulse, bandwidth, 150 Hz per pixel, turbo factor, 13;
acquisition time, 2:30 minutes) images.
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Fig. 1F —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Final confirmation sagittal (F) and
axial (G) true FISP images of drainage catheter in place show catheter
shaft (arrowheads) extending through rectum and within air component
of abscess cavity. Pigtail end (arrows) has been locked in dependent
portion of fluid component.
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Fig. 1G —62-year-old man with presacral abscess secondary to
anastomotic leakage after resection of invasive rectal adenocarcinoma who was
referred for abscess drainage. Final confirmation sagittal (F) and
axial (G) true FISP images of drainage catheter in place show catheter
shaft (arrowheads) extending through rectum and within air component
of abscess cavity. Pigtail end (arrows) has been locked in dependent
portion of fluid component.
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Results
The MRI interventional setup, including the patient access and the guidance
process, was simple and favorable. The interventionist and the assistant had
ready access to the perineum at the center of the short-bore scanner and were
able to interactively guide and monitor the needle progress on the in-room
monitor placed at the same side of the magnet's bore. They were also able to
operate the scanner from the console of the in-room monitor or to communicate
operating instructions to the technologist at the main console.
The procedure was well tolerated by the patient, who did not indicate any
level of discomfort at any stage. The ability to perform an imaging-guided
puncture through the rectal wall without inserting an imaging probe or a
needle attachment device into the rectum contributed significantly to the
tolerability of the procedure. Setting up and using the three-orthogonal-plane
imaging guid ance technique was straightforward and time effective. The
18-gauge puncture needle was clearly visible with minimal artifactual widening
throughout the guid ance process (Figs.
1C,
1D,
1E; for video, see Fig. S1H in
supplemental data online at
www.ajronline.org).
Superb visualization of the target abscess and its surrounding ana tomy was
achieved and facilitated unparal leled tissue detail and clarity compared with
similar procedures using other imaging guidance techniques.
The presence of a large amount of air leaking into the abscess did not
create any image artifacts as would have been encountered on sonography.
Retrieval of pus was achieved in 4.5 minutes (measured from the time the
puncture needle was inserted into the rectum). Handling and visualizing the
non-MR-compatible guidewire within the magnetic field were challenging because
of significant torque and artifact. This was not, however, technically
prohibitive because we only performed a brief confirmation scanning of the
final guidewire location. Securing the pigtail catheter in its final position
was achieved in 41 minutes (measured from the time the puncture needle was
inserted into the rectum). The total magnet time including the preprocedural
diagnostic MRI study, administration of sedation and institution of patient
monitoring, sterile draping, placing and securing the drainage catheter, and
performing the postprocedural imaging was 108 minutes.
Discussion
This report introduces a technique for draining deep pelvic abscesses via
the transrectal route under direct MRI guidance. It capitalizes on using
emerging interventional MRI technology to help a subset of patients who have
restricted percutaneous access and limited utility of alternative imaging
guidance techniques.
The use of sonography to guide transrectal pelvic abscess drainage is
simple and cost-effective. However, sonographic guidance entails the
introduction of a relatively sizeable transrectal probe, a biopsy guide, and a
punc ture needle. This can create significant discomfort in certain patients,
such as in immediate postoperative individuals, in patients with proctitis,
and in the pediatric age group. In addition, the presence of a large amount of
air within the abscess cavity creates significant back shadowing artifacts
that preclude adequate delineation of anatomic details on sonography
[4].
The MRI-guided transrectal drainage technique described here was used to
drain a presacral abscess in a patient with a dehiscent rectal anastomosis
resulting in bowel air communicating freely with the abscess cavity. The
ability to perform this drainage while introducing only a thin plastic sheath
harboring an 18-gauge needle into the rectum, to continuously monitor the
needle in three planes, and to exploit the unequaled soft-tissue contrast and
resolution of MRI appeared well suited for this particular setting. The
patient reported a complete lack of intraprocedural discomfort despite his
immediate postoperative status and the presence of pelvic infection. The
three-plane, high-contrast, high-resolution, artifact-free imaging assured
safe and accurate guidance and guarded against complications resulting from
unexpected postoperative anatomy. The development of the triorthogonal imaging
plane guidance [5] represented
a significant departure from the single-plane (or multiple parallel-plane)
guidance of earlier MR interventions
[6,
7] and helped significantly
shorten the guidance duration. The guidance time could have been further
shortened by reducing the number of signals averaged used and thereby
increasing the temporal frame rate of the guidance images. This would,
however, occur at the expense of the signal-to-noise ratio (SNR). In our
opinion, the three signal averages we used allowed us a sufficiently fast
frame rate (3.11 seconds) while providing an excellent SNR to allow safe
navigation of the interventional device. Conceivably, with more widespread use
of the technique, various interventionists may elect to modify these
parameters to achieve their own comfortable balance between speed and image
quality.
The described technique is limited by the narrow selection of available
MR-compatible devices, particularly U.S. Food and Drug Administration
(FDA)-approved devices in the U.S. market. The duration of this procedure
could be further shortened to equal that of the puncture needle insertion if
the currently available single-stick catheters could be offered with
MR-compatible stylets. A need also exists for reliable MR-safe guidewires. In
this context, safety primarily entails guidewires that do not heat in response
to the time-varying magnetic field gradients. In addition, they should be
reliably visualized under MR guidance. Suboptimal visualization of a
0.035-inch guidewire included in an MR-compatible drainage kit has been
reported [8]. Recent reports
describe preclinical testing of glass-fiber
[9] and polymer-based
[10] MR-safe guidewires.
In summary, we have described a new technique for performing transrectal
drainage of deep pelvic abscesses under continuous interactive triorthogonal
MRI guidance. The technique is best suited for circumstances in which it is
desirable to avoid the discomfort associated with inserting a relatively size
able ultrasound probe, biopsy guide, and punc ture needle into the rectum,
such as in postoperative patients, patients with proc titis, and the pediatric
population. It is also suitable for abscesses with large air contents pre
cluding adequate visualization with sonog raphy. This report also emphasizes a
current need for more MRI-compatible devices, particularly guidewires and
single-stick catheters.
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Abstract
Introduction
