DOI:10.2214/AJR.07.2282
AJR 2008; 190:W157-W160
© American Roentgen Ray Society
A Hybrid Radiography/MRI System for Combining Hysterosalpingography and MRI in Infertility Patients: Initial Experience
Cynthia B. Freeman-Walsh1,2,
Rebecca Fahrig3,
Arundhuti Ganguly3,
Viola Rieke3 and
Bruce L. Daniel1
1 Department of Radiology, Stanford Hospital, Stanford, CA.
2 Present address: Department of Radiology, The Ottawa Hospital, 1053 Carling
Ave., Ottawa, ON K1Y 4E9, Canada.
3 Department of Radiology, Lucas MRS Center, Stanford, CA.
Received March 20, 2007;
accepted after revision September 13, 2007.
Address correspondence to C. B. Freeman-Walsh.
Supported by National Institutes of Health grant R01 EB000198.
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Abstract
OBJECTIVE. We evaluated the feasibility of a prototype hybrid
radiography/MRI system in evaluating infertility patients. Pelvic MRI was
followed by hysterosalpingography (HSG) without moving the patient. This
system allowed evaluation of tubal patency and cross-sectional imaging with
one examination.
CONCLUSION. Our hybrid radiography/MRI system provided good-quality
HSG and MR images. We were able to assess tubal anatomy and patency and
uterine anatomy and to detect pelvic abnormalities, including fibroids and
adenomyosis. Furthermore, MR images and radiographs were superimposed to
clarify HSG findings.
Keywords: gynecology • hysterosalpingography • infertility • MRI • obstetrics • women's imaging
Introduction
The imaging workup of infertility patients utilizes several techniques.
Hysterosalpingography (HSG) is the gold standard for assessing fallopian tube
patency [1]. However, MRI is
necessary to characterize uterine anomalies and pelvic abnormalities
[2]. The workup of infertility
may be accomplished by several different techniques and sometimes requires
multiple different examinations. A truly hybrid radiography/MRI system
developed at our institution enables MRI and fluoroscopy of the same imaging
volume without moving the patient
[3]. This system combines HSG
and MRI in one examination. Our purpose was to evaluate the clinical
feasibility of obtaining images using our hybrid radiography/MRI system to
evaluate infertility patients.
The truly hybrid radiography/MRI system is unique because fluoroscopy and
MRI are performed without moving the patient between techniques. Other systems
that combine fluoroscopy and MRI use a system whereby adjacent MRI and
radiography suites are connected using a moving-bed patient system
[4]. Our unit is truly hybrid
in that a fixed X-ray source and digital flat-panel detector are located
inside the bore of a 0.5-T magnet (Signa-SP, GE Healthcare). This fully
integrated setup allows easy and rapid switching between radiography and MRI
without needing to move the patient. For evaluation of infertility, HSG and
pelvic MRI are performed without moving the patient, aside from elevating the
legs to the lithotomy position to achieve cannulation of the cervix for HSG.
The two examinations were thereby effectively combined
[3], which enables evaluation
of tubal patency and cross-sectional pelvic abnormalities in one examination.
In addition, using the same field of view and plane of imaging allows us to
superimpose HSG and MR images.
Using our hybrid radiography/MRI system, we performed pelvic MRI and HSG
for the evaluation of infertility patients. We evaluated the performance and
image quality and report our initial experience with this new technique.
Materials and Methods
We obtained institutional review board approval for our study and informed
consent from patients, and the study was compliant with HIPAA. We recruited
patients who were scheduled to undergo HSG for infertility. One patient was
examined for uterine dehiscence. Examinations were performed by two
radiologists: an experienced body imager and a body imaging fellow.
The hybrid radiography/MRI system is a prototype created at our institution
[3]. A fixed-anode fluoroscopic
X-ray tube and digital flat-panel detector are positioned between the two
magnetic poles of a 0.5-T magnet (Signa-SP) as shown in
Figure 1. A prototype
X-ray-transparent pelvic phased-array coil was used
[5]. With patients in the
supine position, axial STIR (TR/TE, 4,016/61), coronal T1 (450/18), sagittal
T2 fast spin-echo (3,800/105), and coronal T2 fast spin-echo (3,000/111)
sequences were acquired. Patients were then placed in the lithotomy position.
The cervix was cannulated using sterile technique and MR-compatible equipment.
A 6.8-French 30-cm balloon HSG catheter (Sholkoff balloon HSG catheter, Cook
OB/Gyn) was advanced and the balloon was inflated. The patient was returned to
the supine position and a second coronal T2 fast spin-echo sequence was
performed to correspond to the subsequent HSG images. Catheter positioning was
confirmed with this sequence. Iohexol (Omnipaque 240, GE Healthcare) was
injected under fluoroscopic guidance until bilateral free peritoneal spill was
observed. Tubal patency, uterine anatomy, ovaries, and other abnormalities
were assessed. When appropriate, MR and HSG images were superimposed. Image
quality was assessed—in particular, with regard to whether the
fluoroscopic images were adequate to be used to evaluate tubal patency.
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Fig. 1 —Photograph of hybrid radiography/MRI system shows position of
X-ray tube (thin black arrows) and flat-panel detector (long
white arrow) between two donut-shaped magnetic poles (thick black
arrows) of 0.5-T magnet (Signa-SP, GE Healthcare). Foot pedals for
fluoroscopy are indicated with short white arrow. Patients were placed in
supine position for acquisition of MR images. For cannulation of cervix,
patient was placed in lithotomy position using stirrups attached to inside of
magnet.
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Results
Ten patients were examined. Nine were referred for infertility and one for
uterine dehiscence after cesarean delivery. An example of a normal study with
a superimposed composite of the MR and HSG images is shown in
Figure 2. The fluoroscopic
images were of good quality in all but one case. Inadequate X-ray tube output
in an early prototype was the cause of poor image quality in that study. In
the other nine cases, bilateral tubal patency was shown, with good resolution
of the contrast-filled tubes and peritoneal spill. In two patients, contour
abnormalities of the endometrial cavity were detected.
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Fig. 2 —Normal study in 36-year-old woman with infertility.
Superimposition of coronal MR image and hysterosalpingogram (red) can
be performed because two techniques have same field of view and are obtained
without moving patient between studies.
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Thirteen fibroids in five patients were shown on MRI. In four patients, the
fibroids were undetectable on HSG, including one case with bulky, exophytic
lesions. In the fifth patient, an intramural fibroid abutting the endometrium
distorted the endometrial cavity, causing a contour abnormality on HSG (Figs.
3A and
3B). Superimposition of the MR
and fluoroscopic images confirmed that the abnormality on HSG corresponded to
the fibroid (Fig. 3C).
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Fig. 3B —40-year-old woman with infertility. HSG finding shown in
A corresponds to intramural fibroid (arrow) that abuts
endometrial lining on coronal T2 fast spin-echo MR image. MR image clearly
shows that partially submucosal fibroid is responsible for contour abnormality
shown on hysterosalpingogram (A).
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In another case, HSG showed a fundal contour abnormality that was
interpreted as an arcuate uterus. MRI showed that the contour abnormality
corresponded to an area of focal adenomyosis (Figs.
4A and
4B). The contour abnormality on
HSG was associated with subtle irregularity, likely representing diverticula
extending into the myometrium, which is a documented HSG finding suggestive of
adenomyosis [6].
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Fig. 4B —42-year-old woman with infertility. Coronal T2 fast spin-echo
MR image confirms that contour abnormality (arrow) shown on HSG
(A) corresponds to area of high T2 signal intensity, which is
consistent with focal adenomyosis.
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Cervical defects were seen on MRI in two patients from surgical procedures.
In one case, the lesion was retrospectively visible on HSG. In a third
patient, a cesarean delivery defect and possible fistulous tract were noted.
MRI showed malposition of the HSG catheter in three patients. After the
catheter was repositioned, MR images were obtained to confirm its proper
placement.
Vertical shadowing artifact was noted in some fluoroscopic images. This
artifact appeared because images obtained using our prototype system are not
corrected for gain due to pixel-to-pixel variation. This artifact can be
removed by postprocessing; however, we did not perform postprocessing because
images with the artifact remained of diagnostic quality.
Discussion
The most common female component of infertility is related to tubal patency
[7]. Most clinical MRI
techniques do not provide the spatial resolution necessary to show the
fallopian tubes. Therefore, HSG remains the gold standard for the evaluation
of tubal patency. MRI remains the gold standard for evaluating uterine contour
abnormalities [2]. The low
specificity of HSG for contour abnormalities—in particular, for
distinguishing bicornuate from septate uteri—is well known
[8]. Our data support the
results of previous studies that show MRI is more sensitive than HSG for
identifying fibroids. Currently, therefore, both techniques are often
necessary.
We believe that our hybrid radiography/MRI system offers the advantage of
incorporating two techniques into one system, thereby streamlining the workup
of infertility and identifying unsuspected abnormalities. An exciting
opportunity provided by the hybrid radiography/MRI system is the exact
coregistration of the two techniques. As we have shown, this system has the
potential to show the cause of hysterographic contour abnormalities with
cross-sectional images of myometrial abnormalities, such as fibroids and
adenomyosis. Improved image quality and coregistration of images may increase
the utility of this new technology.
A limitation of this study is small sample size. This report is intended as
a description of our initial clinical experience. We intend to increase our
experience and sample size. Another limitation is that none of our patients
had a significant uterine anomaly. Such a finding would emphasize the
advantage of incorporating MRI into the initial imaging workup. Several
technical limitations are inherent to this study: The use of a 0.5-T magnet
results in decreased signal-to-noise ratio, lower spatial resolution,
decreased imaging speed, and inability to perform sequences with conventional
chemical fat suppression when compared with 1.5-T MRI. The limitations of our
radiography unit are the fixed projection angle and lower power compared with
rotating tubes. Although this poses a limitation to angiographic studies, the
power is sufficient for HSG.
In conclusion, our initial experience shows that our unique, truly hybrid
radiography/MRI system provides information regarding tubal patency, uterine
anatomy, and pelvic abnormalities in one examination. Furthermore, MR images
and radiographs can be superimposed to clarify HSG findings. Our study
confirmed that uterine abnormalities, such as fibroids and adenomyosis, can be
missed on HSG. Based on this initial experience, we believe that our hybrid
radiography/MRI system has the potential to streamline the imaging workup of
infertility patients. Additional studies are necessary to determine the
incremental benefit of the new technique compared with conventional
hysterography in identifying unsuspected abnormalities.
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Abstract
Introduction
