DOI:10.2214/AJR.07.2505
AJR 2008; 190:1271-1278
© American Roentgen Ray Society
3-T MRI of Rectal Carcinoma: Preoperative Diagnosis, Staging, and Planning of Sphincter-Sparing Surgery
Xiao Ming Zhang1,2,
Hong Lei Zhang2,
Dexin Yu1,
Yong Dai3,
Dongsong Bi3,
Martin R. Prince2 and
Chuanfu Li1
1 Department of Radiology, Qilu Hospital of Shandong University, 107 Wenhuaxi
Rd., Jinan, Shandong, China 250012.
2 Department of Radiology, Weill Medical College of Cornell University, New
York, NY.
3 Department of Surgery, Qilu Hospital of Shandong University, Jinan, Shandong,
China.
Received May 3, 2007;
accepted after revision November 12, 2007.
Address correspondence to C. Li
(chuanfu.li{at}gmail.com).
Supported by the Foundation of Shandong Province, Department of Health (no.
2005JW017), People's Republic of China.
Abstract
OBJECTIVE. The purpose of this study was to assess the accuracy of
3-T MRI in the preoperative diagnosis, staging, and planning of surgical
management of rectal carcinoma.
SUBJECTS AND METHODS. Thirty-eight patients (23 men, 15 women) with
clinically suspected rectal carcinoma underwent 3-T MRI. Coronal, axial, and
sagittal T2-weighted sequences with and without fat suppression; axial
T1-weighted spin-echo sequences; axial T1-weighted gradient-echo sequences
with and without fat suppression; oblique 2D MR hydrography; and 3D
fat-suppressed dynamic contrast-enhanced MRI were performed. Image quality
with these sequences was evaluated by three radiologists experienced in body
MRI. The significance of difference in results with the sequences was tested.
The manner in which MRI staging and feasibility of sphincter-sparing surgery
agreed with operative and pathologic findings was evaluated with kappa
statistics.
RESULTS. Rectal carcinoma was identified on MRI and confirmed
histologically in all 38 patients. MRI findings were correctly predictive of T
category in 35 cases (accuracy, 92.1%). In 31 (96.9%) of 32 resectable
cases,sphincter-sparing surgical approaches were accurately chosen on the
basis of MRI findings. Among the 11 sequences, 3D fat-suppressed dynamic
contrast-enhanced MRI best delineated tumor margins. Coronal and axial
T2-weighted images also well depicted tumor margins with minimal artifact.
T2-weighted images were superior to unenhanced T1-weighted images.
CONCLUSION. MRI of rectal cancer at 3 T is accurate for prediction
of T category and the feasibility of sphincter-sparing surgery. The best
images were obtained with coronal, sagittal, and axial T2-weighted sequences
and 3D fat-suppressed dynamic contrast-enhanced MRI.
Keywords: dynamic contrast enhancement • MRI • rectal carcinoma
Introduction
Colorectal carcinoma is the second most common cancer in Western society
with 148,620 new cases and 55,170 deaths in the United States each year
[1], and the worldwide
incidence is rapidly increasing as diet and lifestyles change. Accurate
preoperative diagnosis and staging of rectal carcinoma, which are essential
for treatment planning and prognosis, can be achieved with endorectal
sonography
[2–5]
and CT [6,
7]. Because of its superior
soft-tissue contrast and multiplanar capability, MRI is becoming increasingly
accepted by radiologists, surgeons, and patients for imaging of the rectum.
Use of MRI also eliminates the risks of ionizing radiation and nephrotoxicity
from iodinated contrast material.
Most studies of rectal MRI have been performed with a field strength of 1.5
T or lower
[8–11]
because susceptibility artifacts from bowel gas increase at higher field
strength. This artifact, however, can be reduced with the use of spin-echo
sequences and distention of the rectum with warm water. In a preliminary
study, Chun et al. [12] found
that 3-T high-field-strength MRI with only four MR sequences and without
gadolinium enhancement or MR hydrography was almost as accurate as endorectal
sonography for staging rectal carcinoma. Another study
[13] of the use of 3-T MRI
with a four-channel phased-array coil in the diagnosis of rectal cancer also
showed promising results with T2-weighted fast spin-echo sequences in the
axial and sagittal planes and 2D T1-weighted sequences with fat saturation
before and after gadolinium enhancement. There remains uncertainty, however,
about the optimal pulse sequences, and there are limited data on the
diagnostic accuracy of rectal MRI at 3 T. The lack of a standard protocol
causes inconsistent diagnostic accuracy among institutions. The purpose of
this study was to evaluate the image quality of various 3-T MRI sequences for
preoperative staging and planning of sphincter-sparing resection of rectal
cancer.
Subjects and Methods
Patients
From January 2005 to February 2006, 38 patients (23 men, 15 women; mean
age, 60 years; range, 21–85 years) consecutively referred for MRI of the
rectum because of clinical suspicion of rectal carcinoma were invited to
participate in this research study on preoperative imaging. Clinical
manifestations included guaiac-positive stool (n = 34), narrowing of
the stool (n = 16), constipation (n = 6), abnormal finding
at digital rectal examination (n = 24), and abnormal finding at
endoscopy (n = 35). All invited patients agreed and gave written
informed consent as authorized by the hospital ethics committee.
Before MRI, bowel preparation included laxative cleansing (oral
administration of magnesium sulfate at a dose of 20 g/100 mL followed by oral
hydration the night before rectal MRI for inpatients or 20-mL glycerin enema 1
hour before rectal MRI for outpatients), luminal distention with warm sodium
chloride enema, and 10 mg of anisodamine by intramuscular injection 10 minutes
before the examination to reduce bowel peristalsis. Before anisodamine was
administered, patients were interviewed to exclude contraindications to use of
this agent, such as glaucoma, prostate gland hyperplasia, and cardiac
disease.
MRI Technique
All patients were examined freely breathing in the supine position on a 3-T
MRI unit (Signa Excite, GE Healthcare). The body coil was used for signal
transmission, and an eight-channel phased-array surface coil was used for
signal reception. A landmark was made on the pubic symphysis.
An initial three-plane localizer view covering the entire pelvis was
obtained. Subsequent sequences included coronal, axial, and sagittal
T2-weighted images; axial T2-weighted images with fat suppression; axial
T1-weighted gradient-echo images; axial T1-weighted gradient-echo images with
fat suppression; radial oblique 2D MR hydrographic single-shot fast spin-echo
images; and axial 3D fat-suppressed dynamic gadolinium-enhanced MR images
(Fig. 1A,
1B,
1C,
1D,
1E,
1F,
1G,
1H,
1I,
1J). An axial T1-weighted
spin-echo sequence was added for the last 14 patients. Coronal and sagittal
T2-weighted sequences with fat suppression were added if necessary as
determined by the supervising radiologists. The imaging parameters for each
sequence are listed in Table 1.
Two-dimensional MR hydrography was performed with at least five slices
prescribed radially centered on the tumor at the position of any luminal
stenosis.
View larger version (161K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Coronal T2-weighted fast-recovery fast spin-echo image.
|
|
View larger version (149K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Sagittal T2-weighted fast-recovery fast spin-echo image.
|
|
View larger version (135K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Axial T2-weighted fast-recovery fast spin-echo image.
|
|
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Axial T2-weighted fat-suppressed fast-recovery fast spin-echo
image.
|
|
View larger version (138K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1E —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Axial T1-weighted fast spoiled gradient-recalled echo image.
|
|
View larger version (149K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1F —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Axial T1-weighted fat-suppressed fast spoiled gradient-recalled
echo image.
|
|
View larger version (138K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1G —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Axial T1-weighted fast spin-echo image.
|
|
View larger version (97K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1H —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Three-dimensional fat-suppressed fast spoiled gradient-recalled
echo dynamic gadolinium-enhanced image.
|
|
View larger version (98K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1I —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Two-dimensional MR hydrographic single-shot fast spin-echo
image.
|
|
View larger version (117K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1J —75-year-old man with poorly differentiated rectal
adenocarcinoma (arrows). Preoperative MRI T category was T2 (smooth
outer tumor border within rectal wall and no invasion into fat surrounding
rectum), and preoperative 3-T MRI showed tumor had invaded anal sphincter. MRI
findings were confirmed at surgery, and patient underwent abdominoperineal
resection. Photograph shows surgical specimen.
|
|
Three-dimensional dyn a mic gadolinium-enhanced MRI was performed with an
axial multiphase spoiled gradient-echo se quence with fat suppression. The
temporal resolu tion was 13–16 seconds per phase. Dynamic
contrast-enhanced MRI acquisition was started simultaneously with IV injection
of a standard dose (0.1 mmol/kg) of gadopentetate dimeglumine (Magnevist,
Bayer HealthCare) and repeated continuously for 15–20 phases with a
total data acquisition time of approximately 4 minutes. The gadolinium
contrast agent was injected at a rate of 3 mL/s with a power injector
(Spectris MR, Medrad) and followed by a bolus of 20 mL of normal saline
solution at the same injection rate.
Image Analysis
MR images were evaluated independently by three radiologists with more than
8 years of experience in interpreting body MR images. The reviewers were
blinded to all clinical information. Images obtained with all sequences were
presented to each reviewer simultaneously without control of the order in
which the reviewers focused on the MR sequences. In this way the reviewers
could directly compare images obtained with the various sequences side by side
to assess relative image quality.
Overall image quality was graded on a four-point scale as follows: 0,
nondiagnostic; 1, poor image quality but still diagnostic; 2, good image
quality; 3, excellent image quality. Other factors evaluated were artifacts
(0, artifact interfering with diagnosis; 1, moderate artifact not interfering
with diagnosis; 2, mild artifact; 3, no artifact) and depiction of the border
between rectal tumor and normal rectum (0, no distinct border visualized; 1,
moderate blurring of rectal wall, rectal tumor border not clearly identified;
2, mild blurring of rectal wall, rectal tumor border identified; 3,
well-demarcated tumor border).
Each rectal tumor was staged according to MRI features and later correlated
with the operative and pathologic findings. T1 and T2 categories were not
differentiated in this study. T1 and T2 lesions were differentiated from T3
lesions by identification of a smooth outer tumor border within the rectal
wall with no invasion into fat surrounding the rectum. T3 lesions had
irregular outer borders and invasion into fat surrounding the rectum with
plaque, mass, or cordlike signal intensity projecting into perirectal fat. In
T4 lesions, fat planes between rectal carcinoma and surrounding organs
disappeared. Lymph nodes 1 cm or larger within the field of view were
diagnosed on MRI as lymph node metastasis. Metastasis to other organs within
the field of view also was identified. Metastatic disease outside the field of
view of pelvic MRI was not assessed.
To predict the feasibility of sphincter-sparing surgery, the distance from
the lower margin of a rectal tumor to the point at which the levator ani
muscle attached to the rectum was measured. The surgeons preferred this
landmark to the dentate line because it was considered easier to identify on
MRI, particularly on coronal T2-weighted images, and because it is a more
reliable marker of the superior sphincter margin. If the distance was 2 cm or
greater, sphincter- and anus-sparing surgery was considered feasible. Surgical
plans determined with MRI findings were correlated with the operative
findings.
Statistical Method
The significance of differences among sequences was tested with ridit
analysis (a statistical method used to describe differences between groups on
an ordered categoric basis) and ordinal logistic regression for image quality,
artifacts, and depiction of rectal tumor border with normal rectal wall. The
kappa statistic was used to evaluate the manner in which MRI staging and
judgment about feasibility of sphincter-sparing surgery for rectal cancer
agreed with the operative and pathologic findings. A value of p <
0.05 in a two-tailed test was considered statistically significant. All
analyses were performed with SAS software (version 9.1, SAS Institute).
Results
All patients tolerated the pre-MRI bowel preparation well; the average
volume of sodium chloride enema was 360 mL (range, 200–500 mL). All MRI
examinations were of diagnostic quality. The average imaging time was 35
minutes (range, 30–40 minutes) plus approximately 10 minutes for patient
preparation.
Rectal carcinoma was identified on MRI in all 38 patients and was confirmed
at histologic examination of surgical (n = 32) and biopsy (n
= 6) specimens. The mean tumor size was 5.2 cm (range, 2.5–10 cm).
Histologic classification of the tumors showed seven well-differentiated
adenocarcinomas (Fig. 2), 14
moderately well-differentiated adenocarcinomas
(Fig. 3), 13 poorly
differentiated adenocarcinomas, and four signetring cell carcinomas.
Histopathologic staging revealed two lesions in category T1, 11 in category
T2, 21 in category T3 (Fig.
4), and four in category T4
(Fig. 5). Lymph node
metastasis was confirmed in 17 patients. Two patients were found to have
distal metastasis (liver, lung), which was identified with separate abdominal
MRI and chest CT examinations performed on a later date. Twenty-five patients
underwent sphincter-sparing resection of the rectum, and seven underwent
abdominoperineal excision. In four patients, the tumor was not completely
resected owing to local tumor extent. Instead, diverting colostomy was
performed to relieve intestinal obstruction. The two patients with distal
metastasis were treated with chemotherapy without undergoing surgery. One of
these two patients also underwent radiation therapy.
View larger version (153K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2 —57-year-old man with T1 well-differentiated rectal
adenocarcinoma (arrow). Coronal T2-weighted MR image shows distance
from lower margin of rectal cancer to upper margin of external sphincter,
where levator ani muscle (arrowheads) attached to rectum, was 5 cm
(double arrow). Patient underwent sphincter-sparing resection of
rectum.
|
|
View larger version (153K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3 —58-year-old man with T2 moderately differentiated rectal
adenocarcinoma (arrow). Coronal T2-weighted MR image shows distance
from lower margin of rectal tumor to point where levator ani muscle
(arrowheads) attaches to rectum is 1.5 cm (double arrow).
Patient underwent internal sphincter resection with prolapsing technique to
save external sphincter and anus.
|
|
MR Image Quality
The mean ridits of image quality scores for each 3-T MRI sequence are shown
in Table 2 with a statistically
significant difference (p < 0.0001). According to the mean ridit
of each sequence, among the 11 sequences, 3D fat-suppressed dynamic
gadolinium-enhanced MRI was considered to provide the best delineation of
tumor margins. Coronal T2-weighted and axial T2-weighted images also depicted
tumor margins well and had the highest image quality score with the least
artifact. In general, T2-weighted images were superior to T1-weighted images
(p < 0.0001) in ordinal logistic regression. For T1-weighted
images, the fast spin-echo sequence was better than the spoiled
gradient-recalled echo sequence (p < 0.05) in ordinal logistic
regression, although the acquisition time was longer. The lesions were
depicted more clearly on sequences without fat suppression than on those with
fat suppression because the high signal intensity of fatty tissue surrounding
the rectum gave better contrast to the tumor with lower signal intensity.
Radially oblique MR hydrography depicted the rectal lumen similarly to barium
enema, showing endoluminal features such as filling defects and ulcerations,
but did not show mural features.
Diagnosis, Staging, and Planning of Sphincter-Saving Surgery
With MRI, T category was correctly estimated for 35 of the 38 patients
(accuracy, 92.1%; 
= 0.86, p < 0.0001)
(Table 3). In the evaluation of
tumor invasion into fat tissue surrounding the rectum to differentiate T3 or
higher from T2 or lower, surgical findings confirmed 25 cases with invasion
and 13 without invasion; 35 of 38 cases were depicted accurately with MRI
(accuracy, 92.1%; = 0.83; p < 0.0001). MRI showed four of
four rectal carcinomas with invasion to adjacent organs, which differentiated
category T4 from category T3 with an accuracy of 100%. With MRI, 11 of 17
patients with lymph node metastasis and 19 of 21 patients without nodal
metastasis were correctly identified (accuracy, 79.0%; = 0.56;
p < 0.001) (Table
4).
For the 32 resectable tumors, with a 2 cm or greater distance between the
lower margin of rectal cancer to the point at which the levator ani muscle
attached to the rectum as the criterion for predicting the feasibility of
sphincter-sparing surgery, MRI was accurate for determining the surgical
approach in 31 cases (accuracy, 96.9%; = 0.9; p < 0.0001).
The only patient with less than 2 cm between the tumor and the levator ani
muscle had T2 well-differentiated rectal adenocarcinoma. This patient
underwent internal sphincter resection with prolapsing technique to save at
least the external sphincter and anus, although the distance was only 1.5 cm
on MRI.
Discussion
The anatomic location, fixation in the pelvic fat, and lack of peristalsis
make the rectum an ideal organ for imaging with MRI
[14]. Although rectal tumors
can be diagnosed with digital examination, barium enema, and colonoscopy or
sigmoidoscopy, these endoluminal techniques do not provide sufficient
information about the extraluminal spread of tumor for preoperative planning.
Rectal MRI has the benefits of multiplanar imaging and excellent contrast
between tumor and perirectal fat, which helps precisely show the tumor and its
extent for surgical planning and staging. Some authors
[11] recommend MRI for imaging
low-lying rectal cancer because MRI has better soft-tissue contrast than CT in
the delineation of invasion of rectal cancer into perianal muscles, prostate
gland, and vagina. MRI also clearly shows the mesorectal fascia, which is the
border for total mesorectal excision
[11,
15]. Because it depicts the
characteristic mucinous lakes, MRI is highly accurate in differentiating
mucinous from nonmucinous adenocarcinoma
[16–18].
MRI also may help in differentiation of early recurrence from postoperative
changes and in evaluation of peri anal fistulas and sinus tracks
[19–22].
For young patients and patients undergoing multiple examinations, MRI has the
advantage of eliminating the risks of ionizing radiation and contrast
nephrotoxicity.
Various MRI sequences have been used to image the rectum. The image-quality
data in this study confirmed that for 3-T units, images obtained with
T2-weighted spin-echo sequences are superior to those obtained with
T1-weighted sequences, as has been shown for 1.5-T MRI
[23]. On T2-weighted images,
tumors were slightly better evaluated without fat suppression because on
T2-weighted images perirectal fat with its high signal intensity has excellent
contrast to the tumor. In some cases, however, high-signal-intensity
perirectal inflammation was better visualized on T2-weighted images with fat
suppression. For the two T1-weighted sequences studied, image quality was
better with axial T1-weighted fast spin-echo sequences, albeit with a longer
acquisition time than for the axial T1-weighted gradient-echo sequence, but
was still substantially inferior to that of the T2-weighted images. Coronal
and sagittal images were especially useful for showing the relations among the
tumor, levator ani muscle, and sphincter.
All three reviewers identified dynamic contrast-enhanced MRI as the best
sequence for depicting tumor margins even through respiratory motion artifact
was present. All reviewers considered this sequence essential in the rectal
MRI protocol. This finding was consistent with those of a study by Wallengren
et al. [24]. In the detection
of rectal cancer, those investigators reported 100% sensitivity and 70%
specificity of MRI performed with contrast enhancement by superparamagnetic
ferristene enema. This double-contrast method also was clinically valuable for
staging and determining the depth of tumor invasion into the rectal wall,
which was not possible in this study because of our goal of assessing MR
hydrography performed with saline enema.
MR hydrography has been used successfully to visualize the lumens of
biliary ducts, pancreatic ducts, the ureters, and the bladder through
depiction of static fluid. In this study, sodium chloride was introduced into
the rectum to show the rectal lumen distended with water in a manner similar
to that used for 2D single-shot fast spin-echo MR hydrography performed
radially to view the endoluminal features from different angles. Depiction of
the rectal lumen was similar to that on images from barium enemas.
Bowel preparation is crucial to avoid interference from feces and to reduce
susceptibility artifact from air–tissue borders. In this study, a
simplified 20-mL glycerin enema 1 hour before the examination was adequate for
patients with rectal cancer in the middle and lower sections who had not yet
undergone magnesium sulfate bowel cleansing for surgery. Distention of the
rectum is useful but often is not possible owing to encasement by tumor; at
least one group of authors
[25] has suggested that bowel
preparation and distention are unnecessary. Lauenstein et al.
[26] suggested oral
administration of multiple doses of gadolinium or barium sulfate beginning 3
days before MRI examination to label feces, entirely avoiding enemas. Many
contrast materials have been used to distend the rectum, including air
[27], water
[28], dilute gadolinium, and
other paramagnetic agents [24,
29]. In our study, warm sodium
chloride was used mainly because of its low cost, absence of toxicity, and
acceptance by patients.
In addition to facilitating the diagnosis and staging of rectal tumors, MRI
contributes to surgical planning by showing the relations among the tumor, the
sphincter, and the levator ani muscle. Sphincter invasion is identified with
an accuracy of 87% [30,
31]. Complete tumor resection
and sphincter sparing are important goals of rectal surgery to improve quality
of life and have fewer complications than abdominoperineal excision. A rectal
cancer distal resection margin greater than 2 cm is considered optimal for
avoiding recurrence [32]. Thus
the length of normal rectum above the levator ani muscle is the key to
determining whether sphincter-sparing surgery can be performed. In this study,
the distance from the lower margin of rectal cancer to the upper margin of the
external sphincter (the point at which the levator ani muscle attaches to the
rectum) was measured on good-quality coronal and sagittal images to assess the
feasibility of sphincter-sparing surgery with adequate tumor margins. Data on
32 patients with surgical confirmation showed that findings on 3-T MRI were
accurate predictors of the feasibility of sphincter-sparing surgery in 31
(96.9%) of the patients. In one patient with a 1.5-cm distance between the
tumor and the levator ani muscle, MRI helped the surgeons to plan a modified
procedure that spared the external sphincter and anus.
The data on the diagnostic performance of 3-T MRI compare favorably with
data on sonography, which is reported to have 69–97% accuracy, and on
CT, which has a reported accuracy of 52–87% for TNM T categorization of
rectal cancer
[4–6,
33,
34]. Endoluminal sonography is
reliable in assessing depth of penetration by tumor into the rectal wall, but
this technique is invasive and operator dependent. Endoluminal sonography
cannot be used to assess tumor close to the sigmoid colon or tumor extension
into adjacent organs. CT cannot be used to assess depth of invasion into the
rectal wall, but it has the benefits of being fast, having a large field of
view, and enabling simultaneous evaluation for distant metastasis.
As in other cancers, detecting lymph node metastasis is the most
challenging aspect of MRI diagnosis of rectal cancer. Kim et al.
[34] found that the accuracy
rates of MRI, CT, and endoluminal sonography for local lymph node metastasis
of rectal cancer were 63%, 56.5%, and 63.5%, respectively. The accuracy of
imaging is low mainly because the diagnosis of metastasis is made only on the
basis of the size and shape of lymph nodes, and thus micrometastasis is
missed. Because lymph nodes enlarge in both inflammatory and neoplastic
processes, which are difficult to differentiate morphologically,
false-positive and false-negative results occur. In numerous studies, lymph
nodes larger than 1 cm have been considered metastasis
[35]; in other studies,
cutoffs of 8 mm [36] and 6 mm
[37] have been used. With
greater than 6 mm as the criterion for the diagnosis of lymph node metastasis
around rectal wall and surrounding fat, the sensitivity, specificity, and
accuracy were only 57%, 88%, and 76%, respectively
[37]. Brown et al.
[38] analyzed 437 lymph nodes
and concluded that benign and malignant lymph nodes were similar in size.
Those authors believed that accuracy could be increased by evaluating lymph
node borders and signal intensity. They proposed that using irregular border
and mixed signal intensity as the criteria for metastatic lymph nodes would
improve sensitivity to 85–95% and specificity to 95–97%.
Heterogeneous contrast enhancement is another indicator of lymph node
metastasis [39]. New contrast
agents have been developed for detection of metastatic lymph nodes
[40,
41], but they were not used in
this study.
There were additional limitations to this study. With the small number of
patients, there were only two T1 lesions, and insufficient number for
assessment of the utility of 3-T MRI in differentiating T1 and T2 disease.
Therefore, T1 and T2 lesions were combined as T1 and T2 for statistical
analyses. Imaging with an endorectal coil to depict the layers of the rectal
wall and differentiate T1 from T2 lesions has a reported accuracy of 92%
[42,
43]. However, the technique
has a limited field of view and requires expertise for coil insertion to avoid
rectal injury. The failure rate can be as high as 40%
[44]. Endorectal coils can
produce artifacts and are of limited use in imaging of tumors close to the
sigmoid colon or of obstructing lesions. Phased-array surface coils are more
acceptable because of their simplicity and larger, more homogeneous field of
view [15,
33], but tumor invasion into
the submucosa and muscularis propria of the rectal wall has not been well
evaluated.
Despite the larger field of view of the eight-channel phased-array coil
compared with endorectal coils, this study was limited to the pelvis. Separate
examinations of the abdomen and chest were performed to assess the presence of
hepatic and pulmonary metastasis. Newer body-array coils and use of total
image matrix technique for greater anatomic coverage may make it possible to
cover the abdomen and pelvis in a single examination.
To save time, three of the sequences—axial T1-weighted spin echo and
coronal and sagittal T2-weighted with fat suppression— were not
performed for all of the patients. This omission caused bias in comparison of
image-quality scores. The added value of 3 T compared with 1.5 T was not
directly assessed because the patients underwent only 3-T imaging. It is our
impression, however, that the signal-to-noise ratio at 3 T is noticeably
greater than that at 1.5 T.
We conclude that MRI of rectal cancer at 3 T is accurate for prediction of
tumor stage and the feasibility of sphincter-sparing surgery. In clinical
practice, a basic imaging protocol can be simplified to four sequences:
coronal, sagittal, and axial T2-weighted sequences and 3D fat-suppressed
dynamic gadolinium-enhanced MRI. MR hydrographic images and axial T1-weighted
fast spin-echo and axial T2-weighted images with fat suppression add only
slightly more information.
References
- Jemal A, Siegel R, Ward E, et al. Cancer statistics, 2006.
CA Cancer J Clin 2006;56
: 106–130[Abstract/Free Full Text]
- Hunerbein M. Endorectal ultrasound in rectal cancer.
Colorectal Dis 2003;5
: 402–405[CrossRef][Medline]
- Schaffzin DM, Wong WD. Endorectal ultrasound in the preoperative
evaluation of rectal cancer. Clin Colorectal Cancer2004; 4:124
–132[Medline]
- Siddiqui AA, Fayiga Y, Huerta S. The role of endoscopic ultrasound
in the evaluation of rectal cancer. Int Semin Surg
Oncol 2006; 3:36[CrossRef][Medline]
- Kim JC, Kim HC, Yu CS, et al. Efficacy of 3-dimensional endorectal
ultrasonography compared with conventional ultrasonography and computed
tomography in preoperative rectal cancer staging. Am J
Surg 2006; 192:89
–97[CrossRef][Medline]
- Sinha R, Verma R, Rajesh A, Richards CJ. Diagnostic value of
multidetector row CT in rectal cancer staging: comparison of multiplanar and
axial images with histopathology. Clin Radiol2006; 61:924
–931[CrossRef][Medline]
- Mainenti PP, Cirillo LC, Camera L, et al. Accuracy of single phase
contrast enhanced multidetector CT colonography in the preoperative staging of
colorectal cancer. Eur J Radiol 2006;60
: 453–459[CrossRef][Medline]
- Beets-Tan RG, Beets GL, Borstlap AC, et al. Preoperative assessment
of local tumor extent in advanced rectal cancer: CT or high-resolution MRI?
Abdom Imaging 2000;25
: 533–541[CrossRef][Medline]
- Fuchsjager MH, Maier AG, Schima W, et al. Comparison of transrectal
sonography and double-contrast MR imaging when staging rectal cancer.
AJR 2003; 181:421
–427[Abstract/Free Full Text]
- Gagliardi G, Bayar S, Smith R, Salem RR. Preoperative staging of
rectal cancer using magnetic resonance imaging with external phase-arrayed
coils. Arch Surg 2002;137
: 447–451[Abstract/Free Full Text]
- Brown G, Kirkham A, Williams GT, et al. High-resolution MRI of the
anatomy important in total mesorectal excision of the rectum.
AJR 2004; 182:431
–439[Abstract/Free Full Text]
- Chun HK, Choi D, Kim MJ, et al. Preoperative staging of rectal
cancer: comparison of 3-T high-field MRI and endorectal sonography.
AJR 2006; 187:1557
–1562[Abstract/Free Full Text]
- Winter L, Bruhn H, Langrehr J, et al. Magnetic resonance imaging in
suspected rectal cancer: determining tumor localization, stage, and
sphincter-saving resectability at 3-tesla-sustained high resolution.
Acta Radiol 2007;48
: 379–387[CrossRef][Medline]
- Paley MR, Ros PR. MRI of the rectum: non-neoplastic disease.
Eur Radiol 1998;8
: 3–8[CrossRef][Medline]
- Iafrate F, Laghi A, Paolantonio P, et al. Preoperative staging of
rectal cancer with MR imaging: correlation with surgical and histopathologic
findings. RadioGraphics 2006;26
: 701–714[Abstract/Free Full Text]
- Kim MJ, Park JS, Park SI, et al. Accuracy in differentiation of
mucinous and nonmucinous rectal carcinoma on MR imaging. J Comput
Assist Tomogr 2003; 27:48
–55[CrossRef][Medline]
- Kim MJ, Huh YM, Park YN, et al. Colorectal mucinous carcinoma:
findings on MRI. J Comput Assist Tomogr1999; 23:291
–296[CrossRef][Medline]
- Hussain SM, Outwater EK, Siegelman ES. Mucinous versus nonmucinous
rectal carcinoma: differentiation with MR imaging.
Radiology 1999;213
: 79–85[Abstract/Free Full Text]
- Dicle O, Obuz F, Cakmakci H. Differentiation of recurrent rectal
cancer and scarring with dynamic MR imaging. Br J
Radiol 1999; 72:1155
–1159[Abstract]
- Markus J, Morrissey B, deGara C, Tarulli G. MRI of recurrent
rectosigmoid carcinoma. Abdom Imaging1997; 22:338
–342[CrossRef][Medline]
- Morris J, Spencer JA, Ambrose NS. MR imaging classification of
perianal fistulas and its implications for patient management.
RadioGraphics 2000;20
: 623–635[Abstract/Free Full Text]
- Halligan S, Buchanan G. MR imaging of fistulain-ano. Eur
J Radiol 2003; 47:98
–107[CrossRef][Medline]
- Brown G, Daniels IR, Richardson C, et al. Techniques and
trouble-shooting in high spatial resolution thin slice MRI for rectal cancer.
Br J Radiol 2005;78
: 245–251[Abstract/Free Full Text]
- Wallengren NO, Holtas S, Andren-Sandberg A, et al. Rectal
carcinoma: double-contrast MR imaging for preoperative staging.
Radiology 2000;215
: 108–114[Abstract/Free Full Text]
- Brown G, Richards CJ, Newcombe RG, et al. Rectal carcinoma:
thin-section MR imaging for staging in 28 patients.
Radiology 1999;211
: 215–222[Abstract/Free Full Text]
- Lauenstein T, Holtmann G, Schoenfelder D, Bosk S, Ruehm SG, Debatin
JF. MR colonography without colonic cleansing: a new strategy to improve
patient acceptance. AJR 2001;177
: 823–827[Abstract/Free Full Text]
- Matsuoka H, Masaki T, Sugiyama M, et al. Gadolinium enhanced
endorectal coil and air enema magnetic resonance imaging as a useful tool in
the preoperative examination of patients with rectal carcinoma.
Hepatogastroenterology 2004;51
: 131–135[Medline]
- Kim MJ, Lim JS, Oh YT, et al. Preoperative MRI of rectal cancer
with and without rectal water filling: an intraindividual comparison.
AJR 2004; 182:1469
–1476[Abstract/Free Full Text]
- Debatin JF, Patak MA. MRI of the small and large bowel.
Eur Radiol 1999;9
: 1523–1534[CrossRef][Medline]
- Ferri M, Laghi A, Mingazzini P, et al. Preoperative assessment of
extramural invasion and sphincteral involvement in rectal cancer by magnetic
imaging with phased-assay coil. Colorectal Dis2005; 7:387
–393[CrossRef][Medline]
- Holzer B, Urban M, Hölbling N, et al. Magnetic resonance
imaging predicts sphincter invasion of low rectal cancer and influences
selection of operation. Surgery 2003;133
: 656–661[CrossRef][Medline]
- Ota DM, Jacobs L, Kuvshinoff B. Rectal cancer: the
sphincter-sparing approach. Surg Clin North Am2002; 82:983
–993[CrossRef][Medline]
- Regina GH, Geerard LB. Rectal cancer: review with emphasis on MR
imaging. Radiology 2004;232
: 335–346[Abstract/Free Full Text]
- Kim NK, Kim MJ, Yun SH, et al. Comparative study of transrectal
ultrasonography, pelvic computerized tomography, and magnetic resonance
imaging in preoperative staging of rectal cancer. Dis Colon
Rectum 1999; 42:770
–775[CrossRef][Medline]
- Urban M, Rosen HR, Hölbling N, et al. MR imaging for the
preoperative planning of sphincter-saving surgery for tumors of the lower
third of the rectum: use of intravenous and endorectal contrast materials.
Radiology 2000;214
: 503–508[Abstract/Free Full Text]
- Zhou C, Li J, Zhao X. Preoperative staging of colorectal cancer
with spiral CT. Chin J Oncol 2002;24
: 272–277
- Hadfield MB, Nicholson AA, MacDonald AW, et al. Preoperative
staging of rectal carcinoma by magnetic resonance imaging with a pelvic
phased-array coil. Br J Surg 1997;84
: 529–531[CrossRef][Medline]
- Brown G, Richards CJ, Bourne MW, et al. Morphologic predictors of
lymph node status in rectal cancer with use of high-spatial-resolution MR
imaging with histopathologic comparison. Radiology2003; 227:371
–377[Abstract/Free Full Text]
- Kim JH, Beets GL, Kim MJ, et al. High-resolution MR imaging for
nodal staging in rectal cancer: are there any criteria in addition to the
size? Eur J Radiol 2004;52
: 78–83[CrossRef][Medline]
- Harisinghani MG, Saksena MA, Hahn PF, et al.
Ferumoxtran-10-enhanced MR lymphangiography: does contrast-enhanced imaging
alone suffice for accurate lymph node characterization?
AJR 2006; 186:144
–148[Abstract/Free Full Text]
- Koh DM, Brown G, Temple L, et al. Rectal cancer: mesorectal lymph
nodes at MR imaging with USPIO versus histopathologic findings—initial
observations. Radiology 2004;231
: 91–99[Abstract/Free Full Text]
- Gualdi GF, Casciani E, Guadalaxara A, et al. Local staging of
rectal cancer with transrectal ultrasound and endorectal magnetic resonance
imaging: comparison with histologic findings. Dis Colon
Rectum 2000; 43:338
–345[CrossRef][Medline]
- Torricelli P, Lo Russo S, Pecchi A, et al. Endorectal coil MRI in
local staging of rectal cancer. Radiol Med (Torino)2002; 103:74
–83[Medline]
- Hunerbein M, Pegios W, Rau B, et al. Prospective comparison of
endorectal ultrasound, three-dimensional endorectal ultrasound, and endorectal
MRI in the preoperative evaluation of rectal tumors: preliminary results.
Surg Endosc 2000;14
:1005
–1009[CrossRef][Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Abstract
Introduction
