Study population
A total of 118 patients who underwent rectal MRI and preoperative CTC with manual room air insufflation immediately after OC or automated insufflation using CO2 immediately after OC between January 2012 and August 2014 were retrospectively analyzed.
An experienced radiologist assessed tumor invasion depth using 2D and multi-planar reconstructed images on both rectal MRI and CTC.
The consistency of the findings with the results of histopathological examination was evaluated.
McNemar’s test was used to compare the detectability of tumor invasion depth.
Values of p<0.05 were considered significant.
Bowel preparation
Bowel preparation was performed using 2 L of polyethylene glycol lavage solution (Niflec; Ajinomoto Pharma,
Tokyo,
Japan) the day before and 10 mL of sodium picosulfate (Laxoberon; Teijin Pharma,
Tokyo,
Japan) in the morning prior to OC.
All patients maintained a low-fiber diet for 24 h before OC and were not allowed to eat anything after midnight other than a small amount of water.
Optical colonoscopy (OC)
OC was performed the same day by an experienced endoscopist using standard procedure.
Administration of 20 mg of scopolamine butyl bromide (Buscopan; Boehringer Ingelheim,
Berkshire,
England) was infused before OC for all patients if the patient had no history of side effects or prostatomegaly.
CTC was subsequently performed on the same day immediately after colonoscopy if there were no complications.
Rectal MRI
Rectal MRI examination was obtained using a 1.5-Tesla MAGNETON Avanto (Siemens Medical Solutions,
Forchheim,
Germany),
a 3.0-Tesla MAGNETON Skyra (Siemens Medical Solutions),
or a 1.5-Tesla Achiva (Philips Healthcare,
Best,
The Netherlands) with Gd- Contrast enhanced T1WI and T2WI (Table 1).
Sequence |
TR(msec) |
TE(msec) |
Flip angle |
VOxel size(mm) |
Slice |
No.
of Slices |
T2WI(TSE) |
3000 |
90 |
90 |
0.29x0.9x3.0 |
3 |
23 |
Gd FS T1WI(MPRAGE) |
8.4 |
4.1 |
16 |
0.75x0.75x0.8 |
0.8 |
234 |
Table 1.
The parameters of Gd-contrast-enhanced T1WI and T2WI
In our institute,
200 mL of rectal jelly was infused into the rectal cavity via the anus using a 24-Fr Foley catheter with a retention cuff inflated with 10 mL of water when rectal MRI was performed.
This unique jelly contains 100 mL of warmed saline and 100 mL of ultrasound jelly.
All patients were placed in the left-lateral decubitus position outside of the MRI room,
and a urinary catheter was gently inserted into the anus.
The operator infused the jelly using a 50-mL syringe.
The patent was shifted to the sitting position and then moved to the MRI room.
Insufflation technique: manual room air technique
Manual room air insufflation was performed by four radiologists and was achieved using a standard barium enema bag (Horii Pharm,
Tokyo,
Japan) filled with approximately 2 L of room air.
The barium enema bag was attached to a thin rectal soft tube via a connecting tube that could be sealed with a plastic clip.
All patients were placed in the left-lateral decubitus position,
and an enema tube was gently inserted into the anus.
The operator compressed the barium enema bag gently over approximately 3 min.
The patient was gradually shifted to a supine position after the bag was approximately empty.
A standard scout image was obtained to assess colonic distention.
Additional room air was insufflated using the enema bag if inadequate colorectal distention was suggested on the scout view.
Insufflation technique: automated insufflation technique
Automated carbon dioxide insufflation was also performed by the same four radiologists.
Before CTC was performed,
a thin rectal tube with a retention cuff was inserted into the rectum by the radiologists and inflated with 30 mL of room air.
Placement and insufflation were started with all patients in the left-lateral decubitus position.
Colonic insufflation was achieved with carbon dioxide using an automated device (PROTOCO2L; E-Z-EM,
Monroe Township,
NJ)(Fig.1).
Fig. 1: Automated CO2 insufflation device (PROTOCO2L; E-Z-EM, Monroe Township, NJ)
The patient was gradually moved into the supine position after rectal pressure reached 18-20 mmHg,
and the upper limit of pressure was set to 25 mmHg.
A standard scout view was also obtained with the patient in the supine position,
and more gas was introduced using the automated device by elevating the pressure if findings on scout images suggested areas of collapse.
CTC
Following insufflation for each procedure,
contrast-enhanced CTC was performed in both supine and prone positions using 1.8 mg/kg when the body weight was < 47 kg,
or 2.1 mg/kg when body weight was ≥ 47 kg,
of non-ionic iodine contrast material (Iomeron; Eisai,
Tokyo,
Japan) administered over a period of 25 s.
CTC examination was obtained using a 128-detector row multi-detector row CT scanner (Somatom Definition Flash or Somatom Definition AS; Siemens Medical Solutions) with these parameters: beam collimation,
0.8 mm; reconstruction interval,
1 mm; automated exposure control,
120-220 mAs; and 120 kV.
The balloon of the rectal tube was deflated for prone position imaging to obtain adequate visualization if the tumor was located in the rectum defined by prior OC findings.
No tagging material was used in this procedure.
Image analysis
Axial T2-weighted MRI images and oblique axial T2-weighted images (Fig.2,
3),
and multi-planar reconstruction CT images (Fig.4) were assessed by an experienced radiologist using a viewer program.
Rectal lumens showing severe narrowing or obstruction caused by the tumor itself were excluded.
The T staging of the rectal tumor was defined by the National Cancer Institute as follows: T1,
tumor invades submucosa; T2,
tumor invades muscularis propria; T3,
tumor invades extended muscularis propria or into nonperitonealized perirectal tissues; T4,
tumor directly invades other structures or organs and/or adipose tissues.
Fig. 2: A 59-year-old male with MP tumor invasion depth on an oblique axial T2-weighted image. The tumor is located on the left lateral side of Rb, and the muscularis propria is partially unclear, defined as MP invasion tumor (T2).
Fig. 3: A 68-year-old female with extra duct invasion depth on an axial T2-weighted image. The rough appearance of the tumor is located at Rb and projected into the perirectal adipose tissue (white arrow) (T4).
Fig. 4: A 47-year-old male on an axial contrast-enhanced CTC image (supine). The rough appearance of the tumor is expanded into the adipose tissue (T4 suspected).
Statistical analysis
Statistical analyses were performed using SPSS version 21.0 software (IBM,
Armonk,
NY).
McNemar’s test was used to compare the detectability of tumor invasion depth and the tendency for understaging or overstaging between CTC and OC and between rectal MRI and OC.
Values of p<0.05 were considered significant.