Harpreet K. Pannu,
M.D.1, Robert Bristow, M.D.2, Frederick Montz, M.D.2, Elliot K. Fishman, M.D.1,
The Russell H. Morgan Department of Radiology and Radiological Science1 and
The Kelly Gynecologic Oncology Service2
Johns Hopkins Medical Institutions, Baltimore, Maryland
This exhibit presents
the appearance of metastatic ovarian cancer imaged using a new technique with
multi detector row computed tomography (MDCT). The purpose is to demonstrate
the utility of thin sections and multiplanar reconstruction for demonstrating
peritoneal metastases.
Technique: thin sections, close interscan spacing, arterial and venous phase
acquisitions, multiplanar reconstruction and 3D rendering of the abdomen and
pelvis.
Emphasis: on peritoneal metastases which are the most common as well as the
most difficult to detect due to their small size. Tumor nodules and plaques
will be demonstrated at commonly recognized sites such as the diaphragm, liver,
paracolic gutters, omentum, bowel and spleen.
Attention will be drawn to sites where metastatic disease may be overlooked
on CT: abdominal sites such as the stomach, lesser sac, porta hepatis, gallbladder
fossa and pelvic sites such as the uterosacral ligaments, peritoneal reflection
over the pelvic organs, cul-de-sac and vaginal cuff.
BACKGROUND:
Clinical:
90% of ovarian cancers arise from the surface epithelium of the ovary. Tumor
cells slough off the ovary and seed the peritoneal fluid. Normal circulation
pathways of the peritoneal fluid carry the tumor cells from the pelvis to the
right upper abdomen and the commonest sites of implant deposition are the right
subphrenic area, right paracolic gutter, greater omentum, and cul-de-sac.
Therapy for ovarian cancer consists of optimal surgical debulking of the tumor.
The abdomen and pelvis are explored and tumor deposits are removed. Sites that
are difficult to evaluate at surgery are the diaphragm, gastrocolic ligament,
lesser sac, gall bladder fossa, and porta hepatis. CT can be used to detect
the extent of metastatic disease prior to staging laparotomy and in follow-up
to detect recurrences.
Computed Tomography:
Single detector row CT has low sensitivity and specificity for peritoneal metastases
which are often only a few millimeters in size and can be located from the diaphragm
to the pelvis. The sensitivity is reported as 50% for 5 mm lesions and 28% for
< 5 mm lesions.
Potential factors responsible for low sensitivities: 1) thin sections through
the large volume of tissue from the diaphragm to the pubic symphysis are not
possible due to pitch restrictions and tube heating. Typically, section thickness
of 5-8 mm is obtained which can be larger than the size of the metastatic deposit.
2) partial volume averaging of structures oblique or parallel to the axial plane
such as the diaphragm and cul-de-sac can limit visualization of disease at these
sites.
Possible solutions
using multi detector row CT:
- acquisition of thin sections to detect subcentimeter deposits
- three dimensional (3D) and multiplanar reconstructions to detect presence
and extent of disease at sites such as the diaphragm, paracolic gutters and
pelvis. 3D display of the volume of the tumor may aid in resection by demonstrating
disease as seen at surgery.
- optimize attenuation differences between tumor and viscera to detect lesions.
This difference may vary with the phase of imaging post intravenous contrast
This exhibit illustrates
the appearance of the spectrum of peritoneal metastatic disease from ovarian
cancer in the abdomen and pelvis using the above mentioned technique of dual
phase imaging, thin sections, and multiplanar and 3D reconstruction with multi
detector row CT.
TECHNIQUE:
Scanner:
Somatom Volume Zoom scanner (Siemens Medical Systems, Iselin, NJ, U.S.A.)
Oral contrast: 750-1000 cc of water over a 15-30 minute period prior
to the study
Intravenous contrast: 120 cc of nonionic contrast injected intravenously
(IV) at 3 cc/second
Scan delay: 30 seconds and 60 seconds
Scan volume: Diaphragm through pubic symphysis
Detector collimation: 2.5 mm
Section thickness: 3 mm
Slices reconstruction interval: 2 mm
Image display: Axial, multiplanar reconstruction, and 3D volume rendering.
Peritoneal metastases from ovarian cancer can vary in size from a few millimeters to several centimeters and lesions can occur from the diaphragm to the pelvis. Optimizing the CT technique for evaluating patients with multi detector row CT and 3D rendering may improve the sensitivity of CT for the detection of metastatic deposits.