3D IMAGE-GUIDED ADAPTIVE BRACHYTHERAPY FOR GYNECOLOGY
Imaging of CT/MRI Anatomy and tumor extension
Radiology department, Tokyo Kita Social Insurance Hospital Ayako Tamura, MD Contents
1. Normal anatomy of the female pelvis 2. Imaging of cervical cancers 3. Cervical cancer staging 4. Additional findings - Uterine body invasion - Ovarian metastasis - Lymph node ( LN ) metastasis 3
1. Anatomy of the female pelvis Zonal anatomy 4
T2WI sag T2WI ax
Uterine body Uterine cervix Vagina - endometrium - epithelium - Junctional zone (JZ) (endocervical mucosa) - Vaginal fornix - myometrium - cervical stroma - myometrium - vaginal part - supravaginal part Vagina 5 H-shaped
T2WI sag T2WI ax
- mucosal epithelium and mucous secretion - muscle layer - adventitia surrounding vaginal wall Plicae palmatae
T2WI ax
There is a longitudinal line of hypointensity in the cervical canal. This is a relatively large median longitudinal ridge on the endocervical wall, and can be mistaken for a cervical septum. Abdom Imaging. 34:277-9. 2009 7 Zonal anatomy is unclear on T1WI because of less contrast.
T2WI sag T1WI sag CT : Uterine body
Zonal anatomy of the uterus is difficult to be identified.
Endometrium central low density commonly ovoid or triangular in shape
pre contrast post contrast CT : Uterine cervix
endocervical mucosa and cervical stroma low density
pre contrast post contrast
The cervix typically less enhances compared with the uterine myometrium. CT : Uterine cervix
Most outer part of the cervix (myometrium) is well enhanced. Multiple vessels in the cardinal ligament (paracervical plexus) are visualized.
cervical myomatrium
vessels in the cardinal ligament
post contrast CT Adnexa 11
T2WI ax post contrast CT
・Ovaries - follicles - ovarian stroma
・Normal fallopian tubes are not identified. Supporting structures of the Uterus
• broad ligament：two layers of the peritoneum
• round ligament：running through the broad ligament into the inguinal canal, keep the uterus anteflexed Broad ligament - fallopian tube - vessels : uterine arteries and veins Round ligament
tube
Round ligament
Atlas of Human Anatomy 4th Ed. T2WI 13 Supporting ligaments around the uterine cervix
Cardinal ligament cardinal ligament ( lateral part ) uterosacral ligament ( posterior part ) uterovesical ligament ( anterior part )
Uterosacral ligament These form the parametrium, containing vessels and lymphatics. T2WI 14
2. Imaging of cervical cancers Cervical cancer MRI : T2WI
Moderately higher signal intensity (SI) than cervical stroma on T2WI
T2WI sag T2WI ax Cervical cancer MRI : DWI
Diffusion is usually restricted ( ADC is lower in cervical cancer compared with normal cervical tissue ). b1000 ADC
Eur Radiol 15 : 71-78, 2005 DWI : intermediate SI
T2WI ax DWI b1000 Cervical cancer : dynamic contrast enhanced MRI Early enhancement and washout
pre 30s 80s 180s
On dynamic study, cervical cancers tend to show malignant enhancement pattern, early enhancement and washout. Cervical caner enhances less intensely than the myometrium does. Cervical cancer : CT ( same patient as MRI shown in previous slides )
The cervical cancer is post contrast sag isodensity to cervical stroma pre contrast
On the contrast study, the cervical cancer shows slightly lower density relative to cervical stroma. But it is not clearly post contrast demonstrated. Cervical cancer MRI vs. CT
T2WI ax DWI b1000 contrast CT
CT has limited value in cervical cancer evaluation, especially when it is small, because of the inferior soft tissue contrast compared with MRI. Uterine cervix : CT
Normal uterine cervix sometimes looks large as cervical cancer.
pre contrast
25y normal cervix 49y with cervical cancer 22
3. Cervical cancer staging Cervical cancer staging : CT vs. MRI
MRI is better than CT in cervical cancer staging.
・MRI is the method of choice for tumor staging and treatment planning. It has a superior accuracy in determining the size and location of the tumor, depth of stromal and parametrial invasion.
・CT is mainly used in the detection of lymphadenopathy and distant metastasis, and for guiding percutaneous biopsies and planning radiation treatment.
Radiology 175 : 45-51, 1990 Cancer 116 : 5093-5101, 2010 Gynecol Oncol 91 : 59-66, 2003 J Reprod Med. 56 : 485-90, 2011 Cervical cancer : MRI
・T2WI is the most useful sequence in tumor depiction and staging, because it provides optimal contrast resolution between the tumor and the cervical stroma.
・Optional oblique plane images perpendicular to the axis of the endocervical canal may improve staging accuracy.
・The use of dynamic contrast-enhanced MRI in assessing tumor staging is controversial.
Eur Radiol 21 : 1850-1857, 2011 Cervical cancer staging ( FIGO 2008 ) Stage Ⅰ 26
The carcinoma is strictly confined to the cervix ( extension to the corpus would be disregardedⅠA：Invasive ) carcinoma which can be diagnosed only by microscopy not visible on images ⅠB：Clinically visible lesions limited to the cervix uteri or pre-clinical cancers greater than stage ⅠA ⅠB1 : ≦ 4.0 cm in greatest dimension ⅠB2 : ＞ 4.0 cm in greatest dimension
ⅠB : Moderately high SI cervical cancers are surrounded by low SI cervical stroma.
T2WI Squamous cell cancerⅠB1 47y
T2WI sag
T2WI ax
The cervical cancer is limited to the cervix and surrounded by low SI cervical stroma. Adenosquamous cancer ⅠB2 43y
T2WI sag T2WI ax
Sagittal T2WI shows a large cervical cancer that protrudes into the upper vagina. Although the tumor is adjacent to the vaginal wall, low SI vaginal wall is intact and the cancer is limited to the cervix. Stage Ⅱ 29
Cervical carcinoma invadesS beyond the uterus, but not to the pelvic wall or to the lower third of the vaginat ⅡA : Without parametriala invasion ⅡA1 : ≦ 4.0 cm ing greatest dimension ⅡA2 : ＞ 4.0 cm ine greatest dimension ⅡB : With obvious parametrial invasion Ⅱ ⅡA Disruption of low SI vaginal頸 wall by high SI tumor. 部 ⅡB を Nodular or irregular tumor extension into こ the parametrium. え た 進 展
T2WI Squamous cell cancer ⅡA2 23y
T2WI sag
T2WI ax
Inferior tumor extension into upper two thirds of the vagina. The low SI vaginal wall is disrupted by the cervical cancer. ⅠB or ⅡA T2WI sag ⅠB2 ⅡA2
Preservation of the normal low SI of the vaginal wall suggests stage ⅠB. When tumor invades to the vagina, the low SI vaginal wall is replaced by high SI tumor. ⅡB
Obvious parametrial invasion Squamous cell cancer ⅡB 41y
Disruption of the low SI stromal ring with nodular or irregular tumor SI extension into the parametrium.
T2WI ax ⅡB : T2WI vs. DWI
Tumor extension into the parametrium is better visualized on T2WI than on DWI.
T2WI ax DWI b1000 ⅡB : T2WI vs. CE-MRI
On contrast MRI, the tumor seems to be surrounded by cervical or vaginal wall.
T2WI ax Dynamic 80s
Tumor extension is better demonstrated on T2WI than on CE-MRI. ⅡB : T2WI vs. CECT CECT Axial contrast-enhanced CT shows the cervical cancer as a heterogeneous low attenuation mass. There seems to be soft tissue density in the parametrial fat, but indistinct.
T2WI ax ⅠB/ⅡA or ⅡB T2WI SqCC ⅡA2 SqCC ⅡB SqCC ⅠB2
・In the case of full thickness stromal invasion, the low SI cervical stroma or vaginal wall is completely replaced by high SI tumor. Smooth tumor- parametrial interface excludes parametrial invasion.
・Disruption of the stromal ring with nodular or irregular tumor extension into the parametrium. This irregular tumor-parametrial interface indicates parametrial invasion. Stage Ⅲ Stage Ⅲ
The tumor extends to the pelvic wall and / or involves lower third of the vagina and / or hydronephrosis or non-functioning kidney ⅢA : Tumor involves lower third of the vagina, with no extension to the pelvic wall ⅢB : Extension to the pelvic wall and / or hydronephrosis or non-functioning kidney
ⅢA lower third of the anterior (lt.) / posterior (rt.) vaginal wall invasion
T2WI
Courtesy of Dr. K. Ando, Department of Radiation Oncology, Gunma Univ. IIIB
T2WI ax
Tumor extension to the left pelvic wall. This is classified as stage ⅢB as well. Courtesy of Dr. K. Ando, Department of Radiation Oncology, Gunma Univ. Where is the border of the pelvic wall ?
Atlas of Human Anatomy 4th Ed.
Muscles ( ex. obturator internus, levator ani, pyriformis muscles )are in the pelvic wall. Vessels and ureter are just medial to these pelvic wall muscles with surrounding connective tissues. The boundary of the pelvic wall is not the muscles themselves but thought to be around these internal iliac vessels. No tumor invasion to the pelvic wall. T2WI ax
No fat infiltration around the iliac vessels
post contrast CT Squamous cell cancer ⅢB 43
Left pelvic wall invasion
T2WI ax CEax
Irregular low SI on T2WI and strong enhancement extends around the left internal iliac vessels. Hydronephrosis ⅢB
Hydronephrosis is an indication of ureteral invasion. Evaluation of the urinary tract is better on CT than on MRI.
post contrast CT
Courtesy of Dr. K. Ando, Department of Radiation Oncology, Gunma Univ. 45 Stage Ⅳ
The carcinoma has extended beyond the true pelvis or has involved ( biopsy proven ) the mucosa of the bladder or rectum. A bullous edema, as such, does not permit a case to be allotted to stage Ⅳ. ⅣA : Spread of the growth to adjacent organs ⅣB : Spread to distant organs Urinary bladder invasion ⅣA
T2WI sag
cystoscopy
T2WI ax
T2WI shows a large cervical cancer invading the posterior urinary bladder wall. Mucosal invasion was proved by cystoscopy.
Courtesy of Dr. K. Ando, Department of Radiation Oncology, Gunma Univ. Rectal invasion ⅣA T2WI ax
A large cervical cancer invading the anterior rectal wall. Mucosal invasion was proved by rectoscopy. T2WI sag Courtesy of Dr. K. Ando, Department of Radiation Oncology, Gunma Univ. IVB distant metastasis
Liver metastasis para-aortic LN metastasis
post contrast CT 49
4. Additional findings
- uterine body invasion - ovarian metastasis - lymph node (LN) metastasis
Although these are not the criteria in staging, but closely related to prognosis and affect treatment planning. Uterine body invasion
Squamous cell cancer ⅡA2 with uterine body invasion, 56y
T2WI sag Dynamic 80s
MRI shows a large cervical cancer that extends and invades to lower uterine body ( also extends into the upper vagina ). Metastasis to the left adnexa Endocervical mucinous adenocarcinoma ⅡA 46y dynamic 30s
CEAX DWI b2000
Heterogeneous strong enhancement is noted in the left ovary. DWI shows slightly high SI. Ovarian metastasis is proved histopathologically. Ovarian metastasis is rare (ⅠB 0.2%, ⅡB 2%). The frequency is higher in adenocarcinoma than in squamous cell carcinoma. Gynecol Oncol 101 : 234-236, 2006 Lymph node (LN) metastasis Lymphatic drainage of the uterus
route 1) parametrial LN → pelvic LN → para-aortic LN route 2) along the ovarian suspensory ligament → para-aortic LN route 3) along the round ligament → inguinal LN (rare)
Main drainage route of the cervical cancer is route 1) Regional LNs of the cervical cancer post contrast CT
Parametrial nodes Obturator nodes
・parametrial nodes ・obturator nodes ・external iliac nodes ・internal iliac nodes ・common iliac nodes ・sacral nodes Para-aortic LN metastasis = distant metastasis = ⅣB
post contrast CT
* Mediastinal LN, supraclavicular LN metastases are also distant metastasis Assessing LN metastasis
The only accepted criterion is size, short axis dimension ≧ 10mm
・Microscopic LN metastasis will me missed. ・To differentiate enlarged reactive lymph nodes from malignant lymph nodes is difficult.
・The presence of central necrosis and compactly-grouped LNs are likely to be metastasis. ・LN metastasis frequency is closely related to advanced stage, tumor size and vascular invasion. Squamous cell cancer ⅡA2 Left obturator node metastasis T2WI sag
T2WI ax
Left obturator node is enlarged with slightly irregular margin. A bit enlarged left obturator LN, but no metastasis
T2WI sag
T2WI ax
CECT Left obturator LNs metastases Squamous cell cancer ⅡA2 ( body invasion )
post contrast CT
Each left obturator LN is only slightly enlarged, but they are grouped and densely compacted, suggesting metastasis. LN metastasis
・CT and MRI have been found to have similar sensitivity and specificity in assessing lymph node metastasis.
・PET-CT (positron emission tomography-computer tomography) is a good modality to evaluate distant metastasis.
・PET-CT also has higher sensitivity (90-91%) and specificity (95- 100%) in detection of lymph node metastasis. But regional LN metastasis is not included in staging criteria, and because of the limited spatial resolution of PET and limited soft tissue contrast of CT, the use of PET- CT for local staging of the cervical cancer is currently not routinely recommended.
Gynecol Oncol 91 : 59-66, 2003 Gynecol Oncol 97 : 183-191, 2005 Cancer Sci 101 : 1471-1479, 2010 Conclusion
・In cervical cancer detection and staging, MRI surpasses CT because of its superior soft tissue contrast.
・MRI can accurately determine tumor size, location, depth of stromal invasion and tumor extension.
・T2WI is the most important sequence for cervical cancer staging. ・The use of contrast enhancement in cervical cancer evaluation is controversial.
・The major limitation of CT is the inadequacy in differentiating between tumor, normal cervical tissue and parametrial tissue. ・CT is mainly used in the detection of lymphadenopathy, distant metastasis, and for guiding percutaneous biopsies and planning radiation treatment.