Ultrasound examination (ultrasound)
Ultrasound (Ultrasound, US) is the primary imaging modality for the pelvis. It is indispensable for evaluating the causes of postmenopausal bleeding, screening, and guidance during biopsies or intracavitary applicator placement.
- Transabdominal US: Requires a strictly full urinary bladder. Fluid displaces gas-filled bowel loops and creates an acoustic window. 3.5–5.0 MHz transducers are used.
- Transvaginal US (TVUS): Performed with an empty urinary bladder. High-frequency transducers (5.0–7.5 MHz) provide a detailed anatomical picture. For example, an endometrial thickness (M-echo) greater than 5 mm in menopause is an indication for biopsy.
Despite its availability, safety, and multiplanar capability, US is limited by operator dependence and patient body habitus. For malignant staging, US is inferior to CT and MRI.
Computed tomography (CT)
Computed Tomography (Computed Tomography, CT) is the main tool for detecting distant metastases and staging ovarian cancer. The standard protocol involves scanning the abdomen and pelvis in the portal-venous phase (70 seconds after contrast administration).
Method features:
- Oral contrast: Essential for bowel opacification. This helps differentiate bowel loops from serosal deposits and affected lymph nodes.
- Role in oncology: CT accurately assesses peritoneal spread, the presence of omental caking, and enlarged lymph nodes. This directly influences the choice between cytoreductive surgery and chemotherapy.
- Limitations: Due to low soft-tissue resolution, CT often understages endometrial cancer and cannot accurately assess the depth of myometrial invasion.
Magnetic resonance imaging (MRI)
Magnetic Resonance Imaging (Magnetic Resonance Imaging, MRI) has superior tissue contrast and is the preferred method for local staging of endometrial and cervical cancer.
The standard gynecological protocol includes:
- T2-weighted images (T2WI): The basis for assessing anatomy. Slices are oriented strictly perpendicular to the uterine cavity or cervical canal.
- T1-weighted images with fat suppression: Allow differentiation of fatty tissue from hemorrhage in complex cystic adnexal masses.
- Diffusion-weighted images (DWI): Detect restricted diffusion within the tumor. They help clarify the depth of myometrial invasion, especially if contrast is contraindicated.
- Dynamic contrast enhancement (gadolinium): Healthy myometrium enhances rapidly, while endometrial cancer enhances more slowly. In late phases, the tumor appears hypointense, which helps clearly define its borders.
Positron Emission Tomography (PET/CT)
PET/CT uses the radiopharmaceutical FDG (a glucose analog) to locate areas of accelerated metabolism. The method combines functional data (glycolysis rate) with structural CT or MRI slices.
PET/CT is indispensable for detecting extrauterine spread, evaluating lymph nodes in advanced cervical cancer, and identifying recurrences. However, the method is not without pitfalls:
- False-negative results: Possible if the lesion is smaller than 0.5 cm or the tumor has low metabolic activity.
- False-positive results: Observed in inflammatory, infectious processes, or post-treatment changes.
Imaging specifics by nosology
Radiation diagnostics algorithms depend on the FIGO staging system:
- Endometrial cancer: Diagnosed by biopsy. MRI is critical for pre-treatment risk stratification. It shows the depth of invasion: involvement of less than 50% of the myometrial thickness corresponds to stage Ia.
- Cervical cancer: MRI assesses tumor size, parametrial invasion, and pelvic sidewall involvement. This determines whether fertility-sparing surgery is feasible or chemoradiotherapy is required.
- Ovarian cancer: Primary screening is performed via US, while detailed staging and therapy monitoring (including elevated CA-125 levels) are performed using CT.
Briefly: answers to topical questions
What anatomical structures are evaluated on MRI for local staging of cervical cancer?
For local staging of cervical cancer, MRI evaluates the tumor and pelvic structures.
- Cervix — determines tumor size and location, distance to the internal os, and cervical length.
- Parametrium — detects the presence of parametrial invasion.
- Vagina — assesses the extent of involvement, including the upper 2/3 or lower third.
- Adjacent structures — assess invasion into the pelvic sidewalls, bladder mucosa, and rectal mucosa.
- Lymph nodes — detect enlargement.
What ultrasound signs indicate malignancy of an ovarian cystic mass?
Malignancy of an ovarian cystic mass on ultrasound is indicated by a series of structural changes and vascularity features.
- Septations — presence of thick septations within the cyst.
- Papillary projections — detection of multiple exophytic structures.
- Solid component — presence of a vascularized soft-tissue component within the mass.
- Internal vascularity — detection of blood flow within the solid component on color Doppler mapping.
- Ascites — presence of free fluid in the abdominal cavity.
Which groups of lymph nodes are regional for the ovaries and are metastasized to first?
The regional lymph nodes for the ovaries that develop metastases are the pelvic and retroperitoneal groups.
These include the following lymph nodes:
- Internal iliac
- External iliac
- Common iliac
- Obturator
- Sacral
- Lumbar (retroperitoneal)
Involvement of inguinal lymph nodes is not considered regional metastasis and is classified as distant metastases corresponding to stage IV disease.
For quick memorization of staging priorities, use the "MM-OC" rule: Muterus — MRI (maximum detail of layers and soft tissues is needed), Ovaries — CT (rapid search for metastases across a vast peritoneal and omental area is necessary).
Class and exam questions
Why is a full bladder required for a gynecological ultrasound?
During transabdominal scanning, a full bladder displaces gas-filled bowel loops upward. This creates an "acoustic window," allowing ultrasound waves to reach the uterus and adnexa unimpeded.
Which method is more accurate for determining cancer invasion into the uterine wall: CT or MRI?
MRI. Due to poor soft-tissue contrast on CT, the border between the tumor and normal myometrium often blends, leading to understaging of the disease.
In what cases is PET/CT indicated?
PET/CT is indicated when distant metastases are suspected, for precise radiation therapy field planning, and for differential diagnosis between tumor recurrence and post-radiation fibrosis.
What else to study on this topic
- MRI semiotics features of endometrial cancer on T2WI and DWI
- FIGO classification for uterine and cervical cancer
- Differential diagnosis of ovarian masses on CT
- The role of dynamic contrast-enhanced gadolinium in gynecologic oncology
- False-positive PET/CT results: inflammation versus tumor
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