Prostate, Uterus and Adnexa MRI Flashcards
Prostate Anatomy
From an imaging standpoint, what are the two components to the prostate that can be resolved on MR?
Can you distinguish the central zone and transition zone on MR?
In younger men, the central gland is composed mostly of what?
How about in older males?
Describe all the zones of the prostate.
What percent of prostate cancers originate in each zone?
- From an imaging standpoint, there are two components to the prostate that can be resolved on MRI: The peripheral zone and the central gland. The central gland refers to both the central zone and the transition zone, as they cannot be distinguished on MRI.
- In younger men, the central gland is composed mostly of the central zone; however, the transition zone enlarges as benign prostatic hyperplasia develops. These changes result in thecentral gland becoming predominantly composed of the transition zone in older males.
- Transition zone surrounds the prostatic urethra. This zone enlarges in aging men resulting in benign prostatic hyperplasia - makes sense since you get all those BPH symptoms!
- Central zone lies in the base of the prostate behind the transition zone and surrounds the left and the right ejaculatory duct.
- Anterior fibromuscular stroma is a small area of tissue that is situated on the anterior side of the prostate.
- Peripheral zone is situated on the posterior and lateral side of the prostate.
- 70-75% of all prostate cancers originate in the peripheral zone (PZ).
- The posterior aspect of this zone can be examined with digital rectal exam.
- 25% of prostate cancers originate in the transition zone (TZ).
- Very few prostate cancers manifest in the central zone or in the anterior fibromuscular stroma.
What MR sequence can delineate the postatic zonal anatomy?
What is used to enhance the image?
- MRI is able to clearly delineate the prostatic zonal anatomy (central gland versus peripheral zone) with T2-weighted sequences.
- Imaging is enhanced with an endorectal coil.
Can we screen for prostate cancer with MR?
- MRI is inappropriate for screening due to cost and low sensitivity and specificity.
What is the typical MR appearance of prostate cancer?
Does prostate cancer show diffusion restriction?
What does dynamic contrast-enhanced MR typically show?
MR spect may show what in prostate cancer?
- The typical MRI appearance of prostate cancer is a T2 hypointense region within the T2 hyperintense peripheral zone.
- Prostate cancer typically shows restricted diffusion.
- Dynamic contrast-enhanced MRI typically shows prostate cancer to have early enhancement relative to the peripheral zone.
- MRI spectroscopy of prostate cancer may show elevated choline and depressed citrate peaks compared to normal prostate.
Can MR detect all prostate cancers? If so, why not?
- MRI may not detect all prostate cancer because:
- Some cancer is not hypointense on T2- weighted images
- Central zone cancers are difficult to detect on T2-weighted images
- Cancer conspicuity is decreased if the peripheral zone is not T2 hyperintense.
Is MR specific in diagnosing prostate cancer?
What is the DDx of a region of peripheral zone T2 hypointensity?
What techniques can be sued to increase specificity?
- MRI is not specific: In addition to prostate cancer, the differential diagnosis of a region of peripheral zone T2 hypointensity includes
- Prostatitis
- Hemorrhage
- Involutional changes from androgen-deprivation therapy.
- Advanced MRI techniques, such as MRI spectroscopy, dynamic contrast-enhanced imaging, and diffusion imaging may increase specificity.
What is the most important goal of prostate MR?
- The most important goal of MRI is to distinguish between surgical and nonsurgical disease.
- Cancer that is contained within the gland (tumor stage T2) is generally amenable to radical prostatectomy.
- Cancer that has spread outside of the gland (T3 and above) is typically treated non surgically (e.g., anti-androgen and radiation therapy).
- Per Dr. Parker: something like to double check if a bx of a prostate cancer is actually consistent with disease burden (since its more difficult to bx the anterior portion of the prostate)
MR TNM staging of prostate cancer
- T-staging:
- T1: Tumor apparent by biopsy only.
- T2: Tumor confined within the prostate.
- T2a: <50% of one lobe
- T2b: >50% of one lobe
- T2c : Tumor involves both lobes.
- T3: Tumor extends through the prostate capsule. May involve seminal vesicles.
- T3a: Extracapsular extension
- T3b: Invasion of seminal vesicles
- T4: Tumor invades adjacent structures other than seminal vesicles.
- N-staging: Any regional lymph node metastasis is N1; however, extra-pelvic nodes are M1a.
- M-staging:
- M0: No metastases.
- M1a: Nonregional lymph nodes
- M1b : Bone metastasis
- M1c : Other metastasis.
- M0: No metastases.
Example of T2a Prostate Cancer
- Staging example: T2a prostate cancer, which can be treated with radical prostatectomy.
Example of T3b N1 Prostate Cancer
- Staging example: T3b N1 prostate cancer, which is typically treated non surgically.
PI-RADS V2
What is it? Based on the findings of what MRI parameters?
What does PI-RADS determine?
- The PI-RADS assessment categories are based on the findings of multiparametric MRI, which is a combination of T2-weighted (T2W), diffusion weighted imaging (DWI) and dynamic contrast-enhanced (DCE) imaging.
- Although there is debate about the value of using DCE imaging, it is still included in the PIRADS version 2.0.
- The PI-RADS assessment category determines the likelihood of clinically significant prostate cancer, which is defined as a tumor with a Gleason score of 7 or more.
Gleason Score
- The Gleason score is used by pathologists to grade prostate cancers. If the cancer cells and their growth patterns look very abnormal, a grade of 5 is assigned.
- Since prostate cancers often have areas with different grades, a grade is assigned to the two areas that make up most of the cancer.
- These 2 grades are added to yield the Gleason score.
- The highest Gleason score therefore is 10.
- The first number assigned is the grade that is most common in the tumor.
- For example, if the Gleason score is written as 3+4=7, it means that most of the tumor is grade 3 and the second most common grade is 4.
- A new pathology grading system was recently proposed by the International Society of Urological Pathology (ISUP), dividing the relavant Gleason scores into 5 Grade Groups to simplify prostate cancer grading (table).
PI-RADS Assesment Categories
Based on what sequences?
Where is the peripheral zone of the prostate located?
What is the primary determining MR sequence to assign PI-RADS assessment in the peripheral zone?
Where is the transition zone of the prostate?
What is the primary determining MR sequence to assign PI-RADS assessment in the transition zone?
- Assignment of a PI-RADS assessment category for each lesion is based on the scoring of T2w, DWI/ADC, and DCE sequences, according to zonal anatomy.
- Peripheral zone (PZ): The peripheral zone is situated on the posterior and lateral side of the prostate, surrounding the transition zone. For the peripheral zone the DWI/ADC is the primary determining sequence (dominant technique) to assign the PI-RADS assessment category (figure). Since the dominant sequence for PI-RADS assessment in the peripheral zone is different from the transition zone, identification of the zonal location of a lesion is vital.
- Transition zone (TZ): The transition zone surrounds the prostatic urethra and enlarges in aging men as a result of benign prostatic hyperplasia. For the transition zone the T2w imaging is the primary determining sequence (dominant technique) to assign the PI-RADS assessment category.
PI-RADS in Peripheral Zone
Assessment category of a lesion is determined primarily on what sequence and correlated to what images?
- In the peripheral zone, the PI-RADS assessment category of a lesion is determined primarily on DWI/ADC and correlated to T2W-images.
- Examples of PI-RADS 1-5 are given in the table.
What is the role of DCE for PI-RADS in the peripheral zone?
- In the peripheral zone an equivocal lesion (PI-RADS category 3) is assigned to PI-RADS category 4 if DCE is positive, i.e focal or earlier contrast enhancement.
- The lesion remains assigned to PI-RADS category 3 if the DCE is negative, i.e. no early enhancement or diffuse enhancement and not corresponding to the focal T2W / DWI lesion or focal enhancement corresponding to BPH.
PI-RADS in the Transition Zone
Assessment category of a lesion is determined primarily on what sequence and correlated to what images?
- In the transition zone, the PI-RADS assessment category of a lesion is determined primarily on T2W-images and correlated to DWI/ADC.
- MNEMONIC: Transition zone - TTwo
- Examples of PI-RADS 1-5 are given in the table.
What is the role of DCE for PI-RADS in the transitional zone?
In the transitional zone an equivocal lesion (PI-RADS category 3) is assigned to PI-RADS category 4 if the DWI corresponds with category 5 (markedly intense greater than 1.5cm).
The lesion remains assigned to PI-RADS category 3 if the DWI corresponds to DWI category 4 (markedly intense but less than 1.5cm) or a lower category.
N-Staging of Prostate Cancer
What is the best sequence for the detection of lymph nodes?
What is T1 weighted images useful for in eval of lymph nodes?
What characteristics are considered suspicious?
What are the regional lymph nodes?
What are the distant lymph nodes?
- DWI is the best sequence for detection of lymph nodes.
- T1W series are useful for interpretation of the border contour and signal characteristics of lymph nodes.
- MR has a low accuracy for distinguishing positive or negative lymph nodes if characterization is based on size alone.
- The following characteristics are considered suspicious:
- round shape and short axis of ≥8mm
- oval shape and short axis of ≥10mm
- heterogeneous appearance
- irregular margins
- Regional lymph nodes (green) are below the level of the common iliac junction and are staged N1:
- pelvic
- hypogastric
- sacral
- iliac (internal, external)
- Distant lymph nodes (red) are outside these regions and are staged as metastatic disease M1a:
- aortic
- common iliac
- inguinal
- supraclavicular
Prostatitis
Can it occur in the absence of clinical hx or symptoms?
Prostatitis and what other benign features can mimic prostate cancer in the peripheral zone, and why?
How to differentiate benign features vs prostate cancer?
Does DCE help?
How does chronic inflammation appear on imaging?
- Prostatitis is a common finding in men and can occur in the absence of any clinical history or symptoms.
- Prostatitis and other benign features like fibrosis, scarring, atrophy and post-biopsy hemorrhage can mimic prostate cancer in the peripheral zone, since all present as a focus of low signal on ADC.
- However benign features mostly presents as a band-like or wedge-shaped or diffuse area of low signal intensity, while prostate cancer is more round or droplet-shaped.
- The hypointensity on ADC in prostatitis is usually not accompanied by hyperintensity on high b-value DWI series.
- Also, ADC values in prostate cancer tend to be lower than ADC levels in prostatitis.
- On DCE there is an increased enhancement, which is therefore not helpful in the differentiation.
- In case of chronic inflammation, concordant fibrosis and focal atrophy may be observed, which presents as focal retraction in the normal anatomic convexity of the peripheral zone.
DWI in Prostate MR
How do you confirm diffusion restriction?
The exact ADC value of a lesion is inversely correlated to the likelihood of what?
High or low b-values are necessary to create a high signal-to-noise ratio?
What b-value is recommended?
- This sequence has to contain both DWI and an ADC map.
- Diffusion restriction is present when a lesion with high DWI signal corresponds to low signal on the ADC map, which is highly correlated to malignant cells.
- The exact ADC value of the lesion is inversely correlated to the likelihood of a malignant lesion.
- High b-values are necessary to create a high signal-to-noise ratio.
- A b-value of at least 1400 is recommended.
- Notice the difference between the B1000 and B1400 images.
- MR/US fusion guided biopsies of the lesion anterior in the prostate demonstrated Gleason 3+4.
What is the significance of prostate volume?
How do you determine PSA density?
What is the significance of PSA density?
- Prostate volume determines the feasibility of external radiation therapy, which can be performed up to a volume of 55cc.
- PSA density-values of ≥ 0.20 contributes towards the suspicion of a clinically significant prostate malignancy.
Normal T2 Zonal Anatomy of Uterus
Endometrial stripe signal?
Junctional zone signal? What should it measure? Increased thickness indicates what?
Outer myometrium signal?
- T2-weighted MRI can distinguish the three layers of the uterus.
- Endometrial stripe: Hyperintense on T2.
- Junctional zone (first zone of myometrium): T2 hypointense. The hypointense T2 signal is due to the extremely compact smooth muscle. The junctional zone should measure <12 mm: Thickening of the junctional zone is seen in adenomyosis.
- Outer myometrium: Relatively T2 hypointense, although less so than junctional zone.
Adenomyosis on MR
What is it?
How can it present?
Best seen on what sequence? How to diagnose?
What can it mimic and how can you differentiate?
- Adenomyosis represents ectopic endometrial glands within the myometrium. In contrast to endometriosis, the ectopic endometrial tissue seen in adenomyosis is nonfunctioning.
- Adenomyosis can present with similar symptoms to leiomyomas, with pain and bleeding.
- Adenomyosis is best seen on T2-weighted images as a thickened junctional zone (>12 mm), often with multiple small foci of T2 hyperintensity. Borderline thickening of the junctional zone (8-12 mm) may be due to adenomyosis but is not diagnostic of the condition.
- Focal adenomyosis may mimic a leiomyoma, appearing as a localized low-signal mass on T1- and T2-weighted images. Typically, adenomyosis features indistinct margins, in contrast to the characteristically sharp margins of a leiomyoma. However, the imaging features between these two entities do sometimes overlap.
Leiomyoma
What is it?
Affects up to how many females of child-bearing age?
What locations relative to the uterus can fibroids be found?
Imaging appearance?
Can you differentiate a malignant leiomyosarcoma from a fibroid?
Why would we use MRI for fibroids? What can mimic a fibroid?
What kind of fibroids are not effectively treated with UAE?
- A leiomyoma, commonly known as a fibroid, is an extremely common benign tumor of smooth muscle, which affects up to 40% of reproductive-age women.
- Fibroids are often multiple and may be intramural (within the myometrial wall), submucosal (directly underneath the endometrial mucosa), or subserosal (directly underneath the outer uterine serosa).
- Small leiomyomas are hypointense on T2-weighted images due to compact smooth muscle. However, cystic or myxoid degeneration may increase T2 signal heterogeneously. Carneous or hemorrhagic degeneration may appear hyperintense on T1-weighted images.
- Malignant leiomyosarcoma is very rare and may arise de-novo or from malignant degeneration of a fibroid. Imaging cannot reliably differentiate between leiomyoma and leiomyosarcoma unless clearly malignant behavior is identified (such as invasion of adjacent structures or metastases). In the absence of obvious malignant imaging findings, an unusual-looking fibroid is overwhelmingly likely to represent a degenerating benign fibroid rather than a leiomyosarcoma.
- A uterine contraction may mimic a leiomyoma.
- MRI is often performed for treatment planning prior to uterine artery embolization (UAE). Hemorrhagic or necrotic leiomyomas are not treated effectively by UAE. Surgical myomectomy or hysterectomy would be the preferred treatment in these cases. Additionally, there is less chance of UAE success if an ovarian-uterine artery anastomosis is present.
Endometrial Carcinoma
Prevalence relative to other female gynecologic malignancies?
What is thought to cause endometrial CA? Specific risk factors?
Typical presentation?
Role of MR?
What is key for staging? What correlates with the presence of lymph node metastasis?
What demonstrates the highest conspicuity of the tumor?
- Endometrial carcinoma is the most common female gynecologic malignancy and is thought to be caused by prolonged estrogen exposure. Specific risk factors include nulliparity, hormone replacement, and Tamoxifen therapy.
- Endometrial carcinoma typically presents with post-menopausal bleeding.
- MRI can be used for staging once carcinoma is confirmed by histologic sampling.
- The presence and extent of myometrial invasion is key for staging. In a premenopausal patient, an intact junctional zone confirms that there is no myometrial invasion. The junctional zone cannot be distinguished in post-menopausal patients, however. The depth of myometrial invasion highly correlates with the presence of lymph node metastasis.
- Post-contrast images demonstrate the tumor with the highest conspicuity, as endometrial cancer enhances less avidly than the surrounding myometrium.
Cervical Adenocarcinoma
Prevalence relative to other gynecologic malignancies?
What has lead to the decrease in prevalence over the past 50 years?
MR’s role?
What is the key landmark in the staging of cervical cancer? Significance?
Other key findings?
- Cervical carcinoma is the third most common gynecologic malignancy, with a steep decline in prevalence over the past 50 years due to screening with Pap smears.
- A cervical mass >1.5 cm should be evaluated by MRI for staging.
- The cervical stroma is the key landmark in the staging of cervical cancer: If the tumor extends through the cervical stroma into the parametrium, the cancer is stage IIB and treatment is typically non-surgical.
- Other key findings to note are involvement of bladder or rectum, which denotes stage IV disease (if shown to extend to the mucosal surface with cystoscopy or endoscopy).
- FIGO has a staging system for cervical cancer
Septate Uterus
What is this caused by?
Is infertility more common in a septate or bicornuate uterus?
What can be done to fix in cases of a fibrous septum? How about if the septum is muscular?
- Septate uterus is caused by incomplete resorption of the septum of fused müllerian ducts.
- A septate uterus has a single external fundus but a fibrous or muscular septation dividing two endometrial canals. Infertility is more common in women with septate uterus compared to bicornuateuterus. Metroplasty (resection of the septum) can be performed hysteroscopically if the septum is fibrous, or via an open approach if the septum is muscular.
Bicornuate Uterus
What is this due to?
Contrast this to the septate uterus
If treated, how so?
- Bicornuate uterus is due to incomplete fusion of the müllerian ducts.
- A bicornuate uterus describes a partially split uterus with two separate uterine fundi. In contrast to a septate uterus, the fundus of a bicornuate uterus pinches inwards >15 mm.
- If treated, metroplasty must be performed transabdominally, which is a more invasive procedure compared to hysteroscopic metroplasty.
Endometriosis
What is it?
Typical MR appearance?
Tiny hemorrhagic endometrial implants may only be apparent as what on T1w images?
What might a ruptured endometrioma present as and what can it cause in the peritoneal cavity?
What is the gold standard for evaluation of suspected endometriosis?
- Endometriosis represents ectopic foci of endometrial tissue that are hormonally responsive and therefore may be composed of blood products of varying ages.
- The typical MRI appearance of endometriosis is multiple hyperintense masses on T1- weighted images, which demonstrate shading (a gradient of signal intensity) on T2- weighted images. Endometriosis does not suppress on fat-saturated sequences. Less commonly, endometriosis may appear hyperintense on both T1- and T2-weighted images.
- Tiny hemorrhagic endometrial implants may only be apparent as tiny hyperintense foci on T1-weighted images.
- A ruptured endometrioma may be a cause of acute pelvic pain and may produce free fluid that is hyperintense on both T1- and T2-weighted images.
- Laparoscopy is the gold standard for evaluation of suspected endometriosis.
Ovarian Cancer
Prevalence compared to other gynecologic malignancies? Mortality?
MR’s role?
Most common locations of peritoneal implantation?
What are findings that suggest a malignant lesion?
- Ovarian cancer is the second most common female pelvic malignancy but is one of the most lethal malignancies as 65% of patients present with advanced disease.
- MRI is used to characterize indeterminate adnexal masses, rather than for staging.
- MRI is highly sensitive to detect peritoneal implants, which occur most commonly in the pouch of Douglas, paracolic gutters, bowel surface, greater omentum, and liver surface.
- The presence of a solid enhancing component, intra-lesional necrosis, ascites, or peritoneal nodularity suggests a malignant lesion, although no finding is 100% specific.
Ovarian Cancer
Histologic origins of ovarian cancers?
Most common origin? Most common subtypes in decreasing order?
Which one is frequently bilateral? Characteristic findings of this tumor?
How does mucinous cystadenocarcinoma tend to appear?
Which subtype(s) are associated with endometriosis?
What are the malignant germ cell tumors and seen in what population?
What are the sex-cord tumors?
Are mets to ovaries common? What primaries can mets to ovaries? Are they often bilateral?
- Ovarian cancer may be epithelial, germ cell, sex-cord stromal, or metastatic in origin.
- Approximately 90% of malignant tumors are of epithelial origin. Serous tumors are the most common epithelial subtype, followed by mucinous, endometrioid, and clear cell.
- Serous cystadenocarcinomas are frequently bilateral and typically appear as mixed solid and cystic masses. The solid portions demonstrate avid enhancement. There is often concomitant ascites.
- Mucinous cystadenocarcinomas are large, most commonly unilateral, and occur in older patients compared to serous cystadenocarcinomas. Mucinous cystadenocarcinomas typically present as a multiloculated cystic mass containing mucin-rich T1 hyperintense fluid.
- Clear cell carcinoma and less commonly endometrioid carcinoma are associated with endometriosis.
- Malignant germ cell tumors occur in younger patients and include dysgerminoma, endodermal sinus tumor, and immature teratoma.
- Sex-cord stromal tumors include granulosa cell (hormonally active) and Sertoli-Leydig (rare).
- Metastases are uncommon but may result from gastric cancer (Krukenberg tumor), colon cancer, pancreatic cancer, breast cancer, and melanoma. Metastases are often bilateral.
