Genitourinary: basics

T2-W MR imaging provides exquisite soft tissue contrast for evaluation of pelvic pathology. Maximising contrast and spatial resolution is fundamental to achieving a high diagnostic accuracy. Adequate signal-to-noise ratio with sufficient T2-weighting requires appropriate consideration of available hardware and software. Patient-related factors that result in image degradation can be reduced by careful patient preparation. Motion from bowel peristalsis may be controlled with antiperistaltic agents (Buscopan [hyoscine butylbromide] 20mg or glucagon 1mg); intramuscular administration is crucial as intravenous delivery produces a short period of antiperistalsis insufficient to last through the scanning period. Bladder filling during the scan also can substantially degrade image quality, and therefore an empty bladder at the outset is essential. To minimise diuresis during scanning, caffeine-containing drinks should be avoided and fluid intake limited for 4 hours prior to scanning. Images dedicated to the uterus should be acquired along the long and short axis of the organ, with as small a field of view as feasible without compromising signal-to-noise ratio. For large field-of-view images, T2-W scans in true orthogonal planes to the B0 field are preferred. The sagittal plane is best for visualising the uterus, while the transverse plane is ideal for assessing parametria, adnexae and pelvic sidewall. For the ovaries, the coronal plane may be helpful. 3D acquisitions provide high spatial resolution with the flexibility of multiplanar reconstruction. High-quality T2-W images in orthogonal planes are usually sufficient for detecting, characterising and staging pelvic malignancy, monitoring treatment response and assessing disease recurrence in a range of gynaecological pathologies.

Gadolinium-based contrast material is not usually necessary for evaluating benign uterine disease, but is recommended in fibroid evaluation. Gadolinium-enhanced sequences are performed for staging endometrial carcinoma, being useful in the assessment of the depth of myometrial tumour invasion. The optimal tumour/myometrial contrast timing was reported between 90 and 150 seconds. Thus, the utility of dynamic acquisition has been debated. Contrast-enhanced imaging will not be routinely performed in cervical carcinoma, but can be valuable in selected cases. It is recommended in the MR assessment of sonographically indeterminate adnexal masses and mandatory for staging ovarian carcinoma. Dynamic contrast-enhanced MRI may provide quantitative information about tumour perfusion, being useful for monitoring the therapeutic effects and predicting the therapeutic outcome. MR angiography should be performed in patients scheduled for fibroid embolisation or in suspected pelvic congestion syndrome. Gadolinium-based contrast agents will cross the placenta and enter the foetal bloodstream. The agents are excreted into the amniotic fluid and will not be removed effectively from the foetal environment. Contrast agents should be avoided in the pregnant patient. Only a small amount of gadolinium is excreted into the breast milk and absorbed by the infant, without any adverse effects being reported. Therefore, breast feeding can be continued, but it might be the preference of the mother to discard the breast milk in the 24 hours after contrast medium. If contrast agents need to be administered in these patients, linear gadolinium chelates should be avoided.

Diffusion-weighted Imaging (DWI) has become a powerful imaging technique in the female pelvis providing functional information. It improves tissue characterisation and facilitates lesion depiction. This is based on visualisation of differences of random motion of water molecules within tissues, changes of tissue cellularity, and altered cell membranes. DWI is typically assessed in conjunction with findings obtained by conventional MR imaging sequences. Although several b values may be used, at least two b values (low <100 and high >800-1000mm²/sec) will provide visual information as well as quantitative analysis, the apparent diffusion coefficient (ADC). DWI has emerged as an available complementary sequence in staging gynaecological cancers, in differentiation of benign from malignant masses, and in imaging recurrent disease. DWI has also been linked to lesion aggressiveness and emerges as an imaging biomarker for tumour response. In pregnancy or in impaired renal function, DWI serves also as an alternative to i.v. contrast media. The main clinical applications include assessment of depth of myometrial invasion in endometrial cancer and identification of local tumour extent in small size or in diffusely growing cervical or endometrial cancers difficult to depict on T2WI. It also aids in characterisation of adnexal masses and facilitates identification of metastatic spread in advanced gynaecologic cancers, particularly to the peritoneum or to lymph nodes. The added value of DWI in various applications in clinical practice will be highlighted and the pitfalls will be demonstrated.

In this lecture, the current approach to uterine imaging and the advantages and limits of the various imaging modalities will be discussed. Ultrasound, usually using the high-resolution transvaginal approach, is the imaging modality of choice for the uterus. It is widely available and relatively inexpensive. Shortcomings with this imaging test are the limited field of view, obscuration of pelvic organs by the presence of bowel gas, inherent limitations dependent, and its dependence on the experience of the operator. The role of hysterosalpingography has become very limited in recent years. CT has an inferior soft tissue contrast compared to MRI and the disadvantage of ionising irradiation; its role is thus mainly limited to the emergency setting as well as oncologic staging of disease. With its high-contrast resolution, its ability to provide good tissue characterisation, and its multiplanar imaging capabilities, MRI is increasingly used to evaluate pathologies of the uterus. In this lecture, indications and contraindications of MRI will be reviewed. Patient’s preparation for pelvic MRI and the imaging sequences, tailored to the specific clinical questions, will be discussed.The audience will learn about the normal zonal anatomy of the uterus, congenital anomalies as well as variations of the uterus during the menstrual cycle and in the postmenopausal phase. The spectrum of normal and pathologic findings and the most important benign and malignant pathologies of the uterus will be reviewed and the role of MRI for staging cervical and endometrial cancer will be discussed.

Foetal MRI can be done at 1.5T or at 3T. Body or cardiac coils are used and ultrafast seqeunces are applied, the duration of which does not exceed 20-30 seconds on average. The emphasis of foetal MRI lies on providing information that cannot be received by ultrasound which is still the mainstay of prenatal imaging diagnosis. Cerebral malformations involving cortical development and/or infratentorial regions are among the most frequent indications for foetal MRI, as information on these structures may alter the prognosis of gross malformations considerably and thus change the further management of these pregnancies. Acquired pathologies of the brain comprise infection and/or haemorrhage. The high sensitivity of MRI to visualize parenchymal damage and blood breakdown products allows to give accurate information on such processes. in the foetal body, MRI is used in many centres for the assessment of lung development in a variety of pathologies such as, for instance, congenital diaphragmatic hernia, other lung malformations, or premature rupture of membranes which may also be associated with impaired lung development. Complex malformations including more tha one organ system can be classified , establishing a respective prognosis and sometimes allowing a conclusion on a genetic background. Prerequisites of performing foetal MRI successfully is a wide knowledge on prenaatl cerebral and extracerebral development and deviations thereof. In addition, a training at a foetal MRI centre might be useful to learn the methodical details and troubleshooting, as foetal MRI differs from other MRI methods.

Kidneys and adrenals are retroperitoneal organs contained within a perirenal space. Variants of adrenals involve essentially their shape, whereas many variants involve kidneys including ectopia, fusion, dystopia and duplication. Renal masses are frequent. Most are simple cysts. Cystic masses must be classified according to Bosniak classification to guide management. Conversely, most of the solid masses are malignant, but diagnosis of benign angiomyolipoma can be confirmed by imaging only. Adrenal masses are usually solid, and most of them are benign with typical imaging features based on evaluation of their lipid content and perfusion level. The role of imaging in parenchymal disease remains limited, except for infections, acute or chronic.

Imaging has a very important role in evaluating the urinary tract. Over the past years, computed tomographic urography (CTU) has become the main imaging modality for this purpose in various clinical settings. Dose reduction techniques have also enabled us to obtain CTUs with very low radiation doses. Several anomalies of the ureter may be seen, including duplication, muscular dysfunction or abnormal termination. An intraluminal disease process in the ureter might cause obstruction. Ureteral stone is by far the most frequent with high attenuation values on unenhanced CT. Dual-energy CT may contribute to the prediction of the chemical composition of the stone. A filling defect seen on CTU usually raises the suspicion of urothelial neoplasm. Other entities such as clot, metastasis, and tuberculosis might also obstruct the ureter and must be considered in the differential diagnosis of selected patients. The prevalence of urothelial neoplasms is high in elderly patients with a history of smoking, analgesic use or occupational exposure to chemical carcinogens. Urothelial cancer has to be considered as a ‘systemic’ disease, with often multiple, synchronous or metachronous lesions. CTU not only depicts the neoplastic lesion, but also enables the examination of the entire urothelium during staging or follow-up. Several treatment options are available and imaging plays an important role for tailoring this treatment. In case of haematuria, where CTU is the main diagnostic tool for upper urinary tract evaluation, cystoscopy is the primary diagnostic tool for screening for bladder neoplasms. CTU is indicated for the evaluation of upper urinary tract and staging purposes.

Prostate imaging is increasingly performed using multiparametric MRI (mpMRI) to detect and stage significant prostate cancer as well as for active surveillance in patients with a known cancer. The requirements to perform correct mpMRI including high-resolution T2w, diffusion-weighted MRI (DW-MRI) and dynamic contrast-enhanced MRI (DCE-MRI) are specified in PIRADS vs 2 (Prostate Imaging and Reporting Data System). The aim of prostate imaging is to detect a significant cancer defined as a tumour with a volume > 0.5 cc or a Gleason score of > 7 and/or extraprostatic extension. PIRADS version 2 uses a 5-point scale based on the likelihood that a combination of mpMRI findings on T2w, DW-MRI and DCE-MRI correlates with the presence or absence of clinically significant prostate cancer for each lesion in the prostate gland. PIRADS 1 or 2 means that clinically significant cancer is unlikely to be present, PIRADS 3 is intermediate/equivocal and PIRADS 4 and 5 indicate a high likelihood of significant prostate cancer (PIRADS 4: size< 1.5cm, PIRADS 5: size< 1.5 cm). Most of the prostate cancers are located in the peripheral zone, where DW-MRI is the dominant sequence to make the correct diagnosis. In the transition zone, T2w is the dominant sequence. In this presentation, typical findings will be discussed and also benign diseases such as prostatitis and benign prostatic hyperplasia will be demonstrated as potential differential diagnoses.