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MP MRI PROSTATE.pptx
- 1. Published in EuropeanRadiology Experimental, 2019 SUMANTRA DEY 1ST YR PDT
- 2. BACKGROUND • Prostate MRIis becoming of central importance in the contemporary management of PCa by improving the detection of clinically significant cancer (csPCa) while minimising overdiagnosis and overtreatment of indolent disease • CURRENT USES OF MRI – detecting and localising csPCa lesions – triaging biopsy, guiding targeted biopsy or focal therapy – stratifying the risk before treatment – monitoring patients during active surveillance – Planning and choosing surgery or radiation therapy techniques – assessing recurrence
- 3. THE MULTIPARAMETRIC STANDARD •ESUR guidelines 2012 – defined mpMRI as the combination of anatomic T2- weighted imaging (T2WI) with at least two functional MRI techniques out of DWI, DCE and MRS – proposed detailed and stringent technical requirements for detection and staging – DWI and DCE to be used mandatorily and MRSI optionally • protocols were presented together with the first version of the prostate imaging reporting and data system (PI-RADS)
- 4. THE MULTIPARAMETRIC STANDARD •PI-RADS version 2 (2014) led to consistent simplification of several technical and interpretation aspects – MRSI was excluded from the examination, restricting the mp standard to the use of T2WI, DWI, and DCE – less (even if stringent) technical parameters to obtain an acceptable mpMRI examination, leaving space for protocols optimisation – introducing the concept of dominant sequence
- 5. Dominant Sequence • Likelihodthat an image represents csPCa is expressed on a 1 to 5 scale • Depends on appearance on DWI for the peripheral zone (PZ) and on T2WI for the transition zone (TZ) • DCE assigned secondary role of a tiebreaker for PZ lesions, DWI for TZ lesions
- 6. Brief discussion onmpMRI
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- 10. • DWI studyconsists of 2 images 1. High b value DWI image 2. Apparent Diffusion Coefficient map • normal PZ demonstrates homogenous low SI on DWI and high SI on ADC map • More restricted environment of cancer leads to high SI on DWI and low SI on the ADC map
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- 14. (A) Axial T2WI ofthe prostate midgland shows a 1.2-cm circumscribed hypointense nodule (arrow) in the enlarged right transition zone. (B)The nodule is hyperintense on high b-value DWI (C)hypointense on ADC map (D)shows early enhancement on the axial contrast enhanced T1WI DCE
- 15. (A) Axial T2WI showsa lenticular, noncircumscribed mass with low signal intensity in the anterior midgland (arrows) compatible with a PI-RADS category 5 lesion. (B) mass shows markedly high signal intensity on high b-value DWI (C)markedly low signal intensity on ADC map (D) early enhancement on contrast- enhanced T1WI DCE
- 16. THE MP STANDARD- DISADVANTAGES • mpMRI requires prolonged time (30–45 min) • use of IV gadolinium-based contrast agents • drawbacks of PIRADS v2 – Incomplete interpretation criteria for TZ cancers – lack of definite rules for the CZ or anterior fibromuscular stroma involvement • High costs
- 17. Less-is-better strategies 1. Non-contrastbiparametric MRI 2. Reduced acquisition time 3. Abbreviated protocols 4. Less variability from human readers
- 18. Non-contrast biparametric MRI •Anatomic T2WI coupled with DWI as the only retained functional technique • DCE has been classically assumed to improve the sensitivity of T2WI alone or T2WI combined with DWI • Whether DCE should be included in the mp standard has always been a controversial issue • PI-RADS v2 revised role for DCE to PZ only and limiting it to a problem-solving tool • bpMRI does not apply to the setting of tumour recurrence after radical prostatectomy, radiation therapy, or focal therapy - DCE still plays a key-role in this scenario
- 20. Reduced acquisition time •T2WI is obtained with 2D turbo spin-echo sequences - need to acquire transverse, sagittal, and coronal planes separately; most time consuming • (3D) volumetric T2WI provides a unique slab with isotropic voxels, to be reconstructed in any plane – shortened acquisition time up to 44% • reduce volume-averaging artefacts, leading to better delineation of subtle anatomic features affecting the diagnosis (“erased charcoal sign” around TZ nodules)
- 21. Reduced acquisition time •Trade offs with 3D slab technique – – reduced soft tissue contrast – blurring and loss of resolution even for subtle motion – greater motion artefacts • 3D T2WI is not yet accepted as a state-of-the- art tool for detecting and staging PCa
- 22. Abbreviated protocols • consistof cutting redundant scans while preserving the informative core of the test • Abbreviated bpMRI - transverse T2WI and DWI only, with total acquisition time of 8 min 45 s (compared to 34 min 19 s of mpMRI) • Technical solution to face the increasing demand for prostate imaging • needs further validation and should be investigated in terms of cost-effectiveness
- 23. Less variability fromhuman readers • Computer-aided diagnosis (CAD) algorithms – a form of machine learning technology, trained on real cases to extract and classify image features, and in turn recognise intermediate- to-high-risk cancers
- 24. Different-is-better strategies • thereis a parallel pathway of prostate MRI development, searching for objective and reproducible MRI-related biomarkers for the prediction of PCa aggressiveness or overcoming inter-reader variability
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- 26. TAKE HOME MESSAGE •Multiparametric magnetic resonance imaging is the standard of care for assessing prostate cancer. • Alternative protocols are emerging to increase availability and offer a patient-centred approach. • Less-is-better strategies are promising for clinical practice, but require validation. • Different-is-better strategies are a matter for intensive research. • Prostate MRI technical standard and interpretation rules are still evolving.
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