Prostate Cancer Imaging: most common pitfalls in multiparametric Magnetic Resonance

Transcription

1 Prostate Cancer Imaging: most common pitfalls in multiparametric Magnetic Resonance Poster No.: C-0698 Congress: ECR 2017 Type: Educational Exhibit Authors: L. Basso, M. Baglietto, S. Migone, V. Prono, A. Villa, G Perugin, F. Rosa, G. Rescinito, C. E. Neumaier ; Genova/IT, 2 3 Genoa/IT, Sarzana, It/IT Keywords: Tissue characterisation, Neoplasia, Image verification, Normal variants, Education, Decision analysis, MR-Functional imaging, MR-Diffusion/Perfusion, MR, Professional issues, Pelvis, Oncology DOI: /ecr2017/C-0698 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 19

2 Learning objectives The purpose of this Educational Poster is to explain and illustrate the characteristics of multiparameter diagnostic protocol and to show the spectrum of the main diagnostic pitfalls that can occur in the study of the prostate gland using MRI. Page 2 of 19

3 Background Nowadays, Multiparametric MRI (mp-mri) combining anatomical, biological and metabolic information, is the best imaging modality for the diagnosis, staging and evaluation of response to therapy in prostate malignancy. Because of these properties the mp-mri was defined by the American College of Radiology (ACR) and the European Society of Uroradiology (ESUR), as the gold standard imaging method for the study of the prostate gland [1] [2]. To allow standardization of MRI findings, inspired by the Bi-RADS, was developed PiRADS, recently revisited in its second version. Although prostate cancer has peculiar signal in T2-Weighted Images (T2WI), in Diffusion Weighted Images (DWI) and Dynamic Contrast Enahncement (DCE-MRI), a variety of interpretive and technical pitfalls can interfere with a proper assessment of the radiological findings. It is important to recognize these pitfalls because an increase of false positives (FP) can lead to overtreatment of clinically insignificant lesions, but especially, the lack of recognition of aggressive cancerous lesions can result in a suboptimal outcome for the patient. Page 3 of 19

4 Findings and procedure details The goal of this Educational Poster is to explain and show the most frequent diagnostic pitfalls in mp-mri of the prostate gland. We divided the explained pitfalls in 3 groups: Normal Anatomical Structures Interventional procedure or post-treatment changes Technical artifacts NORMAL ANATOMICAL STRUCTURE Central area: 'moustache sign' or 'handlebar sign' According to the scheme proposed by McNeal [3] Fig. 1 on page 8, three regions can be identified in prostate gland: 1. The Peripheral zone (PZ) 2. The Transition Zone (TZ) 3. The Central Zone (CZ) With aging process, the CZ may be compressed by growing TZ due to benign hyperplasia (BPH). This increase in size can lead to no longer recognize the two anatomical areas and to indicate with the term 'Central Gland' a single entity formed by both zones. However, the CZ can often be recognized as a symmetrical band of tissue that extends from the lower edge of the seminal vesicles to veromontanum: this tissue shows hypointense signal on T2-WI, appearing as a 'drop' on coronal images and oval in axial plane; moreover, it shows restricted signal on DWI and ADC maps mimicking cancer [4]. Fig. 2 on page 8 A variant of such benign finding is represented by the 'handlebar sign' or 'moustache sign' in which, due to growing BPH in TZ, the CZ is compressed and displaced bilaterally and symmetrically, taking a handlebar aspect in axial images [1] [5]. Fig. 3 on page 9 However, do not forget that less than 5% of prostate cancers arise in the central area and the presence of neoplastic lesion should be strongly suspected in the case of asymmetry [4]. Venous Plexus periprostatic Fig. 4 on page 10 Page 4 of 19

5 The Venous Periprostatic Plexus is a vascular structure along the edge of the peripheral gland and it may represent a pitfall in the diagnosis of peripheral focal lesions: in axial sections, in fact, it presents hypointense signal on T2-weighted images with focal signal restriction on DWI and ADC maps. In this case, the evaluation of the T2-WI on sagittal and coronal planes is essential: especially, DCE-MRI highlight a late and symmetrical enhancement helpful in the recognition of such structures [1]. Anterior Fibromuscular stroma Hypertrophic Fig. 5 on page 10 The hypertrophic Anterior Fibromuscular Stroma (AFMS) is an anatomical structure located anteriorly, hardly discriminated from the surrounding stroma. It is composed by smooth muscle cells, with homogeneously hypointense signal on T2-WI, showing 2 restricted signal on DWI but with ADC values typically > 1000 mm /s and with benign contrastographic behavior [7] [8]. Conversely, the neoplasm arising from this portion of the prostate gland have lenticular or polygonal shape, well defined or, sometimes, indistinct margins and typically asymmetric respect to the midline. Nodule of ectopic Hyperplasia Nodular Hyperplasia (BPH) Fig. 6 on page 11 BPH consists in a dimensional increase of the TZ with nodular growth of the glandular tissue mixed with stromal tissue, which shows markedly heterogeneous signal on T2WI. Sometimes, uncontrolled growth of hypertrophic TZ may present as a hypertrophic focal nodule within the PZ, mimicking the presence of cancer. Ectopic nodules have a circular or oval shape, with well-defined margins, and contrast enhancement behaviour similar to malignant lesions: also in this case, DWI and ADC maps are crucial for a 2 correct diagnosis: ADC values in hypertrophic nodules are > 1000 mm /s and expressive of benign disease. A correct interpretation of these findings on T2-WI along 3 axes can demonstrate the continuity between the TZ and the focal nodule within the PZ: the research of hyperintense spots in ectopic nodule, corresponding to dilated acinis, are typical of BPH. INTERVENTIONAL PROCEDURE OR POST-TREATMENT CHANGES Post-biopsy hemorrhage Fig. 7 on page 11 Approximately 80% of cases, post-biopsy bleeding can present characteristically hypointense on T2-WI and may mimic the presence of PCa. The correct interpretation of this findings can be easily demonstrated consulting the T1-WI without contrast: on this sequence signal is tipically hyperintense due to the presence of meta-hemoglobin. Post-biopsy residuals can be appreciated up to 4 months after sampling [9]. Furthermore, the high concentration of citrate in PZ, due to its anti-coagulant property, obstructs clots dissolution. For these reason, several studies suggest a minimum time gap of at Page 5 of 19

6 least 4-8 weeks between the biopsy sampling and MR examination [10] [11]. Latest literature studies suggest the possibility to discriminate these areas from tumour using subtraction techniques, or more, having regard to the reduced concentration of citrate in cancer lesions, on the basis of the so-called 'haemorrhage exclusion sign', in which the neoplastic tissue is easily identified within post-biopsy bleeding. Radiation Therapy changes Fig. 8 on page 12 Radiation therapy effects may represent a common pitfall in routinarely clinical practice. It should be kept in mind that on T2-WI hypointense focal areas within PZ can represent a prostate cancer under radiation therapy and not necessarily a tumour recurrence [1]. In this case, the DWI and Perfusion are important tools, significantly improving the diagnostic performance of the T2-weighing alone, with an Area Under the Curve (AUC) that in some studies reaches 0.95 [12]. Acute and Chronic prostatitis Fig. 9 on page 13 Fig. 10 on page 13 Acute and chronic inflammatory processes are very frequent, and they can result in fibrosis or atrophy. The signal spectrum of these processes is extremely various and, sometimes, focal nodular lesions with well-defined margins can even simulate a cancer; in a silent clinical context the precise diagnosis can be more difficult. However, in a substantial number of cases, inflammatory lesions show fuzzy linear margins, with lobar distribution or spread in the peripheral gland [13]. Calcification Fig. 11 on page 14 Fig. 12 on page 15 Prostatic calcifications are caused by prostatic secretions or amylaceous bodies. They are localized more frequently between the transition zone and peripheral gland, or, sometimes, in the middle adenoma: in most cases, they are clinically indolent and only rarely are associated with lower urinary tract symptoms. Signal on T2-WI it is typically hypointense, with restriction signs on ADC maps, because of diamagnetic effect, so mimicking the presence of malignancy. Their nature is confirmed by the absence of signal restriction in the sequences in Diffusion and hypointensity in T1WI. TECHNICAL ARTIFACTS Malpositioned Endorectal Coil Fig. 13 on page 15 Use of endorectal coil is strongly recommended for examinations carried out on 1.5T field and, for an acceptable images quality, the correct positioning is essential, with the antennas perpendicular to laterolateral axis. Otherwise, a malpositioned coil make the Page 6 of 19

7 diagnosis more difficult, creating artifacts affecting the image quality and mimicking the presence of cancer, especially in adjacent peripheral gland. Page 7 of 19

8 Images for this section: Fig. 1: Anatomical Zones of Prostate Gland according to McNeal. Nature, Cancer Page 8 of 19

9 Fig. 2: Central Zone A. T2WI axial B. T2WI coronal C. DWI (b=1000) D. ADC maps E. DCE-MRI axial Fig. 3: Moustache sign or Handlebar sign A. T2WI axial B. T2WI coronal C. DWI (b=1000) D. ADC maps E. DCE-MRI axial Page 9 of 19

10 Fig. 4: Venous Periprostatic Plexus A. T2WI axial B. DWI (b=1000) C. ADC map D. T1WI without contrast media E. DCE MRI Page 10 of 19

11 Fig. 5: Hypertrophic Anterior Fibromuscular Stroma A. T2WI axial B. T1WI axial with contrast media C. DWI (b=1000) D. ADC map Fig. 6: Nodule of ectopic Hyperplasia Nodular Hyperplasia (BPH) A. T2WI axial B. T2WI coronal C. T2WI sagittal D. DWI (b=1000) E. ADC maps F. DCE MRI Page 11 of 19

12 Fig. 7: Post-biopsy hemorrhage A. T2WI B.T1WI whithout contrast agent C. DWI D. ADC map Patient underwent 3T prostate multiparametric MRI, 6 weeks later prostate biopsy. Peripheral Zone shows signal modifications due to post-biopsy hemorrhage mimicking Prostate Cancer. Page 12 of 19

13 Fig. 8: Post Radiation Therapy changes. Before treatment (A-D) and after tretatment (E-H). A. T2WI axial B. DWI (b=1000) C. ADC map D. DCE MRI E. T2WI axial F. DWI (b=1000) G. ADC map H. DCE MRI Fig. 9: Chronic prostatitis A. T2WI axial B. DCE MRI C. DWI (b=1000) D. ADC map Page 13 of 19

14 Fig. 10: Focal Chronic prostatitis A. T2WI axial B. DWI (b=1000) C. ADC map D. T1WI E. DCE MRI F. DCE MRI Fig. 11: Calcification A. T2WI axial B. DWI (b=1000) C. ADC map D. T1WI without contrast media E. DCE MRI Page 14 of 19

15 Fig. 12: Calcification A. T2WI axial B. DWI (b=1000) C. ADC map D. DCE MRI Page 15 of 19

16 Fig. 13: Malpositioned Endorectal Coil on 1.5T scanner A. T2WI axial B. DWI (b 0, 90, 400, 800) C. ADC map Page 16 of 19

17 Conclusion Radiologist should be aware of different technical and clinical pitfalls that can occur performing MRI for PCa diagnosis in daily practice: in this educational poster we have only shown some of the more common 'pitfalls' that can occur in the diagnostic workup of patients with suspected prostate cancer. It is important that all radiologists keep in mind benign conditions that can affect prostate gland in each stage of the disease history and consider technical artifacts and physiological post-treatment changes mimicking PCa and simulate recurrence, because an error of interpretation can result an incorrect clinical management with sub-optimal outcome for the patient. Moreover, they should avoid misdiagnosis and consequently mistreatment. Page 17 of 19

18 Personal information All the autors are affiliated with the Radiology School of the University of Genoa, AOUIRCCS San Martino-IST, Genoa Page 18 of 19

19 References Pitfalls in Interpreting mp-mri of the Prostate: A Pictorial Review with Pathologic Correlation. Insights Imaging (2015) 6: Prostate 1981; 2:35-49 Normal central zone of the prostate and central zone involvement by prostate cancer: clinical and MR imaging implications. Radiology 2012; 262: Page 19 of 19