MR imaging-guided prostate interventional imaging: Ready for a clinical use?

Prostate interventional magnetic resonance imaging (MRI) is now routinely performed in many centers. Its more widespread acceptance is limited by the cost of the use of MRI largely related to the long duration time of the procedures. However, the benefit of a robotic assistance has generated a new interest, because it substantially shortens the procedure time, while improving the accuracy. MRI-guided biopsy is considered as an appealing alternative to transrectal ultrasound (TRUS)-guided fusion biopsy, given the limitations of TRUS-MRI image registration systems. MRI-guided focal treatment also benefits from robotic assistance and from the unique property of MRI, which allows the measurement of the temperature in real-time during tumor ablation. The transrectal and transperineal approaches can be used and the respective indications of each pathway will depend on several factors, including the location of the tumor and the examination time, which will condition the occupation time of the MR room, a major factor influencing the overall cost of MRI-guided procedures. This review addresses the current practice of prostate MRI-guided interventional procedures and potential future applications.

[Pathological findings of visible and non-visible tumors on multiparametric magnetic resonance imaging (MRI) prior to radical prostatectomy]. / Caractéristiques anatomopathologiques des tumeurs apparentes et non apparentes en IRM multiparamétrique de la prostate avant prostatectomie totale.

INTRODUCTION: As urologists are questioned about the overtreatment of localized prostate cancer, multiparametric MRI can diagnose significant prostate cancer thanks to targeted biopsies. However, some tumors cannot be detected by MRI. What are the pathological characteristics of those tumors? MATERIALS AND METHODS: We have selected 144 consecutive patients treated with radical prostatectomy for clinically localized prostate cancer diagnosed on systematic and targeted biopsies (Koelis®) according to multiparametric MRI findings. On MRI, each suspicious area was graded according to the PI-RADS score v1.0. On radical prostatectomy specimen, tumor foci with a Gleason score greater than 3+3 and/or a tumor volume greater than 0,5cm3 were considered significant. The grade-four tumoral volume was calculated by multiplying the tumoral volume by grade 4 tumoral percentage. RESULTS: Two hundred and seventy seven tumors were identified. A hundred and thirty nine were non-visible on MRI. They had a significantly lower volume (0.15cm3 versus 1.45cm3, P<0.0001) and a Gleason score significantly lower (P<0.0001) than apparent tumors. 17.3% of non-apparent tumors were significant. Moreover, the grade-four tumoral volume of significant non-apparent tumors was significantly lower than that of significant apparent tumors (0.11cm3 versus 0.66cm3, P<0.0001). CONCLUSION: Non-apparent prostate tumors on multiparametric MRI have a Gleason score, a tumor volume - and consequently - a grade 4 tumor volume significantly lower than apparent tumors. LEVEL OF PROOF: 4.

Pitfalls in Interpreting mp-MRI of the Prostate: A Pictorial Review with Pathologic Correlation.

OBJECTIVES: The purpose of this pictorial review is to present a wide spectrum of prostate multiparametric MRI (mp-MRI) pitfalls that may occur in clinical practice, with radiological and pathological correlation. METHODS: All examinations were performed according to ESUR Guidelines protocols. RESULTS AND CONCLUSION: mp-MRI imaging of the prostate often leads to interpreting doubts and misdiagnosis due to the many interpretative pitfalls that a tissue, whether healthy or treated, may cause. These "false-positive" findings may occur in each stage of the disease history, from the primary diagnosis and staging, to the post-treatment stage, and whether they are caused by the tissue itself or are iatrogenic, their recognition is critical for proper treatment and management. Knowledge of these known pitfalls and their interpretation in the anatomical-radiological context can help radiologists avoid misdiagnosis and consequently mistreatment. MAIN MESSAGES: • Some physiological changes in the peripheral and central zone may simulate prostate cancer. • Technical errors, such as mispositioned endorectal coils, can affect the mp-MRI interpretation. • Physiological changes post-treatment can simulate recurrence.

Characteristics of undetected prostate cancer on diffusion-weighted MR Imaging at 3-Tesla with a b-value of 2000s/mm(2): Imaging-pathologic correlation.

OBJECTIVE: To assess the accuracy of Diffusion-Weighted MR Imaging (DW-MRI) at 3-Teslas (3T) with a b-value of 2000s/mm(2) (b-2000 DW-MRI) to detect prostate cancer (PCa) and to describe the histological features of missed tumors. METHODS: Prior to radical prostatectomy, 35 patients with a mean age of 64±6.2years old [51-77years old] had a b-2000 DW-MRI at 3-T, without rectal coil (acquisition time: 2min, 15s), and were analysed on an eight-sector basis by two independent readers blinded to the rest of the multiparametric-MRI protocol. Pathological tumor foci were matched with high intensity focal areas on MRI and correlated for Gleason score, sector location and largest axial diameter. RESULTS: Of the 280 sectors analysed, histology showed PCa in 113 (113/280, 40%). Overall DW-MRI sensitivity, specificity and accuracy for tumor detection were 79-81%, 99-95% and 92-82% for readers 1 and 2, respectively (kappa test: 0.78). Of all, 28 (28/113, 25%) and 22 (22/113, 20%) tumor foci were not detected by reader 1 and 2 respectively. These undetected tumor foci had a mean pathological axial axis of 5mm (range: 3-15mm) and a Gleason score of 6, 7 (3+4), 7 (4+3) and>7 in 15/28 (54%), 9/28 (32%), 3/28 (10%) and 1/28 (4%) of cases for reader 1, and in 11 (50%), 5 (23%), 5 (23%) and 1 (4%) of cases for reader 2. CONCLUSION: A normal b-2000 DW-MRI at 3-T may miss small tumors without or with a minor Gleason 4 component.

[Full field optical coherence tomography of prostate biopsies: a step towards pre-histological diagnosis?]. / Tomographie par cohérence optique plein champ des biopsies de la prostate: un pas vers le diagnostic pré-histologique?

OBJECTIVES: To evaluate the value of full field optical coherence tomography (FFOCT) for cancer detection on prostate biopsies PATIENTS AND METHODS: Eight consecutive patients who underwent prostate biopsies for an elevated PSA or suspicious DRE findings were included in the study. For each patient, one to three biopsy cores were imaged with FFOCT immediately after sampling. Images obtained were analyzed by a pathologist blinded to the pathological results, and classified into three categories: non-cancerous tissue, suspicion of malignancy and prostate carcinoma. A pathological correlation analysis was further performed. RESULTS: Sixteen biopsy cores were analyzed. The median FFOCT procedure time was of 4 (3-5) minutes. No artifact was noted in subsequent pathological analysis. Six cores were involved with cancer and eight cores showed no evidence of cancer. On two cores, diagnosis was uncertain, and immuno-histochemical analysis confirmed cancer involvement in one of them. The agreement rate between standard histological analysis and FFOCT evaluation was of 81% (13/16). The three cases of disagreement were due to one false positive and two false negatives of FFOCT analysis. CONCLUSIONS: FFOCT of prostate biopsy cores seemed to be feasible and to allow concordant results with those of pathological analysis in the majority of the cases.

Tumor target volume for focal therapy of prostate cancer-does multiparametric magnetic resonance imaging allow for a reliable estimation?

PURPOSE: We determined whether endorectal multiparametric magnetic resonance imaging at 1.5 Tesla could predict tumor target volume in the perspective of focal therapy of prostate cancer. MATERIALS AND METHODS: A total of 84 consecutive patients underwent multiparametric magnetic resonance imaging before radical prostatectomy. The volume of each suspicious area detected on magnetic resonance imaging and of all surgical histological foci was determined by planimetry. We first used each magnetic resonance imaging sequence (T2-weighted, diffusion weighted and dynamic contrast enhanced) and then the sequence showing the largest tumor area (multiparametric volume). Finally, the largest area of any sequence was used to calculate a target volume according to the volume of a cylinder. Agreement between magnetic resonance imaging and pathological findings was assessed by linear regression and residual analysis. RESULTS: Histology revealed 99 significant tumors with a volume of greater than 0.2 cc and/or a Gleason score of greater than 6. Of the tumors 16 (16.2%) were undetected by multiparametric magnetic resonance imaging. Linear regression analysis showed that tumor volume estimated by T2-weighted or diffusion weighted imaging correlated significantly with pathological volume (r(2) = 0.82 and 0.83, respectively). Residuals from diffusion weighted imaging volume estimations did not significantly differ from 0. Nevertheless, diffusion weighted imaging underestimated pathological volume in 43 of 87 cases (49%) by a mean of 0.56 cc (range 0.005 to 2.84). Multiparametric and target volumes significantly overestimated pathological volume by a mean of 16% and 44% with underestimation in 28 (32%) and 15 cases (17%), respectively. Volume underestimation was significantly higher for tumor foci less than 0.5 cc. The percent of Gleason grade 4 did not influence tumor volume estimation. CONCLUSIONS: Magnetic resonance imaging can detect most significant tumors. However, delineating a target volume may require further adjustment before planning magnetic resonance imaging targeted focal treatment.

TRUS-MRI image registration: a paradigm shift in the diagnosis of significant prostate cancer.

Accuracy of multiparametric MRI has greatly improved the ability of localizing tumor foci of prostate cancer. This property can be used to perform a TRUS-MR image registration, new technological advance, which allows for an overlay of an MRI onto a TRUS image to target a prostate biopsy toward a suspicious area Three types of registration have been developed: cognitive-based, sensor-based, and organ-based registration. Cognitive registration consists of aiming a suspicious area during biopsy with the knowledge of the lesion location identified on multiparametric MRI. Sensor-based registration consists of tracking in real time the TRUS probe with a magnetic device, achieving a global positioning system which overlays in real-time prostate image on both modalities. Its main limitation is that it does not take into account prostate and patient motion during biopsy. Two systems (Artemis and Uronav) have been developed to partially circumvent this drawback. Organ-based registration (Koelis) does not aim to track the TRUS probe, but the prostate itself to compute in a 3D acquisition the TRUS prostate shape, allowing for a registration with the corresponding 3D MRI shape. This system is not limited by prostate/patient motion and allows for a deformation of the organ during registration. Pros and cons of each technique and the rationale for a targeted biopsy only policy are discussed.

Multiparametric MRI features of granulomatous prostatitis and tubercular prostate abscess.

The authors report the diffusion and contrast-enhanced MRI appearance of five cases of granulomatous prostatitis (GP), non-specific (two cases) and infectious post-Bacillus Calmette-Guerin (BCG) therapy (three cases, with a tubercular abscess in two of them). All patients had raising PSA levels and abnormal DRE. History of BCG therapy or acute prostatitis was present in four patients. Multiparametric MRI (T2W-MRI, DW-MRI and DCE-MRI) was performed before biopsies. Diagnosis was confirmed by TRUS-guided biopsies in four cases and by transurethral resection in one case. MRI showed a tumor-like appearance in three cases, an abscess-like appearance in one case and a combined tumor/abscess-like appearance in one case. Extraprostatic fat was infiltrated in three patients, simulating T3a disease. Histologically, caseous necrosis was found when MRI showed abcedation. Demonstration of occult tubercular abscesses in post-BCG GP may have therapeutic implications and MRI is useful prior to surgical or interventional drainage of large caseous abscesses.

[Prebiopsy multiparametric MRI of the prostate: the end of randomized biopsies?]. / IRM mutiparamétrique de la prostate avant biopsies : la fin des biopsies systématisées ?

OBJECTIVE: To evaluate the value of multiparametric MRI-targeted prostate biopsies in patients with suspected low-risk prostate cancer. PATIENTS AND METHOD: Patients with normal digital rectal examination and a PSA level between 4 and 10 ng/mL were prospectively included. A multiparametric MRI of the prostate was performed prospectively before the biopsies. 12-core randomized biopsies were performed, with additional targeted samples in each suspicious area identified on MRI. Detected cancers and their histological characteristics were compared between those two biopsy protocols. A micro focal cancer (MFC) was defined by the presence of less than 4mm of Gleason score 3+3 cancer on a single core. RESULTS: Seventy-one consecutive patients were included. The overall detection rate was of 53% (38/71). It was of 70% (26/37) in the presence of suspicious area on MRI versus 35% (12/34) in the absence of any suspicious area (P=0.004). MRI-targeted biopsies alone detected three cancers, none of which was a MFC. 12-core biopsies alone detected 14 cancers, including ten MFC (71%). In 21 patients, prostate cancer was detected by both the MRI-targeted and 12-core biopsies. The Gleason score in the MRI-targeted area was the highest Gleason score in 90% of the cases. It was high (>6) in 76% (16/21) of the patients. CONCLUSIONS: MRI-targeted biopsies detected less micro focal cancers than randomized 12-core biopsies. They did not seem however to decrease the detection of clinically significant cancers.

[Imaging of male infertility: techniques and results]. / Imagerie de l'hypofertilité masculine : technique et résultats.

Assessment of male infertility includes clinical examination, laboratory tests (semen analysis, hormones dosage) and sonographic examination of the urogenital tract. Male infertility is due to testicular abnormalities (secretory type) or obstructive disorder (excretory type). Imaging should provide accurate definition of anatomical causes of infertility in order to deliver appropriate treatment. Testicular Doppler ultrasound with transrectal ultrasound is the gold standard imaging technique to explore male infertility. MRI, because of its high resolution, provides a multiplanar study especially in congenital and inflammatory abnormalities of the urogenital tract. This pictorial review illustrates the most frequent causes of male infertility.

Imaging in lower urinary tract infections.

In epididymo-orchitis, a sonogram shows a non-homogenous and hypertrophied epididymis and testis, with increased vascularisation seen on a Doppler sonogram. Abscesses must be investigated using sonography so that a necrotic tumour is not misdiagnosed. In prostatitis, sonography is indicated to investigate urine retention and where treatment has failed (to look for a blockage, an abscess, or pyelonephritis). Endorectal sonography is the best imaging modality for analysing the parenchyma, but otherwise has limited value. Chronic prostatitis is the main differential diagnosis from prostate cancer; the two may be distinguished using diffusion MRI. In cases of cystitis, imaging is indicated when a patient has recurrent cystitis (to investigate what the causative factors might be), or an infection with a less common bacterium (to look for calcifications, emphysema, any involvement of the upper urinary tract), and in cases of cystitis with pseudotumour.

Endorectal 3D T2-weighted 1mm-slice thickness MRI for prostate cancer staging at 1.5Tesla: should we reconsider the indirects signs of extracapsular extension according to the D'Amico tumor risk criteria?

PURPOSE: To evaluate the accuracy of a 3D-endorectal 1mm-thick slices MRI acquisition for local staging of low, intermediate and high D'Amico risk prostate cancer (PCa). MATERIALS AND METHODS: 178 consecutive patients underwent a multiparametric MRI protocol prior to radical prostatectomy (RP). T2W images were acquired with the 3D sampling perfection with application optimized contrasts using different flip angle evolutions (SPACE) sequence (5mn acquisition time). Direct and indirect MRI signs of extracapsular extension (ECE) were evaluated to predict the pT stage. The likelihood of SVI (seminal vesicle invasion) was also assessed. RESULTS: Histology showed ECE and SVI in 38 (21%) and 12 (7%) cases, respectively. MRI sensitivity and specificity to detect ECE were 55 and 96% if direct signs of ECE were used and 84 and 89% (p<0.05), if both direct and indirect signs were combined. D'Amico criteria did not influence MRI performance. Sensitivity and specificity for SVI detection were 83% and 99%. CONCLUSIONS: 3D data sets acquired with the SPACE sequence provides a high accuracy for local staging of prostate cancer. The use of indirect signs of ECE may be recommended in low D'Amico risk tumors to optimise patient selection for active surveillance or focal therapy.

Value of multiparametric MRI in the work-up of prostate cancer.

The role of magnetic resonance imaging (MRI) in prostate cancer evaluation is controversial and likely underestimated. Technological advances over the past 5 years have demonstrated that multiparametric MRI, including diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MRI, can evaluate the actual tumor burden of a newly diagnosed prostate cancer more accurately than sextant biopsy protocols. Tumor risk, defined by the D'Amico criteria, hence can be re-evaluated by multiparametric MRI. As a result, there is increasing evidence that MRI before repeat or even initial biopsy can accurately select patients who require immediate biopsies and those in whom biopsy could be deferred. Also, a relationship between apparent diffusion coefficient (ADC), calculated from DWI, and Gleason score was found. Thus, MRI before biopsy helps to detect high-grade tumors to target biopsies within areas of low ADC values. To achieve good targeting accuracy, transrectal ultrasound (TRUS)-MRI image registration is necessary. Three-dimensional deformable registration is sufficiently accurate to match TRUS and MRI volumes with a topographic precision of 1 mm. Real-time MRI-guided biopsy is another technique under evaluation. Both approaches will allow for increasing acceptance of focal therapies, should these techniques be validated in the future.

Multiparametric MRI is helpful to predict tumor focality, stage, and size in patients diagnosed with unilateral low-risk prostate cancer.

To study the staging accuracy of multiparametric magnetic resonance imaging (MRI) in patients showing unilateral low-risk cancer on prostate biopsy. A total of 58 consecutive patients with low-risk cancer (D'Amico classification) and unilateral cancer involvement on prostate biopsies were included prospectively. All patients underwent multiparametric endorectal MRI before radical prostatectomy, including T2-weighted (T2W), diffusion-weighted (DW) and dynamic contrast enhanced (DCE) sequences. Each gland was divided in eight octants. Tumor foci >0.2 cm(3) identified on pathological analysis were matched with MRI findings. Pathological examination showed tumor foci >0.2 cm(3) in 50/58 glands (86%), and bilateral tumor (pathological stagepT2c) in 20/58 (34%). For tumor detection in the peripheral zone (PZ), T2W+DWI+DCE performed significantly better than T2W+DWI and T2W alone (P<0.001). In the transition zone (TZ), only T2W+DWI performed better than T2W alone (P=0.02). With optimal MR combinations, tumor size was correctly estimated in 77% of tumor foci involving more than one octant. Bilateral tumors were detected in 80% (16/20) of cases. In patients with unilateral low-risk prostate cancer on biopsy, multiparametric MRI can help to predict bilateral involvement. Multiparametric MRI may therefore have a prognostic value and help to determine optimal treatment in such patients.