Magnetic resonance spectroscopic imaging: current status in the management of prostate cancer

In the past decade several advances have been made in the field of nuclear magnetic resonance (NMR) imaging. MR spectroscopic imaging (MRSI) is one such advance which holds promise for detecting biochemical change on imaging of the prostate, and that can be used in several ways for improving the management of patients with prostate cancer. We review the literature, technique and basics of MRSI, with its current status in various situations as applied to the management of prostate cancer.     

磁共振弥散加权结合直肠B超联合定位经会阴前列腺穿刺90例报告

目的：检测前列腺癌影像学诊断新技术一磁共振弥散加权成像（MRDWI）诊断前列腺癌的准确性（敏感度和特异度）,探索TRUS引导的MRDWI图像上可疑病灶穿刺方法,并比较联合MRDWI及TRUS定位与单纯TURS定位经会阴前列腺穿刺活检的准确性。方法：2007年4月～2008年12月间MRDWI或TRUS检查提示可疑前列腺结节的前列腺穿刺患者90例（平均年龄69岁,平均PSA10．9μg／1）;MRI医师、超声医师、泌尿外科医师联合读片确定可疑病灶（MRDwI表观弥散系数减低及B超低回声结节）;穿刺方案为TRUS引导下经会阴可疑病灶穿刺加系统10针前列腺穿刺;MRDWI可疑结节在TRUS图像上的定位方法：在MRDWI上详细定位病灶（病灶直径,病灶中心距中线X,距膀胱颈部L、距前列腺背侧缘距离H）,再在TRUS图像上依据L确定病灶所在横断面,根据X及H确定病灶中心,再测量该横断面上病灶中心距B超探头距离O,在通过病灶中心的纵切面上以高于探头平面O的距离平行进针,即可在TRUS图像上实时精确的穿刺到MRDWI可疑结节。穿刺各针标本注明穿刺部位后分瓶送病理检查;统计各针的影像学诊断及对应的病理,分别计算MRDWI和TRUS的敏感度和特异度。结果：共获963条前列腺穿刺组织标本。前列腺癌阳性针数171个,其中MRDWI阳性123个,敏感度为71．9％（123／171）,阳性预测值（PPV）54．7％（123／225）;B超阳性39个,敏感度为22．8％（39／171）,PPV56．5％（39／69）。阴性针数792个,其中MRDWI阴性690个,特异度为87．1％（690／792）,B超阴性762个,特异度为96．2％（762／792）。MRDWI发现而B超未发现90处（52．6％）,B超发现而MRDWI未发现6处（3．5％）,MRDWI、B超均发现33处,两者均未发现42处（24．6%）。联合定位穿刺敏感度75．4％（129／171）,较之传统B超定位敏感度提高52．6％。结论：MR弥散加权成像诊断前列腺癌的初步结果显示准确性较高,敏感度显著优于TRUS。TRUS引导穿刺MRDWI可疑前列腺结节简单、准确、易行,可藉此联合MRDWI及TRUS联合定位进行前列腺穿刺,提高前列腺癌病灶直接穿刺的敏感度。但目前情况下,仍需要结合系统穿刺来减少漏诊率。     

Raman spectral imaging of prostate cancer: can Raman molecular imaging be used to augment standard histopathology?

Study Type – Diagnostic (exploratory cohort)
Level of Evidence 2b

OBJECTIVE

To evaluate whether Raman molecular imaging (RMI, which combines digital imaging and analytical spectroscopy to evaluate the biochemical composition of interrogated material) can be used to identify biochemical differences in patients with Gleason 7 prostate cancer who progress to metastatic disease and die from prostate cancer.

PATIENTS AND METHODS

We identified 38 patients who had a radical prostatectomy for Gleason 7 adenocarcinoma of the prostate. Half progressed to metastatic disease and half had no evidence of disease after treatment. Patients were matched for preoperative prostate‐specific antigen level, surgical margin status, pathological stage, tumour volume, age at surgery, year of surgery and DNA ploidy. Sequential 5 µm sections were obtained from paraffin‐embedded tissue and one genitourinary pathologist selected areas of tumour for study. Principal component analysis was used to investigate the correlation between spectral response and clinical outcome.

RESULTS

The analysis was able to distinguish between those with progressive disease and those with no evidence of disease, most notably within the Gleason 3 regions when evaluating the epithelium and stroma as separate histological elements. A two‐sample t‐test gave P < 0.01 for both the Gleason 3 and 4 epithelium and stroma classes.

CONCLUSIONS

RMI is a novel technique that shows promise for identifying patients at risk of progression by visualizing molecular information not seen using other current methods. In Gleason 7 disease, RMI shows distinctive chemical differences in patients who progress to metastatic disease in both Gleason pattern 3 and 4 regions. This preliminary work lays the foundation for the further study of RMI for evaluating prostate tissue.     

The potential role of prebiopsy magnetic resonance imaging combined with prostate-specific antigen density in the detection of prostate cancer

Aim:   Two-thirds of patients with a gray-zone prostate-specific antigen (PSA) level undergo unnecessary biopsy. Sensitivity is not yet sufficient to permit the use of modified PSA parameters or magnetic resonance (MR) imaging alone for prostate cancer screening. Thus, we evaluated the combination of MR imaging and PSA density (PSAD) for specificity and sensitivity.
Methods:   During the period April 2004 through March 2006, 185 patients with a PSA level of 4.0–10.0 ng/mL underwent MR imaging and transrectal ultrasonography-guided 8-core biopsy (systemic sextant biopsy of the peripheral zone plus two cores of transition zone). All MR images were interpreted prospectively by two radiologists. An image was considered positive for prostate cancer if any feature indicated a cancerous lesion. Receiver operating characteristic (ROC) curves were used to compare the usefulness of the PSA level, PSAD and PSA transitional zone density (PSATZ) for the detection of prostate cancer.
Results:   Of the 185 patients, 62 had prostate cancer. Sensitivity and specificity of the axial T2-weighted MR imaging findings for cancer detection were 79.0% and 59.4%, respectively. The area under the ROC curve was 0.590 for the PSA level, 0.718 for PSAD and 0.695 for PSATZ. MR imaging findings and PSAD were shown by multivariate analysis to be statistically significant independent predictors of prostate cancer ( P  < 0.001). With a PSAD cut-off value of 0.111, sensitivity was 96.8%, but specificity was 19.5%. Combining MR imaging findings with PSAD increased the specificity to 40% and retained 95% sensitivity.
Conclusion:   MR imaging findings combined with PSAD provide high sensitivity and improve the specificity for the early detection of prostate cancer.     

影像融合技术诊断前列腺癌

超声(US)在目前前列腺癌诊断中应用广泛,但US的灵敏度和特异性较差,漏诊率较高。经直肠腔内超声(TRUS)引导下前列腺穿刺与手术病理结果的符合度也不超过50%。目前除了超声造影及实时弹性技术外,国外已发展其他超声新技术,如前列腺组织扫描(PHS)、经会阴粒子植入模板引导定位活检和MRI/US融合技术。PHS的特点为采用计算机协助分析组织性质。定位活检取样于整个前列腺,准确率更高。MRI/US融合将术前MRI和实时US相融合,既保证图像清晰度又便于穿刺。目前US正在不断进步,仍将具有较高的临床应用价值。     

Role of magnetic resonance imaging in defining a biopsy strategy for detection of prostate cancer

Prostate cancer is the second most common male cancer worldwide. It has a broad spectrum, from low‐risk, clinically indolent disease, to high‐risk aggressive cancer. This variety conveys certain diagnostic and management challenges. The use of prostate‐specific antigen as a screening test for prostate cancer is increasing the diagnosis of low‐grade, low‐volume disease. By targeting biopsies towards suspicious areas on multiparametric magnetic resonance imaging, we can accurately diagnose clinically significant prostate cancer, reducing identification of low‐risk, clinically indolent disease. This could avoid the radical treatment of histopathological cancer that might never have become clinically apparent. In the present review, we consider the use of multiparametric magnetic resonance imaging to inform the biopsy strategy. By identification of suspicious lesions on multiparametric magnetic resonance imaging, biopsy targets can be identified, and the sampling bias associated with blind standard transrectal prostate biopsy can be reduced. We consider the reliability of these radiological lesions for detection of clinically significant prostate cancer, and the methods of targeting them to ensure the radiological lesion is accurately sampled. Evidence suggests that targeted biopsy is efficient and accurate for diagnosis of clinically significant prostate cancer. By rationalizing diagnosis, and subsequently preventing overtreatment of clinically insignificant disease, magnetic resonance imaging‐informed prostate biopsy can provide a method for streamlining the diagnostic pathway in prostate cancer.     

Course of localized adenocarcinoma of the prostate treated by radical prostatectomy

Among 562 patients with histologic stage B-1, B-2, or C adenocarcinoma of the prostate treated by radical prostatectomy and pelvic lymphadenectomy, analysis revealed that increasing histologic stage, tumor size, degree of capsular invasion, seminal vesicle involvement, and histologic grade all were highly correlated with both local and systemic progression (log-rank two-sided P less than or equal to 0.0001). No variable correlated with survival--a result that may reflect appropriate adjuvant therapy given at the time of progression. The death rate from prostatic cancer did appear to rise progressively with increase of stage. Overall, the projected 10-year survival was 76%.     

Technique for a hybrid system of real‐time transrectal ultrasound with preoperative magnetic resonance imaging in the guidance of targeted prostate biopsy

Diagnostic magnetic resonance imaging (MRI) for prostate has achieved increasingly higher levels of accuracy. Because real‐time MR‐guided targeted biopsy is still a complicated and expensive procedure, there is considerable interest in a technique of MR/transrectal ultrasound (TRUS) hybridized image‐guided biopsy. However, because the 3‐D shapes of the prostate at the time of image‐acquisition at preoperative MRI are likely to be different from the intra‐operative TRUS images, the precise registration of each 3‐D volume data is critical. To reduce the potential errors in registration of TRUS with MRI, we introduce new procedural techniques in a rigid image fusion technique. First, preoperative MR images were obtained with a specifically‐made plastic outer‐frame, with exactly the same shape as the real TRUS probe, placed in the rectum, in order to simulate the deformation of the prostate caused by the absence or presence of a TRUS probe during the acquisition of MR or TRUS images. Second, instead of using a single plane of longitudinal image, we applied biplane TRUS images to be shown in parallel on a multiplanar display with corresponding reconstructed MRI, in order to register both horizontal and longitudinal images of the prostate simultaneously, thereby achieving improved 3‐D anatomical matching.