Sonoelasticity imaging: results in in vitro tissue specimens

The authors present a method for imaging tissue stiffness (sonoelasticity) that has been developed and tested in a laboratory setting by using in vitro canine and human prostate glands. A low-frequency acoustic source was used to induce vibration in tissue under examination, and a color Doppler ultrasound (US) instrument was modified to detect vibration amplitude. The resulting image is a color "map" of tissue vibration superimposed on conventional gray-scale US images. Stiffer tissues vibrated less in response to audible sound, regardless of echogenicity. Normal human and canine prostate glands demonstrated a uniform vibration pattern. Four of four human prostatic adenocarcinomas and two stiff inclusions injected into canine prostate glands demonstrated a lack of vibration in comparison with normal surrounding tissue. The authors conclude that while further study is necessary, sonoelasticity imaging may enhance the detection of neoplasms by enabling their identification solely on the basis of stiffness.     

Diffusion-weighted MR imaging for the evaluation of seminal vesicle invasion in prostate cancer: initial results

PURPOSE: To evaluate the accuracy of T2-weighted (T2WI) with diffusion-weighted imaging (DWI) as compared with T2WI alone for predicting seminal vesicle invasion (SVI) of prostate cancer. MATERIALS AND METHODS: A total of 30 patients with SVI and 136 patients without SVI who underwent prostate MR imaging were included in the study. MR images were analyzed retrospectively and independently by two readers for SVI on T2WI and T2WI with DWI using a 5-point scale. RESULTS: For predicting SVI, the specificity for T2WI with DWI and for T2WI was 97% and 87%, respectively, and accuracy was 96% and 87%, respectively, as determined by the experienced reader (P < 0.01). For the less experienced reader, the specificity for T2WI with DWI and for T2WI was 96% and 81%, respectively, and accuracy was 90% and 77%, respectively (P < 0.01). The diagnostic performance of the less experienced reader with T2WI with DWI led to significant improvement of the area under the receiver operating characteristic curve (Az) as compared with T2WI alone (Az = 0.815 versus 0.696; P < 0.01). Interreader agreement showed a substantial agreement (kappa = 0.613) for T2WI, and a substantial agreement (kappa = 0.737) for T2WI with DWI. CONCLUSION: For predicting SVI, T2WI with DWI showed a better diagnostic performance than T2WI alone. Additionally, the accuracy of the less experienced reader using T2WI with DWI showed a significant improvement as compared with T2WI alone.     

MR imaging of prostate cancer

PURPOSE: Accurate diagnosis and staging of prostate cancer (PC) is developing into an important health care issue in light of the high incidence of PC and the improvements in stage-adapted therapy. The purpose of this paper is to provide an overview on the current role of MR imaging and MR spectroscopy in the diagnosis and staging of PC. MATERIAL AND METHODS: Pertinent literature was searched and evaluated to collect information on current clinical indications, study techniques, diagnostic value, and limitations of magnetic resonance imaging and spectroscopy. RESULTS: Major indications for MR imaging of patients with suspected PC are to define tumor location before biopsy when clinical or TRUS findings are inconclusive, and to provide accurate staging of histologically proven PC to ascertain effective therapy. Current MR imaging techniques for the evaluation of PC include multiplanar high-resolution T2-weighted FSE and T1-weighted SE sequences using combined endorectal and phased-array coils. Using these techniques, the reported accuracy of MR imaging for the diagnosis of extracapsular tumor extension ranges between 82 and 88% with sensitivities between 80 and 95%, and specificities between 82 and 93%. Typical MR findings of PC in different stages of disease, as well as diagnostic problems, such as chronic prostatitis, biopsy-related hemorrhage and therapy-related changes of prostatic tissue are discussed. In addition, the current perspectives and limitations of MR spectroscopy in PC are summarized. CONCLUSIONS: Current MR imaging techniques provide important diagnostic information in the pretherapeutic workup of PC including a high staging accuracy, and is superior to TRUS.     

Diffusion-weighted imaging of prostate cancer

OBJECTIVE: The purpose of this study was to assess whether T2-weighted (T2W) imaging with diffusion-weighted (DW) imaging could improve prostate cancer detection as compared with T2W imaging alone. METHODS: The subjects consisted of 37 patients with prostate cancer and 23 without cancer undergoing magnetic resonance (MR) imaging. Using a 1.5-T superconducting magnet, all patients underwent T2W and DW imaging with parallel imaging. Images were independently reviewed by 3 readers to determine the detectability of prostate cancer. The detectability of T2W imaging without and with DW imaging was assessed by means of receiver operating characteristic analysis. RESULTS: Mean areas under the receiver operating characteristic curve for T2W imaging alone and for T2W imaging with DW imaging were 0.87 and 0.93, respectively. The receiver operating characteristic analysis showed that the addition of DW imaging to conventional T2W imaging significantly improved tumor detection (P = 0.0468) compared with T2W imaging alone. CONCLUSIONS: The addition of DW imaging to conventional T2W imaging provides better detection of prostate cancer.     

前列腺癌的多模态成像

前列腺癌是一种高度异质性疾病,目前治疗重点是识别与治疗预后不良的高危肿瘤,减少对惰性、低风险肿瘤的过度治疗。近年来,影像学在前列腺癌的探查、分期、治疗后评估和复发检测中的重要性逐渐增加。在不同的临床场景中,包括传统与功能检测在内的多种成像方式各有其优势与限制。该文概述目前应用于前列腺癌的影像学检测方法,从初期诊断到晚期...     

前列腺癌的MR扩散成像初步研究

目的初步评价MR扩散成像(DWI)对前列腺癌的诊断可行性。方法28例前列腺癌患者及20例前列腺正常的对照组受试者行MR DWI检查,使用回波平面扩散张量成像序列,b值为1000s/mm2。测量正常前列腺外周带及前列腺癌区域的表观扩散系数(ADC)值。同时测量每位受检者膀胱区域的ADC值。结果48例中44例(91.7%)获得前列腺外周带和膀胱的ADC值。24例前列腺癌灶的ADC值为(0.35±0.06)×10-3mm2/s,20例正常前列腺外周带的ADC值为(1·35±0.30)×10-3mm2/s,前列腺癌灶较正常前列腺外周带ADC值低(t=11.99,P=0.00)。前列腺癌患者膀胱的ADC值为(1.27±0.21)×10-3mm2/s,对照组膀胱ADC值为(1.29±0.30)×10-3mm2/s,2组之间差异无统计学意义(t=1.15,P=0.48)。结论MR DWI可用于前列腺的检查。前列腺癌灶与正常前列腺外周带ADC值的差别有可能用于前列腺癌的鉴别诊断。     

Molecular imaging of prostate cancer: PET radiotracers

OBJECTIVE: Recent advances in the fundamental understanding of the complex biology of prostate cancer have provided an increasing number of potential targets for imaging and treatment. The imaging evaluation of prostate cancer needs to be tailored to the various phases of this remarkably heterogeneous disease. CONCLUSION: In this article, I review the current state of affairs on a range of PET radiotracers for potential use in the imaging evaluation of men with prostate cancer.     

Diffusion weighted imaging in prostate cancer

Diffusion-weighted imaging has generated substantial interest in the hope that it can be developed into a robust technique to improve the accuracy of MRI for the evaluation of prostate cancer. This technique has the advantages of short acquisition times, no need for intravenous administration of contrast medium, and the ability to study diffusion of water molecules that indirectly reflects tissue cellularity. In this article, we review the existing literature on the utility of DWI in tumour detection, localisation, treatment response, limitations of the technique, how it compares with other imaging techniques, technical considerations and future directions.     

The role of imaging in prostate cancer

For patients with prostate cancer, diagnostic imaging can play three roles: screening, staging, and monitoring. Bayesian analysis dictates that if the prior probability of cancer is relatively low or if the consequences of a false-positive result are unacceptable, the test must be optimally specific. If the prior probability of cancer is high or if the consequences of missing it are unacceptable, the test must be optimally sensitive. For screening, the consequences of a miss are slight, and the consequences of labeling an insignificant cancer significant are serious. Thus, a very specific test is required. No current imaging modality fulfills this criterion. For staging, the prior probability of significant disease is relatively high, and the consequences of a miss serious, so a very sensitive test is required. Transrectal sonography, plus biopsy under sonographic control, fulfills this criterion for local disease, as does a bone scan for bone metastases. For monitoring, the prior probability is high, and the consequences of a miss serious, so a very sensitive test is needed. The bone scan is sensitive for bone metastases. Although CT is not sensitive for detecting lymph node metastases, it has practical clinical advantages over other imaging modalities for monitoring purposes in that it can detect disease in multiple structures at once. It is the only test that can monitor prostate size, the size of the lymph nodes, and whether hydronephrosis or liver metastases are present all in the scope of one examination.     

Functional imaging for prostate cancer: therapeutic implications

Functional radionuclide imaging modalities, now commonly combined with anatomical imaging modalities computed tomography (CT) or magnetic resonance imaging (single photon emission computed tomography [SPECT]/CT, positron emission tomography [PET]/CT, and PET/magnetic resonance imaging), are promising tools for the management of prostate cancer, particularly for therapeutic implications. Sensitive detection capability of prostate cancer using these imaging modalities is one issue; however, the treatment of prostate cancer using the information that can be obtained from functional radionuclide imaging techniques is another challenging area. There are not many SPECT or PET radiotracers that can cover the full spectrum of the management of prostate cancer from initial detection to staging, prognosis predictor, and all the way to treatment response assessment. However, when used appropriately, the information from functional radionuclide imaging improves, and sometimes significantly changes, the whole course of the cancer management. The limitations of using SPECT and PET radiotracers with regard to therapeutic implications are not so much different from their limitations solely for the task of detecting prostate cancer; however, the specific imaging target and how this target is reliably imaged by SPECT and PET can potentially make significant impact in the treatment of prostate cancer. Finally, although the localized prostate cancer is considered manageable, there is still significant need for improvement in noninvasive imaging of metastatic prostate cancer, in treatment guidance, and in response assessment from functional imaging, including radionuclide-based techniques. In this review article, we present the rationale of using functional radionuclide imaging and the therapeutic implications for each of radionuclide imaging agent that have been studied in human subjects.     

Nonpalpable prostate cancer: detection with MR imaging

The pathologic specimens and magnetic resonance (MR) images of 53 patients with clinically palpable prostate cancer confined to one lobe were studied to evaluate the ability of MR imaging to depict clinically nonpalpable prostate cancer. All patients had undergone imaging with a 1.5-T imager with T1- and T2-weighted sequences in both axial and sagittal planes before undergoing radical retropubic prostatectomy. At pathologic examination, only the palpable tumor was present in 30 of the 53 patients (57%), and 33 unsuspected tumors were present in an area distinct from the palpable tumor in 23 of the patients (43%). MR imaging successfully depicted 51 palpable tumors for a sensitivity of 96% and 19 of the 33 unsuspected tumors for a sensitivity of 58%. The sensitivity of MR imaging in the detection of nonpalpable, posteriorly located tumors was greater than for those located anteriorly (85% vs 15%). MR imaging was false-positive for nonpalpable tumor in 17 of 30 patients for a specificity of 43%. On the basis of these data, MR imaging has greater sensitivity in the depiction of posteriorly located cancer and is limited by a high false-positive rate in the depiction of nonpalpable tumors.     

前列腺癌的功能MRI

前列腺癌是老年男性最常见的恶性肿瘤之一。在2005年232090个美国人被诊断为前列腺癌，30350例患者因此死亡。在美国6个人中有1人患前列腺癌。大部分前列腺癌生长缓慢，早期诊断可以根治。但是，超过85％的前列腺癌患者发现多个癌灶。前列腺癌的诊断依靠超声引导下经直肠穿刺活检。由于超声对前列腺癌检测及定位准确性低，所以往往进行随机穿刺。     

MR imaging of treated prostate cancer

Many management options are available to patients with newly diagnosed prostate cancer. Magnetic resonance (MR) imaging plays an important role in initial staging of prostate cancer, but it also aids in tumor detection when there is clinical or biochemical suspicion of residual or recurrent disease after treatment. The purpose of this review is to describe the normal appearances of the prostatic region after different kinds of treatment for prostate cancer and to discuss how these appearances differ from those of recurrent and residual disease. Several MR imaging techniques used in evaluating patients with prostate cancer are described, including conventional MR imaging sequences (mainly T1- and T2-weighted sequences), MR spectroscopic imaging, diffusion-weighted imaging, and dynamic contrast agent-enhanced MR imaging. Clinical considerations, together with the different approaches for interpreting serum prostate-specific antigen values in the posttreatment setting, are also presented. All forms of treatment alter the MR imaging features of the prostatic region to a greater or lesser extent, and it is important to be able to recognize expected posttreatment appearances and distinguish them from the features of recurrent or residual cancer to aid subsequent clinical management.     

前列腺癌功能磁共振成像诊断研究

近年来,随着MR技术的发展,一些功能成像技术,如扩散加权成像、动态增强MRI和MR波谱技术也越来越多地应用于前列腺研究。通过其对组织生理、病理和血供改变的观察,获悉活体器官功能状态,为前列腺癌早期发现,正确的诊断、分期和鉴别诊断提供了依据。