Staging of colon cancer: whole-body MRI vs. whole-body PET-CT—initial clinical experience

Background  To assess the accuracy of whole-body MR imaging (WB-MRI) in comparison with whole-body [18^F]-2-fluoro-2-deoxy-d-glucose (FDG) PET-CT in staging patients with diagnosed colorectal carcinoma (CRC). Methods  Twenty consecutive patients with previously diagnosed CRC underwent WB-MRI (3T) and PET-CT for staging of lymph node (N) and distant metastases (M). Evaluation was done according to the American Joint Committee on Cancer Staging Criteria. MR images were evaluated by two radiologists while PET-CT images by one radiologist and one nuclear medicine physician. Histology and/or a clinical follow-up of 3–6 months served as standard of reference. Results  Lymph node involvement was determined in 10/20 cases as N-positive in WB-MRI and in 15/20 in PET-CT. M-stage was evaluated for liver metastases (27 lesions in 15 patients with WB-MRI, 23/15 patients with PET-CT), lung (19/5 patients with WB-MRI, 25/7 patients with PET-CT), and bone (9/3 patients with WB-MRI, 9/3 patients with PET-CT). Two patients showed peritoneal implants and three patients demonstrated local recurrence at the surgery site on both modalities. No brain metastases were found. Conclusions  WB-MRI is a feasible method for examining colon cancer patients but cannot displace the present role of PET-CT.     

Whole-body MR/PET: applications in abdominal imaging

Over the last few decades it has been shown that novel technologies and technological progress rapidly change the working environment of radiologists and nuclear medicine physicians. Thus, new possibilities, e.g., in tumor staging and therapy monitoring, but also new challenges arise. Recently, it could be shown that the integration of magnetic resonance imaging (MRI) and positron emission tomography (PET) is technically possible. The evolvement of new dedicated hybrid MR/PET systems for whole-body imaging in humans offers new potential in multimodal imaging. Especially simultaneous measurement of PET and MRI datasets allows for insights in metabolic and functional processes, particularly in oncologic demands, but also in cardiovascular and cerebral imaging. In this work-in-progress review article, a technical summary including the method-inherent challenges are given. Furthermore, possible clinical applications and research interests are addressed.     

恶性黑色素瘤的全身磁共振-弥散成像与CT对比研究

【目的】评估全身磁共振成像（WB-MRI）包括全身弥散成像（WB-DWI）与全身CT在恶性黑色素瘤分级能力的差异,并进一步评价WB-DWI在病变检出方面与WB-MRI比较的差异。【方法】wB_DwI用于23例病患的胸、腹、盆扫描,并全部进行包括CT、WB-MRI检查,全部病例均经过组织学确诊恶性黑色素瘤。在MRI检查之前及随访中均采用CT作为参照。【结果]WB-MRI及wB_Dwl分别检查到345和302个病灶。CT检查出397个病灶,在不同部位WB-MRI和WB-DWI检查敏感性存在显著差异,肺部转移灶WB-MRI的检出率为38（个）灶／17例,WB-DWI为28（个）灶／14例,CT为60（个）灶／21例;骨的检出率wBMRI和wB_DWI均为56（个）灶／12例,而cT为42（个）灶／8例。【结论】w昏MRI尚不能取代CT来进行恶性黑色素瘤分级,特别是胸部;对于骨转移病灶而言,wB、MRI具有优势,在进行MRI检查时必须同时使用wB-DwI和w＆MRI序列才能够达到病灶检出的要求。     

Applications and software techniques for integrated cardiac multimodality imaging

Several imaging technologies are available for diagnostic cardiac imaging, such as coronary computed tomography angiography (CTA), single photon emission computed tomography (SPECT) positron emission tomography (PET) and magnetic resonance imaging (MRI). Each of these techniques offers unique advantages, but also suffers from specific limitations. Software techniques are being developed to combine cardiac images from different modalities and generate composite multimodality images, allowing better diagnosis than that possible from images analyzed separately. Hybrid scanners (SPECT/CT and PET/CT) have also been proposed for integrated cardiac imaging. Physicians are presented with integrated fused images that contain complementary information from separate scans containing physiological and anatomical information. In this review, we present the latest approaches for integration of cardiac images from multiple modalities.     

Applications and software techniques for integrated cardiac multimodality imaging

Several imaging technologies are available for diagnostic cardiac imaging, such as coronary computed tomography angiography (CTA), single photon emission computed tomography (SPECT) positron emission tomography (PET) and magnetic resonance imaging (MRI). Each of these techniques offers unique advantages, but also suffers from specific limitations. Software techniques are being developed to combine cardiac images from different modalities and generate composite multimodality images, allowing better diagnosis than that possible from images analyzed separately. Hybrid scanners (SPECT/CT and PET/CT) have also been proposed for integrated cardiac imaging. Physicians are presented with integrated fused images that contain complementary information from separate scans containing physiological and anatomical information. In this review, we present the latest approaches for integration of cardiac images from multiple modalities.     

Whole-body magnetic resonance imaging

Whole-body magnetic resonance imaging is a fast and accurate modality for the detection of disease throughout the entire body. Technical improvements including the availability of different high image quality MR sequences, the remote movement of the imaging table, and the use of specialized surface coils have rendered whole-body screening with MRI a feasible method. In this article we describe underlying techniques and report on first clinical experiences of whole-body magnetic resonance imaging as a staging and screening method. Furthermore, advantages and limitations compared with whole-body imaging based on computed tomography are discussed.     

Application of MR/PET in Oncologic Imaging

The present review aims to depict the possibilities offered by hybrid imaging with magnetic resonance positron emission tomography (MR/PET). Recently, new whole-body MR/PET scanners were introduced allowing for the combination of both modalities outside the brain. This is a challenge for both modalities: For MRI, it is essential to provide anatomical images with high resolution. Additionally, diffusion-weighted imaging (DWI), proton spectroscopy, but also dynamic contrast-enhanced imaging plays an important role. With regard to PET, the technical challenge mainly consists of obtaining an appropriate MR-based attenuation correction for the PET data. Using MR/PET, it is possible to acquire morphological and functional data in one examination. In particular, children and young adults will benefit from this new hybrid technique, especially in oncologic imaging with multiple follow-up examinations. However, it is expected that PET/CT will not be replaced completely by MR/PET because PET/CT is less cost-intensive and more widely available. Moreover, in lung imaging, MRI limitations still have to be accepted. Concerning research, simultaneous MR/PET offers a variety of new possibilities, for example cardiac imaging, functional brain studies or the evaluation of new tracers in correlation with specific MR techniques.     

Best Practices in PET/CT: Consensus on Performance of Positron Emission Tomography–Computed Tomography

Positron emission tomography-computed tomography (PET-CT) using the glucose metabolism tracer 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) has become a widespread and preferred imaging modality for evaluating most cancers. Since commercial PET-CT scanners became available in 2001, there has been rapid dissemination of this hybrid imaging modality and PET-CT scanners have largely replaced stand-alone PET scanners. How PET-CT scans are performed and applied to cancer management has varied considerably, in part reflecting the varied background of the practice settings and training experience of the physicians performing and interpreting the PET-CT studies. Combined PET/CT with FDG has become the gold standard in oncologic imaging by accurately defining anatomy and function of many tumors. From April 2-4, 2008, a focus group composed of physicians and technologists from different practice settings and training backgrounds entitled "Best Practices in PET/CT Symposium" was held in Sonoma, California. The symposium focused on optimization of PET-CT protocols but also included other pertinent topics related to PET-CT imaging in oncology. This article summarizes areas of consensus reached by the group regarding many of the discussion topics. The summary consensus covered in this article is meant to provide direction for future discussions on how to improve the application of this hybrid modality to patient care.     

Colorectal cancer staging: comparison of whole-body PET/CT and PET/MR

Purpose

Correct staging is imperative for colorectal cancer (CRC) since it influences both prognosis and management. Several imaging methods are used for this purpose, with variable performance. Positron emission tomography–magnetic resonance (PET/MR) is an innovative imaging technique recently employed for clinical application. The present study was undertaken to compare the staging accuracy of whole-body positron emission tomography–computed tomography (PET/CT) with whole-body PET/MR in patients with both newly diagnosed and treated colorectal cancer.

Methods

Twenty-six patients, who underwent same day whole-body (WB) PET/CT and WB-PET/MR, were evaluated. PET/CT and PET/MR studies were interpreted by consensus by a radiologist and a nuclear medicine physician. Correlations with prior imaging and follow-up studies were used as the reference standard. Correct staging was compared between methods using McNemar’s Chi square test.

Results

The two methods were in agreement and correct for 18/26 (69%) patients, and in agreement and incorrect for one patient (3.8%). PET/MR and PET/CT stages for the remaining 7/26 patients (27%) were discordant, with PET/MR staging being correct in all seven cases. PET/MR significantly outperformed PET/CT overall for accurate staging (P = 0.02).

Conclusion

PET/MR outperformed PET/CT in CRC staging. PET/MR might allow accurate local and distant staging of CRC patients during both at the time of diagnosis and during follow-up.

     

Whole-body PET/CT-colonography: a possible new concept for colorectal cancer staging

Background Colorectal cancer (CRC) is a leading cause of death, and necessitates a conjointly performed staging. Until now, a multi-step-examination including optical colonoscopy, cross-sectional and functional imaging is recommended. However, a single examination for whole-body staging with a dedicated CRC staging protocol is desirable. Thus, we developed and evaluated a combined whole-body PET/CT-colonography protocol for dedicated CRC staging in routine clinical use. Methods We integrated CT-colonography into a whole-body PET/CT protocol to achieve a specific “all-in-one” examination for patients suspected of having CRC. After oral and rectal bowel distension, PET/CT-colonography has been performed in 55 patients. All patients had optical colonoscopy one day before PET/CT. PET/CT data sets were evaluated concerning detection and evaluation of colorectal tumour sites, lymph nodes and distant metastases; these results were compared to the results of CT-colonography alone. Surgical resection and/or biopsy served as standards of reference in all patients. Results All examinations were fully diagnostic and well tolerated by the patients. PET/CT-colonography showed highly accurate results for overall TNM-evaluation and was significantly more accurate than CT-colonography alone. Conclusions Staging patients with whole-body PET/CT-colonography is technically feasible and accurate. Patients with incomplete colonoscopy or potential synchronous bowel lesions might benefit from this approach.     

Whole-body MR imaging. Practical issues, clinical applications, and future directions.

Whole-body MR imaging is in evolution, and although accepting and recognizing limitations, it is likely that both technique and incurred acquisition times will shorten over the next decade. Although the development of dedicated whole-body MR scanners appears to offer the greatest promise for the future, the development of moving table tops, optimized pulse sequences, and advances in gradient technology now facilitate practical whole-body MR imaging using existing clinical systems.     

Main applications of hybrid PET‐MRI contrast agents: a review

In medical imaging, the continuous quest to improve diagnostic performance and optimize treatment strategies has led to the use of combined imaging modalities. Positron emission tomography (PET) and computed tomography (CT) is a hybrid imaging existing already for many years. The high spatial and contrast resolution of magnetic resonance imaging (MRI) and the high sensitivity and molecular information from PET imaging are leading to the development of this new hybrid imaging along with hybrid contrast agents. To create a hybrid contrast agent for PET‐MRI device, a PET radiotracer needs to be combined with an MRI contrast agent. The most common approach is to add a radioactive isotope to the surface of a small superparamagnetic iron oxide (SPIO) particle. The resulting agents offer a wide range of applications, such as pH variation monitoring, non‐invasive angiography and early imaging diagnosis of atherosclerosis. Oncology is the most promising field with the detection of sentinel lymph nodes and the targeting of tumor neoangiogenesis. Oncology and cardiovascular imaging are thus major areas of development for hybrid PET‐MRI imaging systems and hybrid contrast agents. The aim is to combine high spatial resolution, high sensitivity, morphological and functional information. Future prospects include the use of specific antibodies and hybrid multimodal PET‐MRI‐ultrasound‐fluorescence imaging with the potential to provide overall pre‐, intra‐ and postoperative patient care. Copyright © 2015 John Wiley & Sons, Ltd.     

PET组合融合成像在分化型甲状腺癌复发和转移中的应用进展

甲状腺癌是最常见的内分泌系统恶性肿瘤之一，其中分化型甲状腺癌约占甲状腺癌发病率的90%以上，预后良好。但中国甲状腺癌患者5年相对生存率与一些发达国家差距较大。早期、准确地发现复发性疾病并应用适当的治疗策略，可改善复发性疾病患者的预后。因此，早期发现这些病人的复发和转移是至关重要的。随着诊断技术从系统向分子水平的过渡，多模态分子成像的作用越来越重要。PET能提供肿瘤细胞的功能学信息，而CT、MRI则能提供肿瘤的解剖学信息。功能成像技术和解剖学成像技术相结合能够实现优势互补，对于疾病复发和转移的诊断意义重大。随着近年来PET-CT在分化型甲状腺癌诊断、分期、疗效及预后评估上都较常规影像学检查更具优势，而PET-MRI是继PET-CT之后又一项优秀的多模态成像技术，因其软组织高分辨率和多序列多参数成像特性，所发挥的作用也愈发重要。因此，本文就PET-CT和PET-MRI在分化型甲状腺癌术后复发/转移中临床应用及未来前景进行综述。      

State of the Art in Cardiac Hybrid Technology: PET/MR

Simultaneous PET/MRI is an emerging technique combining two powerful imaging modalities in a single device. The wide variety of available tracers for perfusion and metabolic studies and the high sensitivity of positron emission tomography (PET) combined with the high spatial resolution and soft tissue contrast of magnetic resonance imaging (MRI) in depicting cardiac morphology and function as well as MRI’s absence of ionizing radiation makes PET/MRI very attractive to radiologists and clinicians. Nevertheless, PET/MR scientific and clinical promise is to be considered in the context of numerous technical challenges that hinder its use in the clinical setting. For example, in order for a PET system to work correctly within an MR field, major changes are required to the photon detection chain such as the elimination of photomultiplier tubes, etc. Another significant limitation of PET/MRI is the lack of an electron density map (as is the case with PET-CT) that can be readily obtained from MRI (the latter measures proton not electron density) and used to correct PET data for attenuation. Moreover, as with PET-CT, cardiac and respiratory motions cause image degradations that affect image quality and accuracy both in static and dynamic PET imaging. As a result, overcoming these (and other) technical limitations is a very active area of research both in academic institutions as well as industry. In this paper, we review recent literature on cardiac PET/MRI, present the state-of-the-art of this technology, and explore promising preclinical and clinical cardiac applications where PET/MRI could play a substantial role.     

Magnetic resonance imaging in the characterization of pelvic masses.

Female pelvic masses most commonly arise from the reproductive tract, although masses may arise from other structures in the pelvis, such as the gastrointestinal or urinary tracts. The evaluation of a pelvic mass often begins with the physical exam and proceeds to ultrasound, computed tomography, or magnetic resonance imaging. Each of these modalities has a role in the work-up of pelvic masses and each modality has inherent advantages and disadvantages. The focus of this article is to demonstrate the imaging features and role of MRI, in contrast to CT, for detecting, characterizing, and staging pelvic masses. The differential diagnosis for pelvic masses is extremely broad. Clinical history, precise anatomical localization, and MR imaging characterization can significantly narrow the differential diagnosis. With recent advances in therapeutic strategies, a non-invasive, preoperative diagnosis is highly desirable to suggest prognosis and to tailor the treatment approach.     

Protocol considerations for positron emission tomography-computed tomography of the abdomen and pelvis

New developments in positron emission tomography-computed tomography (PET-CT) have included the introduction of scanners with multidetector 16- to 64-row CT that allow thin-section essentially isotropic imaging datasets to be acquired rapidly in multiple time phases. "Diagnostic quality" CT with both oral and intravenous enhancement is now routinely possible in PET-CT and allows greater potential for the accurate diagnosis and staging of the full range of cancers involving the abdomen and pelvis. This article explores the considerations for more tailored, specific tumor-related protocols for PET-CT in the abdomen and pelvis, with emphasis on the use and value of fully optimized CT as part of an integrated PET-CT examination.     

Preoperative staging of colorectal cancer: CT vs. integrated FDG PET/CT

Accurate preoperative staging is essential in determining the optimal therapeutic planning for individual patients. The computed tomography (CT) in the preoperative staging of colorectal cancer, even if controversial, may be useful for planning surgery and/or neoadjuvant therapy, particularly when local tumor extension into adjacent organs or distant metastases are detected. There have been significant changes in the CT technology with the advent of multi-detector row CT (MDCT) scanner. Advances in CT technology have raised interest in the potential role of CT for detection and staging of colorectal cancer. In recent studies, MDCT with MPR images has shown promising accuracy in the evaluation of local extent and nodal involvement of colorectal cancer. Combined PET/CT images have significant advantages over either alone because it provides both functional and anatomical data. Therefore, it is natural to expect that PET/CT would improve the accuracy of preoperative staging of colorectal cancer. The most significant additional information provided by PET/CT relates to the accurate detection of distant metastases. For the evaluation of patients with colorectal cancer, CT has relative advantages over PET/CT in regard to the depth of tumor invasion through the wall, extramural extension, and regional lymph node metastases. PET/CT should be performed on selected patients with suggestive but inconclusive metastatic lesions with CT. In addition, PET/CT with dedicated CT protocols, such as contrast-enhanced PET/CT and PET/CT colonography, may replace the diagnostic CT for the preoperative staging of colorectal cancer.     

淋巴瘤磁共振成像新进展

磁共振是淋巴瘤的重要检查方法,对淋巴瘤早期发现、准确分期、疗效监测起到重要作用。目前磁共振发展的方向有特异性对比剂,全身磁共振,以及扩散加权成像、灌注成像、磁共振波谱等功能成像,本文对以上磁共振新技术在淋巴瘤中的应用予以综述。     

Nodal staging in genitourinary cancers

In patients with genitourinary cancers nodal staging is an integral part of the pretreatment evaluation. The presence of nodal metastatic disease plays an important role in predicting prognosis and treatment planning. Although some nodal groups can be evaluated clinically, most patients undergo various imaging studies for nodal staging. Each modality has its own unique attributes and applications. This article reviews various imaging modalities, namely, contrast enhanced computerized tomography, magnetic resonance imaging (MRI), and positron emission tomography, used for nodal staging in patients with genitourinary cancers and highlights their strengths and weaknesses. Emerging novel techniques such as lymphotropic nanoparticle enhanced MRI are also highlighted.     

Magnetic resonance angiography of chest and abdomen at 3 T

During the past decade, contrast-enhanced magnetic resonance angiography (CE-MRA) has been proven to be a powerful tool to visualize the thoracoabdominal vasculature and, consequently, has become a widely accepted noninvasive imaging modality. With the more recent introduction of high-field whole-body magnetic resonance scanners, a further improvement of diagnostic accuracy can be expected. General considerations for performing high-resolution CE-MRA at higher field strength include the benefits of higher signal-to-noise ratio and an improved contrast between vascular and background tissues. Although there are many positive attributes for performing CE-MRA at 3 T, there are also some tradeoffs, such as static magnetic field inhomogeneity and increase in specific absorption rate. This review describes the main technical innovations of advanced CE-MRA techniques at 3 T, illustrated by characteristic cases.