PET/MRI in children

During the past decade, combined PET/MRI has been translated from a basic technical concept to a clinical research tool and a clinically applied hybrid imaging modality. Numerous clinical and scientific applications have been proposed for this novel hybrid modality including oncologic, neurologic and cardiovascular imaging. Among these, PET/MRI in children has emerged as a key application, not only due to possible diagnostic advantages but also because of reduced radiation exposure compared to alternative techniques. A variety of clinical indications exists for the use of PET/MR imaging in children mainly in but not limited to the field of paediatric oncology. The purpose of this review article is to discuss possible applications of combined PET/MR in paediatric imaging and to illustrate these by presenting cases from clinical practice.     

FDG Whole-Body PET/MRI in Oncology: a Systematic Review

The recent advance in hybrid imaging techniques enables offering simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) in various clinical fields. ¹⁸F-fluorodeoxyglucose (FDG) PET has been widely used for diagnosis and evaluation of oncologic patients. The growing evidence from research and clinical experiences demonstrated that PET/MRI with FDG can provide comparable or superior diagnostic performance more than conventional radiological imaging such as computed tomography (CT), MRI or PET/CT in various cancers. Combined analysis using structural information and functional/molecular information of tumors can draw additional diagnostic information based on PET/MRI. Further studies including determination of the diagnostic efficacy, optimizing the examination protocol, and analysis of the hybrid imaging results is necessary for extending the FDG PET/MRI application in clinical oncology.     

MR/PET: a new challenge in hybrid imaging

OBJECTIVE: This article provides a short overview of hybrid imaging and the potential advantages of combined MR/PET. We will address some of the challenges that had to be met before MR/PET could become clinically available as well as further scientific work that has to be done to increase the potential benefit of this emerging hybrid modality. CONCLUSION: Hybrid imaging, the combination of two imaging modalities into one, promises the compensation of specific deficits of the modalities involved. PET/CT has gained wide acceptance for oncologic imaging in recent years; however, MRI has certain advantages that could make combined MR/PET more tempting in various clinical applications. The development of new clinical whole-body MR/PET systems offers new insights in metabolic and functional processes in oncology as well as cardiovascular and neurologic diseases.     

Oncologic PET/MRI, part 1: tumors of the brain, head and neck, chest, abdomen, and pelvis

In oncology, staging forms the basis for prognostic consideration and directly influences patient care by determining the therapeutic approach. Cross-sectional imaging techniques, especially when combined with PET information, play an important role in cancer staging. With the recent introduction of integrated whole-body PET/MRI into clinical practice, a novel metabolic-anatomic imaging technique is now available. PET/MRI seems to be highly accurate in T-staging of tumor entities for which MRI has traditionally been favored, such as squamous cell carcinomas of the head and neck. By adding functional MRI to PET, PET/MRI may further improve diagnostic accuracy in the differentiation of scar tissue from recurrence of tumors such as rectal cancer. This hypothesis will have to be assessed in future studies. With regard to N-staging, PET/MRI does not seem to provide a considerable benefit as compared with PET/CT but provides similar N-staging accuracy when applied as a whole-body staging approach. M-staging will benefit from MRI accuracy in the brain and the liver. The purpose of this review is to summarize the available first experiences with PET/MRI and to outline the potential value of PET/MRI in oncologic applications for which data on PET/MRI are still lacking.     

Competitive advantage of PET/MRI

Multimodality imaging has made great strides in the imaging evaluation of patients with a variety of diseases. Positron emission tomography/computed tomography (PET/CT) is now established as the imaging modality of choice in many clinical conditions, particularly in oncology. While the initial development of combined PET/magnetic resonance imaging (PET/MRI) was in the preclinical arena, hybrid PET/MR scanners are now available for clinical use. PET/MRI combines the unique features of MRI including excellent soft tissue contrast, diffusion-weighted imaging, dynamic contrast-enhanced imaging, fMRI and other specialized sequences as well as MR spectroscopy with the quantitative physiologic information that is provided by PET. Most evidence for the potential clinical utility of PET/MRI is based on studies performed with side-by-side comparison or software-fused MRI and PET images. Data on distinctive utility of hybrid PET/MRI are rapidly emerging. There are potential competitive advantages of PET/MRI over PET/CT. In general, PET/MRI may be preferred over PET/CT where the unique features of MRI provide more robust imaging evaluation in certain clinical settings. The exact role and potential utility of simultaneous data acquisition in specific research and clinical settings will need to be defined. It may be that simultaneous PET/MRI will be best suited for clinical situations that are disease-specific, organ-specific, related to diseases of the children or in those patients undergoing repeated imaging for whom cumulative radiation dose must be kept as low as reasonably achievable. PET/MRI also offers interesting opportunities for use of dual modality probes. Upon clear definition of clinical utility, other important and practical issues related to business operational model, clinical workflow and reimbursement will also be resolved.     

Whole‐body PET/MRI for colorectal cancer staging: Is it the way forward?

Magnetic resonance imaging (MRI) is presently the modality of choice for the local staging of rectal cancer, with positron emission tomography (PET) being optional for the evaluation of colorectal cancer. Indeed, previous studies have demonstrated that liver MRI using hepatocyte‐specific contrast agents can provide high diagnostic performance in the detection of colorectal cancer liver metastases. Recently, however, whole‐body PET/MRI, which can provide information regarding both anatomy and metabolism, has been introduced to clinical imaging, and studies are under way to assess whether it can improve diagnostic performance for oncologic diseases as well as provide additional information regarding the disease phenotype and biology compared to conventional imaging modalities of computed tomography (CT), PET, or MRI. This review offers a brief overview of the technical considerations of the PET/MRI system, and the current status of imaging modalities in the staging of colorectal cancer. The potential of whole‐body PET/MRI to improve the performance of colorectal cancer staging and the results of several recent studies will be discussed, and workflow considerations of whole‐body PET/MRI for patients with colorectal cancer will be addressed. Level of Evidence: 5 J. Magn. Reson. Imaging 2017;45:21–35.     

Initial experience of MR/PET in a clinical cancer center

Magentic Resonance/positron emission tomography (PET) has been introduced recently for imaging of clinical patients. This hybrid imaging technology combines the inherent strengths of MRI with its high soft‐tissue contrast and biological sequences with the inherent strengths of PET, enabling imaging of metabolism with a high sensitivity. In this article, we describe the initial experience of MR/PET in a clinical cancer center along with a review of the literature. For establishing MR/PET in a clinical setting, technical challenges, such as attenuation correction and organizational challenges, such as workflow and reimbursement, have to be overcome. The most promising initial results of MR/PET have been achieved in anatomical areas where high soft‐tissue and contrast resolution is of benefit. Head and neck cancer and pelvic imaging are potential applications of this hybrid imaging technology. In the pediatric population, MR/PET can decrease the lifetime radiation dose. MR/PET protocols tailored to different types of malignancies need to be developed. After the initial exploration phase, large multicenter trials are warranted to determine clinical indications for this exciting hybrid imaging technology and thereby opening new horizons in molecular imaging. J. Magn. Reson. Imaging 2014;39:768–780. © 2013 Wiley Periodicals, Inc .     

Ganzkörper-MRT und FDG-PET/CT in der bildgebenden onkologischen Diagnostik

The advent of whole-body MRI (WB-MRI) has introduced a systemic approach to oncologic imaging compared to established sequential, multi-modal diagnostic algorithms. Hardware innovations, such as whole-body scanners at 1.5 Tesla and also recently 3 Tesla, combined with acquisition acceleration techniques, have made WB-MRI clinically feasible. With this method dedicated assessment of individual organs with various soft tissue contrast, high spatial resolution and contrast media dynamics can be combined with whole-body anatomic coverage. PET/CT has established itself as a powerful modality in the staging of patients suffering from malignant tumors. In addition to the morphologic information provided by the CT component of this hybrid modality, the PET component contributes invaluable metabolic information, which greatly enhances accuracy in the assessment of lymphatic spread and viability of tumor tissue. Whole-body MR diffusion imaging is a novel and promising technique which may contribute to superior sensitivity in the detection of tumor manifestations. In the assessment of distant metastatic spread WB-MRI is highly sensitive and has advantages over PET/CT, especially in those tumors frequently spreading to the liver, bone or brain. WB-MRI is also very attractive as a radiation-free alternative for imaging of pediatric tumor patients in whom multiple follow-up examinations may be required. WB-MRI allows for precise assessment of the bone marrow and has been proven to be highly accurate for the staging of hematologic diseases, such as multiple myeloma. In this article recent developments and applications of WB-MRI in oncologic imaging are addressed and compared to the results of PET/CT.     

Positron Emission Tomography (PET) and breast cancer in clinical practice

The landscape of oncologic practice has changed deeply during the past few years and there is now a need, through a multidisciplinary approach, for imaging to provide accurate evaluation of morphology and function and to guide treatment (Image Guided Therapy). Increasing emphasis has been put on Position Emission Tomography (PET) role in various cancers among clinicians [Juweid ME, Cheson BD. Positron-emission tomography and assessment of cancer therapy. N Engl J Med 2006;354:496-507; Koh DM, Cook GJR, Husband JE. New horizons in oncologic imaging. N Engl J Med 2003;348:25; Tafra L, positron emission tomography (PET) and mammography (PEM) for breast cancer: importance to surgeons. Ann Surg Oncol 2006;14(1):3-13] and patients despite a general context of healthcare expenditure limitation. Positron Emission Tomography has currently a limited role in breast cancer, but also general radiologists and specialists should be aware of these indications, especially when staging aggressive cancers and looking for recurrence. Currently, the hybrid systems associating PET and Computed Tomography (CT) and in the same device [Rohren EM, Turkington TG, Coleman RE. Clinical applications of PET in oncology. Radiology 2004;231:305-32; Blodgett TM, Meltzer CM, Townsend DW. PET/CT: form and function. Radiology 2007;242:360-85; von Schulthess GK, Steinert HC, Hany TF. Integrated PET/CT: current applications and futures directions. Radiology 2006;238(2):405-22], or PET-CT, are more commonly used and the two techniques are adding their potentialities. Other techniques, MRI in particular, may also compete with PET in some instance and as far as ionizing radiations dose limitation is considered, some breast cancers becoming some form of a chronic disease. Breast cancer is a very complex, non-uniform, disease and molecular imaging at large may contribute to a better knowledge and to new drugs development. Ongoing research, Positron Emission Mammography (PEM) and new tracers, are likely to bring improvements in patient care [Kelloff GJ, Hoffman JM, Johnson B, et al. Progress and promise of FDG-PET Imaging for cancer patient management and oncologic drug development. Clin Cancer Res 2005;1(April (8)): 2005].     

Clinical use of cardiac PET/MRI: current state-of-the-art and potential future applications

Combined PET/MRI is a novel imaging method integrating the advances of functional and morphological MR imaging with PET applications that include assessment of myocardial viability, perfusion, metabolism of inflammatory tissue and tumors, as well as amyloid deposition imaging. As such, PET/MRI is a promising tool to detect and characterize ischemic and non-ischemic cardiomyopathies. To date, the greatest benefit may be expected for diagnostic evaluation of systemic diseases and cardiac masses that remain unclear in cardiac MRI, as well as for clinical and scientific studies in the setting of ischemic cardiomyopathies. Diagnosis and therapeutic monitoring of cardiac sarcoidosis has the potential of a possible ‘killer-application’ for combined cardiac PET/MRI. In this article, we review the current evidence and discuss current and potential future applications of cardiac PET/MRI.     

Present and future role of FDG-PET/CT imaging in the management of breast cancer

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[18F]fluoro-2-deoxy-d-glucose (FDG) is a useful tool for acquisition of both glucose metabolic and anatomic imaging data using a single device in a single diagnostic session, and has opened a new field in clinical oncologic imaging. FDG-PET/CT has been used successfully for the diagnosis, initial staging, restaging, early treatment response assessment, evaluation of metastatic disease response, and prognostication of breast cancer as well as various malignant tumors. We herein review the current place and role of FDG-PET/CT in the management of breast cancer, focusing on its usefulness and limitations in the imaging of these patients.     

Imaging of malignant bone involvement by morphologic, scintigraphic, and hybrid modalities.

Detection of bone involvement is essential for optimal therapy of oncologic patients. The purpose of imaging is to identify early bone involvement, to determine the full extent of the skeletal disease, to assess the presence of accompanying complications-such as fractures and cord compression-and to monitor response to therapy. Detection of bone involvement by various imaging modalities is based on either direct visualization of tumor infiltration or detection of the reaction of bone to the malignant process. MRI can identify early involvement of bone marrow. CT, which depends mainly on bone destruction, provides detailed bone morphology. In nuclear medicine, uptake of (18)F-FDG is directly into tumor cells, thus allowing for early detection and monitoring the response to therapy of tumor sites in the marrow, bone, and soft tissue, whereas increased uptake of (18)F-fluoride and (99m)Tc-methylene diphosphonate reflects the osteoblastic reaction of bone to the presence of tumor cells. The hybrid techniques SPECT/CT and PET/CT, recently introduced into clinical practice, provide a better anatomic localization of scintigraphic findings and may improve the diagnostic accuracy of SPECT and PET in detecting malignant bone involvement. The current review discusses the basis for the detection of malignant bone involvement by various morphologic and scintigraphic imaging modalities and the advantages and the limitations of each. Special emphasize is placed on the newer integrated technique of PET/CT. The role of imaging in identifying bone involvement in different malignant diseases is also discussed.     

Established, emerging and future applications of FDG-PET/CT in the uterine cancer

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[1?F]fluoro-2-deoxy-D-glucose (FDG) is a useful technique to acquire both glucose metabolic and anatomic imaging data using a single device in a single diagnostic session and has opened a new field in clinical oncologic imaging. FDG-PET/CT has been used successfully for the staging, optimization of treatment, re-staging, therapy monitoring, and prognostic prediction of uterine cervical cancer and endometrial cancer as well as various malignant tumours. The present review discusses the current role of FDG-PET/CT in the management of uterine cancer, discussing its usefulness and limitations in the imaging of these patients.     

Utility of positron emission tomography-magnetic resonance imaging in musculoskeletal imaging

Differentiation between neoplastic and nonneoplastic conditions magnetic resonance imaging (MRI) has established itself as one of the key clinical tools in evaluation of musculoskeletal pathology. However, MRI still has several key limitations which require supplemental information from additional modalities to complete evaluation of various disorders. This has led to the development hybrid positron emission tomography (PET)-MRI which is rapidly evolving to address key clinical questions by using the morphological strengths of MRI and functional information of PET imaging. In this article, we aim to review physical principles and techniques of PET-MRI and discuss clinical utility of functional information obtained from PET imaging and structural information obtained from MRI imaging for the evaluation of musculoskeletal pathology. More specifically, this review highlights the role of PET-MRI in musculoskeletal oncology including initial diagnosis and staging, treatment planning and post-treatment follow-up. Also we will review utility of PET-MRI in evaluating musculoskeletal infections (especially in the immunocompromised and diabetics) and inflammatory condition. Additionally, common pitfalls of PET-MRI will be addressed.     

Clinical performance of PET/CT in evaluation of cancer: additional value for diagnostic imaging and patient management.

This study assessed the clinical performance of a combined PET/CT system using (18)F-FDG in oncologic patients. METHODS: (18)F-FDG PET/CT was used to evaluate 204 patients with 586 suspicious lesions. All patients had available follow-up data, enabling assessment of the clinical significance of hybrid PET/CT findings. Differences in interpretation between PET, CT, and fused PET/CT data were prospectively documented for detection, localization, and characterization of each evaluated site. The additional value of PET/CT for data interpretation over that of separate PET and CT was classified into several criteria, including change in lesion characterization to either definitely benign or definitely malignant, precise anatomic localization of malignant (18)F-FDG uptake, and retrospective lesion detection on PET and CT. The clinical impact of information provided by PET/CT on patient management was assessed on the basis of follow-up data concerning further diagnostic or therapeutic approach. Analysis of data was performed for the whole study population, for different types of cancer, and for different anatomic sites. RESULTS: PET/CT provided additional information over the separate interpretation of PET and CT in 99 patients (49%) with 178 sites (30%). PET/CT improved characterization of equivocal lesions as definitely benign in 10% of sites and as definitely malignant in 5% of sites. It precisely defined the anatomic location of malignant (18)F-FDG uptake in 6%, and it led to retrospective lesion detection on PET or CT in 8%. The results of PET/CT had an impact on the management of 28 patients (14%). Hybrid PET/CT data obviated the need for further evaluation in 5 patients, guided further diagnostic procedures in 7 patients, and assisted in planning therapy for 16 patients. CONCLUSION: Hybrid PET/CT improves the diagnostic interpretation of (18)F-FDG PET and CT in cancer patients and has an impact on both diagnostic and therapeutic aspects of patient management.     

PET/MRI在肺癌中的潜在临床应用价值

PET/MRI作为新出现的融合影像技术,其临床应用价值尚未得到充分证实。与CT相比,MRI具有软组织对比分辨力高、无辐射、多参数成像、能够提供更多功能信息的优势,PET与MRI的融合对于肺癌的潜在应用价值可能要优于PET/CT。简述不同的PET/MRI系统的设计,并从肺结节的检出、鉴别诊断、TNM分期、预后/早期疗效评价/肿瘤复发4个方面介绍PET/MRI在肺癌中的潜在临床价值。     

Lokal- und Ganzkörperdiagnostik weiblicher Beckentumore

Integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) scanning has recently become established in clinical imaging. Various studies have demonstrated the great potential of this new hybrid imaging procedure for applications in the field of oncology and the diagnostics of inflammatory processes. With initial studies demonstrating the feasibility and high diagnostic potential of PET/MRI comparable to PET-computed tomography (CT), the focus of future studies should be on the identification of application fields with a potential diagnostic benefit of PET/MRI over other established diagnostic tools. Both MRI and PET/CT are widely used in the diagnostic algorithms for malignancies of the female pelvis. A simultaneous acquisition of PET and MRI data within a single examination provides complementary information which can be used for a more comprehensive evaluation of the primary tumor as well as for whole body staging. Therefore, the aim of this article is to outline potential clinical applications of integrated PET/MRI for the diagnostic work-up of primary or recurrent gynecological neoplasms of the female pelvis.     

Positron emission tomography as a diagnostic tool. A reassessment based on literature review.

Currently used clinical diagnostic imaging modalities, such as magnetic resonance imaging (MRI) and x-ray computed tomography (CT) provide predominantly anatomic information. CT images reflect x-ray attenuation distribution in the body, whereas MRI signals depend primarily on proton density and tissue relaxivity. In contrast to these predominantly anatomic modalities, positron emission tomography (PET) reflects tissue physiology and metabolism. Although PET has been used predominantly as a research tool, the clinical use of this technique for the detection, noninvasive characterization, and treatment planning of selected disease processes has been extensively studied in oncology, cardiology, and neurology. The author examined currently available literature to reassess the potential role of PET as a diagnostic tool in the following specific clinical situations: (1) the differentiation of radiation necrosis from tumor recurrence; (2) the characterization of the physiologic significance of coronary stenosis and the evaluation of the myocardial viability; and (3) the localization of the epileptogenic foci.     

Present and future role of FDG-PET/CT imaging in the management of gynecologic malignancies

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[18F]fluoro-2-deoxy-d-glucose (FDG) is a useful technique for acquiring both glucose metabolic and anatomic imaging data using a single device in a single diagnostic session, and has opened up a new field of clinical oncologic imaging. FDG-PET/CT has been used successfully for the staging, treatment optimization, re-staging, therapy monitoring, and prognostication of uterine and ovarian cancers as well as various malignant tumors. The present review discusses the current role of FDG-PET/CT in the management of gynecologic malignancies, focusing on its usefulness and limitations for imaging such patients.