[Possibilities of sonographic image fusion: Current developments]. / Möglichkeiten der sonographischen Fusionsbildgebung: Aktuelle Entwicklungen.

CLINICAL/METHODICAL ISSUE: For diagnostic and interventional procedures ultrasound (US) image fusion can be used as a complementary imaging technique. METHODICAL INNOVATIONS: Image fusion has the advantage of real time imaging and can be combined with other cross-sectional imaging techniques. PERFORMANCE: With the introduction of US contrast agents sonography and image fusion have gained more importance in the detection and characterization of liver lesions. ACHIEVEMENTS: Fusion of US images with computed tomography (CT) or magnetic resonance imaging (MRI) facilitates the diagnostics and postinterventional therapy control. PRACTICAL RECOMMENDATIONS: In addition to the primary application of image fusion in the diagnosis and treatment of liver lesions, there are more useful indications for contrast-enhanced US (CEUS) in routine clinical diagnostic procedures, such as intraoperative US (IOUS), vascular imaging and diagnostics of other organs, such as the kidneys and prostate gland.

Segmentation and Image Analysis of Abnormal Lungs at CT: Current Approaches, Challenges, and Future Trends.

The computer-based process of identifying the boundaries of lung from surrounding thoracic tissue on computed tomographic (CT) images, which is called segmentation, is a vital first step in radiologic pulmonary image analysis. Many algorithms and software platforms provide image segmentation routines for quantification of lung abnormalities; however, nearly all of the current image segmentation approaches apply well only if the lungs exhibit minimal or no pathologic conditions. When moderate to high amounts of disease or abnormalities with a challenging shape or appearance exist in the lungs, computer-aided detection systems may be highly likely to fail to depict those abnormal regions because of inaccurate segmentation methods. In particular, abnormalities such as pleural effusions, consolidations, and masses often cause inaccurate lung segmentation, which greatly limits the use of image processing methods in clinical and research contexts. In this review, a critical summary of the current methods for lung segmentation on CT images is provided, with special emphasis on the accuracy and performance of the methods in cases with abnormalities and cases with exemplary pathologic findings. The currently available segmentation methods can be divided into five major classes: (a) thresholding-based, (b) region-based, (c) shape-based, (d) neighboring anatomy-guided, and (e) machine learning-based methods. The feasibility of each class and its shortcomings are explained and illustrated with the most common lung abnormalities observed on CT images. In an overview, practical applications and evolving technologies combining the presented approaches for the practicing radiologist are detailed.

[Future of mammography-based imaging]. / Zukunft mammographiebasierter Bildgebung.

Mammography is the central diagnostic method for clinical diagnostics of breast cancer and the breast cancer screening program. In the clinical routine complementary methods, such as ultrasound, tomosynthesis and optional magnetic resonance imaging (MRI) are already combined for the diagnostic procedure. Future developments will utilize investigative procedures either as a hybrid (combination of several different imaging modalities in one instrument) or as a fusion method (the technical fusion of two or more of these methods) to implement fusion imaging into diagnostic algorithms. For screening there are reasonable hypotheses to aim for studies that individualize the diagnostic process within the screening procedure. Individual breast cancer risk prediction and individualized knowledge about sensitivity and specificity for certain diagnostic methods could be tested. The clinical implementation of these algorithms is not yet in sight.

[Criteria for radiological assessment of therapy response: criteria-based appraisal]. / Kriterien für die radiologische Beurteilung des Therapieansprechens: Kriterienbasierte Befundung.

Oncologic imaging and reporting are an important part of clinical trials and have to be performed according to standardized criteria that clearly define how certain changes in the size and number of tumorous lesions have to be rated. Knowledge of these criteria is not only crucial when interpreting cases for a clinical trial but may also be used as guidelines for everyday clinical reporting as they aid decision making and can increase the validity of radiologic reporting.This article summarizes the most important and frequently used criteria: the response evaluation criteria in solid tumors (RECIST) criteria which are only used in solid malignancies, the Choi criteria that have been designed for the assessment of gastrointestinal stroma tumors (GIST), and the Cheson criteria that are applied to malignant lymphomas. The compilation of these criteria is designed to be used as a repetitorium for experts and can also serve as training guidelines for junior radiologists who want to become involved in clinical trial reporting.

[Oncologic imaging: indications for and limitations of modern cross-sectional imaging techniques]. / Bildgebende Methoden in der onkologischen Diagnostik: Indikationen und Limitationen moderner Schnittbildverfahren.

Cross-sectional imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) CT are an integral part of the modern oncological workup. They are used for tumor detection and staging as well as for treatment evaluation and monitoring. Due to pathophysiological and histological differences there is no universal imaging protocol for the assessment of different forms of cancer. For instance, CT is still the standard technique for the detection and staging of lung cancer supplemented by PET which aids the exclusion of nodal involvement and the detection of distant metastases. For hepatocellular carcinoma on the other hand, MRI is the preferred imaging technique, particularly when used in conjunction with liver-specific contrast media - PET/CT is only of limited value. Finally, for neuroendocrine tumors there is a focus on special radiotracers, which, in the context of PET/CT, enable a highly specific whole-body assessment. Thus, knowledge of the pathophysiological and imaging characteristics of different tumors is essential for a personalized, state-of-the art management of oncology patients.

Nuclear medicine and multimodality imaging of pediatric neuroblastoma.

Neuroblastoma is an embryonic tumor of the peripheral sympathetic nervous system and is metastatic or high risk for relapse in nearly 50% of cases. Therefore, exact staging with radiological and nuclear medicine imaging methods is crucial for defining the adequate therapeutic choice. Tumor cells express the norepinephrine transporter, which makes metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, an ideal tumor specific agent for imaging. MIBG imaging has several disadvantages, such as limited spatial resolution, limited sensitivity in small lesions and the need for two or even more acquisition sessions. Most of these limitations can be overcome with positron emission tomography (PET) using [F-18]2-fluoro-2-deoxyglucose [FDG]. Furthermore, new tracers, such as fluorodopa or somatostatin receptor agonists, have been tested for imaging neuroblastoma recently. However, MIBG scintigraphy and PET alone are not sufficient for operative or biopsy planning. In this regard, a combination with morphological imaging is indispensable. This article will discuss strategies for primary and follow-up diagnosis in neuroblastoma using different nuclear medicine and radiological imaging methods as well as multimodality imaging.

ISMRM workshop on fat-water separation: insights, applications and progress in MRI.

Approximately 130 attendees convened on February 19-22, 2012 for the first ISMRM-sponsored workshop on water-fat imaging. The motivation to host this meeting was driven by the increasing number of research publications on this topic over the past decade. The scientific program included an historical perspective and a discussion of the clinical relevance of water-fat MRI, a technical description of multiecho pulse sequences, a review of data acquisition and reconstruction algorithms, a summary of the confounding factors that influence quantitative fat measurements and the importance of MRI-based biomarkers, a description of applications in the heart, liver, pancreas, abdomen, spine, pelvis, and muscles, an overview of the implications of fat in diabetes and obesity, a discussion on MR spectroscopy, a review of childhood obesity, the efficacy of lifestyle interventional studies, and the role of brown adipose tissue, and an outlook on federal funding opportunities from the National Institutes of Health.

[SPECT-CT of the foot]. / SPECT-CT des Fußes.

UNLABELLED: During the last years SPECT-CT combining the high resolution of CT with high sensitivity of bone SPECT has gained widespread clinical application. Especially in complex anatomic situations, SPECT-CT allows to exactly define the area of the skeleton which is responsible for pain. This holds true especially in patients with foot diseases. CONCLUSION: Bone SPECT-CT gives additional useful information in arthrodesis, infection, accessory bones (sesamoids) as well as tarsal coalition.

Simultaneous PET/MR imaging in a human brain PET/MR system in 50 patients--current state of image quality.

OBJECTIVES: The present work illustrates the current state of image quality and diagnostic accuracy in a new hybrid BrainPET/MR. MATERIALS AND METHODS: 50 patients with intracranial masses, head and upper neck tumors or neurodegenerative diseases were examined with a hybrid BrainPET/MR consisting of a conventional 3T MR system and an MR-compatible PET insert. Directly before PET/MR, all patients underwent a PET/CT examination with either [18F]-FDG, [11C]-methionine or [68Ga]-DOTATOC. In addition to anatomical MR scans, functional sequences were performed including diffusion tensor imaging (DTI), arterial spin labeling (ASL) and proton-spectroscopy. Image quality score of MR imaging was evaluated using a 4-point-scale. PET data quality was assessed by evaluating FDG-uptake and tumor delineation with [11C]-methionine and [68Ga]-DOTATOC. FDG uptake quantification accuracy was evaluated by means of ROI analysis (right and left frontal and temporo-occipital lobes). The asymmetry indices and ratios between frontal and occipital ROIs were compared. RESULTS: In 45/50 patients, PET/MR examination was successful. Visual analysis revealed a diagnostic image quality of anatomical MR imaging (mean quality score T2 FSE: 1.27±0.54; FLAIR: 1.38±0.61). ASL and proton-spectroscopy was possible in all cases. In DTI, dental artifacts lead to one non-diagnostic dataset (mean quality score DTI: 1.32±0.69; ASL: 1.10±0.31). PET datasets of PET/MR and PET/CT offered comparable tumor delineation with [11C]-methionine; additional lesions were found in 2/8 [(68)Ga]-DOTATOC-PET in the PET/MR. Mean asymmetry index revealed a high accordance between PET/MR and PET/CT (1.5±2.2% vs. 0.9±3.6%; mean ratio (frontal/parieto-occipital) 0.93±0.08 vs. 0.96±0.05), respectively. CONCLUSIONS: The hybrid BrainPET/MR allows for molecular, anatomical and functional imaging with uncompromised MR image quality and a high accordance of PET results between PET/MR and PET/CT. These results justify the application of this technique in further clinical studies and may contribute to the transfer into whole-body PET/MR systems.

[Ultrasound-guided image fusion with computed tomography and magnetic resonance imaging. Clinical utility for imaging and interventional diagnostics of hepatic lesions]. / Ultraschallgestützte Bildfusion mittels CT und MRT. Klinische Bedeutung für die bildgebende und interventionelle Diagnostik von Leberläsionen.

Abdominal ultrasound is often the first-line imaging modality for assessing focal liver lesions. Due to various new ultrasound techniques, such as image fusion, global positioning system (GPS) tracking and needle tracking guided biopsy, abdominal ultrasound now has great potential regarding detection, characterization and treatment of focal liver lesions. Furthermore, these new techniques will help to improve the clinical management of patients before and during interventional procedures. This article presents the principle and clinical impact of recently developed techniques in the field of ultrasound, e.g. image fusion, GPS tracking and needle tracking guided biopsy and discusses the results based on a feasibility study on 20 patients with focal hepatic lesions.

Molecular imaging in oncology: the acceptance of PET/CT and the emergence of MR/PET imaging.

In the last decade, PET-only systems have been phased out and replaced with PET-CT systems. This merger of a functional and anatomical imaging modality turned out to be extremely useful in clinical practice. Currently, PET-CT is a major diagnostic tool in oncology. At the dawn of the merger of MRI and PET, another breakthrough in clinical imaging is expected. The combination of these imaging modalities is challenging, but has particular features such as imaging biological processes at the same time in specific body locations.

Functional and molecular imaging with MRI: potential applications in paediatric radiology.

MRI is a very versatile tool for noninvasive imaging and it is particularly attractive as an imaging technique in paediatric patients given the absence of ionizing radiation. Recent advances in the field of MRI have enabled tissue function to be probed noninvasively, and increasingly MRI is being used to assess cellular and molecular processes. For example, dynamic contrast-enhanced MRI has been used to assess tissue vascularity, diffusion-weighted imaging can quantify molecular movements of water in tissue compartments and MR spectroscopy provides a quantitative assessment of metabolite levels. A number of targeted contrast agents have been developed that bind specifically to receptors on the vascular endothelium or cell surface and there are several MR methods for labelling cells and tracking cellular movements. Hyperpolarization techniques have the capability of massively increasing the sensitivity of MRI and these have been used to image tissue pH, successful response to drug treatment as well as imaging the microstructure of the lungs. Although there are many challenges to be overcome before these techniques can be translated into routine paediatric imaging, they could potentially be used to aid diagnosis, predict disease outcome, target biopsies and determine treatment response noninvasively.

Response assessment in oncology: limitations of anatomic response criteria in the era of tailored treatments.

Evaluation of tumor response is a vital element in clinical oncology research, particularly in the development of new drugs. Tumor response also plays a significant role in treatment decisions made by clinicians in practice. The underlying concept of tumor response, however, was developed as a result of limited understanding of tumor biology coupled with restricted availability of both effective treatments and imaging modalities. In recent years, impressive advances have been made in the treatment of cancer. Groundbreaking advances in our understanding of the molecular biology of tumor growth and proliferation have been made. New biologic agents have been approved for the treatment of several malignancies and, in many cases, biomarkers have been identified that can help predict those patients who will benefit. Pre-operative chemotherapy is now established for a number of tumor types. Modern imaging technologies allowing functional characterization of tumors have been introduced into clinical practice. In this new therapeutic landscape, the existing concept of tumor response risks becoming an anachronism, and revision of the criteria used to define tumor response is warranted. In this paper, we critically review the limitations of the classic criteria for tumor response assessment, and briefly discuss the potential role of alternative methodologies in providing a new, functional definition of tumor response.

CT and MRI in monitoring response: state-of-the-art and future developments.

The present review is aimed at updating the reader with the current role of computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of tumor response, contextualizing the imaging methods advantages and limitations. CT has been the most frequent and widely adopted diagnostic tool. The main advantages of such method include wide availability, high reproducibility, capability to contemporarily evaluate soft tissues, bone and lung parenchyma, besides being easy to perform. Its main limitation is related to the use of ionizing radiation. MRI has emerged as a feasible alternative to CT, particularly in patients with contraindications to the use of iodinated contrast agents, with advantages related to its high soft tissues contrast. The disadvantages are based on its operational complexity and the many technical variables involved which may influence and compromise the reproducibility and broad implementation of the method. New criteria for evaluation of tumor response have recently been proposed, contemplating lately developed drugs and therapeutic strategies that demand the utilization of functional parameters. In this context, the technological developments incorporated in the CT and MRI imaging techniques, such as perfusion analysis, diffusion studies (DW-RM) and MR spectroscopy (MRS), among others, have provided relevant information regarding the tumor response to targeted therapies, anticipating dimensional alterations and guiding physicians in the course of the treatment. Despite such developments, further efforts are needed to establish reproducible protocols, functional response criteria and time intervals for response evaluation in order to allow a definitive incorporation of these new technologies in the assessment of tumor response.

Use of PET/CT to evaluate response to therapy in lymphoma.

(18)F-FDG-PET is a well established standard procedure for most lymphoma subtypes. In particular the advantage of metabolic imaging stands in its strong predictivity in response. Indeed PET scan has been incorporated into revised response criteria for aggressive lymphomas and recommended to be performed at baseline and after therapy. At the same time, several ongoing clinical trials are investigating the value of treatment adaptation based on interim PET (PETi) results for Hodgkin Lymphoma (HL) and aggressive Non-Hodgkin Lymphoma (NHL). On the other hand, scientific literature provides limited detailed information regarding the numerous non aggressive NHL subtypes. Usually indolent NHL are typically less FDG avid, furthermore their long natural history and high incidence of recurrence decreases the clinical impact of a potential risk-adapted or response-adapted approach. We reviewed, from a nuclear medicine point of view and a clinical point of interest, evidence for the use of FDG-PET in monitoring early and end treatment response.

(18)F-FDG-PET/CT in evaluating response to therapy in solid tumors: where we are and where we can go.

In the past, enormous public and private investments have been made to reduce cancer incidence and mortality. Despite some improvements over the last 10 years, the overall outcome of the "war on cancer" has been disappointing. Among the reasons for this limited success is our inability to determine, whether the therapeutic target is present, and whether the target is reached by the drug. A further important issue is our limited ability to correctly assess response to treatment early after start of therapy which would allow for more individualized treatment approaches. PET and PET/CT with the glucose analogue 2'-[(18)F]-fluoro-2'-deoxy-D-glucose (FDG) are increasingly used to assess response to therapy in patients, and a converging large body of evidence is emerging that suggests that changes in glucose utilization during therapy can be used to predict clinical outcome. In this article we provide an overview of the utility of (18)F-FDG PET/CT imaging for early monitoring of cancer therapy and address current and future challenges for its more widespread adoption. First, we discuss general requirements that any imaging modality must meet to provide valid and valuable treatment response assessment. We will then review the strengths and limitations of CT (RECIST) and PET based response criteria. Finally, we will examine the role of FDG-PET/(CT) imaging for response assessments in solid tumors.