Total-Body PET/CT: Current Applications and Future Perspectives.

OBJECTIVE. The purpose of this article is to describe the clinical applications of a total-body PET scanner and discuss future expectations. CONCLUSION. PET has been widely used in the fields of oncology, neurology, and cardiology. However, current PET scanners have limitations, including long scanning time, low signal-to-noise ratio, and high dose of ionizing radiation. Total-body PET with a long scan range provides solutions to these problems, markedly increasing the sensitivity of the system.

Characteristics, changes and influence of body composition during a 4486 km transcontinental ultramarathon: results from the TransEurope FootRace mobile whole body MRI-project.

BACKGROUND: Almost nothing is known about the medical aspects of runners doing a transcontinental ultramarathon over several weeks. The results of differentiated measurements of changes in body composition during the Transeurope Footrace 2009 using a mobile whole body magnetic resonance (MR) imager are presented and the proposed influence of visceral and somatic adipose and lean tissue distribution on performance tested. METHODS: 22 participants were randomly selected for the repeated MR measurements (intervals: 800 km) with a 1.5 Tesla MR scanner mounted on a mobile unit during the 64-stage 4,486 km ultramarathon. A standardized and validated MRI protocol was used: T1 weighted turbo spin echo sequence, echo time 12 ms, repetition time 490 ms, slice thickness 10 mm, slice distance 10 mm (breath holding examinations). For topographic tissue segmentation and mapping a modified fuzzy c-means algorithm was used. A semi-automatic post-processing of whole body MRI data sets allows reliable analysis of the following body tissue compartments: Total body volume (TV), total somatic (TSV) and total visceral volume (TVV), total adipose (TAT) and total lean tissue (TLT), somatic (SLT) and visceral lean tissue (VLT), somatic (SAT) and visceral adipose tissue (VAT) and somatic adipose soft tissue (SAST). Specific volume changes were tested on significance. Tests on difference and relationship regarding prerace and race performance and non-finishing were done using statistical software SPSS. RESULTS: Total, somatic and visceral volumes showed a significant decrease throughout the race. Adipose tissue showed a significant decrease compared to the start at all measurement times for TAT, SAST and VAT. Lean adipose tissues decreased until the end of the race, but not significantly. The mean relative volume changes of the different tissue compartments at the last measurement compared to the start were: TV -9.5% (SE 1.5%), TSV -9.4% (SE 1.5%), TVV -10.0% (SE 1.4%), TAT -41.3% (SE 2.3%), SAST -48.7% (SE 2.8%), VAT -64.5% (SE 4.6%), intraabdominal adipose tissue (IAAT) -67.3% (SE 4.3%), mediastinal adopose tissue (MAT) -41.5% (SE 7.1%), TLT -1.2% (SE 1.0%), SLT -1.4% (SE 1.1%). Before the start and during the early phase of the Transeurope Footrace 2009, the non-finisher group had a significantly higher percentage volume of TVV, TAT, SAST and VAT compared to the finisher group. VAT correlates significantly with prerace training volume and intensity one year before the race and with 50 km- and 24 hour-race records. Neither prerace body composition nor specific tissue compartment volume changes showed a significant relationship to performance in the last two thirds of the Transeurope Footrace 2009. CONCLUSIONS: With this mobile MRI field study the complex changes in body composition during a multistage ultramarathon could be demonstrated in detail in a new and differentiated way. Participants lost more than half of their adipose tissue. Even lean tissue volume (mainly skeletal muscle tissue) decreased due to the unpreventable chronic negative energy balance during the race. VAT has the fastest and highest decrease compared to SAST and lean tissue compartments during the race. It seems to be the most sensitive morphometric parameter regarding the risk of non-finishing a transcontinental footrace and shows a direct relationship to prerace-performance. However, body volume or body mass and, therefore, fat volume has no correlation with total race performances of ultra-athletes finishing a 4,500 km multistage race.

Ultrahigh field systems and applications at 7 T and beyond: progress, pitfalls, and potential.

About 150 researchers around the world convened at the Chateau Lake Louise on February 20-23, 2011 to present and discuss the latest research in human and animal imaging and spectroscopy at field strengths of 7 T or above (termed ultrahigh field) at the third ISMRM-sponsored high field workshop. The clear overall message from the workshop presentations and discussion is that ultrahigh field imaging is gaining momentum with regard to new clinically relevant findings, anatomic and functional MRI results, susceptibility contrast advancements, solutions to high field-related image quality challenges, and to generally push the limits of resolution and speed of high field imaging. This meeting report is organized in a manner reflecting the meeting organization itself, covering the seven sessions that were approximately titled: (1) high field overview from head to body to spectroscopy; (2) susceptibility imaging; (3) proffered session on susceptibility, ultrafast imaging, unique contrast at 7 T, and angiography; (4) neuroscience applications; (5) proffered session on coils, shimming, parallel imaging, diffusion tensor imaging, and MRI-PET fusion; (6) high field animal imaging and spectroscopy, as well as a vendor overview, and (7) Cutting edge technology at 7 T.

Low b-value diffusion-weighted imaging: emerging applications in the body.

Thanks to recent advances in magnetic resonance imaging technology, it has become possible to perform intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) in any part of the body. Extracranial applications of DWI are currently under active investigation, especially for oncological imaging. However, the use of non-quantitative low b-value (10-100 s/mm(2)) DWI in the body is still a relatively unexplored field, and its potential is not fully recognized. Non-quantitative low b-value DWI may especially be useful for the evaluation of structures that have an inherently low signal at high b-value DWI, including (but not limited to) the liver, heart, and small bowel. This article will review and discuss the basic principles and potential applications of nonquantitative low b-value DWI in the body.

Whole-body MR imaging in children: principles, technique, current applications, and future directions.

In whole-body magnetic resonance (MR) imaging, the entire body from the vertex to the toes is imaged in one or more planes with one or multiple sequences to allow evaluation of multisystem diseases in a single examination. Whole-body MR imaging is particularly useful for examining children because it does not involve exposure to radiation and allows a complete work-up for disease staging within a single session of sedation or anesthesia. At whole-body MR imaging with a sliding table platform, a body coil may be used, but the resultant images have a low signal-to-noise ratio (SNR) and low resolution; use of a combination of phased-array coils results in images with an improved SNR and higher resolution. As whole-body MR imaging techniques undergo further refinement, the role of the modality in oncologic and nononcologic imaging continues to expand. Its use in the staging of lymphoma and other malignancies has been studied extensively. Whole-body MR imaging does not provide functional information and cannot yet be used to differentiate benign from malignant lymphadenopathy. However, whole-body MR imaging performed with integrated diffusion-weighted sequences may complement or replace positron emission tomography, which involves substantial radiation exposure. Other promising avenues for future research include whole-body MR imaging at 3 T and the combination of molecular imaging or positron emission tomography with whole-body MR imaging.

Clinical Applications of PET/MR Imaging.

PET/MR imaging is in routine clinical use and is at least as effective as PET/CT for oncologic and neurologic studies with advantages with certain PET radiopharmaceuticals and applications. In addition, whole body PET/MR imaging substantially reduces radiation dosages compared with PET/CT which is particularly relevant to pediatric and young adult population. For cancer imaging, assessment of hepatic, pelvic, and soft-tissue malignancies may benefit from PET/MR imaging. For neurologic imaging, volumetric brain MR imaging can detect regional volume loss relevant to cognitive impairment and epilepsy. In addition, the single-bed position acquisition enables dynamic brain PET imaging without extending the total study length which has the potential to enhance the diagnostic information from PET.

[Whole-body MRI and FDG-PET/CT imaging diagnostics in oncology]. / 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.

Diffusion-weighted whole-body MR screening.

Diffusion-weighted sequence (DWI) of the entire body is a new promising technique feasible to evaluate multifocal disease. DWI has revealed great potential in the evaluation of patients with cancer or benign disease, as it supplies both quantitative and qualitative information of the whole body. The technical aspects of the diffusion-weighted whole body (DWWB) MR sequence are described with special emphasis on the processing and analysis of the imaging. DWWB MR sequence should be used combined with the other standard sequences such as FSE T1-weighted and STIR images. A complete whole-body MR imaging protocol including the DWI can be performed in less than 40 min. The possibilities, limitations and the preliminary clinical results of the whole-body MR imaging using a DWI of the entire body are reviewed.

The promise of nuclear medicine technology: status and future perspective of high-resolution whole-body PET.

Positron emission tomography has rapidly emerged over the past 50+ years resulting in highly sophisticated tools for medical diagnosis. However, spatial resolution is still one of the drawbacks of PET. Modern whole-body PET devices provide a spatial resolution in the range of 4-6mm FWHM. Physical constraints are equally responsible for limited spatial resolution as factors caused by geometrical effects or by detector crystal properties. This paper focuses on the question why it is still a major challenge--despite the invention of new crystals and readout electronics--to build a high-resolution whole-body PET system for humans. Physical constraints are discussed and possible solutions for high-resolution PET are presented.

Technical challenges and opportunities of whole-body magnetic resonance imaging at 3T.

An increasing number of magnetic resonance whole-body units operating at field strengths of 3T and beyond are currently installed in research institutions as well as clinical facilities. This review wants to describe the changes in physical properties at higher field strength and the resulting implications for clinical and experimental examinations of the whole body. An overview is provided on the resulting advantages and disadvantages for anatomical, functional and biochemical MR examinations in different regions of the body (except the brain). It is demonstrated that susceptibility and chemical shift effects increase linearly with field strengths and provide clearly higher sensitivity of most spectroscopic or blood oxygen level dependent (BOLD) techniques. On the other hand, homogeneity of the radiofrequency (RF) field is reduced in the body trunk at higher field strength due to the shorter wavelength. Examinations of the head or extremities provide sufficient homogeneity of the RF field for common examination techniques in most cases, whereas abdominal and pelvic examinations are still sometimes hampered by undesired dielectric effects. Nearly quadratic increase of RF energy deposition with increasing field strengths results in clear limitations for some common sequence types which work without any problems at 1.5 T. New strategies with multi-channel RF excitation have the potential to overcome limitations due to RF inhomogeneities, but a few years of further technological development seem necessary. Many problems have to be solved in the near future regarding the variety of MR techniques and applications in all parts of the human body.

[What are the benefits of MRI scans for people without symptoms?] / Wat levert MRI-onderzoek op bij mensen zonder klachten?

Commercial enterprises are selling MRI scans with the promise of longer and happier lives. A recent paper summarises the literature on this claim. We notice that, despite decades of this practice, very little careful research can be found. However, it does seem that serious issues are discovered in about 4% of people. When examining the supplementary materials, most of these issues turn out not to be of a serious nature, despite having been classified as such. Finally, scant and low-quality follow-up shows that only 0.4% of people end up with a serious diagnosis and we remain in the dark about whether the scans had any impact on their clinical outcomes. The paper also does not address the myriad of downsides related to scanning healthy people, such as needless distress and interventions for false-positives. We propose to incentivise proper collection of data by transferring the cost of following up on false-negative findings from the healthcare system to the MRI companies.

Whole-Body MR Imaging: The Novel, "Intrinsically Hybrid," Approach to Metastases, Myeloma, Lymphoma, in Bones and Beyond.

Whole-body MR imaging (WB-MR imaging) has become a modality of choice for detecting bone metastases in multiple cancers, and bone marrow involvement by multiple myeloma or lymphoma. Combination of anatomic and functional sequences imparts an inherently hybrid dimension to this nonirradiating tool and extends the screening of malignancies outside the skeleton. WB-MR imaging outperforms bone scintigraphy and CT and offers an alternative to PET in many tumors by time of lesion detection and assessment of treatment response. Much work has been done to standardize procedures, optimize sequences, validate indications, confirm preliminary research into new applications, rendering clinical application more user-friendly.

Improvements in cancer staging with PET/CT: literature-based evidence as of September 2006.

PET/CT with 18F-FDG is increasingly being used for staging, restaging, and treatment monitoring for cancer patients. CT is still frequently used only for attenuation correction and lesion localization. However, increasing sales of high-end scanners that combine PET with 64-detector CT strongly suggest that the field is moving toward a comprehensive concept, whereby diagnostic CT studies during intravenous contrast material application are combined with the highest-quality PET studies. At many institutions, in-line PET/CT has replaced separately acquired PET and CT examinations for many oncologic indications. This replacement has occurred despite the fact that only a relatively small number of well-designed prospective studies have verified imaging findings against the gold standard of histopathologic tissue evaluation. However, a large number of studies have used acceptable reference standards, such as pathology, imaging, and other clinical follow-up findings, for validating PET/CT findings. From these data, we believe, has emerged reliable evidence in support of the notion that PET/CT offers diagnostic advantages over its individual components for the major cancers.

Diffusion-weighted MRI in the body: applications and challenges in oncology.

OBJECTIVE: In this article, we present the basic principles of diffusion-weighted imaging (DWI) that can aid radiologists in the qualitative and quantitative interpretation of DW images. However, a detailed discussion of the physics of DWI is beyond the scope of this article. A short discussion ensues on the technical aspects of performing DWI in the body. The emerging applications of DWI for tumor detection, tumor characterization, distinguishing tumor tissue from nontumor tissue, and monitoring and predicting treatment response are highlighted. The challenges to widespread adoption of the technique for cancer imaging in the body are discussed. CONCLUSION: DWI derives its image contrast from differences in the motion of water molecules between tissues. Such imaging can be performed quickly without the need for the administration of exogenous contrast medium. The technique yields qualitative and quantitative information that reflects changes at a cellular level and provides unique insights about tumor cellularity and the integrity of cell membranes. Recent advances enable the technique to be widely applied for tumor evaluation in the abdomen and pelvis and have led to the development of whole-body DWI.

Body MR imaging at 3.0 T: understanding the opportunities and challenges.

The development of high-field-strength magnetic resonance (MR) imaging systems has been driven in part by expected improvements in signal-to-noise ratio, contrast-to-noise ratio, spatial-temporal resolution trade-off, and spectral resolution. However, the transition from 1.5- to 3.0-T MR imaging is not straightforward. Compared with body imaging at lower field strength, body imaging at 3.0 T results in altered relaxation times, augmented and new artifacts, changes in chemical shift effects, and a dramatic increase in power deposition, all of which must be accounted for when developing imaging protocols. Inhomogeneities in the static magnetic field and the radiofrequency field at 3.0 T necessitate alterations in the design of coils and other hardware and new approaches to pulse sequence design. Techniques to reduce total body heating are demanded by the physics governing the specific absorption rate. Furthermore, the siting and maintenance of 3.0-T MR imaging systems are complicated by additional safety hazards unique to high-field-strength magnets. These aspects of 3.0-T body imaging represent current challenges and opportunities for radiology practice.

Search by X-rays applied technology.

X-rays and gamma-rays are part of different methods of imaging for control purpose. The main and most widely used method is conventional fluoroscopy with transmission images. Dual energy imaging, backscatter imaging and computed tomography allow visualizing of interesting items or of single layers without superposition; these methods have been developed recently or have been adapted to imaging for security reasons. Dual energy uses the specific absorption characteristics of a substance. Spectroscopy permits the identification of substances in packages or luggage, without direct access. Industry offers technical solutions which combine different methods. Comparing the different methods, one has to conclude that the disadvantage of the transmission image is due to superimposition, which limits the recognition of searched items. The combination with other methods increases the reliability of recognition. Future will bring more controls for security reasons and in consequence, more "control imaging" by X-rays. Imaging for security reasons will be combined with pattern recognition; politicians will answer the demand for security and impose more controls.

Search for persons.

X-rays and gamma-rays are used to detect hidden persons in vehicles, containers, and railway wagons. They are produced with accelerators, X-ray tubes, cobalt 60 and caesium 137. Fan beams adjusted to a line of digital detectors produce the image. The resolution is sufficient to recognise a human being. The recognition of persons with transmission images is limited by superimposition; backscatter imaging produces clearer images but of one single layer only. The future will bring new applications of search for persons with X-rays. Crimes and terrorist attacks will induce added demand for security, where search with X-rays and gamma-rays will keep its important role or even increase it.

X-ray security scanners for personnel and vehicle control: dose quantities and dose values.

After the security related occurrences in the past few years, there is an increasing need for airport security and border controls. In the combat against terror and smuggling, X-rays are used for the screening of persons and vehicles. The exposure of humans to ionising radiation raises the question of justification. To solve this question, reliable and traceable dose values are needed. A research project of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety was initiated. Its task is to measure the ambient dose equivalent, H*(10), and the personal dose equivalent, H(p)(10), for typical types of personnel and vehicle X-ray scanners, using the transmission and/or backscatter method. In the following, the measuring quantities which are to be used for these investigations will be discussed and the measuring instruments will be presented. Furthermore, the experimental set-up is described. For the personnel X-ray scanners investigated, the obtained dose values are in the range from 0.07 to 6 microSv. These values will be compared to the dose values of the natural environmental radiation and some exposures in the field of medicine.

Vehicles, containers, railway wagons.

PURPOSE: Findings shall be shown which have been obtained employing X-rays, accelerator rays and gamma rays for control. MATERIAL AND METHOD: The observations have been made with transmission imaging, backscatter imaging, and with the combination of transmission with backscatter imaging. The images come from the manufacturers and from personal collections. RESULTS: One has to look for the extra spaces room, which are often hidden and for the objects themselves. CONCLUSION: Weapons, explosive, cigarettes, drugs and other contraband can be found. The smugglers react to possible controls with X-rays. The controls of the future will combine different technologies.