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.

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.

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.

[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.

Advances in Clinical PET/MRI Instrumentation.

In 2010, the first whole-body PET/MRI scanners installed for clinical use were the sequential Philips PET/MRI with PMT-based, TOF-capable technology and the integrated simultaneous Siemens PET/MRI. Avalanche photodiodes as non-magneto-sensitive readout electronics allowed PET integrated within the MRI. The experiences with these scanners showed that improvements of software aspects, such as attenuation correction, were necessary and that efficient protocols combining optimally PET and MRI must be still developed. In 2014, General Electric issued an integrated PET/MRI with SiPM-based PET detectors, allowing TOF-PET. Looking at the MRI components of current PET/MR imaging systems, primary improvements come from sequences and new coils.

F-18 FDG PET/CT imaging in the diagnostic work-up of thyroid cancer patients with high serum thyroglobulin, negative I-131 whole body scan and suppressed thyrotropin: 8-year experience.

OBJECTIVE: Fluorodeoxyglucose positron emission tomography/computed tomography imaging in the follow-up of patients with differentiated thyroid carcinoma who have high serum thyroglobulin, negative iodine-131 whole body scan and suppressed thyrotropin. PATIENTS AND METHODS: A total of 90 patients (31 male and 59 female) with differentiated thyroid carcinoma who have high serum thyroglobulin and negative iodine-131 whole body scan were included in the study between July 2006 and March 2014. All patients had undergone surgery (total thyroidectomy ± lymph node dissection) followed by iodine-131 ablation. Of the patients, 82 had papillary thyroid carcinoma and 8 follicular thyroid carcinoma. Serum thyrotropin was suppressed (< 2 µ IU/ml) during the Fluor-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging procedure. RESULTS: The overall sensitivity of fluor-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging in the detection of metastasis of differentiated thyroid cancer was 84.8%, the specificity 79.1%, respectively. The sensitivity and specificity of fluor-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging in classic type of papillary cancer was 83.3% and 54.5%, respectively. The corresponding figures for the tall cell variant was 85.7% and 87.5%, respectively. The difference between the two histological subtypes was statistically significant (p < 0.05). CONCLUSIONS: Our results suggest that fluor-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging could be a valuable test for the routine follow-up of patients with differentiated thyroid carcinoma.

Integrated whole body MR/PET: where are we?

Whole body integrated magnetic resonance imaging (MR)/positron emission tomography (PET) imaging systems have recently become available for clinical use and are currently being used to explore whether the combined anatomic and functional capabilities of MR imaging and the metabolic information of PET provide new insight into disease phenotypes and biology, and provide a better assessment of oncologic diseases at a lower radiation dose than a CT. This review provides an overview of the technical background of combined MR/PET systems, a discussion of the potential advantages and technical challenges of hybrid MR/PET instrumentation, as well as collection of possible solutions. Various early clinical applications of integrated MR/PET are also addressed. Finally, the workflow issues of integrated MR/PET, including maximizing diagnostic information while minimizing acquisition time are discussed.

Practice trends in patients with persistent detectable thyroglobulin and negative diagnostic radioiodine whole body scans: a survey of American Thyroid Association members.

BACKGROUND: Management of patients with thyroglobulin (Tg)-positive/scan-negative thyroid cancer remains challenging. American Thyroid Association (ATA) guidelines recommend potential use of empiric (131)I therapy and various scanning modalities, but no standard for managing such cases exists. METHODS: We surveyed ATA members to assess current practice in management of patients with Tg-positive/scan-negative disease. Members participated in a web-based survey of six case scenarios of Tg elevations but iodine scan negativity. RESULTS: A total of 288 ATA members (80% male) participated. Patient age, sex, and basal and stimulated Tg varied between the cases. Respondents were asked their opinion regarding empiric (131)I therapy use, including (131)I dose, use and duration of low-iodine diet, thyroxine withdrawal or recombinant human thyrotropin (rhTSH), and utilization of additional imaging (neck ultrasound (US) or positron emission tomography/computed tomography (PET/CT)) and reconsideration of (131)I therapy. Between 16% and 51% recommended initial use of empiric (131)I for the various scenarios. The majority chose a (131)I dose between 75 and 150 mCi, and 73% employed a low-iodine diet for two or more weeks. Preference between thyroxine withdrawal versus rhTSH was evenly split. More than 98% obtained a neck US if empiric (131)I was not given; 52-89% would proceed to PET/CT if US was negative. Only 44% used rhTSH stimulation in PET scan preparation. (131)I use was more common with stimulated Tg significantly >10 ng/mL. (131)I therapy was slightly more likely with PET-positive (56%) than PET-negative status (45%). Respondents were split regarding empiric (131)I if basal and stimulated Tg increased ≥150% over two years. Providers in North America less commonly utilized (131)I treatment than those from other areas. In the face of possible heterophilic antibody interference in the Tg assay, the majority did not recommend (131)I therapy. CONCLUSIONS: Empiric (131)I therapy is still utilized for patients with Tg-positive/scan-negative disease. Neck US is frequently used to further evaluate such cases as (18)FDG-PET/CT, albeit the latter is used somewhat less often. Use of (131)I therapy correlated with the degree of Tg elevation or development of Tg antibodies, and was recommended more commonly with PET-positive than PET-negative status in patients with lower Tg levels. (131)I was less commonly used by providers within North America.

GEP-NETS update: functional localisation and scintigraphy in neuroendocrine tumours of the gastrointestinal tract and pancreas (GEP-NETs).

For patients with neuroendocrine tumours (NETs) of the gastrointestinal tract and pancreas (GEP) (GEP-NETs), excellent care should ideally be provided by a multidisciplinary team of skilled health care professionals. In these patients, a combination of nuclear medicine imaging and conventional radiological imaging techniques is usually mandatory for primary tumour visualisation, tumour staging and evaluation of treatment. In specific cases, as in patients with occult insulinomas, sampling procedures can provide a clue as to where to localise the insulin-hypersecreting pancreatic NETs. Recent developments in these fields have led to an increase in the detection rate of primary GEP-NETs and their metastatic deposits. Radiopharmaceuticals targeted at specific tumour cell properties and processes can be used to provide sensitive and specific whole-body imaging. Functional imaging also allows for patient selection for receptor-based therapies and prediction of the efficacy of such therapies. Positron emission tomography/computed tomography (CT) and single-photon emission CT/CT are used to map functional images with anatomical localisations. As a result, tumour imaging and tumour follow-up strategies can be optimised for every individual GEP-NET patient. In some cases, functional imaging might give indications with regard to future tumour behaviour and prognosis.

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.

Non-invasive molecular imaging for preclinical cancer therapeutic development.

Molecular and non-invasive imaging are rapidly emerging fields in preclinical cancer drug discovery. This is driven by the need to develop more efficacious and safer treatments, the advent of molecular-targeted therapeutics, and the requirements to reduce and refine current preclinical in vivo models. Such bioimaging strategies include MRI, PET, single positron emission computed tomography, ultrasound, and optical approaches such as bioluminescence and fluorescence imaging. These molecular imaging modalities have several advantages over traditional screening methods, not least the ability to quantitatively monitor pharmacodynamic changes at the cellular and molecular level in living animals non-invasively in real time. This review aims to provide an overview of non-invasive molecular imaging techniques, highlighting the strengths, limitations and versatility of these approaches in preclinical cancer drug discovery and development.

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.

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.

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.

Utilization of nuclear medicine scintigraphy in Taiwan, 1997-2009.

OBJECTIVE: To analyze the utilization of nuclear medicine scintigraphy in the Taiwanese population within the national health-care system between 1997 and 2009. METHODS: Based on the Taiwan's National Health Insurance Research Database of 1997-2009, a retrospective population-based analysis was conducted. Descriptive statistics and regression analysis were employed to analyze the frequencies and longitudinal trends in the utilization of diagnostic nuclear medicine procedures during the period. In addition, correlation analysis was applied to determine the correlated factors in the utility of nuclear medicine scintigraphy. RESULTS: The annual total nuclear medicine scintigraphy was estimated to be 256,389 on average in 1997-2009 and 11.7 per 1,000 population over the period. The frequency had increased by 67% over the years, from 8.2 per 1,000 population in 1997 to 13.7 per 1,000 population in 2009. The most frequently performed procedures were whole-body bone scans (33.4% of total) and myocardial perfusion scans (29.4% of total), with 4,615 and 5,620 increments per year, respectively. Most patients were in the age group of 41-65 years old when taking examinations. In addition, male subjects were slightly more than female patients (51.5 vs. 48.5%). Furthermore, the frequencies of whole-body bone scans and PET scans were proportional to the incidences of cancers (correlation coefficients were 0.96 and 0.94, respectively). CONCLUSIONS: The utilization of nuclear medicine scintigraphy with the National Health Insurance system in Taiwan has been changed considerably in the past 13 years. Both whole-body bone scan and myocardial perfusion scan were performed most often with significantly increases. The trend of nuclear medicine scintigraphy may have potential impact on making health-care policy in Taiwan.

X-ray control of borders and of internal security.

OBJECTIVE: Security control with X-rays means exposure to ionising radiation and creates the possibility of access to personal privacy. Internal security concerns the police and secret services. The used technologies and their possibilities are described. MATERIAL AND METHOD: Observations and additional information have been collected. The exposure dose has been measured. RESULTS: Several technical set ups are in use: Transmission imaging (fluoroscopy), backscatter imaging, computed tomography and several combinations. The search of persons concerns the interior of the human body, its surface and the clothing together with the luggage. One looks for weapons, explosives and drugs. The exposure dose is low compared to the exposure dose by a flight or due to a holiday in a country with higher environmental radiation by external sources like Finland. CONCLUSION: In the future, the security control will increase. Using X-rays creates the possibility to inspect privacy.