Integrated Positron Emission Tomography Research Articles

Prospective Evaluation of the First Integrated Positron Emission Tomography/Dual-Energy Computed Tomography System in Patients With Lung Cancer.

The aim of this pilot study was to prospectively evaluate the first integrated positron emission tomography (PET)/dual-energy computed tomography (DECT) system performance in patients with non-small cell lung cancer (NSCLC). In this single-center, prospective trial, consecutive patients with NSCLC referred for a PET study between May 2017 and June 2018 were enrolled. All patients received contrast-enhanced imaging on a clinical PET/DECT system. Data analysis included PET-based standard uptake values (SUVmax) and DECT-based iodine densities of tumor masses, lymph nodes, and distant metastases. Results were analyzed using correlation tests and receiver operating characteristics curves. The study population was composed of 21 patients (median age 62 y, 14 male patients). A moderate positive correlation was found between iodine density values (2.2 mg/mL) and SUVmax (10.5) in tumor masses (ρ=0.53, P<0.01). Iodine density values (2.3 mg/mL) and SUVmax (5.4) of lymph node metastases showed a weak positive correlation (ρ=0.23, P=0.14). In addition, iodine quantification analysis provided no added value in differentiating between pathologic and nonpathologic lymph nodes with an area under the curve (AUC) of 0.55 using PET-based SUVmax as the reference standard. A weak positive correlation was observed between iodine density (2.2 mg/mL) and SUVmax in distant metastases (14.9, ρ=0.23, P=0.52). The application of an integrated PET/DECT system in lung cancer might provide additional insights in the assessment of tumor masses. However, the added value of iodine density quantification for the evaluation of lymph nodes and distant metastases seems limited.

Non-invasive assessment of heterogeneity of gliomas using diffusion and perfusion MRI: correlation with spatially co-registered PET.

Heterogeneity of gliomas challenges the neuronavigated biopsy and oncological therapy. Diffusion and perfusion magnetic resonance imaging (MRI) can reveal the cellular and hemodynamic heterogeneity of tumors. Integrated positron emission tomography (PET)/MRI is expected to be a non-invasive imaging approach to characterizing glioma. To evaluate the value of apparent diffusion coefficient (ADC), cerebral blood volume (CBV), and spatially co-registered maximal standard uptake value (SUVmax) for tissue characterization and glioma grading. Thirty-seven consecutive patients with pathologically confirmed gliomas were retrospectively investigated. The relative minimum ADC (rADCmin), relative maximal ADC (rADCmax), relative maximal rCBV (rCBVmax), the relative minimum rCBV (rCBVmin), and the corresponding relative SUVmax (rSUVmax) were measured. The paired t-test was used to compare the quantitative parameters between different regions to clarify tumor heterogeneity. Imaging parameters between WHO grade IV and grade II/III gliomas were compared by t-test. The diagnostic efficiency of multiparametric PET/MRI was analyzed by receiver operating characteristic (ROC) curve. The values of rSUVmax were significantly different between maximal diffusion/perfusion area and minimum diffusion/perfusion area (P < 0.001/P < 0.001) within tumor. The values of rADCmin (P < 0.001), rCBVmax (P = 0.002), and corresponding rSUVmax (P = 0.001/P < 0.001) could be used for grading gliomas. The areas under the ROC curves of rSUVmax defined by rADCmin and rCBVmax were 0.89 and 0.91, respectively. Diffusion and perfusion MRI can detect glioma heterogeneity with excellent molecular imaging correlations. Regions with rCBVmax suggest tissues with the highest metabolism and malignancy for guiding glioma grading and tissue sampling.

Late Sequelae of Radiotherapy—The Effect of Technical and Conceptual Innovations in Radiation Oncology.

Approximately half of all patients with tumors need radiotherapy. Long-term survivors may suffer from late sequelae of the treatment. The existing radiotherapeutic techniques are being refined so that radiation can be applied more precisely, with the goal of limiting the radiation exposure of normal tissue and reducing late sequelae. This review is based on the findings of a selective search in PubMed for publications on late sequelae of conventional percutaneous radiotherapy, January 2000 to May 2020. Late sequelae affecting the central nervous system, lungs, and heart and the development of second tumors are presented, and radiobiological mechanisms and the relevant technical and conceptual considerations are discussed. The current standard of treatment involves the use of linear accelerators, intensity-modulated radiotherapy (IMRT), image-guided and respiratory-gated radiotherapy, and the integration of positron emission tomography combined with computed tomography (PET-CT) in radiation treatment planning. Cardiotoxicity has been reduced with regard to the risk of coronary heart disease after radiotherapy for Hodgkin's lymphoma (hazard ratio [HR] 0.44 [0.23; 0.85]). It was also found that the rate of radiation- induced pneumonitis dropped from 7.9% with conformal treatment to 3.5% with IMRT in a phase III lung cancer trial. It is hoped that neurocognitive functional impairment will be reduced by hippocampal avoidance in modern treatment planning: an initial phase III trial yielded a hazard ratio of 0.74 [0.58; 0.94]. It is estimated that 8% of second solid tumors in adults are induced by radiotherapy (3 additional tumors per 1000 patients at 10 years). Special challenges for research in this field arise from the long latency of radiation sequelae and the need for largescale, well-documented patient collectives in order to discern dose-effect relationships, and take account of cofactors, when the overall number of events is small. It is hoped that further technical and conceptual advances will be made in the areas of adaptive radiotherapy, proton and heavy-ion therapy, and personalized therapy.

Improved PET/MRI accuracy by use of static transmission source in empirically derived hardware attenuation correction

BackgroundAccurate quantification of radioactivity, measured by an integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) system, is still a challenge. One aspect of such a challenge is to correct for the hardware attenuation, such as the patient table and radio frequency (RF) resonators. For PET/MRI systems, computed tomography (CT) is commonly used to produce hardware attenuation correction (AC) maps, by converting Hounsfield units (HU) to a linear attenuation coefficients (LAC) map at the PET energy level 511 keV, using a bilinear model. The model does not address beam hardening, nor higher density materials, which can lead to inaccurate corrections.PurposeIn this study, we introduce a transmission-based (TX-based) AC technique with a static Germanium-68 (Ge-68) transmission source to generate hardware AC maps using the PET/MRI system itself, without the need for PET or medical CT scanners. The AC TX-based maps were generated for a homogeneous cylinder, made of acrylic as a validator. The technique thereafter was applied to the patient table and posterior part of an RF-phased array used in cardiovascular PET/MRI imaging. The proposed TX-based, and the CT-based, hardware maps were used in reconstructing PET images of one cardiac patient, and the results were analysed and compared.ResultsThe LAC derived by the TX-based method for the acrylic cylinder is estimated to be 0.10851 ± 0.00380 cm−1 compared to the 0.10698 ± 0.00321 cm−1 theoretical value reported in the literature. The PET photon counts were reduced by 8.7 ± 1.1% with the patient table, at the region used in cardiac scans, while the CT-based map, used for correction, over-estimated counts by 4.3 ± 1.3%. Reconstructed in vivo images using TX-based AC hardware maps have shown 4.1 ± 0.9% mean difference compared to those reconstructed images using CT-based AC.ConclusionsThe LAC of the acrylic cylinder measurements using the TX-based technique was in agreement with those in the literature confirming the validity of the technique. The over-estimation of photon counts caused by the CT-based model used for the patient table was improved by the TX-based technique. Therefore, TX-based AC of hardware using the PET/MRI system itself is possible and can produce more accurate images when compared to the CT-based hardware AC in cardiac PET images.

Recommendations for Standardizing Thorax PET-CT in Non-Human Primates by Recent Experience from Macaque Studies.

Simple SummaryWith computed tomography (CT) only anatomical information is obtained, but there is no information about function. Positron emission tomography (PET) only gives functional information about a target organ/tissue by the distribution of a specific contrast agent, a radiotracer. Combining the two imaging techniques provides synergy and they can amplify each other. In clinical practice, this combined PET–CT technique is already broadly used. For monkeys, it is increasingly used, with procedures and protocols mainly based on clinical practice. In this publication, we make recommendations about key steps towards standardization and optimization of non-human primate PET–CT (from study preparation to image interpretation).Despite the possibilities of routine clinical measures and assays on readily accessible bio-samples, it is not always essential in animals to investigate the dynamics of disease longitudinally. In this regard, minimally invasive imaging methods provide powerful tools in preclinical research. They can contribute to the ethical principle of gathering as much relevant information per animal as possible. Besides, with an obvious parallel to clinical diagnostic practice, such imaging platforms are potent and valuable instruments leading to a more refined use of animals from a welfare perspective. Non-human primates comprise highly relevant species for preclinical research to enhance our understanding of disease mechanisms and/or the development of improved prophylactic or therapeutic regimen for various human diseases. In this paper, we describe parameters that critically affect the quality of integrated positron emission tomography and computed tomography (PET–CT) in non-human primates. Lessons learned are exemplified by results from imaging experimental infectious respiratory disease in macaques; specifically tuberculosis, influenza, and SARS-CoV-2 infection. We focus on the thorax and use of 18F-fluorodeoxyglucose as a PET tracer. Recommendations are provided to guide various stages of PET–CT-supported research in non-human primates, from animal selection, scan preparation, and operation, to processing and analysis of imaging data.

Radiolabeled PET/MRI Nanoparticles for Tumor Imaging.

The development of integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanners opened a new scenario for cancer diagnosis, treatment, and follow-up. Multimodal imaging combines functional and morphological information from different modalities, which, singularly, cannot provide a comprehensive pathophysiological overview. Molecular imaging exploits multimodal imaging in order to obtain information at a biological and cellular level; in this way, it is possible to track biological pathways and discover many typical tumoral features. In this context, nanoparticle-based contrast agents (CAs) can improve probe biocompatibility and biodistribution, prolonging blood half-life to achieve specific target accumulation and non-toxicity. In addition, CAs can be simultaneously delivered with drugs or, in general, therapeutic agents gathering a dual diagnostic and therapeutic effect in order to perform cancer diagnosis and treatment simultaneous. The way for personalized medicine is not so far. Herein, we report principles, characteristics, applications, and concerns of nanoparticle (NP)-based PET/MRI CAs.

Relationship between lower lumbar spine shape and patient bone metabolic activity as characterised by 18F NaF bio-markers

Chronic lower lumbar pain has been associated with elevated bone metabolic activity in the spine. Diagnosis of bone metabolic activity is currently through integrating Positron Emission Tomography (PET) with Sodium Fluoride (18F–NaF) biomarkers. It has been reported that numerous observable pathologies including lumbar fusion, disc abnormalities and scoliosis have often been associated with increased 18F–NaF uptake. The aim of this study was to identify what features of lower lumbar shape most strongly correlate with 18F–NaF uptake. Following a principal component analysis of 23 patients who presented with lumbar pain and underwent 18F–NaF PET-CT, it was revealed that three modes interpreted as (i) sacral tilt, (ii) vertebral disc spacing and (iii) spine size were the three characteristics that described 88.7% of spine shape in our study population. 18F–NaF was described by two modes including 18F–NaF intensity and spatial variation (anterior-inferior to posterior-superior). 18F–NaF was most sensitive to sacral tilt followed by vertebral disc spacing. A predictive model derived from that spine population was able to predict 18F–NaF ‘hot-spot’ locations with 85 ± 5% accuracy and with 71 ± 3% accuracy for the 18F–NaF magnitude. These results suggest that patients reporting with lower lumbar pain and who present with increased sacral tilt profiles and/or reduced disc spacing are good candidates for further 18F–NaF PET-CT imaging, evidenced by the high association between those shape profiles and 18F–NaF uptake.

Hypoxia with 18F-fluoroerythronitroimidazole integrated positron emission tomography and computed tomography (18F-FETNIM PET/CT) in locoregionally advanced head and neck cancer: Hypoxia changes during chemoradiotherapy and impact on clinical outcome.

Hypoxia is a well-recognized biological characteristic to therapy resistance and negative prognostic factor in patients with head and neck squamous cell carcinoma (HNSCC). This study aims to investigate the changes of hypoxia measured by 18F-fluoroerythronitroimidazole (FETNIM) uptake on integrated positron emission tomography and computed tomography (PET/CT) during chemoradiotherapy and its prognostic value of clinical outcome in locoregionally advanced HNSCC.Thirty-two patients with locoregionally advanced HNSCC who received definitive treatment with concurrent chemoradiotherapy underwent FETNIM PET/CT scans before and after 5 weeks of treatment. The intensity of hypoxia using the maximum standardized uptake value (SUVmax) was evaluated both on primary lesion and metastatic lymph node (MLN). The pre-SUVmax and mid-SUVmax were defined as SUVmax on pre- and mid-FETNIM PET/CT. The local control (LC), regional control (RC), distant metastatic-free survival (DMFS), and overall survival (OS) were collected in patient follow-ups.Mid-SUVmax decreased significantly both in the primary tumor (t = 8.083, P < .001) and MLN (t = 6.808, P < .001) compared to pre-SUVmax. With a median follow-up of 54 months, the 5-year LC, RC, DMFS, and OS rates were 55%, 66.7%, 64.7%, and 55%, respectively, for all of the patients. On univariate analysis, patients with high pre-SUVmax in primary tumor had significantly worse LC (56.3% vs 87.5%, P = .046) and OS (43.8% vs 87.5%, P = .023) than other patients. Patients with high mid-SUVmax had significantly worse DMFS (50% vs 84.6%, P = .049) and OS (33.3% vs 73.1%, P = .028) than other patients. The tumor grade and mid-SUVmax were the significant predictors of OS on multivariate analysis.In this study, hypoxia in tumor significantly decreased during chemoradiotherapy. The persistent hypoxia predicted poor OS. The data provided evidence that FETNIM PET/CT could be used dynamically for selecting appropriate patients and optimal timing of hypoxia-adapted therapeutic regimens.

Prognostic value of 18F-FDG PET/MR imaging biomarkers in oesophageal squamous cell carcinoma

PurposeTo correlate the clinical stage and prognosis of oesophageal squamous cell carcinoma (SCC) using the imaging biomarkers from integrated positron emission tomography (PET)/magnetic resonance imaging (MRI). MethodsIn total, 54 consecutive patients with oesophageal SCC who receive PET/MRI scan were recruited before treatment. The imaging biomarkers used were the mean and minimal apparent diffusion coefficients (ADCmean and ADCmin), standardized uptake value (SUV), metabolic tumour volume (MTV), and total lesion glycolysis (TLG) of tumours. The correlation between each imaging biomarker and survival was investigated using the Cox proportional hazards model. ResultsADCmean was negatively correlated with SUVmax (r = −0.414, P = 0.025). ADCmin was negatively correlated with SUVmax (r = −0.423, P = 0.001) and SUVpeak (r = −0.402, P = 0.003), and was significantly lower in M1 than in M0 tumours (829.6 vs. 1069.8, P = 0.005). MTV was significantly higher in T3 + (P < 0.001), N1 + (P = 0.014) and TNM stage III + (P < 0.001) tumours. TLG was significantly higher in T3 + (P < 0.001), N1 + (P < 0.001), M1 (P = 0.045) and TNM stage III + (P < 0.001) tumours. The MTV/ADCmin ratio exhibited the highest area under the receiver operating characteristic curve (AUROC) for predicting M1 and advanced TNM stage tumours. Multivariate analysis for progression-free survival (PFS) and overall survival (OS) showed that a larger MTV/ADCmin was associated with a shorter PFS and OS (P = 0.024 and 0.046, respectively). ConclusionThe imaging biomarkers in integrated PET/MRI may predict clinical stage and survival in patients with oesophageal SCC.

Dose Reduction in Brain [18F]FDG PET/MRI: Give It Half a Chance.

Integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) offers promising tools for evaluating brain disorders, including the minimization of exposure to ionizing radiation. Considering the length of scanning time with PET/MRI systems and their high sensitivity, we assumed that the activity could be reduced by one half compared with recommended activity for brain 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET exams without degrading image quality. We retrospectively simulated the reduction of injected activity (1 vs. 2MBq/kg, [18F]FDG) in 100 patients assessed for cognitive impairment with simultaneous PET/MRI imaging. A list-mode acquisition was used to generate a 20-min image set as a reference (PETSTD) and to simulate a low-dose injection with a 10-min image (PETLD). We tested the reproducibility between PETLD and PETSTD with a blinded visual interpretation by two nuclear physicians asked to classify metabolic patterns, and a quantitative analysis conducted with regions-of-interest. Voxelwise comparisons between patients suggestive of Alzheimer's disease (AD) and frontotemporal dementia (FTD) were also conducted. The intra-operator agreement was high between the PETSTD and PETLD visual assessments for both readers (kappa 0.92 and 0.99). SUV ratios were strongly reproducible (intraclass correlation coefficient 0.95). The voxelwise and regional comparisons between AD vs. FTD metabolic profiles yielded very similar results with PETSTD and PETLD. A reduction of the [18F]FDG dose down to 1MBq/kg is possible when performing 20-min brain PET/MRI without modifying diagnostic performance and quantitative assessments. The advantage is a significant reduction in the patient effective dose, which is non-negligible in longitudinal follow-up studies and in research protocols involving healthy volunteers.

Feasibility of multiparametric imaging with PET/MR in nasopharyngeal carcinoma: A pilot study

ObjectiveThe aim of this pilot study was to explore the integrated positron emission tomography and magnetic resonance imaging scanner (PET/MR) for biological characterization of nasopharyngeal carcinoma (NPC) and potential therapeutic applications of dose painting (DP). Patients and methodsTwenty-one NPC patients with PET/MR were included in this study. Overlap of tumor volumes was analyzed on T2-weighted images (volume of interest, VOIT2), diffusion-weighted magnetic resonance imaging (VOIDWI) and 18F-fluorodeoxyglucose positron emission tomography (VOIPET). The overlap percentages of low-metabolic sub-region (cluster 1) and high-metabolic sub-region (cluster 2) in VOIPET and VOIDWI were analyzed by cluster analysis. ResultsBoth the VOIDWI and VOIPET were encompassed in the VOIT2, respectively 99.6% and 97.5%. The median tumor overlap was 94.4% (VOIDWI within VOIPET). The median overlap of cluster 2 in VOIPET and VOIDWI was 43.61% (27.67–52.66%) and 21.86%(10.47–40.89%), respectively. The median overlap of cluster 1 in VOIPET and VOIDWI was 48.03% (23.91–63.15%) and 24.40% (7.44–51.44%), respectively. Separation between clusters appeared to be defined by a SUV value. ConclusionFor NPC, the VOIs of DWI and FDG PET were not overlapped completely and the volume defined by cluster-analysis might be meaningful for DP.

Rigid-body motion correction in hybrid PET/MRI using spherical navigator echoes

Integrated positron emission tomography and magnetic resonance imaging (PET/MRI) is an imaging technology that provides complementary anatomical and functional information for medical diagnostics. Both PET and MRI are highly susceptible to motion artifacts due, in part, to long acquisition times. The simultaneous acquisition of the two modalities presents the opportunity to use MRI navigator techniques for motion correction of both PET and MRI data. For this task, we propose spherical navigator echoes (SNAVs)—3D k-space navigators that can accurately and rapidly measure rigid body motion in all six degrees of freedom.SNAVs were incorporated into turbo FLASH (tfl)—a product fast gradient echo sequence—to create the tfl-SNAV pulse sequence. Acquiring in vivo brain images from a healthy volunteer with both sequences first compared the tfl-SNAV and product tfl sequences. It was observed that incorporation of the SNAVs into the image sequence did not have any detrimental impact on the image quality.The SNAV motion correction technique was evaluated using an anthropomorphic brain phantom. Following a stationary reference image where the tfl-SNAV sequence was acquired along with simultaneous list-mode PET, three identical PET/MRI scans were performed where the phantom was moved several times throughout each acquisition. This motion—up to 11° and 14 mm—resulted in motion artifacts in both PET and MR images. Following SNAV motion correction of the MRI and PET list-mode data, artifact reduction was achieved for both the PET and MR images in all three motion trials. The corrected images have improved image quality and are quantitatively more similar to the ground truth reference images.

Utility of 18F-Fluorocholine (FCH) PET/CT to Optimize Treatment Strategy and Radiation Therapy (RT) Planning in Patients with Biochemical Recurrence (BCR) of Prostate Cancer (PCa)

RT is a main component in PCa therapy. After radical prostatectomy (RP), a rising PSA indicates PCa recurrence that may be cured with salvage radiotherapy (SRT). To maximize chances for cure, irradiated volumes should completely encompass the extent of disease. Thus, accurate estimation of disease extension is critical for RT planning in salvage setting. Integration of Positron Emission Tomography (PET) into routine evaluation of PCa patients (pts) may improve both staging accuracy and RT planning. 18F-fluorodeoxyglucose PET/CT is routinely used in radiation planning for several cancers. Additional PET probes, such as FCH, appear to be sensitive and specific in PCa. The objective of this study is to: (i) map the recurrence pattern of early BCR after RP, using FCH-PET/CT; (ii) determine how often volume definition decided prior PET/CT had to be modified to include pelvic and extra-pelvic diseases; (iii) assess the potential impact of FCH-PET/CT on SRT dose modification delivered to the site of recurrence. This study included 51 pts between 2011 and 2016. Median age was 62 (50-77) years. RP used robotic technology in 32 (62%) pts. All patients underwent FCH-PET/CT in a single institution before SRT at the time of BCR with PSA levels >/=0.16 ng/ml. Indications and RT volumes were systematically discussed in the multidisciplinary board meeting. The first definition of the CTV included either the prostate bed (PB) alone or PB + pelvic lymph nodes contoured on the simulation CT-scan dataset by a radiation oncologist blinded to the PET/CT results. PET/CT images were analyzed jointly by a nuclear medicine physician and radiation oncologist. FCH-positive lesions not covered by planning volumes based on the blinded CTV were considered to have a major potential impact on treatment planning. After RP, 9 (17%) pts had T3, Gleason >7 or N+. Median PSA at time of FCH-PET/CT was 1.4 (0.16-37) ng/mL. 19 of 51 (37%) pts had a positive FCH-PET/CT at BCR. The detection rate of FCH uptake was significantly higher in pts with PSA≥0.5ng/mL than in those with PSA <0.5ng/mL (p<0.008). Among the 19 pts with positive FCH-PET/CT, 9 (47%) had at least one metastatic site not covered by the blinded CTV, 6 (31%) had extra-pelvic lesions while 5 (26%) had FCH-positive lesions within the pelvis but not covered by the blinded CTV. The two most common FCH-positive lesion locations outside the blinded CTV were bone (26%) and perirectal lymph nodes (37%). The rate of total RT volume changes was 13/19 (68%). Finally, 2 (10.5%) pts had PB uptake that needed an increased SRT dose up to 70Gy. We confirm that FCH-PET/CT can allow better lesions mapping at the time of BCR. At least one-third of the patients had positive FCH-PET/CT with a trend of significance after a PSA level of 0.5ng/mL. When metastatic disease is detected, FCH uptake changed SRT planning in more than 2/3 of patients. Further investigations and longer follow-up are needed to assess the impact of these changes on outcome.

Development of a bias field-based uniformity correction in magnetic resonance imaging with various standard pulse sequences

To avoid artifacts and interpretation mistakes, improvements in the uniformity of magnetic resonance imaging (MRI) is very important. The aim of this study is to develop a bias field-based uniformity correction algorithm and to confirm the feasibility of its application with an integrated positron emission tomography (PET)/MRI system using standard MRI pulse sequences (T2-weighted, half-Fourier, single-shot turbo spin echo, T2-weighted turbo spin echo with fat suppression, and three-dimensional, volumetric, T1-weighted gradient recalled echo interpolated breath-hold examination using controlled aliasing in parallel imaging that results in increased acceleration). We used phantoms containing NaCl and NaCl + NiSO4 solutions, and considered the percent image uniformity (PIU) as the evaluation parameter. The elicited PIU results using the correction algorithm were distinct for all sequences and phantoms. The results of this study suggested that the bias field-based algorithm allows uniformity improvements in MRI in terms of PIU.

Palliative esophagectomy in unexpected metastatic disease: sense or nonsense?

Background Despite integrated positron emission tomography and computed tomography screening before and after neoadjuvant treatment in patients with locally advanced esophageal cancer, unexpected metastatic disease is still found in some patients during surgery. Should then esophagectomy be aborted or is there a place for palliative resection? Methods Between 2002 and 2015, 681 patients with potentially resectable esophageal cancer were sheduled for neoadjuvant therapy and subsequent esophagectomy. In 552 patients, a potentially curative esophagectomy was performed. In 12 patients, unexpected disease was discovered during surgery but esophagectomy was performed with synchronous resection of metastases; 10 of them had oligometastatic disease (≤4 single-organ metastases). Esophagectomy was not performed in 117 patients (because of disease progression in 50); 14 were also single-organ oligometastatic. Data of 10 single-organ oligometastatic patients who underwent esophageal resection (group 1) were compared those of 10 non-resected but treated counterparts (group 2) and with 228 patients who underwent potentially curative esophagectomy with persistent pathological lymph nodes (group 3). Results Five oligometastatic esophagectomy patients had lung metastases: 1 peritoneal, 2 adrenal, 1 pleural, and 1 pancreatic. Two oligometastatic non-resected patients had lung, 5 liver, and 3 brain metastases. Median overall survival was 21.4, 12.1, and 20.2 months in the respective groups (group 1 vs. group 2 p = 0.042; group 2 vs. group 3 p = 0.002; group 1 vs. group 3 p = 0.88). Conclusions Survival is longer in patients undergoing palliative esophagectomy with unexpected single-organ oligometastatic disease and comparable to survival in patients with persistent pathological lymph nodes. Palliative resection in these patients seems to be justified.

Rationale and design of a prospective study on the first integrated PET/dual-energy CT system for staging and image-based radiation therapy planning of lung cancer

BackgroundThe aim of this prospective study is to investigate the diagnostic performance of integrated positron emission tomography (PET) /dual-energy computed tomography (DECT) imaging in determining the thoracic nodal status of patients with small-cell lung cancer (SCLC) or non-small-cell lung cancer (NSCLC) and the resulting impact on target volume delineation for radiation therapy planning.MethodsThis is a single-center prospective study including approximately 50 patients with suspected or confirmed SCLC or NSCLC, referred for a PET study. All patients will be examined on a clinical PET/DECT system, where a dual-energy detector was recently installed. The patient will be placed in the system 70 min after the administration of 5 MBq/kg of 18F-fluorodeoxyglucose (18F-FDG). Then, DECT will be acquired after the injection of 100 mL of iodine contrast medium. A PET scan will be acquired from the top of the skull through the inguinal region. Data analysis will be performed on the PET, CT, and iodine map datasets. Information regarding tumor detection, adenopathies, and radiation therapy planning will be assessed based on all three sets of images by two experienced radiologists.ConclusionThe results will add insights into the advantages of using PET/DECT for lung cancer staging and for image-guided radiation therapy.Trial registrationClinicalTrials.gov, NCT03146117. Registered on 9 May 2017.

MR Performance in the Presence of a Radio Frequency-Penetrable Positron Emission Tomography (PET) Insert for Simultaneous PET/MRI.

Despite the great promise of integrated positron emission tomography (PET)/magnetic resonance (MR) imaging to add molecular information to anatomical and functional MR, its potential impact in medicine is diminished by a very high cost, limiting its dissemination. An RF-penetrable PET ring that can be inserted into any existing MR system has been developed to address this issue. Employing optical signal transmission along with battery power enables the PET ring insert to electrically float with respect to the MR system. Then, inter-modular gaps of the PET ring allow the RF transmit field from the standard built-in body coil to penetrate into the PET fields-of-view (FOV) with some attenuation that can be compensated for. MR performance, including RF noise, magnetic susceptibility, RF penetrability through and $B_{1}$ uniformity within the PET insert, and MR image quality, were analyzed with and without the PET ring present. The simulated and experimentally measured RF field attenuation factors with the PET ring present were -2.7 and -3.2 dB, respectively. The magnetic susceptibility effect (0.063 ppm) and noise emitted from the PET ring in the MR receive channel were insignificant. $B_{1}$ homogeneity of a spherical agar phantom within the PET ring FOV dropped by 8.4% and MR image SNR was reduced by 3.5 and 4.3 dB with the PET present for gradient-recalled echo and fast-spin echo, respectively. This paper demonstrates, for the first time, an RF-penetrable PET insert comprising a full ring of operating detectors that achieves simultaneous PET/MR using the standard built-in body coil as the RF transmitter.

Role of PET/MRI in oral cavity and oropharyngeal cancers based on the 8th edition of the AJCC cancer staging system: a pictorial essay.

The American Joint Committee on Cancer (AJCC) released the 8th edition of the AJCC cancer staging manual in 2017 that includes significant modifications from the 7th edition in the sections on oral cavity cancer (OCC) and oropharyngeal cancer (OPC). These highlights comprise the incorporation of the depth of invasion and exclusion of extrinsic tongue muscle involvement in the T staging of OCC, the separation of OPC staging based on the high-risk human papilloma virus status, and the inclusion of extranodal extension in N staging. The recent introduction of integrated positron emission tomography and magnetic resonance imaging (PET/MRI) with 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) has demonstrated the advantages of simultaneous PET and MR imaging with higher soft-tissue contrast, multiplanar image acquisition, and functional imaging capability. This pictorial essay discusses the role of 18F-FDG PET/MRI in the diagnosis of OCC and OPC based on the new cancer staging system.

Low cortical iron and high entorhinal cortex volume promote cognitive functioning in the oldest-old

The aging brain is characterized by an increased presence of neurodegenerative and vascular pathologies. However, there is substantial variation regarding the relationship between an individual's pathological burden and resulting cognitive impairment. To identify correlates of preserved cognitive functioning at highest age, the relationship between β-amyloid plaque load, presence of small vessel cerebrovascular disease (SVCD), iron-burden, and brain atrophy was investigated. Eighty cognitively unimpaired participants (44 oldest-old, aged 85–96 years; 36 younger-old, aged 55–80 years) were scanned by integrated positron emission tomography–magnetic resonance imaging for assessing beta regional amyloid plaque load (18F-flutemetamol), white matter hyperintensities as an indicator of SVCD (fluid-attenuated inversion recovery–magnetic resonance imaging), and iron load (quantitative susceptibility mapping). For the oldest-old group, lower cortical volume, increased β-amyloid plaque load, prevalence of SVCD, and lower cognitive performance in the normal range were found. However, compared to normal-old, cortical iron burden was lower in the oldest-old. Moreover, only in the oldest-old, entorhinal cortex volume positively correlated with β-amyloid plaque load. Our data thus indicate that the co-occurrence of aging-associated neuropathologies with reduced quantitative susceptibility mapping measures of cortical iron load constitutes a lower vulnerability to cognitive loss.

Whole-Body Imaging of Tissue-specific Insulin Sensitivity and Body Composition by Using an Integrated PET/MR System: A Feasibility Study.

Purpose To develop, evaluate, and demonstrate the feasibility of a whole-body protocol for simultaneous assessment of tissue-specific insulin-mediated fluorine 18 (18F) fluorodeoxyglucose (FDG) influx rates, tissue depots, and whole-body insulin sensitivity (referred to as the M value). Materials and Methods An integrated positron emission tomography (PET)/magnetic resonance (MR) imaging system combined with hyperinsulinemic euglycemic clamp (HEC) was used. Dynamic whole-body PET imaging was used to determine the insulin-mediated 18F-FDG tissue influx rate (Ki) in the whole-body region by using the Patlak method. M value was determined with the HEC method at PET imaging. Tissue depots were quantified by using water-fat separated MR imaging and manual segmentations. Feasibility of the imaging protocol was demonstrated by using five healthy control participants and five patients with type 2 diabetes. Associations between M value and Ki were studied in multiple tissues by using the Pearson correlation. Results Positive correlations were found between M value and Ki in multiple tissues: the gluteus muscle (r = 0.875; P = .001), thigh muscle (r = 0.903; P , .001), calf muscle (r = 0.825; P = .003), and abdominal visceral adipose tissue (r = 0.820; P = .004). A negative correlation was found in the brain (r = 20.798; P = .006). The MR imaging-based method for quantification of tissue depots was feasible for determining adipose tissue volumes and fat fractions. Conclusion This PET/MR imaging protocol may be feasible for simultaneous assessment of tissue-specific insulin-mediated 18F-FDG influx rates, tissue depots, and M value. © RSNA, 2017 Online supplemental material is available for this article.