Assessment of mediastinal shift angles in congenital pulmonary airway malformation: a new fetal magnetic resonance imaging indicator of congenital lung disease.

BACKGROUND: The mediastinal shift angle is a new fetal magnetic resonance imaging (MRI) index that is reportedly correlated with postnatal survival in fetuses with congenital diaphragmatic hernia. However, its correlation in patients with congenital pulmonary airway malformation (CPAM) has not been assessed. OBJECTIVE: This study aimed to establish a normal range for the right/left mediastinal shift angles, to evaluate the mediastinal shift angle in fetuses with CPAM, to compare the mediastinal shift angle with the CPAM volume ratio, and to evaluate the predictive value of the mediastinal shift angle measurements. MATERIALS AND METHODS: To establish the normal range, we measured the mediastinal shift angle bilaterally in 124 fetuses without any lung abnormality (the control group). Subsequently, the mediastinal shift angle was measured in 32 fetuses pathologically diagnosed with CPAM. Moreover, the mediastinal shift angle and CPAM volume ratio were compared using fetal MRI. RESULTS: The mean values for the right/left mediastinal shift angles were 18.6°/26.3° and 39.2°/35.9° for control fetuses and fetuses with CPAM, respectively. The mediastinal shift angle and the CPAM volume ratio showed a positive statistical correlation. The area under the curve demonstrated high discriminatory accuracy for the mediastinal shift angle (0.76). CONCLUSION: The mediastinal shift angle has potential to replace the CPAM volume ratio for evaluating the severity of CPAM in fetal MRI.

Machine learning-based prediction of conversion coefficients for I-123 metaiodobenzylguanidine heart-to-mediastinum ratio.

PURPOSE: We developed a method of standardizing the heart-to-mediastinal ratio in 123I-labeled meta-iodobenzylguanidine (MIBG) images using a conversion coefficient derived from a dedicated phantom. This study aimed to create a machine-learning (ML) model to estimate conversion coefficients without using a phantom. METHODS: 210 Monte Carlo (MC) simulations of 123I-MIBG images to obtain conversion coefficients using collimators that differed in terms of hole diameter, septal thickness, and length. Simulated conversion coefficients and collimator parameters were prepared as training datasets, then a gradient-boosting ML was trained to estimate conversion coefficients from collimator parameters. Conversion coefficients derived by ML were compared with those that were MC simulated and experimentally derived from 613 phantom images. RESULTS: Conversion coefficients were superior when estimated by ML compared with the classical multiple linear regression model (root mean square deviations: 0.021 and 0.059, respectively). The experimental, MC simulated, and ML-estimated conversion coefficients agreed, being, respectively, 0.54, 0.55, and 0.55 for the low-; 0.74, 0.70, and 0.72 for the low-middle; and 0.88, 0.88, and 0.88 for the medium-energy collimators. CONCLUSIONS: The ML model estimated conversion coefficients without the need for phantom experiments. This means that conversion coefficients were comparable when estimated based on collimator parameters and on experiments.

EBUS versus EUS-B for diagnosing sarcoidosis: The International Sarcoidosis Assessment (ISA) randomized clinical trial.

BACKGROUND AND OBJECTIVE: Endosonography with intrathoracic nodal sampling is proposed as the single test with the highest granuloma detection rate in suspected sarcoidosis stage I/II. However, most studies have been performed in limited geographical regions. Studies suggest that oesophageal endosonographic nodal sampling has higher diagnostic yield than endobronchial endosonographic nodal sampling, but a head-to-head comparison of both routes has never been performed. METHODS: Global (14 hospitals, nine countries, four continents) randomized clinical trial was conducted in consecutive patients with suspected sarcoidosis stage I/II presenting between May 2015 and August 2017. Using an endobronchial ultrasound (EBUS) scope, patients were randomized to EBUS or endoscopic ultrasound (EUS)-B-guided nodal sampling, and to 22- or 25-G ProCore needle aspiration (2 × 2 factorial design). Granuloma detection rate was the primary study endpoint. Final diagnosis was based on cytology/pathology outcomes and clinical/radiological follow-up at 6 months. RESULTS: A total of 358 patients were randomized: 185 patients to EBUS-transbronchial needle aspiration (EBUS-TBNA) and 173 to EUS-B-fine-needle aspiration (FNA). Final diagnosis was sarcoidosis in 306 patients (86%). Granuloma detection rate was 70% (130/185; 95% CI, 63-76) for EBUS-TBNA and 68% (118/173; 95% CI, 61-75) for EUS-B-FNA (p = 0.67). Sensitivity for diagnosing sarcoidosis was 78% (129/165; 95% CI, 71-84) for EBUS-TBNA and 82% (115/141; 95% CI, 74-87) for EUS-B-FNA (p = 0.46). There was no significant difference between the two needle types in granuloma detection rate or sensitivity. CONCLUSION: Granuloma detection rate of mediastinal/hilar nodes by endosonography in patients with suspected sarcoidosis stage I/II is high and similar for EBUS and EUS-B. These findings imply that both diagnostic tests can be safely and universally used in suspected sarcoidosis patients.

Endobronchial ultrasound-guided transbronchial needle aspiration versus mediastinoscopy for mediastinal staging of lung cancer: A systematic review of economic evaluation studies.

INTRODUCTION: The emergence of endobronchial ultrasound (EBUS) changed the approach to staging lung cancer. As a new method being incorporated, the use of EBUS may lead to a shift in clinical and costs outcomes. OBJECTIVE: The aim of this systematic review is to gather information to better understand the economic impact of implementing EBUS. METHODS: This review is reported according to the PRISMA statement and registered on PROSPERO (CRD42019107901). Search keywords were elaborated considering descriptors of terms related to the disease (lung cancer / mediastinal staging of lung cancer) and the technologies of interest (EBUS and mediastinoscopy) combined with a specific economic filter. The literature search was performed in MEDLINE, EMBASE, LILACS, Cochrane Library of Trials, Web of Science, Scopus and National Health System Economic Evaluation Database (NHS EED) of the Center for Reviews and Dissemination (CRD). Screening, selection of articles, data extraction and quality assessment were carried out by two reviewers. RESULTS: Seven hundred and seventy publications were identified through the database searches. Eight articles were included in this review. All publications are full economic evaluation studies, one cost-effectiveness, three cost-utility, and four cost-minimization analyses. The costs of strategies using EBUS-TBNA were lower than the ones using mediastinoscopy in all studies analyzed. Two of the best quality scored studies demonstrate that the mediastinoscopy strategy is dominated by the EBUS-TBNA strategy. CONCLUSION: Information gathered in the eight studies of this systematic review suggest that EBUS is cost-effective compared to mediastinoscopy for mediastinal staging of lung cancer.

Mediastinal hemangiomas: Spectrum of CT and MRI findings - retrospective case series study and systematic review of the literature.

PURPOSE: To analyze the imaging manifestations of mediastinal hemangioma (MH) by CT and MRI to aid in its successful diagnosis and preoperative evaluation. METHODS: Seventeen cases of MH diagnosed by histopathology combined with CT and MRI were retrospectively collected; and their CT and MRI features, including the lesions' site and range, shape, size, margin, density or signal, enhancement pattern, mass-cardiovascular interface, mass-pulmonary interface, and other characteristics were evaluated. RESULTS: The anterior, middle, and posterior mediastinum were involved in 13, 13, and 8 cases, respectively. The masses size varied from 20 to 233 mm. Irregular, dumbbell-like, and oval masses were found in 13, 2, and 2 cases, respectively, while with pampiniform growth in 16 cases and expansive growth in 1 case. Mixed density, homogeneous density solid masses, and heterogeneous density masses with dominant fat were found in 9, 5, and 3 cases, respectively, showing mild or significant enhancement in aortic phase while no or mild enhancement in pulmonary artery phase. Draining veins were found in 16 cases and feeding arteries in 10 cases. Phleboliths were detected in 10 cases, splenic hemangiomas in 6 cases, and left lateral-chest-wall hemangioma in 1 case. In MRI sequences, mixed signal was found on T1WI and heterogeneous hypersignal with nodular or linear hyposignal on T2WI in 5 cases, mild or significant enhancement in 4 cases, draining veins in 2 cases, and no feeding arteries or phleboliths were seen. CONCLUSION: Presence of phleboliths, pampiniform growth pattern, and aberrant draining veins are relatively specific characteristics in diagnosing MH.

Fetal MRI assessment of mediastinal shift angle in isolated left congenital diaphragmatic hernia: A new postnatal survival predictive tool?

OBJECTIVE: To quantify the mediastinal shift angle (MSA) in fetuses with isolated left congenital diaphragmatic hernia (CDH) by magnetic resonance imaging and evaluate survival. METHOD: Fetuses from singleton pregnancies with isolated left CDH were matched for gestational age with controls without thoracic malformations. For all fetuses the MSA was determined by two operators and inter-operator variability and differences between cases and controls were investigated. For all cases total fetal lung volume (TFLV) was calculated and the correlation between MSA and TFLV was assessed, and its predictive value towards survival was determined. RESULTS: Thirty-four fetuses were included as cases and 42 as controls. The mean gestational age for assessment of CDH fetuses was 32 weeks (range 27-38). Twenty-four fetuses survived until discharge and 10 did not. There was an excellent inter-operator reliability for measuring the MSA and a significant difference between MSA in cases and controls. There was an inverse correlation between MSA values and survival, a correlation between TFLV and survival and an inverse correlation between MSA and TFLV. The area under the ROC curve for MSA in predicting survival was 0.931 (95% CI 0.851-1.000). CONCLUSION: The MSA measured late in gestation correlates with postnatal survival in patients with isolated left CDH.

Development and Pilot Testing of an Assessment Tool for Performance of Invasive Mediastinal Staging.

BACKGROUND: To develop and evaluate a surgical trainee competency assessment instrument for invasive mediastinal staging, including cervical mediastinoscopy and endobronchial ultrasound (EBUS), a comprehensive instrument was developed, the Thoracic Competency Assessment Tool-Invasive Staging (TCAT-IS), using expert review and simulated and clinical pilot-testing. METHODS: Validity and reliability evidence were collected, and item analysis was performed. Initially, a 27-item instrument was developed, which underwent expert review with members of the Canadian Association of Thoracic Surgeons (n = 86) in 2014 to 2015 (response rate, 57%). TCAT-IS was refined to 29 items in 4 competency areas: preoperative, general operative, mediastinoscopy, and EBUS. Further refinements were made based on simulated use. The final version was then used to assess competency of 5 thoracic trainees performing invasive mediastinal staging in live patients. RESULTS: Participants were assessed during 20 mediastinoscopy and 8 EBUS procedures, with 47 total assessments completed. Reliability (Cronbach's alpha = 0.94), interrater reliability (κ = 0.80), and correlation with an established global competency scale (κ = 0.75) were high. The most difficult items were "set up and adjust EBUS equipment" and "identify vascular anatomy (EBUS)." Feedback questionnaires from trainees (response rate, 80%) and surgeons (response rate, 100%) were consistently positive regarding user friendliness, utility as an assessment tool, and educational benefit. Participants believed the tool "facilitated communicating feedback to the trainee with specific areas to work on." CONCLUSIONS: TCAT-IS is an effective tool for assessing competence in invasive staging and may enhance instruction. This initial test establishes early validity and reliability evidence, supporting the use of TCAT-IS in providing structured, specific, formative assessments of competency.

'Never say never': the first successful management of a type A aortic dissection in Liberia.

The West African country of Liberia ranks as one of the lowest in the world in most measures of health. The diagnosis and management of complex surgical cases such as aortic dissection is extremely challenging, for reasons ranging from lack of diagnostic imaging capabilities to the high resources required for definitive surgical intervention. We present the first known successfully managed case of aortic dissection in the country's history and with it highlight the challenges faced and a number of lessons learned that are beneficial to anyone working in resource-limited environments.

Prognosticating Outcomes in Interstitial Lung Disease by Mediastinal Lymph Node Assessment. An Observational Cohort Study with Independent Validation.

RATIONALE: Mediastinal lymph node (MLN) enlargement on chest computed tomography (CT) is prevalent in patients with interstitial lung disease (ILD) and may reflect immunologic activation and subsequent cytokine-mediated immune cell trafficking. OBJECTIVES: We aimed to determine whether MLN enlargement on chest CT predicts clinical outcomes and circulating cytokine levels in ILD. METHODS: MLN measurements were obtained from chest CT scans of patients with ILD at baseline evaluation over a 10-year period. Patients with sarcoidosis and drug toxicity-related ILD were excluded. MLN diameter and location were assessed. Plasma cytokine levels were analyzed in a subset of patients. The primary outcome was transplant-free survival (TFS). Secondary outcomes included all-cause and respiratory hospitalizations, lung function, and plasma cytokine concentrations. Cox regression was used to assess mortality risk. Outcomes were assessed in three independent ILD cohorts. MEASUREMENTS AND MAIN RESULTS: Chest CT scans were assessed in 1,094 patients (mean age, 64 yr; 52% male). MLN enlargement (≥10 mm) was present in 66% (n = 726) and strongly predicted TFS (hazard ratio [HR], 1.53; 95% confidence interval [CI], 1.12-2.10; P = 0.008) and risk of all-cause and respiratory hospitalizations (internal rate of return [IRR], 1.52; 95% CI, 1.17-1.98; P = 0.002; and IRR, 1.71; 95% CI, 1.15-2.53; P = 0.008, respectively) when compared with subjects with MLN <10 mm. Patients with MLN enlargement had lower lung function and decreased plasma concentrations of soluble CD40L (376 pg/ml vs. 505 pg/ml, P = 0.001) compared with those without MLN enlargement. Plasma IL-10 concentration >45 pg/ml predicted mortality (HR, 4.21; 95% CI, 1.21-14.68; P = 0.024). Independent analysis of external datasets confirmed these findings. CONCLUSIONS: MLN enlargement predicts TFS and hospitalization risk in ILD and is associated with decreased levels of a key circulating cytokine, soluble CD40L. Incorporating MLN and cytokine findings into current prediction models might improve ILD prognostication.

A decision tree model for predicting mediastinal lymph node metastasis in non-small cell lung cancer with F-18 FDG PET/CT.

We aimed to develop a decision tree model to improve diagnostic performance of positron emission tomography/computed tomography (PET/CT) to detect metastatic lymph nodes (LN) in non-small cell lung cancer (NSCLC). 115 patients with NSCLC were included in this study. The training dataset included 66 patients. A decision tree model was developed with 9 variables, and validated with 49 patients: short and long diameters of LNs, ratio of short and long diameters, maximum standardized uptake value (SUVmax) of LN, mean hounsfield unit, ratio of LN SUVmax and ascending aorta SUVmax (LN/AA), and ratio of LN SUVmax and superior vena cava SUVmax. A total of 301 LNs of 115 patients were evaluated in this study. Nodular calcification was applied as the initial imaging parameter, and LN SUVmax (≥3.95) was assessed as the second. LN/AA (≥2.92) was required to high LN SUVmax. Sensitivity was 50% for training dataset, and 40% for validation dataset. However, specificity was 99.28% for training dataset, and 96.23% for validation dataset. In conclusion, we have developed a new decision tree model for interpreting mediastinal LNs. All LNs with nodular calcification were benign, and LNs with high LN SUVmax and high LN/AA were metastatic Further studies are needed to incorporate subjective parameters and pathologic evaluations into a decision tree model to improve the test performance of PET/CT.

Esophageal ultrasound (EUS) assessment of T4 status in NSCLC patients.

BACKGROUND: Mediastinal and central large vessels (T4) invasion by lung cancer is often difficult to assess preoperatively due to the limited accuracy of computed tomography (CT) scan of the chest. Esophageal ultrasound (EUS) can visualize the relationship of para-esophageally located lung tumors to surrounding mediastinal structures. AIM: To assess the value of EUS for detecting mediastinal invasion (T4) of centrally located lung tumors. METHODS: Patients who underwent EUS for the diagnosis and staging of lung cancer and in whom the primary tumor was detected by EUS and who subsequently underwent surgical- pathological staging (2000-2016) were retrospectively selected from two university hospitals in The Netherlands. T status of the lung tumor was reviewed based on EUS, CT and thoracotomy findings. Surgical- pathological staging was the reference standard. RESULTS: In 426 patients, a lung malignancy was detected by EUS of which 74 subjects subsequently underwent surgical- pathological staging. 19 patients (26%) were diagnosed with stage T4 based on vascular (n=8, 42%) or mediastinal (n=8, 42%) invasion or both (n=2, 11%), one patient (5%) had vertebral involvement. Sensitivity, specificity, PPV and NPV for assessing T4 status were: for EUS (n=74); 42%, 95%, 73%, 83%, for chest CT (n=66); 76%, 61%, 41%, 88% and the combination of EUS and chest CT (both positive or negative for T4, (n=34); 83%, 100%, 100% 97%. CONCLUSION: EUS has a high specificity and NPV for the T4 assessment of lung tumors located para-esophageally and offers further value to chest CT scan.

Conventional Transbronchial Needle Aspiration: The Original Guard Who Still Has a Role in Mediastinal Lymph Node Sampling.

INTRODUCTION: Conventional transbronchial needle aspiration (C-TBNA) is the originally described method for sampling mediastinal lymph nodes (MLN). After the advent of endobronchial ultrasound, the practice and reports of C-TBNA have dwindled. We report a large series of C-TBNA from the Indian subcontinent, highlighting aspects such as pathological spectrum, yield and complications, and reiterating its relevance in MLN sampling. METHODS: The study population included 400 consecutive patients over 6.8 years who had C-TBNA done for MLN ≥1 cm in size. C-TBNA was done using a 19-G needle, with conscious sedation. A maximum of 7 passes per node were done. Rapid-on-site evaluation was done in >95% cases. Lymph nodes sampled were labeled "adequate" if lymphocytes were present, and "diagnostic" if a definitive diagnosis was made. RESULTS: The study included 228 males and 172 females, mean age 49.4±14.7 years. The "adequacy" rate was 383/400 (95.75%), and "diagnostic" yield was 347/400 (86.75%). C-TBNA was the sole diagnostic modality in 215/400 (53.75%) patients. The diagnoses included tuberculosis (43%), sarcoidosis (25.5%) and malignancy (18.25%). Complications were rare. CONCLUSIONS: This is one of the largest studies of C-TBNA in literature, and one of the few studies to define accurate pathologic diagnosis of enlarged MLN in India. This is also the one of the largest series to define the yield of TBNA with rapid-on-site evaluation in MLN sampling. Currently, in many parts of the world, C-TBNA is still the most common MLN sampling procedure, from an availability, expertise, economic, and safety perspective.

Improved assessment of mediastinal and pulmonary pathologies in combined staging CT examinations using a fast-speed acquisition dual-source CT protocol.

OBJECTIVES: To demonstrate the feasibility of fast Dual-Source CT (DSCT) and to evaluate the clinical utility in chest/abdomen/pelvis staging CT studies. METHODS: 45 cancer patients with two follow-up combined chest/abdomen/pelvis staging CT examinations (maximally ±10 kV difference in tube potential) were included. The first scan had to be performed with our standard protocol (fixed pitch 0.6), the second one using a novel fast-speed DSCT protocol (fixed pitch 1.55). Effective doses (ED) were calculated, noise measurements performed. Scan times were compared, motion artefacts and the diagnostic confidence rated in consensus reading. RESULTS: ED for the standard and fast-speed scans was 9.1 (7.0-11.1) mSv and 9.2 (7.4-12.8) mSv, respectively (P = 0.075). Image noise was comparable (abdomen; all P > 0.05) or reduced for fast-speed CTs (trachea, P = 0.001; ascending aorta, P < 0.001). Motion artefacts of the heart/the ascending aorta (all P < 0.001) and breathing artefacts (P < 0.031) were reduced in fast DSCT. The diagnostic confidence for the evaluation of mediastinal (P < 0.001) and pulmonary (P = 0.008) pathologies was improved for fast DSCT. CONCLUSIONS: Fast DSCT for chest/abdomen/pelvis staging CT examinations is performed within 2 seconds scan time and eliminates relevant intrathoracic motion/breathing artefacts. Mediastinal/pulmonary pathologies can thus be assessed with high diagnostic confidence. Abdominal image quality remains excellent. KEY POINTS: • Fast dual-source CT provides chest/abdomen/pelvis staging examinations within 2 seconds scan time. • The sevenfold scan time reduction eliminates relevant intrathoracic motion/breathing artefacts. • Mediastinal/pulmonary pathologies can now be assessed with high diagnostic confidence. • The coverage of the peripheral soft tissues is comparable to single-source CT. • Fast and large-volume oncologic DSCT can be performed with 9 mSv effective dose.

Retrospective assessment of interobserver agreement and accuracy in classifications and measurements in subsolid nodules with solid components less than 8mm: which window setting is better?

OBJECTIVES: To compare interobserver agreements among multiple readers and accuracy for the assessment of solid components in subsolid nodules between the lung and mediastinal window settings. METHODS: Seventy-seven surgically resected nodules with solid components smaller than 8 mm were included in this study. In both lung and mediastinal windows, five readers independently assessed the presence and size of solid component. Bootstrapping was used to compare the interobserver agreement between the two window settings. Imaging-pathology correlation was performed to evaluate the accuracy. RESULTS: There were no significant differences in the interobserver agreements between the two windows for both identification (lung windows, k = 0.51; mediastinal windows, k = 0.57) and measurements (lung windows, ICC = 0.70; mediastinal windows, ICC = 0.69) of solid components. The incidence of false negative results for the presence of invasive components and the median absolute difference between the solid component size and the invasive component size were significantly higher on mediastinal windows than on lung windows (P < 0.001 and P < 0.001, respectively). CONCLUSIONS: The lung window setting had a comparable reproducibility but a higher accuracy than the mediastinal window setting for nodule classifications and solid component measurements in subsolid nodules. KEY POINTS: • Reproducibility was similar between the two windows in nodule classifications. • Reproducibility was similar between the two windows in solid component measurements. • Accuracy for solid component assessment was higher on lung windows.

Assessment of Relationship Between CT Features and Serum Tumor Marker Index in Early-stage Lung Adenocarcinoma.

RATIONALE AND OBJECTIVES: The study aimed to assess the relationship between tumor marker index (TMI) and high-resolution computed tomography features in early-stage lung adenocarcinoma. MATERIALS AND METHODS: Seventy-four stage IA lung adenocarcinomas confirmed pathologically were retrospectively evaluated. Lung nodules were divided into two types: solid nodule (SN) and subsolid nodule (SSN). The maximum diameters on mediastinal window in axial imaging (Dm) and tumor shadow disappearance rate (TDR) were measured. Meanwhile, other computed tomography features of lung nodules were also recorded. TMI represents the geometric mean of normalized CEA and CYFRA 21-1 values, and the discriminatory value of TMI in this study was set at 1.0. The evaluation of discriminatory values for Dm and the TMI between SNs and SSNs was done with Mann-Whitney U-test. The relationship between TDR and TMI in SSNs was evaluated by Pearson correlation analysis. RESULTS: Of 74 cases, 40 cases (54.05%) showed SNs and 34 cases (45.95%) showed SSNs. Dm and TMI were higher in SNs than in SSNs (z = -4.782, P < 0.001; z = -2.647, P = 0.008). TDR demonstrated negative relationship with TMI in SSNs (r = -0.448, P = 0.008). Spiculation (odds ratio [OR] = 14.685; 95% confidence interval [CI]: 2.739-78.729; P = 0.002), nodule type (OR = 6.215; 95% CI: 1.531-25.228; P = 0.011), and gender (OR = 0.227; 95% CI: 0.062-0.833; P = 0.025) were independent factors associated with TMI. CONCLUSIONS: Early-stage lung adenocarcinoma with lower TDR coexisting with spiculation was associated with higher TMI, especially in patients with solid nodule, which tended to have poor prognosis.

Chemical shift and diffusion-weighted magnetic resonance imaging of the anterior mediastinum in oncology: Current clinical applications in qualitative and quantitative assessment.

Recently, the use of magnetic resonance (MR) in clinical practice for the evaluation of the anterior mediastinum has considerably increased due to technological improvements and standardization of thoracic protocols. Currently, MR imaging is increasingly seen as a useful problem-solving modality, especially in equivocal cases at computed tomography, with the advantage of a higher contrast resolution and no radiation exposure. Chemical shift and diffusion-weighted MR are helpful in tissue characterization and present advantages over conventional MR imaging, first in providing quantitative data, without the need for the administration of contrast medium. By detecting microscopic fat in tissue, chemical shift imaging is useful for differentiating normal thymus and rebound hyperplasia from cancer tissue at diagnosis and after chemotherapy in oncologic patients, and for distinguishing lymphoid hyperplasia from thymoma in autoimmune diseases such as myasthenia gravis. Diffusion-weighted MR reflects diffusivity of water molecules within tissue and is increasingly used as a cancer biomarker, even in the thorax, for the detection and characterization of tumors, for their differentiation from benign conditions, and for monitoring treatment response. In this review, based on the current literature, technical considerations about image acquisition and data analysis of chemical shift and diffusion-weighted MR are discussed along with clinical applications in the field of benign and malignant disease of the anterior mediastinum.

The assessment of time-of-flight on image quality and quantification with reduced administered activity and scan times in 18F-FDG PET.

OBJECTIVES: The last decade has seen considerable technological innovations in PET detectors with the availability, among other advances, of time-of-flight (TOF). TOF has been shown to increase the signal-to-noise ratio (SNR), which should allow for a reduction in acquired counts while maintaining image quality. METHODS: Fifty-eight patients referred for routine F-flurodeoxyglucose ((18)F-FDG) oncology PET studies were included in this study. Patients with weight below or above 100 kg were prescribed 350 or 400 MBq of (18)F-FDG, respectively. Listmode data were acquired for 2.5 min per bed position and reconstructed with ordered-subset expectation maximization (OSEM) reconstruction. TOF reconstruction was performed on reduced-count data, with two levels of reduction (-20 and -40% for patients <100 kg and -16 and -30% for patients >100 kg) achieved by clipping the listmode data. Liver SNR, mediastinum mean standardized uptake value (SUV(mean)), and lesion maximum standardized uptake value (SUV(max)) were measured in all images. All images were visually assessed as adequate or suboptimal. RESULTS: No significant difference was seen in mediastinum SUV(mean) or lesion SUV(max) when comparing reduced-count TOF with full-count OSEM images. Compared with the original OSEM images, liver SNR was higher for TOF images using the more conservative -20% reduction of counts (P < 0.001, Wilcoxon's signed-rank test), whereas no significant statistical difference was seen with -40% reductions. CONCLUSION: Incorporation of TOF allows for a reduction in acquired counts; this method has been implemented at our institution, with administered activity reduced for all patients to 280 MBq and a reduction in scan times for all but the largest patients. This has significantly reduced the patient radiation dose and improved scanner flexibility and throughput.