Paul Summers

Purpose: Short echo time (shTE) turbo-spin echo (TSE) pulse sequences are considered very weakly sensitive to blood oxygenation level dependent (BOLD) signal changes, and have been proposed to avoid cancellation of functional responses in blood nulled vascular space occupancy (VASO) fMRI studies where task-related increases in blood volume lead to decreases in signal (1,2). A positive functional contrast in shTE TSE studies has, however, been reported by some authors and attributed to changes in extravascular water distribution termed SEEP (3). Our purpose was to determine whether functional contrast in shTE TSE-based VASO experiments might be contaminated by BOLD or SEEP effects.

The number of functional magnetic resonance imaging (fMRI) studies performed on the human spinal cord (SC) has considerably increased in recent years. The lack of a validated processing pipeline is, however, a significant obstacle to the spread of SC fMRI. One component likely to be involved in any such pipeline is the process of SC masking, analogous to brain extraction in cerebral fMRI. In general, SC masking has been performed manually, with the incumbent costs of being very time consuming and operator dependent. To overcome these drawbacks, we have developed a tailored semiautomatic method for segmenting echoplanar images (EPI) of human spine that is able to identify the spinal canal and the SC. The method exploits both temporal and spatial features of the EPI series and was tested and optimized on EPI images of cervical spine acquired at 3 T. The dependence of algorithm performance on the degree of EPI image distortion was assessed by computing the displacement warping field that best matched the EPI to the corresponding high-resolution T(2) images. Segmentation accuracy was above 80%, a significant improvement over values obtained with similar approaches, but not exploiting temporal information. Geometric distortion was found to explain about 50% of the variance of algorithm classification efficiency.

Introduction: Functional vascular occupancy imaging has demonstrated task correlated MR signal changes using inversion recovery (IR) prepared images, where the inversion time (TI) has been chosen to selectively null blood (vascular space occupancy \u2013 VASO, (Lu et al., 2003)), grey matter (VASO by tissue suppression \u2013 VAST (Wu et al., 2008)), or CSF (VASO-FLAIR (Donahue et al., 2006)). Weakness of these approaches are that functional responses may not be due to volume changes in a single tissue compartment, and that the underlying imaging sequence may be sensitive to other mechanisms (e.g. BOLD) (Donahue et al., 2006). Our purpose was to compare the functional responses from different vascular space occupancy preparations of a short TE turbo-spin echo (TSE) sequence. Methods: Eight healthy subjects were scanned at 3T after providing informed consent. The task consisted of self-paced, left-hand finger tapping. Four variants of vascular occupancy fMRI were tested: VASO (TI = 646ms), VAST (TI = 578ms), VASO-FLAIR (TI = 781ms) and nonInVASO (no inversion pulse VASO), all based on a 3D TSE acquisition (TE/TR 8.4ms/2.4s, 4 shots, time per volume 9.6s, 1.5x1.5x1.5mm, 8 slices, FOV 222x60x12mm, 180\ub0 refocusing pulses, ant/post sat bands). Task blocks were 48s long, and each run consisted of 45 volumes, with the sequence order varied between subjects. These scans were centered on the focus of BOLD response in/adjacent to the right hand knob detected with an EPI acquisition (TE/TR 30ms/3s, 3x3x3mm, 42 slices) performed during execution of the same task (30 second blocks, 70 volumes). Whole-brain T2, 3D T1, and nonInVASO images were also obtained. GLM analysis (1.5mm FWHM smoothing, high pass filter cut-off 100s, default gamma-variate hrf, GRF-based voxel-wise corrected p<0.05) was per formed following motion correction and ICA denoising (4 components) using fsl (v 5.0.1). Due to slight rotations during acquisition, only 6 slices were retained for analysis. Results: Despite operator confirmation of task performance, one subject showed minimal BOLD and no significant vascular occupancy responses, and was therefore excluded from analysis. In the other subjects, VASO, VAST and VASO-FLAIR showed nearly identical patterns and locations of activity (Figure 1) and no significant differences in the grey matter (GM), white matter, CSF distribution of activated voxels. The nonInVASO scans showed smaller volumes of activity. GM was the predominant site of response for all scans. VAST yielded the highest % signal changes; VASO yielded the highest z-score followed closely by VASO-FLAIR; and these all had signal changes negatively correlated with the task. The nonInVASO responses correlated positively with the task and were the smallest % signal change and maximum z-scores roughly one-third lower than VASO. Significant oppositely-signed responses (i.e. positive of VASO, VAST and VASO-FLAIR, negative for nonInVASO) were not observed.Conclusions: Our results suggest that VASO, VAST and VASO-FLAIR are sensitive to volume changes in the same tissue compartment. VAST yielded the highest % signal changes due mainly to the smallest baseline signal but this did not result in greater sensitivity to activation as indicated by maximum z-scores. The negative VAST response however, suggests that the inversion was not fully optimized to grey matter but could reflect T2 blurring of white matter signal. VASO was the most sensitive to activation followed closely by VASO-FLAIR. Similarly located activations were seen with nonInVASO, but with smaller spatial extents and lower sensitivity. The implications and operative mechanism for the nonInVASO functional contrast remain to be established. Possible mechanisms include BOLD contrast (through T2 sensitivity or blurring by the long TSE echo train), vascular space occupancy changes coupled with inherent blood-tissue contrast, diffusion, or changes within the tissue compartment as proposed for SEEP - signal enhancement by extravascular protons (Stroman et al, 2003)

This review provides a formal overview of current automatic segmentation studies that use deep learning in radiotherapy. It covers 807 published papers and includes multiple cancer sites, image types (CT/MRI/PET), and segmentation methods. We collect key statistics about the papers to uncover commonalities, trends, and methods, and identify areas where more research might be needed. Moreover, we analyzed the corpus by posing explicit questions aimed at providing high-quality and actionable insights, including: “What should researchers think about when starting a segmentation study?”, “How can research practices in medical image segmentation be improved?”, “What is missing from the current corpus?”, and more. This allowed us to provide practical guidelines on how to conduct a good segmentation study in today’s competitive environment that will be useful for future research within the field, regardless of the specific radiotherapeutic subfield. To aid in our analysis, we used the larg...

Background Contouring of anatomical regions is a crucial step in the medical workflow and is both time-consuming and prone to intra- and inter-observer variability. This study compares different strategies for automatic segmentation of the prostate in T2-weighted MRIs. Methods This study included 100 patients diagnosed with prostate adenocarcinoma who had undergone multi-parametric MRI and prostatectomy. From the T2-weighted MR images, ground truth segmentation masks were established by consensus from two expert radiologists. The prostate was then automatically contoured with six different methods: (1) a multi-atlas algorithm, (2) a proprietary algorithm in the Syngo.Via medical imaging software, and four deep learning models: (3) a V-net trained from scratch, (4) a pre-trained 2D U-net, (5) a GAN extension of the 2D U-net, and (6) a segmentation-adapted EfficientDet architecture. The resulting segmentations were compared and scored against the ground truth masks with one 70/30 and ...

Objective Deploying an automatic segmentation model in practice should require rigorous quality assurance (QA) and continuous monitoring of the model’s use and performance, particularly in high-stakes scenarios such as healthcare. Currently, however, tools to assist with QA for such models are not available to AI researchers. In this work, we build a deep learning model that estimates the quality of automatically generated contours. Methods The model was trained to predict the segmentation quality by outputting an estimate of the Dice similarity coefficient given an image contour pair as input. Our dataset contained 60 axial T2-weighted MRI images of prostates with ground truth segmentations along with 80 automatically generated segmentation masks. The model we used was a 3D version of the EfficientDet architecture with a custom regression head. For validation, we used a fivefold cross-validation. To counteract the limitation of the small dataset, we used an extensive data augmentat...

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. Parameters of microstructural abnormalities derived from diffusion tensor imaging(DTI) have been reported to be helpful in differentiating between Left and Right TLE (L-TLE and R-TLE) but few of them compared L-TLE and R-TLE with a voxelwise approach. In this study, a whole brain tract based spatial statistical analysis was performed on DTI, diffusion kurtosis and NODDI derived parameters of 88 subjects to identify specific white matter patterns of alteration in patient affected by L-TLE and R-TLE with respect to healthy controls. Our findings demonstrated the presence of specific patterns of white matter alterations, with L-TLE more widely affected both in cerebral and cerebellar regions. This result supports the need to consider patients separately, according to the side of their pathology.

Background The METastasis Reporting and Data System for Prostate Cancer (MET-RADS-P) guidelines are designed to enable reproducible assessment in detecting and quantifying metastatic disease response using whole-body magnetic resonance imaging (WB-MRI) in patients with advanced prostate cancer (APC). The purpose of our study was to evaluate the inter-observer agreement of WB-MRI examination reports produced by readers of different expertise when using the MET-RADS-P guidelines. Methods Fifty consecutive paired WB-MRI examinations, performed from December 2016 to February 2018 on 31 patients, were retrospectively examined to compare reports by a Senior Radiologist (9 years of experience in WB-MRI) and Resident Radiologist (after a 6-months training) using MET-RADS-P guidelines, for detection and for primary/dominant and secondary response assessment categories (RAC) scores assigned to metastatic disease in 14 body regions. Inter-observer agreement regarding RAC score was evaluated fo...

Background The number of studies describing the use of whole-body magnetic resonance imaging (WB-MRI) for screening of malignant tumours in asymptomatic subjects is increasing. Our aim is to review the methodologies used and the results of the published studies on per patient and per lesion analysis, and to provide recommendations on the use of WB-MRI for cancer screening. Main body We identified 12 studies, encompassing 6214 WB-MRI examinations, which provided the rates of abnormal findings and findings suspicious for cancer in asymptomatic subjects, from the general population. Eleven of 12 studies provided imaging protocols that included T1- and T2-weighted sequences, while only five included diffusion weighted imaging (DWI) of the whole body. Different categorical systems were used for the classification and the management of abnormal findings. Of 17,961 abnormal findings reported, 91% were benign, while 9% were oncologically relevant, requiring further investigations, and 0.5% ...

Functional Magnetic Resonance Imaging (fMRI) based on Blood Oxygenation Level Dependent (BOLD) contrast has become one of the most powerful tools in neuroscience research. On the other hand, fMRI approaches have seen limited use in the study of spinal cord and subcortical brain regions (such as the brainstem and portions of the diencephalon). Indeed obtaining good BOLD signal in these areas still represents a technical and scientific challenge, due to poor control of physiological noise and to a limited overall quality of the functional series. A solution can be found in the combination of optimized experimental procedures at acquisition stage, and well-adapted artifact mitigation procedures in the data processing. In this framework, we studied two different data processing strategies to reduce physiological noise in cortical and subcortical brain regions and in the spinal cord, based on the aCompCor and RETROICOR denoising tools respectively. The study, performed in healthy subjects, was carried out using an ad hoc isometric motor task. We observed an increased signal to noise ratio in the denoised functional time series in the spinal cord and in the subcortical brain region.

Vascular space occupancy (VASO) is a magnetic resonance imaging technique sensitive to cerebral blood volume, and is a potential alternative to the blood oxygenation level dependent (BOLD) sensitive technique as a basis for functional mapping of the neurovascular response to a task. Many implementations of VASO have made use of echo-planar imaging strategies that allow rapid acquisition, but risk introducing potentially confounding BOLD effects. Recently, multi-slice and 3D VASO techniques have been implemented to increase the imaging volume beyond the single slice of early reports. These techniques usually rely, however, on advanced scanner software or hardware not yet available in many centers. In the present study, we have implemented a short-echo time, multi-shot 3D Turbo Spin-Echo (TSE) VASO sequence that provided 8-slice coverage on a routine clinical scanner. The proposed VASO sequence was tested in assessing the response of the human motor cortex during a block design finger tapping task in 10 healthy subjects. Significant VASO responses, inversely correlated with the task, were found at both individual and group level. The location and extent of VASO responses were in close correspondence to those observed using a conventional BOLD acquisition in the same subjects. Although the spatial coverage and temporal resolution achieved were limited, robust and consistent VASO responses were observed. The use of a susceptibility insensitive volumetric TSE VASO sequence may have advantages in locations where conventional BOLD and echo-planar based VASO imaging is compromised.

This study was undertaken to assess whether there is a correlation between the response of cervical tumours to nonsurgical therapy (chemo- and/or radiotherapy) and apparent diffusion coefficient (ADC) values. Seventeen consecutive patients prospectively underwent pelvic magnetic resonance (MR) imaging including diffusion-weighted imaging (DWI) sequences before and after nonsurgical therapy for cervical cancer. A control group of 17 patients without cervical pathology was matched to the study group. Differences in baseline ADC maps between the two groups and within the study group before and after therapy were assessed by nonparametric tests. The diameter and volume of cervical cancers decreased after therapy in 14/17 lesions (responders) and increased in 3/17 lesions (nonresponders). The ADC values of responders increased significantly (p=0.0009). Percent changes in ADC values before and after therapy were higher in responders than nonresponders (p=0.04). There was no significant difference in ADC values between responders and nonresponders at the staging MR examination (p=0.09) and no significant correlation between pretreatment ADC values and percentage of tumour reduction. Tumours with higher percent ADC value increase showed higher tumour reduction volume, but this was not significant (p=0.12). ADC values of cervical cancer after therapy showed significant differences compared with pretherapy values, particularly for responders.

To prospectively assess whether choline levels and Apparent Diffusion Coefficient (ADC) values within cervical cancers before, during, and after non-surgical therapy are predictive of tumour response. Patients undergoing MR examination for staging of cervical cancer, candidate for non-surgical therapy, were prospectively enrolled. According to the status at the end of therapies, patients were divided into responders and non-responders. The final outcome after a 5-year follow-up was classified as No Evidence of Disease (NED) or Progression of Disease (PD). Baseline values of mean ADC and Cho/H2O were compared between responders and non-responders, as well as between patients with NED and PD. The percent variation of ADC and Cho/H2O values over time was compared. P values <0.05 were considered significant. 16 patients were included. There was no significant difference at baseline between responders (n = 12) and non-responders (n = 4), nor between NED (n = 11) PD patients (n = 5), i...

Cancer affects a significant percentage of people, and early detection techniques are important for prompt and effective treatment. The use of microwave frequencies to achieve non-invasive and non-destructive cancer detections is currently under investigation by several research groups. In this frequency range, the dielectric properties of the biological tissue determine the interactions of the tissue with electromagnetic fields. Knowledge of the dielectric properties of both the normal and the malignant human tissues is therefore a fundamental starting point. A dielectric spectroscopy system, based on the use of a reflectometry setup, was used to perform an extensive experimental campaign on fresh surgical specimens. The measurement system allowed achieving a broadband dielectric characterisation of biological tissues up to 50 GHz, thus including millmetre-wave (mm-wave) frequencies. In the case of breast tissues, the results showed that the malignant and normal tissues exhibit significantly different complex dielectric permittivities of up to 50 GHz, due to their respective high and low water content. This permittivity difference is well detectable, and this paves the way to new screening methods based on mm-wave imaging systems.

Background and Purpose— According to the International Study of Unruptured Intracranial Aneurysms (ISUIA), anterior circulation (AC) aneurysms of <7 mm in diameter have a minimal risk of rupture. It is general experience, however, that anterior communicating artery (AcoA) aneurysms are frequent and mostly rupture at <7 mm. The aim of the study was to assess whether AcoA aneurysms behave differently from other AC aneurysms. Methods— Information about 932 patients newly diagnosed with intracranial aneurysms between November 1, 2006, and March 31, 2012, including aneurysm status at diagnosis, its location, size, and risk factors, was collected during the multicenter @neurIST project. For each location or location and size subgroup, the odds ratio (OR) of aneurysms being ruptured at diagnosis was calculated. Results— The OR for aneurysms to be discovered ruptured was significantly higher for AcoA (OR, 3.5 [95% confidence interval, 2.6–4.5]) and posterior circulation (OR, 2.6 [95% ...

This paper presents the preliminary design of a mm-wave ultra-wideband (UWB) radar for breast cancer detection. A mass screening of women for breast cancer is essential, as the early diagnosis of the tumour allows best treatment outcomes. A mm-wave UWB radar could be an innovative solution to achieve the high imaging resolution required without risks for the patient. The 20–40 GHz frequency band used in the system proposed in this work guarantees high cross/range resolution performances. The developed preliminary architecture employs two monomodal truncated double-ridge waveguides that act as antennas; these radiators are shifted by microstep actuators to form a synthetic linear aperture. The minimum antenna-to-antenna distance achievable, the width of the synthetic aperture, and the minimum frequency step determine the performance of the 2D imaging system. Measures are performed with a mm-wave vector network analyzer driven by an automatic routine, which controls also the antennas ...

Background Duplex ultrasonography and magnetic resonance angiography (MRA) are becoming competitive alternatives to angiography for determining the degree of internal carotid artery (ICA) stenosis. Varying reports have been published regarding the suitability of each technique for grading ICA disease. This retrospective study compared the merits of these three modalities for measuring ICA stenosis. Methods One hundred and eleven patients being considered for carotid endarterectomy underwent intra-arterial digital subtraction angiography (DSA) via arch injection. Duplex imaging was performed in all patients and MRA in 50. The degree of carotid stenosis estimated by the three modalities was compared. Results There was good correlation between subjectively graded MRA and DSA images (r = 0·87, P < 0·001, n = 82 carotids) but poor correlation for objective estimates. MRA tended to underestimate the degree of stenosis (bias – 4·5 per cent) compared with DSA, but showed good correlation...

Methods for visualising and analysing MR phase images that depict motional properties of blood or molecular diffusion in a way that meets the needs of the expert users has been a topic of intense study in recent years e.g., [2, 3]. The clinical attraction of phase contrast imaging has been its ability to depict flowing blood whereas diffusion imaging is associated both with delineating strokes and identifying patterns or pathways of connectivity within the brain. There are similarities in the pre and post-operative questions asked by experts for these two types of MR images, e.g. does a particular vessel feed or drain a given region or what are the terminal connections of a neuronal tract, and what is the flow pattern in a given region or what is the connectivity of a cortical region. We have developed a graphical tool, Angiotool [1], that attempts to meet some of the requirements of clinical experts by providing a set of low-level and semi-automated visualisation and analysis tools...

This study aimed to identify the main factors that asymptomatic individuals considered when deciding to undergo self-referred Whole-body MRI (WB-MRI) for early cancer diagnosis and the subjective values attributed to each mentioned factor in a Decision tree analysis. Personal characteristics such as risk perception and personality were investigated as possible factors affecting value attribution. Seventy-four volunteers (mean age 56.4; male = 47) filled a simplified decision tree by expressing the expected factors and related subjective values associated with two screening options for early cancer diagnosis (standard procedures vs. WB-MRI+standard procedures) while waiting for a WB-MRI examination. Questionnaires on risk perception and personality traits were also administered. Expected factors were summarized in 5 clusters: diagnostic certainty, psychological well-being, safety, test validity and time/cost. Test validity and time/cost were evaluated as potential losses in both proc...

Whole-body magnetic resonance imaging (WB-MRI) is an imaging method without ionising radiation that can provide WB coverage with a core protocol of essential imaging contrasts in less than 40 minutes, and it can be complemented with sequences to evaluate specific body regions as needed. In many cases, WB-MRI surpasses bone scintigraphy and computed tomography in detecting and characterising lesions, evaluating their response to therapy and in screening of high-risk patients. Consequently, international guidelines now recommend the use of WB-MRI in the management of patients with multiple myeloma, prostate cancer, melanoma and individuals with certain cancer predisposition syndromes. The use of WB-MRI is also growing for metastatic breast cancer, ovarian cancer and lymphoma as well as for cancer screening amongst the general population. In light of the increasing interest from clinicians and patients in WB-MRI as a radiation-free technique for guiding the management of cancer and for...

This study aimed to identify the main factors that asymptomatic individuals considered when deciding to undergo self-referred Whole-body MRI (WB-MRI) for early cancer diagnosis and the subjective values attributed to each mentioned factor in a Decision tree analysis. Personal characteristics such as risk perception and personality were investigated as possible factors affecting value attribution. Seventy-four volunteers (mean age 56.4; male = 47) filled a simplified decision tree by expressing the expected factors and related subjective values associated with two screening options for early cancer diagnosis (standard procedures vs. WB-MRI+standard procedures) while waiting for a WB-MRI examination. Questionnaires on risk perception and personality traits were also administered. Expected factors were summarized in 5 clusters: diagnostic certainty, psychological well-being, safety, test validity and time/cost. Test validity and time/cost were evaluated as potential losses in both proc...

We aimed to describe the relationships between the relative fat fraction (%FF), muscle-normalized diffusion-weighted (DW) image signal intensity and water apparent diffusion coefficient (ADC), sex and age for normal bone marrow, in the normal population. Our retrospective cohort consisted of 100 asymptomatic individuals, equally divided by sex and 10-year age groups, who underwent whole-body MRI at 1.5 T for early cancer detection. Semi-automated segmentation of global bone marrow volume was performed using the DW images and the resulting segmentation masks were projected onto the ADC and %FF maps for extraction of parameter values. Differences in the parameter values between sexes at age ranges were assessed using the Mann–Whitney and Kruskal–Wallis tests. The Spearman correlation coefficient r was used to assess the relationship of each imaging parameter with age, and of %FF with ADC and normalized DW signal intensity values. The average %FF of normal bone marrow was 65.6 ± 7.2%, ...

Using semi-automated software simplifies quantitative analysis of the visible burden of disease on whole-body MRI diffusion-weighted images. To establish the intra- and inter-observer reproducibility of apparent diffusion coefficient (ADC) measures, we retrospectively analyzed data from 20 patients with bone metastases from breast (BCa; n = 10; aged 62.3 ± 14.8) or prostate cancer (PCa; n = 10; aged 67.4 ± 9.0) who had undergone examinations at two timepoints, before and after hormone-therapy. Four independent observers processed all images twice, first segmenting the entire skeleton on diffusion-weighted images, and then isolating bone metastases via ADC histogram thresholding (ADC: 650–1400 µm2/s). Dice Similarity, Bland-Altman method, and Intraclass Correlation Coefficient were used to assess reproducibility. Inter-observer Dice similarity was moderate (0.71) for women with BCa and poor (0.40) for men with PCa. Nonetheless, the limits of agreement of the mean ADC were just ±6% fo...

Functional renal magnetic resonance imaging (MRI) has seen a number of recent advances, and techniques are now available that can generate quantitative imaging biomarkers with the potential to improve the management of kidney disease. Such biomarkers are sensitive to changes in renal blood flow, tissue perfusion, oxygenation and microstructure (including inflammation and fibrosis), processes that are important in a range of renal diseases including chronic kidney disease. However, several challenges remain to move these techniques towards clinical adoption, from technical validation through biological and clinical validation, to demonstration of cost-effectiveness and regulatory qualification. To address these challenges, the European Cooperation in Science and Technology Action PARENCHIMA was initiated in early 2017. PARENCHIMA is a multidisciplinary pan-European network with an overarching aim of eliminating the main barriers to the broader evaluation, commercial exploitation and ...

The rapidly growing field of functional, molecular and structural bio-imaging is providing an extraordinary new opportunity to overcome the limits of invasive liver biopsy and introduce a "digital biopsy" forstudy of liver pathophysiology. To foster the application of bio-imaging in clinical and translational research, there is a need to standardize the methods of both acquisition and the storage of the bio-images of the liver. It can be hoped that the combination of digital, liquid and histologic liver biopsies will provide an innovative synergistic tri-dimensional approach to identifying new aetiologies, diagnostic and prognostic biomarkers and therapeutic targets for the optimization of personalized therapy of liver diseases and liver cancer. A group of experts of different disciplines (Special Interest Group for Personalized Hepatology of the Italian Association for the Study of the Liver, Institute for Biostructures and Bio-imaging of the National Research Council and...

We sought to measure quantitative magnetization transfer (qMT) properties of the substantia nigra pars compacta (SNc) in patients with Parkinson's disease (PD) and healthy controls (HCs) using a full qMT analysis and determine whether a rapid single-point measurement yields equivalent results for pool size ratio (PSR). Sixteen different MT-prepared MRI scans were obtained at 3 T from 16 PD patients and eight HCs, along with B1, B0, and relaxation time maps. Maps of PSR, free and macromolecular pool transverse relaxation times ([Formula: see text], [Formula: see text]) and rate of MT exchange between pools (k mf ) were generated using a full qMT model. PSR maps were also generated using a single-point qMT model requiring just two MT-prepared images. qMT parameter values of the SNc, red nucleus, cerebral crus, and gray matter were compared between groups and methods. PSR of the SNc was the only qMT parameter to differ significantly between groups (p < 0.05). PSR measured via si...