1,721,100 research outputs found
Computer-aided diagnosis of prostate cancer using multiparametric MRI and clinical features:A patient-level classification framework
No full textComputer-aided diagnosis (CAD) of prostate cancer (PCa) using multiparametric magnetic resonance imaging (mpMRI) is actively being investigated as a means to provide clinical decision support to radiologists. Typically, these systems are trained using lesion annotations. However, lesion annotations are expensive to obtain and inadequate for characterizing certain tumor types e.g. diffuse tumors and MRI invisible tumors. In this work, we introduce a novel patient-level classification framework, denoted PCF, that is trained using patient-level labels only. In PCF, features are extracted from three-dimensional mpMRI and derived parameter maps using convolutional neural networks and subsequently, combined with clinical features by a multi-classifier support vector machine scheme. The output of PCF is a probability value that indicates whether a patient is harboring clinically significant PCa (Gleason score ≥3+4) or not. PCF achieved mean area under the receiver operating characteristic curves of 0.79 and 0.86 on the PICTURE and PROSTATEx datasets respectively, using five-fold cross-validation. Clinical evaluation over a temporally separated PICTURE dataset cohort demonstrated comparable sensitivity and specificity to an experienced radiologist. We envision PCF finding most utility as a second reader during routine diagnosis or as a triage tool to identify low-risk patients who do not require a clinical read.</p
Clinical translation of VERDICT MRI biomarkers for Prostate Cancer characterisation
Get PDFProstate Cancer is the second most common cancer worldwide and the second most common cause of cancer death among men in the UK. The introduction of multiparametric magnetic resonance imaging (mpMRI) in the diagnostic pathway in the last 10 years has helped reduce the over-diagnosis of clinically insignificant prostate cancer whilst still detecting clinically significant cancer (csPCa). However, mpMRI is not a perfect test and has important shortcomings. The specificity of mpMRI is modest at 37% due to indeterminate appearances caused by benign pathologies. This causes men to undergo unnecessary invasive biopsies that are negative for cancer. Therefore, there is a need for biomarkers that can aid the assessment of MRI for prostate cancer.
In this thesis, I evaluate whether quantitative imaging biomarkers (QIBs) derived from VERDICT MRI (Vascular, Extracellular and Restricted Diffusion for Cytometry in Tumours) can add more value in classifying which men have csPCa when compared to biomarkers derived from mpMRI in a cohort of men suspected to have prostate cancer.
I first analyse the performance of the current diagnostic pathway in a prospective cohort and identify in which participants there is a need for additional biomarkers. I then compare the diagnostic accuracy of VERDICT QIBs to mpMRI QIBs in differentiating men with csPCa to those without in men who underwent biopsy in the prospective cohort. I also assess the image quality and inter-reader agreement of the most promising VERDICT parameter map when qualitatively assessed by radiologists.
Finally, I identify whether there is a clinical need for biomarkers in monitoring response to hormonal and radiotherapy in patients with locally aggressive prostate cancer. Subsequently, I study the changes in VERDICT QIBs after hormonal and radiotherapy in men with biopsy-proven prostate cancer
A computational investigation of nanoparticle-mediated drug delivery in preclinical scenarios
Get PDFPolymersomes have been identified as a promising vesicle for nanoparticle-mediated chemotherapy delivery, which has been shown to increase treatment efficacy and reduce off target side effects, compared to freely administering the agent, when treating solid tumours.
In this thesis mathematical models are developed and used to simulate chemotherapy drug delivery via polymersomes, in a range of preclinical environments. The preclinical environments are chosen to mimic the therapeutic development process and to identify key properties of polymersomes, that can be fed into experimental design and testing, in order to focus developments.
In the simplest scenario, representative of cell monolayers, analytical solutions are derived to determine the optimal physical properties of the polymersomes. In the most complex scenario, representative of in vivo environments where spatial heterogeneity must be accounted for, whole system properties are investigated, such as blood concentrations and diffusivity through tissue. Chemotherapy delivery, without polymersomes, is also considered to enable comparison between delivery mechanisms. In these in vivo scenarios graphical networks are used to represent blood vessels. These graphical networks are derived from real blood vessels via biomedical imaging and analysis processes.
In addition to mathematical model development, we consider the influence of this image analysis process on the properties of the graphical blood vessel networks. In particular we focus on the how the choice of segmentation and skeletonisation technique influences the properties of the graphical blood vessel networks
Interobserver reproducibility of the PRECISE scoring system for prostate MRI on active surveillance: results from a two-centre pilot study
Get PDFWe aimed to determine the interobserver reproducibility of the Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) criteria for magnetic resonance imaging in patients on active surveillance (AS) for prostate cancer (PCa) at two different academic centres
The use of quantitative magnetic resonance imaging in perinatal brain injury
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DWI and PRECISE criteria in men on active surveillance for prostate cancer: a multicentre preliminary experience of different ADC calculations
Get PDFPURPOSE: The PRECISE score estimates the likelihood of radiological progression in patients on active surveillance (AS) for prostate cancer (PCa) with serial multiparametric magnetic resonance imaging (mpMRI). A PRECISE score of 1 or 2 denotes radiological regression, PRECISE 3 indicates stability and PRECISE 4 or 5 implies progression. We evaluated the inter-reader reproducibility of different apparent diffusion coefficient (ADC) calculations and their relationship to the PRECISE score. MATERIAL AND METHODS: Baseline and follow-up scans (on the same MR systems) of 30 patients with visible lesions from two different institutions were analysed by two radiologists. The PRECISE score was initially assessed in consensus. At least six weeks later, to reduce the likelihood of being influenced by the consensus PRECISE reading, each radiologist independently calculated ADC for the following: lesion, non-cancerous tissue and urine in the bladder. Normalised ADC ratios were calculated with respect to normal prostatic tissue (npADC) and urine. Spearman's correlation (ρ), intraclass correlation coefficients (ICC), differences in ADC and ROC curves were computed. RESULTS: Interobserver reproducibility was very good (ρ > 0.8; ICC > 0.90). Lesion ADC (0.91 vs 0.73 × 10-3 mm2/s; p=0.025) and npADC ratio (0.68 vs 0.53; p=0.012) at follow-up mpMRI were different between patients with radiological regression or stability vs progression. Cut-offs of 0.77 × 10-3 mm2/s (lesion ADC) and 0.59 (npADC ratio) could differentiate the two groups (area under the curve: 0.74 and 0.77, respectively). CONCLUSION: The ADC, npADC ratio and the PRECISE score should be recorded for MRI-based AS
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Diagnostic Accuracy of Abbreviated Bi-Parametric MRI (a-bpMRI) for Prostate Cancer Detection and Screening: A Multi-Reader Study
Get PDFBackground: There is currently limited evidence on the diagnostic accuracy of abbreviated biparametric MRI (a-bpMRI) protocols for prostate cancer (PCa) detection and screening. In the present study, we aim to investigate the performance of a-bpMRI among multiple readers and its potential application to an imaging-based screening setting. (2) Methods: A total of 151 men who underwent 3T multiparametric MRI (mpMRI) of the prostate and transperineal template prostate mapping biopsies were retrospectively selected. Corresponding bpMRI (multiplanar T2WI, DWI, ADC maps) and a-bpMRI (axial T2WI and b 2000 s/mm2 DWI only) dataset were derived from mpMRI. Three experienced radiologists scored a-bpMRI, standard biparametric MRI (bpMRI) and mpMRI in separate sessions. Diagnostic accuracy and interreader agreement of a-bpMRI was tested for different positivity thresholds and compared to bpMRI and mpMRI. Predictive values of a-bpMRI were computed for lower levels of PCa prevalence to simulate a screening setting. The primary definition of clinically significant PCa (csPCa) was Gleason ≥ 4 + 3, or cancer core length ≥ 6 mm. (3) Results: The median age was 62 years, the median PSA was 6.8 ng/mL, and the csPCa prevalence was 40%. Using a cut off of MRI score ≥ 3, the sensitivity and specificity of a-bpMRI were 92% and 48%, respectively. There was no significant difference in sensitivity compared to bpMRI and mpMRI. Interreader agreement of a-bpMRI was moderate (AC1 0.58). For a low prevalence of csPCa (e.g., <10%), higher cut offs (MRI score ≥ 4) yield a more favourable balance between the predictive values and positivity rate of MRI. (4) Conclusion: Abbreviated bpMRI protocols could match the diagnostic accuracy of bpMRI and mpMRI for the detection of csPCa. If a-bpMRI is used in low-prevalence settings, higher cut-offs for MRI positivity should be prioritised
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