2,747 research outputs found
Meta-Analysis and Systematic Review of the Application of Machine Learning Classifiers in Biomedical Applications of Infrared Thermography
Atypical body temperature values can be an indication of abnormal physiological processes
associated with several health conditions. Infrared thermal (IRT) imaging is an innocuous imaging
modality capable of capturing the natural thermal radiation emitted by the skin surface, which is
connected to physiology-related pathological states. The implementation of artificial intelligence
(AI) methods for interpretation of thermal data can be an interesting solution to supply a second
opinion to physicians in a diagnostic/therapeutic assessment scenario. The aim of this work was to
perform a systematic review and meta-analysis concerning different biomedical thermal applications
in conjunction with machine learning strategies. The bibliographic search yielded 68 records for a
qualitative synthesis and 34 for quantitative analysis. The results show potential for the implementation
of IRT imaging with AI, but more work is needed to retrieve significant features and improve
classification metrics.info:eu-repo/semantics/publishedVersio
Statistical Hypothesis Testing for Postreconstructed and Postregistered Medical Images
Postreconstructed and postregistered medical images are typically treated as the raw data, implicitly assuming that those operations are error free. We question this assumption and explore how the precision of reconstruction and affine registration can be assessed by the image covariance matrix and confidence interval, called the confidence eigenimage, using a statistical model-based approach. Various hypotheses may be tested after image reconstruction and registration using classical statistical hypothesis testing vehicles: Is there a statistically significant difference between images? Does the intensity at a specific location or area of interest belong to the “normal” range? Is there a tumor? Does the image require rigid registration? We illustrate statistical hypothesis testing with three examples: breast computed tomography, breast near infrared linear reconstruction, and brain magnetic resonance imaging
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Spectral discrimination of breast pathologies in situ using spatial frequency domain imaging
Introduction: Nationally, 25% to 50% of patients undergoing lumpectomy for local management of breast cancer require a secondary excision because of the persistence of residual tumor. Intraoperative assessment of specimen margins by frozen-section analysis is not widely adopted in breast-conserving surgery. Here, a new approach to wide-field optical imaging of breast pathology in situ was tested to determine whether the system could accurately discriminate cancer from benign tissues before routine pathological processing. Methods: Spatial frequency domain imaging (SFDI) was used to quantify near-infrared (NIR) optical parameters at the surface of 47 lumpectomy tissue specimens. Spatial frequency and wavelength-dependent reflectance spectra were parameterized with matched simulations of light transport. Spectral images were co-registered to histopathology in adjacent, stained sections of the tissue, cut in the geometry imaged in situ. A supervised classifier and feature-selection algorithm were implemented to automate discrimination of breast pathologies and to rank the contribution of each parameter to a diagnosis. Results: Spectral parameters distinguished all pathology subtypes with 82% accuracy and benign (fibrocystic disease, fibroadenoma) from malignant (DCIS, invasive cancer, and partially treated invasive cancer after neoadjuvant chemotherapy) pathologies with 88% accuracy, high specificity (93%), and reasonable sensitivity (79%). Although spectral absorption and scattering features were essential components of the discriminant classifier, scattering exhibited lower variance and contributed most to tissue-type separation. The scattering slope was sensitive to stromal and epithelial distributions measured with quantitative immunohistochemistry. Conclusions: SFDI is a new quantitative imaging technique that renders a specific tissue-type diagnosis. Its combination of planar sampling and frequency-dependent depth sensing is clinically pragmatic and appropriate for breast surgical-margin assessment. This study is the first to apply SFDI to pathology discrimination in surgical breast tissues. It represents an important step toward imaging surgical specimens immediately ex vivo to reduce the high rate of secondary excisions associated with breast lumpectomy procedures
Deep-Learning for Classification of Colorectal Polyps on Whole-Slide Images
Histopathological characterization of colorectal polyps is an important
principle for determining the risk of colorectal cancer and future rates of
surveillance for patients. This characterization is time-intensive, requires
years of specialized training, and suffers from significant inter-observer and
intra-observer variability. In this work, we built an automatic
image-understanding method that can accurately classify different types of
colorectal polyps in whole-slide histology images to help pathologists with
histopathological characterization and diagnosis of colorectal polyps. The
proposed image-understanding method is based on deep-learning techniques, which
rely on numerous levels of abstraction for data representation and have shown
state-of-the-art results for various image analysis tasks. Our
image-understanding method covers all five polyp types (hyperplastic polyp,
sessile serrated polyp, traditional serrated adenoma, tubular adenoma, and
tubulovillous/villous adenoma) that are included in the US multi-society task
force guidelines for colorectal cancer risk assessment and surveillance, and
encompasses the most common occurrences of colorectal polyps. Our evaluation on
239 independent test samples shows our proposed method can identify the types
of colorectal polyps in whole-slide images with a high efficacy (accuracy:
93.0%, precision: 89.7%, recall: 88.3%, F1 score: 88.8%). The presented method
in this paper can reduce the cognitive burden on pathologists and improve their
accuracy and efficiency in histopathological characterization of colorectal
polyps, and in subsequent risk assessment and follow-up recommendations
Computer-Aided, Multi-Modal, and Compression Diffuse Optical Studies of Breast Tissue
Diffuse Optical Tomography and Spectroscopy permit measurement of important physiological parameters non-invasively through ~10 cm of tissue. I have applied these techniques in measurements of human breast and breast cancer. My thesis integrates three loosely connected themes in this context: multi-modal breast cancer imaging, automated data analysis of breast cancer images, and microvascular hemodynamics of breast under compression. As per the first theme, I describe construction, testing, and the initial clinical usage of two generations of imaging systems for simultaneous diffuse optical and magnetic resonance imaging. The second project develops a statistical analysis of optical breast data from many spatial locations in a population of cancers to derive a novel optical signature of malignancy; I then apply this data-derived signature for localization of cancer in additional subjects. Finally, I construct and deploy diffuse optical instrumentation to measure blood content and blood flow during breast compression; besides optics, this research has implications for any method employing breast compression, e.g., mammography
Measuring Chemotherapy Response in Breast Cancer Using Optical and Ultrasound Spectroscopy
Purpose: This study comprises two subprojects. In subproject one, the study
purpose was to evaluate response to neoadjuvant chemotherapy (NAC) using
quantitative ultrasound (QUS) and diffuse optical spectroscopy imaging (DOS)
in locally advanced breast cancer (LABC) during chemotherapy. In subproject
two, DOS-based functional maps were analysed with texture-based image
features to predict breast cancer response before the start of NAC.
Patients and Measurements: The institution’s ethics review board approved
this study. For subproject one, subjects (n=22) gave written consent before
participating in the study. Participants underwent non-invasive, DOS and QUS
imaging. Data were acquired at weeks 0 (i.e. baseline), 1, 4, 8 and before
surgical removal of the tumour (mastectomy and/or lumpectomy);
corresponding to chemotherapy schedules. QUS parameters including the midband fit (MBF), 0-MHz intercept (SI), and the spectral slope (SS) were
determined from tumour ultrasound data using spectral analysis. In the same
patients, DOS was used to measure parameters relating to tumour haemoglobin
and tissue composition such as %Water and %Lipids. Discriminant analysis
and receiver-operating characteristic (ROC) analyses were used to correlate the
measured imaging parameters to Miller-Payne pathological response during
treatment. Additionally, multivariate analysis was carried out for pairwise DOS
and QUS parameter combinations to determine if an increase in the
classification accuracy could be obtained using combination DOS and QUS
parametric models.
For subproject two, 15 additional patients we recruited after first giving
their written informed consent. A pooled analysis was completed for all DOS
baseline data (subproject 1 and subproject 2; n=37 patients). LABC patients
planned for NAC had functional DOS maps and associated textural features
generated. A grey-level co-occurrence matrix (texture) analysis was completed
for parameters associated with haemoglobin, tissue composition, and optical
properties (deoxy-haemoglobin [Hb], oxy-haemoglobin [HbO2], total
haemoglobin [HbT]), %Lipids, %Water, and scattering power [SP], scattering
amplitude [SA]) prior to treatment. Textural features included contrast (con),
vi
correlation (cor), energy (ene), and homogeneity (hom). Patients were
classified as ‘responders’ or ‘non-responders’ using Miller-Payne pathological
response criteria after treatment completion. In order to test if baseline
univariate texture features could predict treatment response, a receiver
operating characteristic (ROC) analysis was performed, and the optimal
sensitivity, specificity and area under the curve (AUC) was calculated using
Youden’s index (Q-point) from the ROC. Multivariate analysis was conducted to
test 40 DOS-texture features and all possible bivariate combinations using a
naïve Bayes model, and k-nearest neighbour (k-NN) model classifiers were
included in the analysis. Using these machine-learning algorithms, the pretreatment DOS-texture parameters underwent dataset training, testing, and
validation and ROC analysis were performed to find the maximum sensitivity
and specificity of bivariate DOS-texture features.
Results: For subproject one, individual DOS and QUS parameters, including
the spectral intercept (SI), oxy-haemoglobin (HbO2), and total haemoglobin
(HbT) were significant markers for response outcome after one week of
treatment (p<0.01). Multivariate (pairwise) combinations increased the
sensitivity, specificity and AUC at this time; the SI+HbO2 showed a
sensitivity/specificity of 100%, and an AUC of 1.0 after one week of treatment.
For subproject two, the results indicated that textural characteristics of
pre-treatment DOS parametric maps can differentiate treatment response
outcomes. The HbO2-homogeneity resulted in the highest accuracy amongst
univariate parameters in predicting response to chemotherapy: sensitivity (%Sn)
and specificity (%Sp) = 86.5 and 89.0%, respectively and an accuracy of
87.8%. The highest predictors using multivariate (binary) combination features
were the Hb-Contrast + HbO2-Homogeneity which resulted in a %Sn = 78.0,
a %Sp = 81.0% and an accuracy of 79.5% using the naïve Bayes model.
Conclusion: DOS and QUS demonstrated potential as coincident markers for
treatment response and may potentially facilitate response-guided therapies.
Also, the results of this study demonstrated that DOS-texture analysis can be
used to predict breast cancer response groups prior to starting NAC using
baseline DOS measurements
Can 3D Camera Imaging Provide Improved Information to Assess and Manage Lymphoedema in Clinical Practice?
Background Accurate diagnosis and measurement of limb volume in people with lymphoedema is important in order to provide best information for treatment, management and self-management. Current assessment methods lack detail and accuracy. Three-dimensional camera imaging (3DCI) holds the potential to be cheap, accurate, and provide additional material about limb shape not provided by current methods. However, there is a need to ensure that this assessment method is valid and reliable. Methodology This prospective, observational, longitudinal study utilised a diagnostic test study framework to determine the validity, reliability and accuracy of 3DCI compared to circumferential tape measurement (CTM) and perometry and to explore whether shape is a feasible alternative to measure upper limb lymphoedema. Twenty women with breast cancer-related lymphoedema were recruited. Phase one assessed criterion validity, intra-rater reliability, and accuracy of 3DCI by measuring limb volume of each participant with CTM, perometry and 3DCI four times over six months. Phase two investigated the use of limb shape as a method of lymphoedema assessment using oedema maps and calculations of shape redundancy derived from the 3DCI images in phase one. These data sets were matched against limb volume to determine criterion validity, intra-rater reliability and accuracy. Results 3DCI had high intra-rater correlation (ICC=0.87; p<0.00). Concurrent validity ranged from 0.82 to 0.86 against perometry and CTM, with good sensitivity (91.7% to 100%) and moderate specificity (50% to 66.7%). Limb shape calculation (shape redundancy) had moderate intra-rater correlation (ICC=0.71; p=0.01); but correlated poorly with limb volume (r=0.19 to 0.39). Coloured oedema maps were sensitive to change over time with colours clearly identifying problem areas and fluctuations within the affected limb. Conclusion Our study shows that 3DCI is a reliable, valid and accurate method of limb volume measurement, and that it could provide supportive information in clinical assessment. In addition, limb shape provides insight into localised areas of swelling, which other methods of lymphoedema measurement do not. However, shape redundancy requires further refinement
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