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Differentiation of Inflammatory from Fibrotic Ileal Strictures Among Patients with Crohn’s Disease through Analysis of Time-intensity Curves Obtained after Microbubble Contrast Agent Injection
Get PDFThe aim was to assess whether the analysis of time-intensity curves obtained after microbubble contrast agent injection could differentiate inflammatory from fibrotic ileal strictures among patients with Crohn’s disease (CD). Sixty-five consecutive patients (40 male and 25 female; mean age ± SD, 42.2 years ± 12.22) with stricture of the terminal ileal loop from CD were scanned after microbubble injection. Time-intensity curves were obtained from quantitative analysis and peak enhancement, rise time, time to peak, area under the time-intensity curve (AUC), AUC during wash-in (AUCWI), and AUC during wash-out (AUCWO) were compared between patients with inflammatory vs patients with fibrotic strictures. Inflammatory (n=40) vs fibrotic strictures (n=25) differed (P<.05) in the peak enhancement, the wash-in rate, the wash-in perfusion index, AUC, AUCWI, AUCWO. The quantitative analysis of small bowel wall contrast enhancement after microbubble contrast agent injection may differentiate inflammatory from fibrotic ileal strictures in patients with CD
Pulmonary Angiography:Technique, Indications and Complications
No full textPulmonary angiography is still regarded as the reference method for diagnosing pulmonary embolisms (PEs), despite the fact that computed tomography pulmonary angiography is nowadays used as a standard method. It is reserved for patients with non-diagnostic test results and a high probability of PE, and those patients in whom interventions are considered. Nevertheless, it is important that one knows the technique, pitfalls and complications of this imaging technique. In this chapter, these aspects of pulmonary angiography are described.</p
Diagnostic Management Strategies in Patients with Suspected Pulmonary Embolism
No full textAdequate diagnosis is essential to prevent pulmonary embolism (PE)-related mortality and morbidity on the one hand and unnecessary treatment on the other. Preferably, excluding the diagnosis is performed using safe, efficient and non-invasive diagnostic methods. Over the last two decades, many new diagnostic methods and strategies for the diagnostic work-up of patients with suspected PE have been introduced and validated. The first step in the approach to patients with suspected PE is a thorough clinical history and physical examination, in order to determine the clinical probability of the presence of PE. The advantage of using pre-test probability in the exclusion of PE is mainly achieved in combination with a D-dimer test result. In patients with a high or likely pre-test clinical probability or patients with an abnormal D-dimer test, additional imaging is required. If the clinical status of the patient permits, the next recommended step is computed tomography (CT) or ventilation-perfusion scintigraphy, followed by additional testing in case of non-diagnostic test results. Selected patients may require a tailored approach, for instance if there is a contraindication for CT scanning. The implementation of diagnostic strategy in clinical practice will increase diagnostic accuracy and reduce costs.</p
MRI and MRA of the Pulmonary Vasculature
No full textMagnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the pulmonary vasculature are still rapidly evolving techniques. However, currently available protocols have already demonstrated high clinical impact. Contrast-enhanced and non-contrast-enhanced angiographic techniques are in widespread use for imaging of the pulmonary vasculature with either high spatial or high temporal resolution. Especially multiphasic protocols, such as MR perfusion, followed by high spatial resolution contrast-enhanced (CE) MRA, seem to be an optimal clinical approach for the assessment of different diseases affecting the pulmonary vasculature. This chapter describes basic knowledge, challenges, considerations and solutions for different MR techniques to be applied to the pulmonary vasculature. Parallel imaging and novel k-space sampling techniques have opened the door for fast volume acquisitions of the pulmonary vasculature. Contrast administration and timing in addition to multiphasic acquisitions are still in the focus to set up an optimal protocol for the pulmonary vasulature. The visualization of the data has to include multiplanar reformats and maximum intensity projections and also volume rendering techniques.</p
Gray Scale Ultrasound, Color Doppler Ultrasound, and Contrast-Enhanced Ultrasound in Renal Parenchymal Diseases
Get PDFDifferentiation of Inflammatory From Fibrotic Ileal Strictures among Patients with Crohn's Disease Based on Visual Analysis: Feasibility Study Combining Conventional B-Mode Ultrasound, Contrast-Enhanced Ultrasound and Strain Elastography
No full textThe aim of this pilot study was to assess prospectively the feasibility of conventional B-mode ultrasound (US) and contrast-enhanced ultrasound (CEUS) combined with real-time strain elastography (SE) in the differentiation of inflammatory from fibrotic ileal strictures among patients with Crohn’s disease (CD) based on visualanalysis.Twentynon-consecutivepatients(15maleand5female;meanage±standarddeviation,40.2±10.22 y) with CD and stricture of the terminal ileal loop were scanned by conventional B-mode US and CEUS and, subsequently, by real-time SE. Two independent readers visually classified each bowel stricture as fibrotic or inflammatory based on conventional B-mode US, CEUS, SE, individually and then for all techniques combined. All techniques combined had a higher (p < 0.05) sensitivity (reader 1, 9/20 [45%]; reader 2, 7/20 [35%]), specificity (reader 1, 5/20 [25%]; reader 2, 8/20 [40%]) and diagnostic accuracy (reader 1, 14/20 [70%]; reader 2, 15/ 20 [75%]) and higher (p < 0.05) area under the receiver operating characteristic curve (reader 1, 0.953; reader 2, 0.921) than individual techniques. Inter-reader agreement was fair for conventional B-mode US (k = 0.46) and CEUS (k = 0.39), moderate for SE (k = 0.6) and fair for all techniques combined (k = 0.38). Conventional B-mode US and CEUS, in combination with SE, may improve differentiation of inflammatory from fibrotic ileal strictures among patients with CD based on visual analysis
Stereology and automated measurement of the human brain
Get PDFStereology supplies image sampling rules to estimate geometric quantities such as volume,
surface area, feature length and number. The method is well suited to non-invasive image
acquisition methods such as Magnetic Resonance Imaging (MRI). Meanwhile, in Magnetic
Resonance (MR) images analysis area, automated software packages have been continuously
developed and become well-established tools especially in human brainMR images processing.
The aims of the thesis are (1) to combine proper rules to sample MR images with automated or
semi-automated data acquisition methods, in order to implement four different design unbiased
stereological volume estimators in the study of the human brain, and (2) to compare volume
estimates with those obtained from automated software packages.In volume estimation of three-dimensional (3D) objects, besides one traditional stereological
method (i.e. the CAVALIERI method), in recent years a number of newly design-based unbiased
methods have been published, which include three used in this thesis (i.e. the ISOTROPIC
CAVALIERI (ICAV), INVARIATOR (INV) and DISCRETIZED NUCLEATOR (DN) methods).
The ICAV and INV methods both allow the estimation of surface area too. The ICAV method
enables volume estimation to be unbiased and precise in individual objects while the INV and
DN methods make it efficient to estimate the mean volume of a big cohort. To make it be practical
in estimating the volume of human brain solely from MR images, in the thesis the ICAV,
INV and DN methods were given two operating protocols for rotation and measurement on a
commercial software (i.e. ANALYZE) and were performed in a fetal brain study. The ICAV,
INV and DN methods were also programmed in three scripts for rotation, gridding and measurement
purposes respectively using three freely available software packages (i.e. FSL, R and
IMAGEJ), which were applied in three adult brain studies.In volume estimation of three-dimensional (3D) objects, besides one traditional stereological
method (i.e. the CAVALIERI method), in recent years a number of newly design-based unbiased
methods have been published, which include three used in this thesis (i.e. the ISOTROPIC
CAVALIERI (ICAV), INVARIATOR (INV) and DISCRETIZED NUCLEATOR (DN) methods).
The ICAV and INV methods both allow the estimation of surface area too. The ICAV method
enables volume estimation to be unbiased and precise in individual objects while the INV and
DN methods make it efficient to estimate the mean volume of a big cohort. To make it be practical
in estimating the volume of human brain solely from MR images, in the thesis the ICAV,
INV and DN methods were given two operating protocols for rotation and measurement on a
commercial software (i.e. ANALYZE) and were performed in a fetal brain study. The ICAV,
INV and DN methods were also programmed in three scripts for rotation, gridding and measurement
purposes respectively using three freely available software packages (i.e. FSL, R and
IMAGEJ), which were applied in three adult brain studies.A fetal brain study was carried out to test the application of the ICAV, INV and DN methods.
Ten fetuses from three maternal backgrounds (i.e. five healthy, three maternal psychological
stress and two maternal substance misuse) were scanned in MRI at both the second and
third trimesters of pregnancy. Then fetal brain images were motion corrected using SLIMMER
software. Volumes of brain parenchyma (the functional tissue of the brain which is made of
two types of brain cells, namely neurons and glia) including ventricles were estimated by the
ICAV method in isotropic (i.e. having no preferred orientation) and uniformly random (i.e. uniformly
distance (interval) apart) (IUR) triplet of orthogonal section planes (i.e. the ICAV ortrip
method) and by the INV and DN methods in isotropically random (IR) triplet of orthogonal
section planes through a fixed pivotal point (i.e. the INV ortrip and DN ortrip methods). Due to
observation of artefacts in MR images and manual input in the methods, inter- and intra-rater
reliability studies were performed to investigate both point counting for the ICAV method and
segment length measurement for the INV and DN methods among three raters on five fetal
brains from the second and five from the third trimesters. Surface area was also estimated using
the ICAV method for error prediction. High reliability (Pearson’s r > 0:997) was shown
in inter- and intra-rater studies. In both the second and third trimesters, there were no significant
difference in mean volumes of all ten brains estimated by the three methods (p > 0:1).
For individual estimates, The predicted coefficients of error (CEs) for the ICAV method were
1:5% ± 0:1% in the second trimester and 2:1% ± 0:1% in the third trimester. Basing on one
IR section plane for each data, empirical CEs for the INV method in both trimesters were
19:4% ± 2:9% and 18:5% ± 11:6%, and were 21:4% ± 4:5% and 24:1% ± 11:7% for the DN
method. CEs could be decreased to 8.1%, 5.5% for the INV ortrip method and 10.3%, 9.7% for
the DN ortrip method in both trimesters. This study showed the ICAV method performed precisely
in individual volume measurements while the INV and DN methods worked efficiently
in population mean volume estimation. Clinically, no significant differences (p > 0:05) of fetal
brain volumes among three maternal groups were detected due to small sample size although
potentially in comparison with normal fetal brain, volume might be bigger in the maternal
stress group and might be smaller in the substance abused group.As the CAVALIERI method is a design-unbiased method, the main source of potential bias
(i.e. if a biased method is applied the mean of the estimated values deviates significantly from
the true value) will come from observers in operation who would be the author in this PhD
study. To examine whether there is bias caused by the author’s manual point counting procedure
in the CAVALIERI method, a slice-by-slice comparison on one adult brain volume estimation
on MR images between the CAVALIERI method and an automatically reconstructing software
(i.e. FREESURFER) was performed. One healthy elderly (male, age 71) brain MRI scan with
good image quality was selected from a dataset of 40 patients affected by the ALZHEIMER’s
disease (AD) and 22 healthy elderly volunteers. FREESURFER was used to perform individual
volumetric analysis on the adult brain automatically, which outlined grey matter and white matter
in the cerebrum on each MR image slice. The CAVALIERI method was applied to a series
of coronal images obtained with random starting position and at 1 cm intervals from the TALAIRACH
transformed and intensity normalized 3D MR image (i.e. nu.mgz) displayed with the
compartment boundaries identified by the FREESURFER pipeline suppressed. The uniformly
random (UR) test system for point counting was superimposed on each image. The CAVALIERI
method in combination with point counting strategy was used to estimate the volume of cerebrum
excluding ventricles (the sum of the two cerebral hemispheres including blood vessels
and meninges) using EASYMEASURE software on the grey scale MR images. Additionally, the
author overlay the brain boundary segmented by FREESURFER on these selected test points
and reassessed the images to compute two scores, namely (i) the total number of test points
which had been counted but which were seen to lie outside the FREESURFER segmentation
and (ii) total number of the new test points that now needed to be additionally included as
lying within the FREESURFER segmentation.. The cerebral volume was 972 cm3 estimated
by FREESURFER and 960 cm3 by the author using the CAVALIERI method with CE of 0.34%.
FREESURFER had 1.3% bigger measure than that estimated by the author. FREESURFER aided
point counting estimate was between 948 cm3 and 982 cm3 with mean volume of 965 cm3.
The ratio of points counted by the author but were outside the pial boundary segmented by
FREESURFER to total points number counted was between 2.6% to 4.0%, and the ratio of test
points not counted by the author but were inside the pial boundary segmented by FREESURFER
to total points number counted was between 2.7% to 4.9%. Therefore the author’s estimate was
in the range of FREESURFER aided estimation by the CAVALIERI method and both volume ratios
were close to each other. No bias could be found between the author using the CAVALIERI
method and FREESURFER, which gives the author confidence in performing following studies.Furthermore, volume difference of cerebrum excluding ventricles between AD patients and
healthy people were investigated using four stereological methods (i.e. the CAVALIERI, ICAV,
INV and DN methods) and the FREESURFER software. From the same dataset of 40 AD
patients and 22 healthy elderly volunteers, brain MR images of 13 patients and 13 volunteers
were selected with good image quality. Inter-reliability and intra-repeatability studies were performed
by two observers on three AD and three normal ageing brains. Both the inter-reliability
and intra-repeatability studies showed good consistency. There was no significant difference
of individual measures among the CAVALIERI and ICAV methods and FREESURFER. The average
time taken for each cerebral volume estimation was less than 15 mins by each of the
CAVALIERI, ICAV, INV and DN methods. Clinically, the cerebral volume was significantly
smaller in the AD patients, which were found using both the CAVALIERI (p = 0:01) and ICAV
(p < 0:01) methods and FREESURFER (p = 0:01) although the INV and DN methods were
not able to detect this difference. In this adult brain group study, the volume estimates from
the CAVALIERI and ICAV methods were competitive with those obtained from FREESURFER,
while the INV and DN methods might be more useful if being applied with a larger sample
size or the INV ortrip and DN ortrip methods were applied.Lastly, a systematic investigation on potential imaging biomarkers for AD was performed
by the FREESURFER software, one of the imaging biomarkers (i.e. volume ratio of cerebrum
excluding ventricles to intra-cranium (the contents of the skull above the level of the foramen
magnum)) was re-examined by the INV method manually. From the same dataset of 40 AD
patients and 22 healthy elderly volunteers, the brain MR images of 27 AD patients and 16
healthy elderly controls between the maximal common age scope of 47 to 71 were selected,
which were analysed by FREESURFER for each brain region. Furthermore, to see the effect of
AD on normal ageing atrophy, the difference of volume ratios of each brain region to whole
brain between AD patients and healthy controls was investigated. Volume ratios of many brain
parenchymal regions (e.g. hippocampus (left p = 0:002, right p < 0:001), amygdala (left
p < 0:001, right p < 0:001), accumbens area (left p = 0:002, right p = 0:001), left putamen
(p = 0:037) and corpus callosum (mid anterior p = 0:03, mid posterior p = 0:032)) to
whole brain were found smaller in AD patients while volume ratios of ventricles (both sides
of lateral, inferior lateral and 3rd ventricles, p < 0:001) to whole brain were bigger in AD
patients. Besides, the INV method was able to detect significant difference of volume ratio
of cerebral parenchyma to intra-cranium between AD patients and healthy elderly subjects
too (p < 0:01). In comparison with normal ageing-related atrophy in healthy subjects, brain
atrophy with ageing in AD patients presented in a different pattern in volume ratios (e.g. right
(p = 0:029) and total cortex (p = 0:013) to brain, total grey matter to brain (p = 0:01),
cerebral white matter to brain (p = 0:003), cerebellar cortex to brain (left p = 0:019, right
p = 0:032), 5th ventricle to brain (p = 0:048), left fimbria to left hippocampus (p = 0:015), left
hippocampal-amygdaloid transition area (HATA) to left hippocampus and right presubiculum
to right hippocampus (p = 0:016)). In this AD study, many volume ratios of brain regions to
whole brain or other brain regions were found different in AD patients and especially volume
ratio of cerebral parenchyma to intra-cranium showed potentiality as an imaging biomarker for
AD. Ageing atrophy pattern was found different in AD patients too.In conclusion, by programming in freely available R, FSL and IMAGEJ software packages,
the CAVALIERI, ICAV, INV and DN methods were able to be performed conveniently and efficiently
on human brain volume estimation using MRI. We made the first applications on the
volume estimation of fetal brains, healthy brains and brains affected by AD using the ICAV,
INV and DN methods. The volume estimates were competitive with those obtained from automated
programme (i.e. FREESURFER)
New insights into the natural history of thrombo-embolic disease provided by imaging and disease quantification
Get PDFVenous thromboembolism (VTE) is a common disease with a myriad of presentation. It is
often difficult to diagnosis with symptoms which are shared with many other disorders.
Because of the overlap in symptomatology with other pathologies it is both commonly
overlooked when present and commonly considered when absent. The threshold for
investigating suspected VTE has dropped over time, in part due to a greater awareness of
the disease among clinicians, but also because of the greater availability of diagnostic
tests which are both accurate at positively diagnosing VTE and are patient friendly. This
has resulted in a mushrooming of the number of diagnostic tests being performed for
suspected VTE in radiology departments. As such radiology provides a window into the
disease in a way that no other speciality can. All branches of medicine having their share
of VTE patients but radiology provides a unique opportunity to study VTE patients as, no
matter from which speciality they arise when the disease is suspected, they will almost
inevitably end up undergoing a definitive radiological test. There is much still to learn
about VTE however developments in modern imaging and computerised databases have
advanced our understanding of this common disease. The window that radiology provides
into VTE has contributed towards those advances
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