Niall R. Moore

Analysis of dynamic MR breast images using a model of contrast enhancement

We describe a model of dynamic contrast enhancement in breast MRI designed to aid the radiologist in cases for which X-ray mammography is ineffective. The breasts are segmented from the image slices by a dynamic programming algorithm after morphological opening. A pharmacokinetic model has been derived to fit the rise in intensities after injection of a contrast agent, in a way that facilitates investigation of the effects of different models of bolus injection. The pharmacokinetic model is used in a modified Horn-Schunck algorithm to correct for motion effects during the seven minute acquisition period. The results show significant localization of tumours and enable discrimination of cancerous tissue. In particular, we illustrate the approach with an image that shows a carcinoma, whose appearance and localization are greatly improved by the registration algorithm.

Extracting and visualizing physiological parameters using dynamic contrast-enhanced magnetic resonance imaging of the breast

An analysis procedure is presented that enables the acquisition and visualization of physiologically relevant parameters using dynamic contrast-enhanced magnetic resonance imaging. The first stage of the process involves the use of a signal model that relates the measured magnetic resonance signal to the contrast agent concentration. Since the model requires knowledge of the longitudinal relaxation time T(1), a novel optimization scheme is presented which ensures a reliable measurement. Pharmacokinetic modelling of the observed contrast agent uptake is then performed to obtain physiological parameters relating to microvessel leakage permeability and volume fraction and the assumptions made in the derivation of these parameters are discussed. A simple colour representation is utilized that enables the relevant physiological information to be conveyed to the clinician in a visually efficient and meaningful manner. A second representation, based on vector maps, is also devised and it is demonstrated how this can be used for malignant tumour segmentation. Finally, the procedure is applied to 14 pre- and post-chemotherapy breast cases to demonstrate the clinical value of the technique. In particular, the apparent improved representation of tissue vascularity when compared to conventional methods and the implications for this in treatment assessment are discussed.

Fusion of contrast-enhanced breast MR and mammographic imaging data

Increasing use is being made of Gd-DTPA contrast-enhanced MRI (CE-MRI) for breast cancer assessment since it provides three-dimensional (3D) functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages as well as patients with post-operative scarring. CE-MRI is complementary to conventional X-ray mammography, since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value in fusing the high-resolution structural information available from mammography with the functional data acquired from MRI. This article is a clinical overview of the results of a technique to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume. An evaluation of the fusion framework is demonstrated with a series of clinical cases and a total of 14 patient examples.

Simultaneous segmentation and registration of contrast-enhanced breast MRI

Breast Contrast-Enhanced MRI (ce-MRI) requires a series of images to be acquired before, and repeatedly after, intravenous injection of a contrast agent. Breast MRI segmentation based on the differential enhancement of image intensities can assist the clinician detect suspicious regions. Image registration between the temporal data sets is necessary to compensate for patient motion, which is quite often substantial. Although segmentation and registration are usually treated as separate problems in medical image analysis, they can naturally benefit a great deal from each other. In this paper, we propose a scheme for simultaneous segmentation and registration of breast ce-MRI. It is developed within a Bayesian framework, based on a maximum a posteriori estimation method. A pharmacokinetic model and Markov Random Field model have been incorporated into the framework in order to improve the performance of our algorithm. Our method has been applied to the segmentation and registration of clinical ce-MR images. The results show the potential of our methodology to extract useful information for breast cancer detection.

A non-rigid registration algorithm for dynamic breast MR images

Abstract Magnetic resonance image analysis is a promising technique for diagnosing breast cancer, particularly in women for whom X-ray mammography is ineffective. If breast motion is not corrected for, diagnostic accuracy is significantly reduced. In this paper, we analyse the kinds of motion that arise during image formation and we describe a model based non-rigid registration algorithm to estimate and correct for breast motion. Registration of breast MR images is complicated by the use of a contrast agent which results in a non-uniform increase in intensity across the image. The work described here forms part of an implemented breast MR analysis system which allows automatic detection and segmentation of regions of focal enhancement and non-rigid image registration.

The role of CT angiography in military trauma.

AIM To review whole-body computed tomography (CT) angiography as an unmatched way of fully assessing battle-injured patients, and the prevalence of vascular, predominantly arterial, injuries identified. MATERIALS AND METHODS A retrospective analysis of 144 patients who underwent whole-body CT angiography in March 2011 was made. A vascular radiologist reviewed all images and imaging reports. Data gathered included positive findings from CT, anatomical region injured, mechanism of injury, time to CT, and the number of casualties per incident. RESULTS One hundred and forty-four patients underwent whole-body CT of which 17% had an occult vascular injury on CT. Twenty of these injuries (56%) were in the lower limbs, excluding extravasation at the site of amputation. Improvised explosive devices (IEDs) accounted for 71% (180 of 253) of battle injuries. The median time from admission to CT was 28 min. An additional 12% longer per patient is taken on average in a multiple casualty incident. Including contrast medium administration, whole-body angiography is completed in less than 2 min (mean 116 s). CONCLUSION A significant proportion of occult vascular injuries occur in penetrating fragmentation and blast injuries in military trauma. A low threshold for single-pass whole-body CT angiography is therefore justified.

Spontaneous Idiopathic Bilateral Adrenal Haemorrhage in Adults

Haemorrhage into the adrenal gland may be unilateral or bilateral. It occurs most frequently in the newborn, but has been well documented in older children and adults [1]. Bilateral adrenal haemorrhage is usually associated with anticoagulant therapy or stress caused by surgery, sepsis or hypotension [1–4]. Less common causes include trauma or hypoxia during obstetric delivery. Bilateral adrenal haemorrhage is rarely diagnosed clinically owing to its relatively non-specific presentation. The clinical importance of bilateral adrenal haemorrhage is that it may lead to acute adrenal insufficiency and possible death [5]. We report for the first time, two cases of idiopathic spontaneous bilateral adrenal haemorrhage in adults, identified at time of computed tomography (CT) imaging performed for abdominal pain.

Segmentation of the bladder wall using coupled level set methods

We describe a novel method to segment the bladder wall in magnetic resonance imaging (MRI) to support the detection of disease, such as endometriosis, and for surgical planning. We segment the inner and outer wall boundary using T2- and T1-weighted MRI images, respectively. A new coupling technique for level sets is formulated and tested on 54 T2- and T1-weighted image pairs. A local phase based dimensionless feature asymmetry measurement using the monogenic signal is used. The results are validated against manual segmentations using the Dice similarity coefficient. Our findings show that the coupling significantly improves the segmentation by preventing leakage due to weak image features and MR bias field. This method shows promising potential for other segmentation tasks involving thin, elongated structures.

MRI-Mammography 2D/3D Data Fusion for Breast Pathology Assessment

Increasing use is being made of contrast-enhanced Magnetic Resonance Imaging (Gd-DTPA) for breast cancer assessment since it provides 3D functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages. Contrast-enhanced MRI (CE-MRI) is complimentary to conventional X-ray mammography since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in-situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy [1]. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value to fusing the high-resolution structural information available from mammography with the functional data acquired from MRI imaging. This paper presents a novel data fusion technique whereby medio-lateral (ML) and cranio-caudal (CC) mammograms (2D data) are registered to 3D contrast-enhanced MRI volumes. We utilise a combination of pharmacokinetic modelling, projection geometry, wavelet-based landmark detection and thin-plate spline non-rigid registration to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume.

Contained Left Ventricular Rupture After Acute Myocardial Infarction Revealed by Cardiovascular Magnetic Resonance Imaging

A 69-year-old man with a 2-day history of chest pain was admitted to our hospital. His ECG was consistent with acute coronary syndrome (Figure 1A) and troponin I was elevated (>50 ng/mL). Coronary angiography showed a totally occluded circumflex with extensive intraluminal thrombus but no other obstructive disease (Figure 1B). Because the chest pain had completely resolved and this was a late-presentation myocardial infarction, management was medical. Echocardiography on day 6 showed inferolateral wall akinesis (Figure 1C and 1D) but preserved overall left ventricular (LV) function. Cardiovascular magnetic resonance (CMR) imaging 24 hours later to assess for viability showed an area of extreme thinning in the inferolateral wall due to myocardial rupture contained by overlying pericardium (Figure 1E and 1F, arrow, and online-only Data Supplement Movie I). Images acquired early after gadolinium contrast showed a layer of thrombus overlying the area of rupture (Figure 1G, arrow) and extensive no-reflow within the inferolateral wall (Figure 1G, arrowheads). Review of the echo images revealed an area in the inferolateral wall that could be …