Sheldon Wiebe

Early Doppler changes in a renal transplant patient secondary to abdominal compartment syndrome

Physiologic changes in renal transplant patients, such as transiently low central venous pressure, may be related to increased intra-abdominal pressure, from the volume of the transplanted kidney itself. Using intraoperative and postoperative Doppler ultrasound of the transplant renal vessels, we identified changes in flow dynamics following closure of the abdomen and reversal of the changes when the abdomen was reopened. This was attributed to abdominal compartment syndrome and a fasciotomy was created in the abdominal wall to accommodate the transplanted kidney. The findings in this case, in keeping with abdominal compartment syndrome, are not often considered in transplant recipients, but may explain some of the postsurgical physiology in some patients, particularly in the pediatric population.

Hemoptysis: a rare cause can be related to a bronchial varix due to pulmonary venous obstruction.

Bronchial varices, which have rarely been described in the radiology literature, can be the result of pulmonary venous obstruction and may present with hemoptysis. This case is an illustration of this rare condition, which correlates CT findings with bronchoscopic findings. We also describe the findings on phase-contrast MR that demonstrated reversed diastolic flow in the branch pulmonary artery supplying the affected lung.

A median-Gaussian filtering framework for Moire pattern noise removal from X-ray microscopy image.

Moiré pattern noise in Scanning Transmission X-ray Microscopy (STXM) imaging introduces significant errors in qualitative and quantitative image analysis. Due to the complex origin of the noise, it is difficult to avoid Moiré pattern noise during the image data acquisition stage. In this paper, we introduce a post-processing method for filtering Moiré pattern noise from STXM images. This method includes a semi-automatic detection of the spectral peaks in the Fourier amplitude spectrum by using a local median filter, and elimination of the spectral noise peaks using a Gaussian notch filter. The proposed median-Gaussian filtering framework shows good results for STXM images with the size of power of two, if such parameters as threshold, sizes of the median and Gaussian filters, and size of the low frequency window, have been properly selected.

Diffraction Enhanced X-ray Imaging of the Distal Radius: A Novel Approach for Visualization of Trabecular Bone Architecture

In Canada, osteoporotic fractures result in direct health care costs that exceed CAD

Ring artifacts removal from synchrotron CT image slices

1.3 billion annually [1]. Fractures are related to compromised bone strength, a parameter that reflects both density (quantity) and architecture (quality) [2]. The current clinical standard for bone assessment, dual energy x-ray absorptiometry, provides only a 2-dimensional areal measurement of density and no architectural information [3]; therefore, the development of improved methods for visualizing and quantifying of bone architecture remains an important goal with respect to improving detection and treatment of osteoporosis. Advances are currently being sought in the development of new technologies [3], such as high-resolution peripheral quantitative tomography [4], and through texture-based analysis of trabecular structure from radiographs [5]. In this pictorial essay, we explore the use of x-rayebased diffraction enhanced imaging (DEI) by using synchrotron radiation [6] as a novel means of visualizing the internal architecture of the human distal radius, a clinically significant fracture site. Imaging for this study was conducted at the Canadian Light Source (CLS) synchrotron during commissioning of the BioMedical Imaging and Therapy (BMIT) bending magnet beam line [7]. As such, our goal here is 2-fold: (1) establishment of proof-of-principle

Partial anterior cervical cord infarction following vertebral artery dissection.

Ring artifacts can occur in reconstructed images from x-ray Computerized Tomography (CT) as full or partial concentric rings superimposed on the scanned structures. Due to the data corruption by those ring artifacts in CT images, qualitative and quantitative analysis of these images are compromised. In this paper, we propose to correct the ring artifacts on the reconstructed synchrotron radiation (SR) CT image slices. The proposed correction procedure includes the following steps: (1). transform the reconstructed CT images into polar coordinates; (2) apply discrete two-dimensional (2D) wavelet transform to the polar image to decompose it into four image components: low pass band image component, as well as the components from horizontal, vertical and diagonal details bands; (3). apply 2D Fourier transform to the vertical details band image component only, since the ring artifacts become vertical lines in the polar coordinates; (4). apply Gaussian filtering in Fourier domain along the abscissa direction to suppress the vertical lines, since the information of the vertical lines in Fourier domain is completely condensed to that direction; (5). perform inverse Fourier transform to get the corrected vertical details band image component; (6). perform inverse wavelet transform to get the corrected polar image; (7). transform the corrected polar image back to Cartesian coordinates to get the CT image slice with reduced ring artifacts. This approach has been successfully used on CT data acquired from the Biomedical Imaging and Therapy (BMIT) beamline in Canadian Light Source (CLS), and the results show that the ring artifacts in original SR CT images have been effectively suppressed with all the structure information in the image preserved.

Diffraction enhanced imaging of a rat model of gastric acid aspiration pneumonitis.

Infarction of the cervical spinal cord is less common than thoracolumbar cord infarction and accounts for 7-25% of cord infarcts.1,2 Causes include venous and arterial thromboses, vasculitis, fibrocartilaginous embolism, cocaine misuse, epidural anaesthesia, systemic hypotension, arteriosclerosis, Caisson disease, spinal tumor, arteriovenous malformations (AVMs) and arterial dissections.3 An increasingly recognized cause for cervical spinal cord infarction is vertebral artery dissection. Twelve reported cases of unilateral or bilateral vertebral artery dissection causing ischemia of the cervical cord were found in a review of literature from 1989-2007.4-14 While more than 80% of patients with vertebral artery dissection are reported to develop posterior circulation brain ischemia, spinal cord infarction is a rare manifestation.15 The clinical presentations and areas of involvement of the spinal cord are quite variable among these cases. Acute cord infarction may present as localized cervical pain3 which may be the cause of diagnostic confusion. In only two of these cases did unilateral vertebral artery dissection cause a clinical anterior cord syndrome.6,7 One vertebral artery frequently supplies the dominant feeder to the anterior spinal artery; therefore compromise of one vertebral artery often causes ischemic changes in the cord bilaterally.16 Laufs et al, however, described unilateral cervical cord involvement following ipsilateral vertebral artery dissection.14

Renal cell carcinoma as a second malignant neoplasm in a patient with non-syndromic hemihypertrophy and previous Wilms tumor

RATIONALE AND OBJECTIVES Diffraction-enhanced imaging (DEI) is a type of phase contrast x-ray imaging that has improved image contrast at a lower dose than conventional radiography for many imaging applications, but no studies have been done to determine if DEI might be useful for diagnosing lung injury. The goals of this study were to determine if DEI could differentiate between healthy and injured lungs for a rat model of gastric aspiration and to compare diffraction-enhanced images with chest radiographs. MATERIALS AND METHODS Radiographs and diffraction-enhanced chest images of adult Sprague Dawley rats were obtained before and 4 hours after the aspiration of 0.4 mL/kg of 0.1 mol/L hydrochloric acid. Lung damage was confirmed with histopathology. RESULTS The radiographs and diffraction-enhanced peak images revealed regions of atelectasis in the injured rat lung. The diffraction-enhanced peak images revealed the full extent of the lung with improved clarity relative to the chest radiographs, especially in the portion of the lower lobe that extended behind the diaphragm on the anteroposterior projection. CONCLUSIONS For a rat model of gastric acid aspiration, DEI is capable of distinguishing between a healthy and an injured lung and more clearly than radiography reveals the full extent of the lung and the lung damage.

Clinical and radiologic findings in an adult male with dysosteosclerosis

Survivors of childhood Wilms tumors are at an increased risk of second malignant neoplasms. Recently, it has been postulated that renal cell carcinoma is among the malignancies for which this population is at risk. We present the unique case of an adult Wilms tumor survivor with non-syndromic hemihypertrophy (NSHH) who developed renal cell carcinoma. This case highlights the need for close follow-up in two populations: adults who have survived Wilms tumor and those with NSHH.

Idiopathic infantile arterial calcification in a 12-year-old girl presenting as chronic mesenteric ischemia: imaging findings and angioplasty results

Dysosteosclerosis is a rare autosomal recessive skeletal dysplasia characterized by osteosclerosis and platyspondyly. A case of dysosteosclerosis in a 17‐year‐old male from our institution was first published by Houston et al. 1978 . This patient has survived into adulthood and to our knowledge, is the only reported adult with dysosteosclerosis. We will review the clinical and radiographic features in our patient.