Peter Corr

Clinical ultrasound physics.

Understanding the basic physics of ultrasound is essential for acute care physicians. Medical ultrasound machines generate and receive ultrasound waves. Brightness mode (B mode) is the basic mode that is usually used. Ultrasound waves are emitted from piezoelectric crystals of the ultrasound transducer. Depending on the acoustic impedance of different materials, which depends on their density, different grades of white and black images are produced. There are different methods that can control the quality of ultrasound waves including timing of ultrasound wave emission, frequency of waves, and size and curvature of the surface of the transducer. The received ultrasound signal can be amplified by increasing the gain. The operator should know sonographic artifacts which may distort the studied structures or even show unreal ones. The most common artifacts include shadow and enhancement artifacts, edge artifact, mirror artifact and reverberation artifact.

The role of ultrasound in the management of intestinal obstruction

Intestinal obstruction (IO) is a common cause of acute abdominal pain. The recent increased use of sonography in the initial evaluation of abdominal pain has made point-of-care ultrasound a valuable tool for the diagnosis of IO. Sonography is as sensitive, but more specific, than plain abdominal X-ray in the diagnosis of IO. Point-of-care ultrasound can answer specific questions related to IO that assist the acute care physician in critical decision making. Sonography can also help in the resuscitation of patients by serial measurement of the IVC diameter. We review the sonographic findings of IO and the role of point-of-care ultrasound in the management of patients having IO.

MRI-based texture analysis: a potential technique to assess protectors against induced-liver fibrosis in rats

MRI-based texture analysis: a potential technique to assess protectors against induced-liver fibrosis in rats Background. In this study, the protective effect of extract of Moringa oleifera against carbon tetrachloride (CCl4)-induced liver fibrosis in rats was evaluated using Magnetic Resonance Imaging-Texture Analysis (MRI-TA) and the results were compared to liver function tests and histopathology. Methods. Twenty-eight male Wistar rats were randomly divided into 4 groups: a) the normal control group (C) received an intra-gastric administration of vehicle for eight weeks; b) the fibrosis group (F) received an intra-peritoneal administration of CCl4 twice a week for eight weeks; c) the silymarin group (S) received 0.2 g/kg orally once a day for eight weeks along with CCl4; d) the M. oleifera protected group (M), received an intra-gastric dose at 0.5 g/kg for 8 weeks concomitantly with CCl4. Histopathology and liver function were performed and both confirmed protection against CCl4-induced liver fibrosis. Results. The fibrosis index showed a remarkable increase in collagen-I contents in the CCl4 - injured animals (12.73±2.37%) while fibrotic indices were significantly less in liver tissues of Moringa-treated and silymarin-treated animals (5.23±0.13% and 1.23±1.01%, respectively). MRI-TA results were consistent with previous histopathological findings. Classification of MRI-TA parameters for the C, F, and M groups showed that the F group was separated from both M and C groups on the MDF-1 axis (Most Discriminating Parameters-1) whereby this group always had negative values. The C and M groups clustered closely on the same axis with positive values. Very similar results were obtained from classification of the C, F and S groups. The texture parameters used in this study measure the coarseness of the imaged tissue, which is influenced by the collagen contents and distribution, that are known to be increased in fibrosis and inhibited by antifibrotic drugs thus affecting image classification. Conclusions. Based on our findings, MRI-TA can be established as a potential tool for assessing the protective or therapeutic effects of tested antifibrotic drug/s. M. oleifera exhibits a partial hepatoprotective effect on rats treated with CCl4 which was proven by histopathology and liver function tests and indicated by MRI-TA performed on liver samples. We recommend MRI-TA as a potential tool for a simpler, easier, and faster way of indicating the therapeutic effect of antifibrotic drugs.

Neuroimaging findings in acute ethylene glycol poisoning

The CT and MR findings of a patient with acute ethylene glycol poisoning are presented. Basal ganglia hemorrhagic infarction especially involving the putamen was detected. The differential diagnosis includes other toxic and hypoxic encephalopathies.

Pulmonary artery aneurysm as a cause of massive hemoptysis: diagnosis and management.

Massive hemoptysis is a life-threatening medical emergency. Prompt radiological diagnosis and management are essential. I present a case of an inflammatory pulmonary aneurysm (Rasmussen aneurysm) from active pulmonary tuberculosis. This is an uncommon cause for massive hemoptysis which was successfully treated by endovascular coiling.

Sonography of gangrenous cholecystitis.

Gangrenous cholecystitis is an acute surgical emergency, which requires early cholecystectomy. Differentiation of patients with gangrenous cholecystitis from those with non-gangrenous cholecystitis can be difficult, both clinically and with imaging. Careful attention to the following sonographic signs suggests the presence of gangrenous cholecystitis decreased focal wall perfusion on Color Doppler, irregular gall bladder mucosal outline, gall bladder wall thickening with signs of de-lamination, gas within the gall bladder, absence of calculi, and large peri-cholecystic collections. Both sonogram with color flow imaging and contrast-enhanced Computed tomography are complementary investigations to establish this important diagnosis in critically ill patients.

Do knees survive the Comrades Marathon? An MRI Study

Objective. To detect by magnetic resonance imaging (MRI) the presence and type of knee injuries in non-professional runners after running an ultra-marathon, and to determine whether ultra-marathon running exacerbates pre-existing knee injuries or results in new permanent injuries. Design. A prospective MRI study of one knee of 10 randomly selected participants who completed the Comrades Marathon between 1997 and 2002. Their knees were scanned 48 hours before the race, and 48 hours and 1 month after the race. Setting. All scans were performed at the Radiology Department, Wentworth Hospital, Durban, and the University of KwaZulu-Natal. Main outcome measures. Scores of all knee injuries detected on MRI scans immediately before the race, compared with the scores after the race. Results. All scanned knees demonstrated an abnormal amount of joint fluid before the race; this increased immediately after the race in 5 runners and remained unchanged in another 5. At 1 month, 5 knees showed decreased joint fluid and 5 remained unchanged, but these were not the same runners as in the post-race groups. There was increased signal intensity in the distal patellar and quadriceps tendons in 4 runners before the race, which increased or remained the same on post-race scans in 6 knees. There was a decrease in signal intensity on scans taken 1 month later in 3 runners, with complete resolution in 2 and no change in 1. Old injuries to ligaments, tendons or other knee structures were unaffected by the race. No bone bruising, cartilage defects or meniscal abnormalities were observed. There was no significant difference in the pre- and post-race or 1-month scan scores. Conclusions. The race appears to have had a detrimental effect on runners who started the ultra-marathon with tendinopathy, which worsened post-race by MRI criteria. One month after the race, the scan appearance of the overuse injury had either improved or resolved completely. Bone bruising or meniscal damage did not appear to occur, and the presence of increased joint fluid probably relates to stress or injury. South African Medical Journal Vol. 98 (11) 2008: pp. 873-876

Neuroimaging findings in a case of fluoxetine overdose.

Brain MRI and ¹⁸F-FDG PET/CT scans were performed in a patient who had survived a suicide attempt by fluoxetine overdose. The patient presented with the following clinical signs and symptoms, and neuroimaging findings: severe signs of serotonin toxicity, including comatose state, akinetic rigid syndrome and dysautonomia; bilateral globus pallidus changes consistent with extensive pallidal necrosis and subsequent reversible diffuse ischemic changes in white matter, with posterior predominance, involving the splenium of the corpus callosum on brain MRI; and marked hypometabolism in the frontal, parietal and temporal cortical regions as well as in both caudate nuclei on ¹⁸F-FDG PET/CT performed 37 days later. These findings suggest that acute severe serotonin toxicity can induce structural and long-standing functional changes in multiple cortical and subcortical brain regions that are associated with cognitive and extrapyramidal syndromes.

Transient involvement of the cerebral cortex in a flare of Behçet’s syndrome

We describe a flare of Behçet’s syndrome in a 42-year-old man who presented with florid mucocutaneous manifestations, headache and vomiting, but without meningeal or neurologic signs. A single, non-enhancing cortical lesion was found in the frontal lobe by computed tomography and magnetic resonance (MR) imaging studies. Diffusion-weighted analysis and MR spectroscopy were consistent with focal inflammation. The patient improved with colchicine, and after 5 months, a repeat MR scan demonstrated resolution of the inflammatory changes suggesting that involvement of the cerebral cortex may be a self-limiting phenomenon, distinct from other more frequent and destructive parenchymal manifestations of neuro-Behçet’s disease.

Case Report: Recognizing Pneumatosis Intestinalis: A Case of Bowel Ischemia Presenting as Renal Colic

The clinical diagnosis of bowel ischemia is often difficult and the diagnosis can easily be missed unless there is a high index of clinical and radiological suspicion. Bowel ischemia and or infarction must be considered in the differential diagnosis in the older patient with pre-existing coronary artery or generalized vascular disease, cardiac failure, or arrhythmias especially atrial fibrillation and hypertension. An elderly patient with caecal infarction is presented who was initially diagnosed and treated for renal colic.