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Imaging techniques for the critical patient

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Abstract

Imaging techniques should be used with care in critically ill patients. It is important to keep the number of procedures to a minimum by selecting appropriate techniques, and to carry out each examination carefully to minimize the need for repeat examinations. This chapter provides guidance on the use of survey radiography, contrast radiography, ultrasonography, computed tomography and magnetic resonance imaging.

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Figures

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24.1 Horizontal X-ray beam standing lateral cranial thoracic radiograph of a skeletally mature dog with severe bronchopneumonia, most likely secondary to aspiration.
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24.2 Dorsoventral views of a skeletally mature canine thorax. (a) This radiograph was acquired prior to positive pressure ventilation. Note the increase in soft tissue opacity throughout the lung fields, with border effacement of the cardiac silhouette, with multiple air bronchograms present. (b) This radiograph is from the same patient after a period of positive pressure ventilation. Note the reduction in diffuse soft tissue opacity throughout the lung fields, absence of air bronchograms, and resolution of the border effacement of the cardiac silhouette indicating resolution of the alveolar pattern previously identified.
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24.3 Dorsoventral view of a skeletally mature canine thorax after a large dog bite showing evidence of ‘flail chest’. Severe trauma has been sustained to the left hemithorax with perforation of the pleural cavity and pulmonary contusion (arrowheads). Segmental rib fractures are present (arrowed), causing a mobile section of thoracic wall. There is severe subcutaneous emphysema, bilateral pneumothorax and severe bilateral pulmonary contusions (alveolar pattern). There is a mediastinal shift to the right.
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24.4 (a) Left lateral and (b) dorsoventral views of a skeletally mature feline thorax with a diaphragmatic rupture. The stomach has passed into the pleural cavity and occupies the majority of the left side of the pleural cavity (arrowed). It is moderately gas distended and there is resultant atelectasis of the surrounding lung fields and a contralateral mediastinal shift secondary to this space-occupying lesion.
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24.5 (a) Horizontal X-ray beam, standing lateral thoracic radiograph of a skeletally mature dog with progressive severe dyspnoea. There is evidence of pneumothorax and pneumoretroperitoneum. The lung fields are increased in opacity with numerous air bronchograms present. Bronchoalveolar lavage confirmed neutrophilic bronchopneumonia. The pneumothorax is presumed to be secondary to spontaneous rupture of a necrotic area of lung or increased transthoracic forces during laboured respiration. (b) Dorsoventral thoracic view of another dog with bilateral pneumothorax. The lung fields are retracted from the margins of the pleural cavity (arrowed) and increased in opacity secondary to atelectasis.
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24.6 (a) Lateral and (b) dorsoventral views of a skeletally mature feline thorax. The trachea is elevated on the lateral view, indicating cardiomegaly. There is border effacement of the cardiac silhouette and an increase in soft tissue opacity throughout the thorax. The lung lobes are retracted from the margins of the pleural cavity (arrowed). Pleural fissure lines are visible between the lung lobes (arrowhead). This is indicative of a pleural effusion. The cat was diagnosed with restrictive cardiomyopathy using echocardiography.
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24.7 Right parasternal short-axis view of the cardiac base showing the pulmonary outflow tract and branching of the main pulmonary artery. Anechoic material is identified within the pleural cavity, indicating pleural effusion (arrowed).
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24.8 (a) Right lateral thoracic radiograph of a skeletally mature cat that has sustained trauma, demonstrating a pneumomediastinum. (b) Close-up lateral thoracic radiograph of a dog after being hit by a car. The trachea, oesophagus and great vessels are visible within the cranial mediastinum abnormally well, indicating pneumomediastinum.
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24.9 Dorsoventral view of a skeletally mature canine thorax of a dog that has recently ingested rodenticide. There is marked widening of the cranial mediastinum (black arrows), which measures greater than two vertebral bodies wide. There is widening of the caudoventral mediastinal reflection, indicating the presence of pleural fluid (white arrow). Ultrasonography confirmed the presence of fluid in the mediastinum consistent with mediastinal haemorrhage.
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24.10 Lateral view of the thoracic inlet of the same dog as in Figure 24.9 . There is marked narrowing of the tracheal lumen in a diffuse fashion, affecting the entire trachea. Ultrasonography confirmed tracheal mucosal thickening, compatible with intramural haemorrhage.
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24.11 Right lateral view of the thorax of a skeletally mature dog with a history of regurgitation and a cough. There is marked widening of the intrathoracic oesophagus, which is dilated with gas. The dorsal border of the trachea forms a composite shadow with the ventral border of the oesophagus, called a tracheo-oesophageal stripe sign (arrowed). There is an increase in soft tissue opacity overlying the cardiac silhouette, with occasional air bronchograms. Radiological diagnosis: megaoesophagus with right middle lobar bronchopneumonia from aspiration.
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24.12 (a) Right lateral and (b) slightly rotated dorsoventral views of a skeletally mature cat with a chronic cough. There is marked widespread bronchial thickening, with a cavitary mass present in the right caudal lung field (arrowed). Multiple small soft tissue opacity interstitial nodules are also visible. The diagnosis in this case was bronchogenic carcinoma with multiple metastases.
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24.13 Left lateral view of the thorax of a skeletally mature dog that presented with severe dyspnoea. The dog was treated with furosemide 4 hours previously. There is a marked increase in soft tissue opacity, with multiple air bronchograms present, most obviously around the hilus of the lung and in the caudodorsal lung fields. The cardiac silhouette is markedly enlarged and left atrial dilatation is visible. There is moderate border effacement of the caudodorsal aspect of the cardiac silhouette, secondary to the overlying lung tissue pathology. Radiological diagnosis: congestive heart failure and cardiogenic pulmonary oedema. On echocardiography, severe dilated cardiomyopathy was seen.
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24.14 (a) Left lateral and (b) dorsoventral views of a skeletally mature canine thorax. The dog presented with a short history of severe acute dyspnoea and pyrexia. There is a marked increase in soft tissue opacity in the cranial aspect of the thorax with consequent border effacement of the cranial mediastinum and cardiac silhouette. On the lateral view, there is a lobar sign overlying the cardiac silhouette. This is an interface between the consolidated right middle lobe and the relatively aerated right caudal lobe (arrowed). Radiological diagnosis: bronchopneumonia, most likely secondary to aspiration. (c) Left lateral thoracic radiograph of the dog after successful management.
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24.15 Dorsoventral radiograph of a skeletally mature canine thorax. There is an increase in soft tissue opacity in the left hemithorax, making evaluation of the left lung difficult. There is also an ipsilateral mediastinal shift, with the cardiac silhouette displaced to the left. Radiological diagnosis: atelectasis. This dog had been sedated and placed in left lateral recumbency prior to the radiograph being obtained.
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24.16 (a) Right lateral and (b) dorsoventral views of a skeletally mature canine thorax. The patient presented with a chronic progressive history of a soft cough and exercise intolerance. There is marked cardiac enlargement, with an increase in dorsoventral cardiac height on the lateral view, and an increase in width on the dorsoventral view. The left atrium is enlarged, seen as a soft tissue opacity at the dorsocaudal aspect of the cardiac silhouette on the lateral view and as a soft tissue opacity between the caudal lobar principal bronchi on the dorsoventral view. The pulmonary veins are also enlarged.
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24.17 (a) Right lateral abdominal radiograph of a skeletally mature cat with a history of anorexia and weight loss. The radiograph was obtained after endoscopy. There is marked pneumoperitoneum with increased serosal detail visible throughout the abdomen. In the ventral abdomen, there is border effacement of the abdominal viscera, secondary to the presence of peritoneal fluid. There is also evidence of subcutaneous emphysema within the inguinal region. There are only six lumbar vertebrae present. Ultrasonography confirmed a grossly thickened stomach and small intestine. Histological diagnosis was lymphoplasmacytic gastritis and enteritis with gastric ulceration, presumably leading to perforation. (b) Horizontal X-ray beam decubitus ventrodorsal view of a skeletally mature dog with a history of vomiting and abdominal pain. Peritoneal gas is visible accumulating anti-dependently within the cranial abdomen around the pylorus and liver lobes. Pneumoperitoneum confirmed that this represented an abdominal emergency, and gastric perforation was confirmed on laparotomy. The dog had been treated with long-term non-steroidal anti-inflammatory drugs for degenerative joint disease.
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24.18 Left lateral view of the abdomen of a skeletally mature dog that has had a recent coeliotomy. The stomach is grossly dilated with gas. The pylorus lies cranial and dorsal to the fundus and there is a soft tissue band (arrowed) between it and the gastric body (compartmentalization). There is a loss of serosal detail, indicating the presence of peritoneal fluid. Gas is present within the peritoneal cavity, indicating pneumoperitoneum, secondary to the recent abdominal surgery. Radiological diagnosis: gastric dilatation–volvulus (GDV) syndrome. Note that a right lateral radiograph is typically recommended as the most valuable view to document the presence of GDV.
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24.19 Right lateral radiograph of a skeletally mature canine abdomen. The dog has undergone recent surgery to remove a gastric foreign body. There is evidence of pneumoperitoneum and peritoneal effusion. Two further radiopaque foreign bodies are present within the small intestine. They are characterized by a central mineral opacity with a peripheral soft tissue opacity. The small intestine is markedly dilated, compatible with complete obstruction (mechanical ileus). Two golf balls were removed at laparotomy.
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24.20 Right lateral radiograph of a skeletally mature canine thorax of a dog with a history of weight loss, vomiting and intermittent abdominal bloating. Loops of small intestine are visible within the thorax, overlying the normal thoracic structures (arrowed). There is border effacement of the cardiac silhouette. Radiological diagnosis: diaphragmatic rupture.
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24.21 (a) Left lateral and (b) ventrodorsal views of a skeletally mature canine abdomen of a large-breed dog with a history of acute vomiting. There is an increase in soft tissue opacity, accompanied by a loss of serosal detail in the cranial abdomen caudal to the stomach. The transverse colon is displaced caudally. On the ventrodorsal view, there is a poorly defined increase in soft tissue opacity within the cranial right aspect of the abdomen. Ultrasonography confirmed the presence of pancreatitis and minimal peritoneal effusion.
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24.22 (a) Right lateral and (b) slightly rotated ventrodorsal views of a skeletally mature Persian cat with anorexia and weight loss. There is marked enlargement of the hepatic silhouette with caudal displacement and tilting of the gastric axis. The left kidney is also markedly enlarged (arrowed), with a normal appearance of the right kidney. There is incidental adrenal mineralization. Radiological diagnosis: left renomegaly and hepatomegaly. On ultrasonography, there were multiple cystic cavitary lesions throughout the liver and kidneys.
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24.23 Right lateral abdominal radiograph of a skeletally mature cat with anorexia, weight loss and polydipsia. There is marked enlargement of the renal silhouette, which measures approximately 3.5 x the length of the vertebral body of L2 (normal range = 2.4–3.0 x L2). There is ventral displacement of the transverse and descending colon.
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24.24 Right lateral abdominal radiograph of a skeletally mature dog. There is marked heterogeneous mineralization of the adrenal glands, which are visible in the dorsal cranial retroperitoneum, dorsal and cranial to the kidneys (arrowed). The dog had no clinical signs that related to adrenal disease. This finding was considered incidental.
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24.25 Right lateral abdominal radiograph of a dog that had a history of dysuria. There is slight enlargement of the prostate gland, caudal to the bladder (arrowed). The bladder appears moderately enlarged. Prostatic wash was consistent with benign prostatic hyperplasia.
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24.26 Right lateral skull radiograph of a skeletally immature dog with pain on opening the mouth. There is marked sclerosis of the mandible and calvarium. A smooth periosteal reaction is present along the ventral aspect of the horizontal mandibular body. Radiological diagnosis: craniomandibular osteopathy.
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24.27 Right lateral radiograph of the neck of a skeletally mature dog with neck pain after running into a tree. There is a short oblique fracture of the body of C2. The body of the vertebra is divided and the caudal aspect is dorsally displaced. This caused ventral impingement of the vertebral canal.
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24.28 Oblique barium oesophagram of a dog with a history of regurgitation. The study shows sliding of the gastric cardia into the caudal mediastinum and moderate gas dilatation of the oesophagus. Radiological diagnosis: sliding hiatal hernia. The lesion was not identified on survey abdominal radiographs.
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24.30 (a) Right lateral view and (b) pneumogastrogram of a skeletally immature dog with a history of chronic vomiting. On the (a) survey film, a poorly defined region of lucency is visible in the region of the gastric pylorus (arrowed). The lesion appears rounded but is difficult to identify definitively. (b) After insufflation of the stomach with air, the gastric foreign body (rubber ball) is easily identified (arrowed).
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24.31 Right lateral radiograph of a dog that has undergone a low-dose double contrast gastrogram. The stomach appears normal.
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24.33 Ventrodorsal abdominal view after intravenous contrast administration (intravenous urogram). This image shows a normal nephrogram phase. The kidneys are easily identified.
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24.34 Ventrodorsal abdominal view after intravenous contrast administration (intravenous urogram). This image shows a normal ureterogram phase. The kidneys, renal pelves and ureters are easily identified.
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24.37 Retrograde urethrogram in a dog with dysuria and haematuria. There is a filling defect in the prostatic urethra. The defect is irregular in margination. The prostate gland is moderately enlarged. Prostatic wash confirmed prostatic carcinoma.
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24.38 Retrograde urethrogram of a cat that has recently suffered road traffic trauma. There is marked extravasation of contrast medium into the peri-urethral soft tissues, indicating urethral perforation.
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24.39 Double contrast cystogram in a dog with haematuria. Several filling defects are present in the contrast puddle within the bladder. These structures are rounded in margination and vary in size. The ventral bladder wall is thickened. Radiological diagnosis: cystic urolithiasis and cystitis.
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24.40 Lateral radiograph of the thoracolumbar spine 0f a dog that has sustained trauma after being hit by a car. The neurological localization was T3–L3. A myelogram has been performed. There is collapse of the T13–L1 intervertebral disc space and mild subluxation of T13–L1, with dorsal subluxation of the caudal aspect of T13 compared with L1. There is compression of both the dorsal and ventral contrast columns, confirming extradural cord compression secondary to the subluxation.
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24.42 Thoracic ultrasonogram 0f a dog with dyspnoea. The left ventricle is visible from this apical view. There is a small volume of pericardial effusion (white arrow) and a moderate volume of pleural effusion (black arrow). A small mass was identified in the atrioventricular septum.
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24.43 Right parasternal short-axis view of the heart at the level of the left atrium of a dog with a soft nocturnal cough and exercise intolerance. There is marked enlargement of the left atrium (arrowed), which should be no more than 1.5 times the size of the aorta at the level of the aortic valve. This dog had severe mitral regurgitation secondary to myxomatous mitral valve disease.
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24.44 (a) Sagittal and (b) right transverse intercostal ultrasonograms of a normal canine liver. The bright hyperechoic walled vessels are hepatic portal veins. The dark hypoechoic walled vessels are hepatic veins.
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24.45 Ultrasonogram of the canine spleen. Note the fine echogenic texture (like fine sand). There is a poorly defined hypoechoic nodule within the splenic parenchyma. Fine-needle aspiration of the lesion revealed extramedullary haematopoiesis.
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24.46 Ultrasonogram of the liver of a cat with icterus. The liver margins are rounded and there is evidence of hepatomegaly. The parenchyma is hypoechoic, with increased visualization of the hepatic portal veins. Histological diagnosis was amyloidosis.
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24.47 (a–b) Longitudinal ultrasonograms of normal canine kidneys. (c) Longitudinal and (d) transverse ultrasonograms of a feline kidney with chronic tubulointerstitial nephritis (chronic kidney disease). The kidney is markedly reduced in size and appears hyperechoic. There is mild pyelectasia and loss of corticomedullary distinction.
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24.48 (a) Ultrasonogram of a normal left adrenal gland. Note the peanut shape. (b) Ultrasonogram of a normal right adrenal gland. (c) Ultrasonogram of a left adrenal gland. There is a heterogeneously isoechoic nodule in the caudal pole of the gland. The origin of this nodule is not clear from imaging alone and should be interpreted in the light of clinical findings, as these nodules are often incidental. (d) Ultrasonogram of the left adrenal gland of a dog undergoing treatment with trilostane. The gland is markedly enlarged and has lost its normal shape. There is increased corticomedullary distinction. This is considered a normal finding in dogs treated with trilostane.
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24.49 Longitudinal ultrasonogram of the bladder of a dog with intermittent haematuria and dysuria. There is a large lesion (a calculus) within the lumen of the bladder that is characterized by a hyperechoic proximal interface and long distal acoustic shadows.
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24.50 Longitudinal ultrasonogram of the duodenum, showing the normal appearance of a pseudoulcer (a region of thinned mucosa for antigen presentation). The normal intestinal wall layering is readily identified.
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24.51 (a) Longitudinal ultrasonogram of the duodenum of a puppy with severe vomiting and diarrhoea. The intestinal wall is markedly thickened and the mucosa is markedly hyperechoic with a slightly corrugated appearance. Peristalsis was slow and static fluid was visualized within the lumen. Diagnosis: duodenitis. (b) Longitudinal ultrasonogram of the duodenum of a dog with acute vomiting. The duodenal lumen can be seen to widen around a large intraluminal mass characterized by a hyperechoic proximal interface and long distal acoustic shadows (arrowed). Diagnosis: duodenal foreign body. (c) Transverse ultrasonogram of a loop of jejunum of a vomiting puppy with a palpable abdominal mass. A normal loop of jejunum (intussusceptum) is identified surrounded by mildly dilated mesenteric blood vessels and fat, within another dilated loop of jejunum (intussuscipiens). Diagnosis: intussusception.
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24.52 (a) Transverse ultrasonogram of the normal appearance of the canine pancreas (right lobe). The duodenum is to the right of the image. The pancreaticoduodenal vein is seen within the pancreas in cross-section. (b) Longitudinal ultrasonogram of the normal feline pancreas. The pancreaticoduodenal vein is identified in longitudinal section. (c) Transverse ultrasonogram of the canine pancreas (right limb). The pancreas is enlarged and heterogeneously hypoechoic. The surrounding mesenteric fat is heterogeneously hyperechoic. The duodenal wall is thickened. Diagnosis: acute pancreatitis, mesenteric steatitis and duodenitis.
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24.53 Lateral radiograph of a canine lumbar spine of a patient that has sustained road traffic trauma. The dog had no deep pain sensation. There is an oblique fracture through the vertebral body of L5 with displacement of the caudal segment cranioventrally. Clearly, advanced imaging is not required in this case, given the severity of the radiological and clinical findings.
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24.54 (a) Transverse ultrasonogram of the brain of a normal puppy. The image is acquired through an open bregmatic fontanelle. Assessment for gross structural disease can be made. (b) T2-weighted transverse magnetic resonance (MR) image of a different dog at the same level. Clearly, the contrast resolution on MRI is substantially increased compared with ultrasonography. (c) Transverse ultrasonogram of the brain of a puppy through the bregmatic fontanelle. The lateral ventricles appear enlarged, presenting as large, paired, well demarcated anechoic structures (arrowed). The lateral recesses of the lateral ventricles also appear enlarged. Visible brain parenchyma is reduced in volume (compared with Figure 24.54a ). (d) Sagittal ultrasonogram of the brain of a normal puppy through an open bregmatic fontanelle. (e) T2-weighted sagittal MR image of the brain of a different dog, for comparison with Figure 25.54d.
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24.55 Computed tomography (CT) images. (a) Dorsal reformatted multiplanar reconstruction (MPR) image of the skull of a dog that has recently sustained trauma, viewed using a bone window and sharp algorithm. A comminuted, slightly depressed fracture of the right temporal bone is visible. (b) Dorsal reformatted MPR image of the skull of the same dog as in (a), viewed using a soft tissue window and soft algorithm after contrast administration. A hypoattenuating region is seen within the masticatory muscles and within the brain parenchyma, directly adjacent to the fracture (arrowed). There is a contralateral midline shift within the brain, suggesting brain swelling. The changes represent cerebral oedema secondary to trauma. (c) Sagittal post-contrast reformatted MPR image of a dog that presented obtunded with a dorsal soft tissue swelling. The dorsal soft tissue swelling is visible. It has non-contrast-enhancing contents surrounded by soft tissue that exhibits contrast enhancement. There is caudal subtentorial herniation at the level of the osseous tentorium cerebelli (arrowed). The cerebellum is displaced caudally and there is indentation of the rostral border of the cerebellum. There is also herniation of the cerebellar vermis at the level of the foramen magnum. These changes are indicative of raised intracranial pressure.
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24.56 (a) Transverse and (b) dorsal multiplanar reconstruction (MPR), (c) oblique MPR and (d) surface-shaded volume-rendered images from a dog that had sustained head trauma after being kicked by a horse. Comminuted fractures involving the nasal cavity, frontal sinuses and orbits are visible. CT lends itself to this sort of orthopaedic detail.
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24.57 CT images: post-contrast transverse images of the skull of a dog that presented with left-sided facial swelling, pyrexia and seizures. (a) Bone window with a sharp algorithm. These display characteristics are most useful to assess bone detail. (b) Soft tissue window with a soft algorithm. These display characteristics are most useful to assess soft tissue injuries. (c) Brain window with a soft tissue algorithm. In this image, the brain can be assessed at the expense of other structures. There is a left temporal extradural abscess with associated increased intracranial pressure.
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24.58 CT images. (a) Paramedian reformatted multiplanar reconstruction (MPR) image of the head of a cat that had been shot with an air gun, viewed using a sharp algorithm and bone window. The air gun pellet is visible surrounded by metallic beam hardening artefacts. However, it can still be identified within the frontal lobe. (b) Transverse image of the forebrain from the same cat as in (a) viewed with a soft tissue algorithm and brain window. Hyperattenuating material is seen within the dorsal right lateral aspect of the brain parenchyma (arrowed). This is compatible with intraparenchymal haemorrhage. (c) Dorsal reformatted MPR image of a dog that had sustained head trauma after being hit by a car. There is a midline shift of brain parenchyma to the left. A hyperattenuating lesion is present in the right rostral fossa, adjacent to the frontal bone. This represents a skull fracture. Around it, the brain parenchyma is hypoattenuating and enlarged, suggesting oedema (arrowed).
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24.59 CT images. (a) Dorsal multiplanar reconstruction image of a normal canine cribriform plate. A stair step artefact is present secondary to non-isometric voxels. Effectively, this is an example of image under-sampling and poor spatial resolution. It is caused by the craniocaudal length of the image voxel being longer than the transverse dimensions and therefore the spatial resolution is much reduced when the image is rotated away from the transverse plane. It is commonplace in images from older single-slice CT units. (b) Similar image of a dog using isometric voxels. In this image, there is no reduction in spatial resolution caused by rotating the image from the transverse plane.
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24.60 Transverse MR images of the cerebellum and brainstem of a dog. (a) T2-weighted image. There is a poorly defined region of mildly increased T2-weighted hyperintensity within the left aspect of the mesencephalon. (b) Gradient recalled echo (GRE) T2*-weighted image. This image shows the region as a signal void (black). This is highly suggestive that the lesion is composed of haemorrhage. The dog was diagnosed with a coagulopathy secondary to angiostrongylosis.
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24.61 Schematic diagrams representing transverse CT images of the forebrain and haemorrhage (red). (a) Epidural: biconvex between the meninges and the periosteum. The haematoma does not cross the suture lines but may cross the midline. (b) Subdural: crescent shape between the dura and the arachnoid mater. The haematoma does cross the suture lines but does not cross the midline. (c) Subarachnoid: blood mixes with cerebrospinal fluid and basal cisterns.
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24.62 MR images. (a) T2-weighted sagittal image of the brain of a cat with increased intracranial pressure. There is caudal displacement of the thalamus and mesencephalon caused by a rostral fossa mass (not shown). This causes caudal subtentorial (arrowed) and cerebellar (arrowhead) herniation. It is a poor prognostic indicator. (b) T1-weighted post-contrast and (c) T2-weighted images of the eye. There is a T1-weighted hyperintense, T2-weighted hypointense region of the caudal aspect of the eye that projects into the vitreous body. This is the optic disc and represents papilloedema. This is an indication of raised intracranial pressure.
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24.63 CT images of the same dog as shown in Figure 24.27 . (a) Transverse image of C2 viewed with a bone window and sharp algorithm. The fracture is clearly identified. (b) Thick-slice sagittally reformatted maximum intensity view of the cervical spine. This method of image display gives more information as to how the fracture fragments relate to each other. The short oblique vertebral body fracture of C2 is clearly visible. There is evidence of narrowing of the vertebral canal secondary to displacement of the caudal fracture fragment. (c) Thick-slice sagittally reformatted maximum intensity view after fracture reduction and surgical stabilization. The vertebral canal diameter has been normalized. Metallic artefacts are present secondary to implants. The screws are embedded in polymethyl methacrylate ventral to the vertebral body of C2. (d) Semi-transparent volume-rendered CT image of the same dog. In this image, the computer software recognizes metallic implants and displays them as a different colour to bone (red).
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24.64 MR images of an intervertebral disc extrusion. (a) Three-dimensional dorsal gradient recalled echo (GRE) fast imaging employing steady-state acquisition (FIESTA) image of the spine of a dog that presented with neurological deficits that localized to the thoracolumbar spine. The image shows a heterogeneously hypointense, well demarcated extradural lesion at the level of the T11–12 intervertebral disc on the right (arrowed). The lesion caused moderate cord compression. (b) T2-weighted transverse image of the same dog as in (a). The extruded disc material presents as an extradural compressive lesion within the vertebral canal on the right of the cord, which is displaced to the left and moderately compressed (arrowed).
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24.65 MR images of low-volume high-velocity disc extrusion. (a) High-resolution three-dimensional GRE FIESTA image showing the hyperintense tract of the nucleus pulposus across the cord (arrowed). (b) T2-weighted sagittal image of the lumbar cord segment. The hyperintense tract is once again clearly visible (arrowed).
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24.66 MR images: myelomalacia. (a) Transverse GRE and (b) T2-weighted paramedian images of the lumbar spine of a dog with an intervertebral disc extrusion. There are regions of signal void (black) within the cord on the GRE image. On the T2-weighted image, this appears as mixed signal intensities within the cord (arrowed). (c) Post-mortem image of a dog that was euthanased secondary to deterioration of neurological signs. A durotomy has been performed. There is evidence of liquefactive necrosis of the cord parenchyma.
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24.67 CT images. (a) Transverse and (b) dorsal multiplanar reconstruction images of a canine abdomen after contrast administration. A poorly defined soft tissue attenuating mass is present medial to the right kidney (arrowed). There is non-contrast-enhancing soft tissue attenuating material filling the retroperitoneum and dissecting between the retroperitoneal fat. Diagnosis: phaeochromocytoma and associated haemorrhage. This was a large dog and obtaining this level of detail by ultrasonography would have been very difficult.

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