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215 Cards in this Set
- Front
- Back
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What is a lateral decubitus view?
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Animal is in left lateral recumbency and the x-ray beam is directed horizontally and centered at the umbilicus
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When is lateral decubitus view used?
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cases where free intra-abdominal gas/air is suspected and requires confirmation- gas will rise and lies under the right cranial abdomen
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How does intra-abdominal fat effect the radiograph contrast?
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improves and permits viewer to identify the various organs
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What types of dogs have poor abdominal contrast normally?
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young animals and athletic dogs
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What are the two most common pathological causes of poor contrast and loss of serosal detail in the abdomen?
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intra-abdominal fluid and peritonitis
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Besides fluid and peritonitis, what is another cause of loss of serosal detail but is far less common?
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metastatic spread throughout omentum such as carcinomatosis
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What is the diagnostic imaging method of choice for peritoneal fluid?
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ultrasonography
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What four processes can peritonitis be secondary to?
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trauma to the abdominal wall or rupture of an abdominal organ, pancreatitis or pancreatic neoplasia, infectious diseases, or rupture of the urinary bladder or biliary tract
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How does peritonitis on a radiograph present?
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granular or patchy increase in opacity
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What three processes cause free intra-abdominal air to be seen on radiographs?
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GI perforation, penetrating injuries to the abdominal wall or gas producing bacteria
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What causes bile peritonitis?
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trauma or a result of chronic obstruction to the outflow into the duodenum
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What are four causes of peritoneal haemorrhage?
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ruptured spleen, ruptured liver, avulsed blood vessel, erosion of a vital structure by a neoplasm
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What is seen on a radiograph with pancreatitis?
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similar to other causes of peritonitis except the poor serosal detail is usually located in the cranioventral section and right cranial area of the abdomen
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What are the two causes of retroperitoneal fluid?
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haemorrhage or urine
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What four signs of retroperitoneal fluid are seen on radiographs?
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poor retroperitoneal detail, ill defined renal shadows, displaced renal silhouettes, displaced colon
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What are the three causes of intra-abdominal free gas?
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abdominal wall trauma, intestinal perforation or post laparotomy
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What three characteristics will be seen on radiographs with intra-abdominal free gas?
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seperation of the diaphragm from teh liver by a gas opacity, gas shadows surrounding and enhancing the renal silhouette, unusual gas patterns throughout abdomen not associated with GI tract
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Radiographically, where does the liver normally lie?
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within the costal arch, with the ventral margin just caudal to the last rib
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What is the usual liver echotexture in ultrasonography?
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finely granular with sharp and well defined edges
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What are the four radiographic signs of hepatomegaly?
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1: Rounding of the caudal margin which projects beyond the costal arch
2: Projection of the liver beyond the costal arch 3: Caudal displacement of the gastric axis 4: Caudal displacement of abdominal organs |
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What are the two characteristics of microhepatica radiographically?
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inability to identify the ventro-caudal liver margin and gastric axis is displaced cranially
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How can porto-systemic shunts be confirmed through imaging?
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portal venography: contrast radiographs, ultrasounds, or nuclear scintigraphy
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What is nuclear scintigraphy?
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radioactive isotope is administered to the patient via the rectum and the length of time taken for the radioactivity to reach the heart and liver is calculated
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What is the radiographic appearance of choleliths? Where are they found?
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discrete radio-opacities in the cranioventral hepatic region
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Is spleen usually seen in normal cats?
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no
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What is the splenic echotexture compared to liver and kidneys in ultrasonography?
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hyperechoic with granular appearance
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How does a splenic rupture appear radiographically?
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poor serosal definition often seen in the cranioventral abdomen due to the haemorrhage or metastatic seeding
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What are three characteristics of splenic rupture in ultrasonography?
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1: echogenic fluid oscillating in the abdomen
2: fibrin tags on serosal surfaces 3: disruption of the normal splenic outline |
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How does splenic torsion appear radiographically?
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enlarged spleen seen on teh left lateral aspect of the abdomen on the V-D view
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What can spenic torsion be confused with on radiographs?
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splenomegaly
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What is the diagnostic imagine method of choice for splenic torsion?
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ultrasonography
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How does splenic torsion appear on ultrasound?
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starry sky appearance
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How does ventral hernia appear radiographically?
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abdominal structures are lying outside of the abdominal cavity but remain under the skin
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How does perineal hernia appear radiographically?
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bladder is absent in caudal abdomen
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How does a hiatal hernia appear radiographically?
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protrusion of part of the stomach through the esophageal hiatus of the diaphragm
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What will an inguinal hernia contain?
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fat, bladder, uterus or intestine
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The basic examination of the abdomen requires how many radiographs and at what views?
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two vies: a right lateral recumbent view and a VD view
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What is the long axis of the stomach?
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an imaginary line drawn from the fundus to the pylorus
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Normally, where does the long axis of the stomach lie on a lateral radiograph?
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parallel to the tenth intercostal space
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How does barium move in a radiograph study in the stomach? Where will it move on a right lateral recumbency view? LLR?
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Barium moves in the opposite direction falling to the most dependant protion: RLR: barium located in the pylorus, LLR: barium located in the fundus
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On a VD study, where is the long axis of the stomach in the dog? Cat?
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Dog:right angles to the vertebral column
Cat: lies completely on the left hand side of the abdomen in a curved C shape |
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What drug can be used to cause castric dilatation?
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Xylazine: alpha 2 agonist
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What is compartmentalization of the stomach? When is it seen?
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a soft tissue stripe seen crossing the area of the area of the stomach, seen in gastric torsion
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Besides compartmentalization, what are five radiographic characteristics seen in gastric dilatation and volvulus?
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food material seen in one of the compartments, small intestine seen on dorso-cranial section of the abdomen, air seen throughout rest of the intestine, megaesophagus, pylorus seen in dorso-cranial abdomen and on left cranial aspects of the abdominal cavity
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What is the normal small intestine diameter on radiographs?
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Up to 1.5 times the vertical body of L5
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What is the GI transit time for liquid barium contrast? How long until the tract should be empty?
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30-120 minutes transit time, completely empty between 3-5 hours post administration
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Outpouchings along the antimesenteric border of the duodenum seen in dogs in a barium swallow are?
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peyers patches or "pseudoulcers"
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What conformation does the duodenum have in cats during a barium swallow?
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string of pearls
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What is the rule of thumb for the width of the wall of the small intestine?
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1/8-1/4 the width of teh lumen
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How does generous amounts of mesenteric fat along the serosal borders of the intestine affect appearance of the intestinal wall thickness?
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appear thicker
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What are the five ultrasonographic layers of the stomach and intestine from outside to inside?
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hyperechoic serosa, hypoechoic muscularis, hyperechoic submucosa, mucosa and hyperechoic lumen
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What are the five characteristics of small intestinal wall thickening caused by inflammation seen on ultrasound?
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1: layering pattern perserved
2: wall thickening or increased mucosal echogenicity 3: generally diffuse 4: Any layer may be affected 5: rarely causes obstruction |
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What are the three characteristics of small intestinal wall thickening caused by neoplasia seen on ultrasound?
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1: layering pattern is disrupted
2: generally focal 3: may or may not cause obstruction |
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What is ileus?
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distension in a segment or segments of small intestine- with either fluid or more usually gas
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What are characteristics of mechanical ileus? What is the usual cause?
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severe, focal distension; caused by obstruction
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What is a "gravel sign" and where is it seen?
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mineralized particulate material build up cranial to a chronic obstruction and is seen in a consistent location within the GI tract
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What are the characteristics of functional ileus?
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moderate generalized distension with hyper or hypomotility on U/S
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What is intussusception? Where is intussusception commonly located?
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telescoping of one section of the intestine into another loop of intestine; located commonly at the ceco-colic or ilieocolic junction
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WHow does intussusception appear with a gas or barium outline?
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coiled spring
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What is a redundant colon?
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descending colon that lies to the right fo the midline
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What is a megacolon?
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gross distention of the colon
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How is acoustic impedance dependent on?
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density of the substance x velocity of sound in the substance
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As ultrasound waves travel through matter, what three actions can occur?
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reflected, refracted or absorbed
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When does ultrasound reflection?
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ultrasound beam encounters an interface between adjacent tissues with different acoustic impedance
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What is the relationship between reflected ultrasound and difference in impedance in ultrasounds?
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the larger the difference in impedence, the larger the proportion of reflected ultrasound
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When does specular reflection occur in ultrasound?
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occurs when the beam encounters large interfaces and the ultrasound beam is reflected at an angle equal to the angle of incicence
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When does scatter occur in ultrasound?
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occurs when ultrasound waves are reflected by small interfaces and are not angle dependent
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Is specular reflection in ultrasound angle dependent?
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Yes, because if at an angle, part of the reflected ultrasound will not reach the transducer
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What do scatter echoes contribute to on an ultrasound?
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parenchymal texture of multiple organs
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What is ultrasound refraction?
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the part of the beam that is not reflected will be transmitted and will change speed and angle according to the type of tissue
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What is ultrasound absorption?
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the part of the beam energy that is absorbed by the tissues due tot eh frictional forces taht oppose the motion of the particles int eh medium
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What factor affects absorption?
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frequency of the ultrasound beam: higher frequencies are attenuated more than low frequency ones
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How does frequency and attenuation affect penetration?
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higher frequency=higher attenuation= less penetration
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In what mode are abdominal ultrasound images displayed?
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B-mode: brightness mode- returning echoes are displayed in a screen as white dots
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How does frequency affect resolution and image in ultrasounds?
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high frequency=poor penetration=great image and high resolution
low frequency=good penetration= poor image and poor resolution |
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What are the two ways of classifying transducer types?
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mechanical and electric transducers
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What is another name for electronic transducers?
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array transducers
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What is the footprint of a transducer?
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surface of the transducer that contacts the skin during the ultrasound
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How does the power of the scanner affect the ultrasound?
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increasing power strengthens the beam
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What occurs if the ultrasound beam is too strong?
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artifacts appear and image quality decreases
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What occurs if the ultrasound beam is too weak?
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amplitude of the returning echoes will not be strong enough to generate an adequate image
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What does focusing do to an ultrasound image?
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focusing allows operator to select one or multiple depths at which the beam of ultrasounds is narrower- the narrower the beam, the higher the resolution
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How does general gain affect ultrasound?
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gain affects the amplification of the signal generated by the returning echoes
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What does time gain compensation do to ultrasound?
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TGC allows control of the gain at different depths to allow for homogenous appearance int eh image
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What does time gain compensation help to compensate for?
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the strength of the ultrasound beam decreases as it travels deeper into the tissue giving the image a darker appearance as depth increases: TGC helps compensate for this
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What is a mirror artefact in ultrasound?
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occurs when an U/S beam encounters a strong interface and most of the beam is reflected back. This reflection encounters other structures which will show a mirror image on the other side of the reflected interface
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When does acoustic enhancement occur?
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occurs when the beam travels through an area that attenuates the ultrasound beam less than the surrounding tissues
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How does acoustic enhancement appear on ultrasound?
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produce an area of increased signal beyond the hypoattenuating structure
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When does side lobe artefact appear on ultrasound?
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structures along the path of the secondary beams will be displayed as if they were on the plane of the primary beam
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When does acoustic shadowing occur on ultrasound?
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highly echogenic structures causing complete reflection of teh ultrasound beam
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How does acoustic shadowing appear on ultrasound?
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areas beyond high echogenic structure will apear black due to lack of echoes
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How can acoustic shadowing in ultrasound be of diagnostic value?
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depicts mineralization within the soft tissue or help identifying foreign bodies
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When does edge shadowing/refraction occur in ultrasound?
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around edges of rounded structures resulting in a change in direction of the ultrasound beam
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How does edge shadowing/refraction appear on ultrasound?
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no echoes will reach areas deeper to the area where refraction occurs and an echo free area will be displayed
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What structures will usually show edge shadowing/refraction artefact?
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kidneys and gall bladder
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When does reverberation artefact occur in ultrasound?
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the ultrasound beam encounters two strong parallel reflectors and some fo the sound waves are "trapped" between both reflectors
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What does reverberation artefact show on an ultrasound?
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creates multiple bright parallel lines with decreasing echo intensity
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When does comet tail artefacts occur on ultrasound?
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created by gas and some metallic objects
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How does comet tail artefacts appear on ultrasound?
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series of close parallel bright echoes
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What is echogenicity?
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the ability of materials and interfaces to reflect the ultrasound beam and generate echoes
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What is anechoic?
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when the ultrasound beam is nto reflected and no echoes are generated
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What materials are usually anechoic on ultrasound?
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clear fluids
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What is echoic/echogenic?
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the brightness of an area
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What is hyperechoic?
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higher echogenicity
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What is hypoechoic?
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of lower echogenicity
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What is isoechoic?
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of similar echogenicity
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What are the two principles by which x-rays are generated?
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Behmsstraulung or braking electrons and characteristic radiation
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How does Behmsstraulung or braking electrons create x-rays?
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High speed electrons interact with the atoms in the target, electrons are deflected and slow down due to the interactions. The energy lost by the electron is released into an x-ray.
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What is the continuous spectrum in x-rays?
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The photons of all energies are produced up to a maximum when an electron loses all its energy in a single interaction
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How does characteristic radiation create x-rays?
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a high speed electron collides with an electron in the target and the target electron is ejected leaving a shell with an empty space and an atom with a positive charge. An electron in the outer shell of the atom will fall down to fill up the space, making it lose energy in the form of a photon that becomes the x-ray.
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What is ionization in characteristic radiation in x-rays?
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electron in the target is ejected, leaving a shell with an empty space and an atom with a positive charge
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How does the characteristic radiation differ from the continuous spectrum in x-rays?
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as the energies of each shell of an atom are constant, the generated x-rays have always the same energy creating peaks of determined photon energy (spiky peaks)
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What two basic components are needed to produce x-rays?
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a source of electrons= CATHODE, a target= ANODE
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What charge does the cathode have in radiographs? Anode?
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Cathode: negatively charged, anode: positively charged
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What does the difference in charges between the cathode and the anode create that is essential to radiographs?
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an electrical potential which accelerates the electrons towards teh target
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What two components make up the cathode in a radiograph?
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filament and focussing cup
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What is a thermionic emission?
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a cloud of electrons around the filament in a cathode when a current is applied through the filament
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What is the anode usually made out of in an x-ray?
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elements with high atomic number, usually tyngsten
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What are the two types of anodes?
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stationary anodes: fixed small tungsten target with electrons colliding in the same spot of the target limiting the amount of x-rays generated; rotating anodes: tungsten is mounted on a rotating disc and the area of impact of electrons is increased
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What insulation is provided by tube housing in an x-ray machine?
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thermal and electric
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What is the main component of tube housing in an x-ray machine?
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evacuated glass tube, containing the cathode and anode, immersed in oil and surrounded by a metal case lined with lead except where the x-ray beam will emerge
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What x-ray machine control regulates teh output of the circuit?
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kilovoltage control= kV
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What are the two main electric circuits in an x-ray machine?
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low voltage circuit and high voltage circuit
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Where does the low voltage work and what does it regulate?
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cathode filament; regulates mA
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Where does the high voltage circuit and what does it regulate?
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creates electric potential between cathode and anode; regulates kV
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What is the mains voltage compensator or line voltage adjuster in the x-ray machine?
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transformer that will correct for any variations in the incoming mains voltage to ensure that the correct voltage is applied to the remainder of the circuit
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What are three main problems with an x-ray machine?
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low voltage, alternating current and it fluctuates
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How can an x-ray machine transform voltage from low to high?
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step up transformer
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What regulates voltage to filament in an x-ray machine?
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step down transformer
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How is voltage transformed from AC into DC in an x-ray machine?
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restification using complex circuits
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What does the miliampere control (mA) do in an x-ray machine?
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regulates the voltage applied to the filament and controls its temperature
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What affect does a higher kV on x-ray energy?
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higher kV= higher electric potential across tube= increase in x-ray energy
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What affect does high kV have on number of x-rays?
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high kV increases number of x-rays
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What affect does higher mA have on x-rays?
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higher mA= higher filament temperature= more electrons available= increased QUANTITY of x-rays
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What does the exposure timer do in an x-ray machine?
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controls the length of time the high tension voltage is applied to the tube and therefore the length of time the x-rays are emitted
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How does an increased exposure time affect the x-ray?
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longer exposure= more electrons are pulled from the cathode= more x-rays
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What are the four types of x-ray machines and their corresponding mA values?
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portable= <100mA, mobile= up to 500mA, fixed single phase= up to 1000mA, fixed three phase= up to 1500/2000 mA
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How is a radiographic image created?
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by the difference in attenuation of the x-ray beam as it travels through different tissues
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What are the two more relevant processes by which beam attenuation occurs in x-rays?
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photoelectric affect and the compton effect
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What are x-rays?
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electromagnetic waves with the ability to penetrate tissues
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How does attenuation occur in an x-ray?
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the beam is either absorbed (energy is deposited and results in a radiation dose to the tissue exposed) or scattered
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How does scattered radiation affect image quality?
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decreases image quality
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What is the photoelectric effect?
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an incident photon encounters and inner orbital electron of the attenuating material and the photon gives up all its energy and eject the electron from the atom
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Where does the energy go in the photoelectric effect?
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part of this energy is used to overcome the binding energy of the electron that is ejected and the rest of the energy is given to the ejected electron in the form of kinetic energy
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What does the kinetic energy of the photo-electron result in during the photoelectric effect?
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ionization of surrounding molecules
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What does the ionization of surrounding tissues during the photoelectric effect cause?
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biological damage
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What is the probability of a photoelectric interaction directly proportional to? Inversely proportional to?
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Directly: cube of the atomic number
Inversely: cube of the applied kilovoltage |
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What three factors does attenuation depend on?
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the atomic number, the physical density and specific gravity of the tissue, and the thickness of the tissue
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What is mainly responsible for the differential absorption of the beam of a radiograph?
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photoelectric absorption
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What is very important for radiographic contrast?
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photoelectric absorption
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What is the compton effect?
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interactions occur between an incident photon and a "free" or loosely bound outer electron. The photon gives part of its energy to the electron and the remaining energy is radiated in a different direction as a lower energy photon
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Does the compton effect cause ionization in surrounding tissue?
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yes, the recoil electron produces an ionization track in the surrounding tissue
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What is the probability of a compton interaction dependent on?
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the specific gravity of the absorbing tissue
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Is compton interaction dependent of atomic number?
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no- independent of Z
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`What is the result of the compton interaction? (4)
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scattered, weakened photon, a free electron and a positively charged atom
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What is the draw back of compton effect and what are the two consequences because of it?
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scattered photon has a random direction outside the primary beam; this leads to safety hazard to personnel and decreased radiographic contrast
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What four effects does an attenuation of >70keV have?
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1: increase in compton absorption and decrease in photoelectron absorption
2: increase in scattered photons 3: decrease in the differential absorption of different tissues 4: poor radiographic contrast |
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What are three ways to record the radiographic image?
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photographic film (conventional radiographs/film-screen combinations), recorded directly or indirectly in to a computer (digital radiographs), fluorescent screens (flurorscopy)
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Radiographic film is poorly sensitive to _______ but very sensitive to______.
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poor: x-ray, sensitive: light
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What is used to overcome radiographic film's poor sensitively to x-rays?
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intensifying screens
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What are intensifying screens composed of?
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crystals of fluorescent phosphor
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How do intensifying screens work?
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the phosphor is an efficient absorber of x-ray energy, once an x-ray is absorbed, the phosphor emits visible light which then will be recorded on film
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What types of layers does the intesifying screen have?
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a reflective layer on one side that reflects the light back towards the film and a protective layer on the other
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How does intensifying screens affect exposure values?
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significant decrease
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What are the two types of phosphor used for intensifying screens in veterinary radiology?
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rare earth (conventional) and calcium tungstate
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Why is it important that the correct film is used with the correct material of intensifying screens?
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different phosphor emit lights of different wavelengths and the film must be sensitive to this wavelength
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How can film-screen radiography speed by increased?
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larger crystals and thicker screen
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What does an increase in film-screen radiography cause in regards to radiograph sharpness?
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causes a loss in sharpness
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Besides increasing film-screen radiography speed, what also causes decreased sharpness?
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poor film-screen contact
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What are the four elements to the film composition in film-screen radiography?
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film base (polyester: support for emulsion), subbing layer (adhesive), emulsion (gelatin with dispersed grains of silver halide) and supercoat (protection from damage)
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What is a silver halide crystal? where is it located?
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an orderly array of silver and bromide ions in a cubical lattice; found int he gelatin layer of films used in film-screen radiographs
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What is the sensitivity speck of a silver halide crystals?
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its an imperfection in the lattice that traps electrons
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What occurs when the silver halide crystals are exposed to radiographs?
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electrons are formed by compton or photoelectric effect and electron is trapped in the sensitivity speck of the grain, neutral bromide ions pass out into the gelatin. The negatively charged speck attracts positively charged interstitial silver, making silver atoms
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During exposure of silver halide crystals, what passes out of the grain into the gelatin and does the speck attract?
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Bromide passes out into the gelatin and silver is attracted by the negatively charged speck
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What forms the latent image in film-screen radiography?
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the exposed silver halide crystals
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How is a latent image converted to a radiographic image in film-screen radiography?
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through processing of the film
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What four elements are responsible for the image quality in radiographs?
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film density, film contrast, image sharpness, image distortion
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What is film density?
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the degree of film blackening
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What determines the film density? (2)
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exposure settings (mA, time and kV) and film focal distance
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What affect does mA have on the film density?
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high mAs= more x-rays= more film density
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How does kV affect film density?
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determines film contrast rather than film density; higher kV= more electrons are pulled from cathode= more photons= more film density
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What does doubling the film focal distance require in regards to mAs?
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doubling the FFD requires a fourfold increase in mAs
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What is the importance of FFD when taking a radiograph?
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use a contast focal distance
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What is the image sharpness?
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sharpness is the narrowness of the transition zone between areas of different density
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What occurs when there is a decrease in sharpness?
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leads to a blurry image= loss of fine detail
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What are the four main sources of decrease in sharpness?
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geometric unsharpness, movement unsharpness, photographic unsharpness and patient unsharpness
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What is geometric unsharpness?
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the focal spot where x-rays are produced is not a focal point, x-rays are generated over an area rather than a single point
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What are the three solutions to geometric unsharpness?
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decreased OFD, increased FFD, smaller focal spot
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What causes photographic unsharpness?
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results mainly from the size of the AgBr crystals in film emulsion and the phosphor crystals in the intensifying screen
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What causes movement unsharpness?
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movement of the x-ray tube, patient or film causing a blurring of the radiographic image
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What are four ways to minimize movement unsharpness?
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using sedatives or anesthesia, confine movement using sandbags/ties/foam pads, use stable x-ray machine stand and table, and using shorter exposure times
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What causes patient unsharpness?
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results from either movement or the edge contour of structures and organs
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How is image distortion prevented?
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keeping objects parallel to film and centered
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How can photographic unsharpness be minimized?
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using thinner screens and good film-screen contact
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What is light crossover in film-screen radiography?
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light from one screen may cross the base film and reach the emulsion in the other side
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What does light crossover in film-screen radiography cause?
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decreases sharpness in a similar manner to poor contact between film and screen
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What are the four steps to film processing in film-screen radiography?
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development, fixation, washing and drying
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What is the developer in film processing?
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alkaline reducing agent
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What does the developer do in film processing
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Donates electrons and penetrates the silver halide grains preferentially, neutralizing all the silver ions and converting them into black opaque silver
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The process of developer in film processing is dependent on what two elements?
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time and temperature
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Since the developer in film processing can be oxidized by air and deteriorates over time, what three steps are taken to ensure quality developer?
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regular replacement with appropriate solution, regular replacement every 4-6 weeks irrespective of usage, for low volumes use dish development with fresh solutions each time then disgard
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What are the three main functions of fixer in film processing?
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1: Stop continued development of the silver halide
2: Remove unexposed and undeveloped grains of silver bromide (clearing the film 3: Hardens teh gelatin |
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How long should the radiograph be "fixed" in film processing?
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10 minutes
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What will result if a radiograph is inadequately fixed during film processing?
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film will not be cleared or hardened leading to a pink-tinged dichroic fog
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How long should a radiograph be "washed"? What step does washing follow in film processing?
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about 30 minutes following fixer
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What is the consequence of inadequate washing during film processing?
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silver sulphide formed will turn the film brown with age
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What is the consequence of excessive washing during film processing?
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emulsion soft "slip" off the film
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What occurs if warmer baths are used during film processing?
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faster development
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What are the five steps to practical positioning using a film-screen radiographer?
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area of interest parallel to the film, area of interest is under the center of the x-ray beam, use short OFD, take two views at right angles to each other, and use a constant FFD
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What is the difference of film density between adjacent areas with high contrast? Low contrast?
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High: black and white
Low: grey scale image |
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What is the consequence of inadequate washing during film processing?
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silver sulphide formed will turn the film brown with age
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What is the consequence of excessive washing during film processing?
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emulsion soft "slip" off the film
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What occurs if warmer baths are used during film processing?
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faster development
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What are the five steps to practical positioning using a film-screen radiographer?
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area of interest parallel to the film, area of interest is under the center of the x-ray beam, use short OFD, take two views at right angles to each other, and use a constant FFD
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What is the difference of film density between adjacent areas with high contrast? Low contrast?
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High: black and white
Low: grey scale image |
