How do these 2 exposures compare
1. 92 kVp, 8 mAs, 40 inches SID
2. 80 kVp, 10 mAs, 50 inches SID
Exposure 1 will have lower contrast and greater overall density than exposure 2. This is because the kVp of the exposure 1 exposure gives greater penetrability to the x-ray beam. In fact, the kVp is 15% higher than the second exposure, which is equivalent to doubling the mAs.
How does the SID effect the image in these 2 exposures
1. 92 kVp, 8 mAs, 40 inches SID
2. 80 kVp, 10 mAs, 50 inches SID
The SID of exposure 1 is 40 inches, which also increases the intensity of the x-ray beam. Exposure 2 will lack detail and density when compared to the first exposure and may limit the reading of the radiograph.
What happens to the amount of shades of grey in a n image as kVp is increased
kVp is the primary controller of contrast. In other words, as kVp increases the number of shades of gray also increases. This is called low contrast or long scale contrast imaging. Likewise, decreasing kVp decreases the number of shades of gray in the image. This is called high contrast or short scale contrast imaging.
What is a problem with a high contrast (low kVp) chest radiograph
When you decrease the number of densities possible on a radiograph, especially of the chest, any pathology outside the contrast range for the exposure will not be seen. This is why it is recommended that chest radiographs be taken using at least 120 kVp for adults. Low contrast imaging for the chest is desirable because it yields a greater number of densities on the radiograph and a wider range of diagnoses possible.
A digital radiographic image is first formed as an electronic image that is displayed on a grid called a matrix. The image is laid out in rows and columns called an image matrix. Each image is made of thousands, preferably millions of small cells that make up the image matrix.
Each cell in the image matrix is called a picture element, or pixel.
This digital chest radiograph shows great detail and contrast created by many shades of gray pixel values. On the right is a magnified portion of the radiograph showing many small square pixels. As you can see there are a large number of different densities that make up the digital image. The brightness of pixels can be further manipulated by the radiologist by "windowing or leveling" the image.
How does the AEC allow for adjustment for fat people
Using automated exposure the technologist is able to increase the phototimer density setting using the +1, +2, +3, or +4 setting. Each increase in the phototimer setting is equivalent to about a 25 percent change in the mAs. Thus the exposure can be increased for large patients and decreased (-1, -2, -3, etc.) for a thin patient or those with chronic obstructive pulmonary disease (COPD).
What parts of the anatomy should not obscure the lung fields
Patient's chin extended out of the lung fields, the scapula rotated out of the field, and if the patient has large breast move them upward and out away from the lungs.
The photograph on the left shows proper positioning of a patient for the PA chest x-ray. Notice the chin is extended, hands on waist and shoulders rolled forward and downward. The collimated area is limited to the lungs (yellow dotted box). A lead apron drapes the lower abdomen and pelvis (yellow arrow) to protect the gonads.
What is done to adequately image a hypersthenic patient
The hypersthenic type (5%) presents with a massive broad deep thorax. The lungs are generally short and wide, therefore, these types usually do not fit on the standard 14 X 17 inch cassette or image receptor lengthwise. To avoid clipping the costophrenic angles the cassette is turned crosswise.
How are the hyposthenic and hypersthenic body types imaged
The PA chest radiograph on the left was taken of a person having the hyposthenic body type. The right radiograph demonstrates a person having the hypersthenic body type. The image receptor is positioned in the lengthwise position for sthenic, hyposthenic, and asthenic types, but is turned crosswise for hypersthenic body types to avoid clipping the costophrenic angles.
What is considered a CXR with good inspiratory effort
The PA/AP chest x-ray is taken on deep inspiration filling the trachea and lungs. Inspiration should adequately visualize at least 10 posterior and 8 anterior ribs.
The radiograph on the right shows a properly made PA chest radiograph that meets the diagnostic criteria. It shows low contrast with good penetration of the medial lung fields and thoracic spine. It also shows deep inspiration as 10-11 posterior ribs are seen. Position and anatomical markers are present on the radiograph as required.
What is the standard for an acceptable AP radiograph
The radiograph is taken on deep inspiration filling the trachea and lungs. Inspiration should adequately visualize at least 8 posterior ribs. The lungs will appear denser since there is less inspiration than when erect.
This patient was unable to get a CT scan because the nurse was unable to get intravenous access. A PICC line was inserted from the right antecubital fossa. Does this AP upright portable radiograph meet the diagnostic criteria for a chest view for PICC line placement?
Digital imaging the radiograph was windowed for more density and contrast. The magnified portion of the radiograph (right) shows the effect of changing the density with a digital image. The PICC line is seen in the subclavian vein (yellow arrow).
This patient complained of chest congestion following 2 days hospitalization. Patient refused to be transported to the radiology department for an upright PA and lateral chest x-ray. Her physician ordered a portable AP CXR instead. Give your critique of this portable upright AP chest radiograph.
This PA CXR was taken to evaluate PICC line placement and the lungs for possible pneumothorax. The lung fields are also questioned because of chest congestion complaints. Does this radiograph meet the diagnostic criteria for the PA CXR? Keep in mind that this radiograph is a digital image using a dedicated chest unit.
The astute radiographer would not repeat this radiograph since the PICC line needs to be repositioned and the radiograph repeated. So, in keeping with ALARA, repeating this radiograph to show the right lung field would not be necessary.
This patient's physician requested a portable chest x-ray to evaluate treatment for congestive heart failure and known pleural effusions. What considerations should the technologist make when performing this radiograph, and tell whether or not it meets the diagnostic criteria for the AP upright portable CXR.
The exposure technique does not adequately penetrate the lung bases. Serial radiographs to evaluate fluid must be made the same way with good fluid penetrating technique. An increase of 15% kVp would be an adequate exposure.
The patient history for this portable AP chest x-ray includes pleural effusions bilaterally, chest tube on right, and obesity. Does this radiograph meet the diagnostic criteria? If no, then what could be done to make this an acceptable radiograph?
Slightly rotated to the right and poor colliimation. Proper collimation. Shutter A: Open to approximately 5cm above the shoulder to include upper airway
Shutter B: Open to the level of the acromioclavicular joints (AC joints) laterally. This will include the lung fields laterally
High contrast study. Thoracic vertebral bodies are not visualized through the heart silhouette, neither are the retrocardiac vessels clearly seen. A high contrast area in the abdomen (blue asterisk) confirms this is a low kVp exposure
Patient positioning: Have the patient stand flush on the floor, shoulder depressed, hands on waist with scapula rolled toward the image receptor. The chin should be over the top of the Bucky with the head straight. These preparations will help align the neck and chest.
better penetration of the costophrenic angles and demonstrating the retrocardiac lung marking is the diagnostic standard for the chest exposure technique. When the lower thoracic spine is seen through the heart silhouette and the medial left lung is demonstrated, the exposure technique is optimal.
This radiograph should be repeated using greater kV to penetrate the lung bases. Correct alignment of the patient is also desirable when this radiograph is repeated. To get an optimal exposure place the patient against the upright Bucky , use at least 120 kVp, and automated exposure control.
This is a good radiograph of the infant chest. Notice that the exposure technique adequately penetrates the thoracic vertebrae. The head is straight so that the clavicles are not rotated. When performing a pediatric chest x-ray, it is important that the chest is not rotated.
A non-rotated chest allows for accurate evaluation of the mediastinum so that the border of the heart and thymus is distinct. Good alignment can help identify anatomical variance due to congenital disorders (e.g. tetrology of fallot, dextrocardia, etc).
This patient was sent to the radiology department for an upright chest x-ray to check progress of treatment for various lung disorders, and to evaluate a newly place PIC catheter. The patient receives continuous oxygen at 8L. What is your assessment of this radiograph?
The main issue with this radiograph is the poor exposure technique. Notice that we cannot see the thoracic vertebral bodies through the heart silhouette. As a result the lung parenchyma is poorly visualized and the tip of the catheter is barely seen.
Notice that the right sternoclavicular joint is projected away from the spine and the right SC joint is over the spine. This is a grossly rotated chest radiograph. The patient should be rotated towards the left until the shoulders are flush against the cassette.
A portable radiograph was taken on this patient with known pleural effusion(s) now suffering decreased oxygen saturation readings. Why is this radiograph not acceptable for a portable AP view of the chest?
Exposure technique demonstrates poorly penetrated lung fields. Patchy infiltrates (yellow arrowheads) developing, which are difficult to see because the chest is under penetrated. Patient is also rotated. A grid should be used if it has not been already.
The patient history for this radiograph stated "chest tube is not working properly, evaluate placement." Based on this history, does this radiograph meet the diagnostic criteria, and state what could have been done to make it a better radiograph?
The patients is supine. Examples of scenarios in which the supine position is indicated include among others unstable low blood pressure, trauma spine precaution, post cardiopulmonary resuscitation, and the like.
The upper chest catheter opening is positioned high, which is great for suctioning air, for example, a pneumothorax. In this case the chest tube has a second opening which should be draining fluid from the chest, which is not appreciated on this radiograph.
This radiograph was taken on a patient who is receiving ventilated breathing support. The technologist thought it would be easier to perform this radiograph supine since the history for exam is to evaluate endotracheal tube placement. What is your critique of this portable radiograph?
The problem with this radiograph is it is under penetrated and is badly rotated. Since the endotracheal tube is in the right bronchus this radiograph should not be repeated until after the endotracheal tube is adjusted. The kVp should be increased approximately 15% to better penetrate the lung and produce low contrast.
Angling the tube cephalic in this case could prove useful. So repeat this radiograph with the head out of the field of view, correct chest rotation, and possible use cephalic angulation to clear the lung fields.
Because the patient is obese and have large amount of breast tissue, the costophrenic angles are poorly penetrated. Increasing the kVp alone will not compensate sufficiently to make this an optimal radiograph. The patient will have to move the breast up and outward away from the chest.
The technologist should increase the mAs by adjusting the automated exposure control to +1 or better +2 gain a 25 to 50% increase. The goal is to achieve an exposure that demonstrates the medial lung bases and costophrenic angles
Corrections for this poor radiograph include: placing the shoulders flush with the cassette and equal distance, tape the head back in extension, align patient with the cassette, use collimation, remove surface foreign bodies, and angle the CR cephalic.
This patient was brought to a local emergency room following a motor vehicle accident. There were decreased breath sounds bilaterally and the patient was intubated at the scene. After seeing this portable radiograph taken in the emergency room, what could have been done to make this a better radiograph?
Part of the evaluation is to look for air-fluid levels in the visualized abdomen, and for air that is not in the bowel (called free air), which may settle beneath the diaphragm when the patient is upright.
Being upright would also allow the patient to take a deeper inspiration to expand the lungs. The inferior limit of the right hemidiaphragm (yellow arrow) is seen, but the left hemidiaphragm cannot be determined.
When positioning for the PA chest projection the shoulders are depressed and the midcoronal plane is parallel to the image receptor. This will project the clavicles horizontal (red dotted line) rather than vertical as is seen on this radiograph.
This is a radiograph that should have never been taken supine. One reason to perform this radiograph upright is that it allows for the shoulders to be depressed. By doing so at least 1 inch of the apices are projected above the clavicles. Did you notice the small pneumothorax in the left upper lung lobe?