Week 1 - History of Radiology

(1) Know when and who invented radiologyWilhelm Conrad Roentgen is recognized as the Father of Radiology/Roentgenology. In 1895, Roentgen began experiments using electric current flow in a partially-evacuated glass tube, known as a cathode-ray tube. He noticed that, whenever the tube was in operation, a piece of barium platinocyanide in line with it gave off light. Roentgen theorized that the interaction of electrons striking the tube's glass wall formed an unknown radiation that caused the fluorescence. He called the mysterious phenomenon X-radiation, or X-rays. Today, the cathode-ray tube is composed of tungsten, except in mammography, where it is composed of molybdenum.

(2) Understand the concept of projection and how it affects image quality The quality of a medical image is determined by the imaging method, the characteristics of the equipment and the imaging variables selected by the operator. Image quality is not a single factor but is a composite of at least 5 factors: contrast, blur, noise, artifacts and distortion.

(3) Understand the concept of how an image is formedIn projection imaging (radiography and fluoroscopy), images are formed by projecting an x-ray beam through the patient's body and casting shadows onto an appropriate receptor that converts the invisible x-ray image into a visible light image. The gamma camera records a projection image that represents the distribution of radioactive material in the body. The primary advantage of this image type: a large volume of the patient's body can be viewed with one image. A disadvantage: structures and objects are often superimposed so that the image of one might interfere with the visibility of another. Projection imaging produces spatial distortion that is generally not a major problem in most clinical applications.Tomographic imaging, i.e., conventional tomography, computed tomography (CT), sonography, single photon emission tomography (SPECT), positron emission tomography (PET), and MRI, produces images of selected planes or slices of tissue in the patient's body. The general advantage of a tomographic image is the increased visibility of objects within the imaged plane. One factor that contributes to this is the absence of overlying objects. The major disadvantage is that only a small slice of a patient's body can be visualized with one image. Therefore, most tomographic procedures usually require many images to survey an entire organ system or body cavity.

(4) Understand the amount of radiation exposure with different radiologic modalities● X-ray: most common imaging technique used today; the most common x-ray ordered is a chest x-ray, and the musculoskeletal x-ray exam comes in second. An x-ray provides a 2-D image of the 3-D interior of the body. A single x-ray passes through the body and exposes the film on a radiograph (or fluorescent screen) placed on the opposite side. ● CT: x-rays move as laser-like beam in an arch around the part of the body being observed. The beam of x-rays passed through the region of the body imaged are collected by a detector that converts the x-rays into electronic pulses, which produce readings of the tissue density into a 1cm slice of the body. From these readings, a computer can assemble a picture of the body, called a CT scan, which can be viewed on a fluorescent screen, then photographed for later examination. It obtains parts of the

body that can't be seen on a standard x-ray with the help of computer algorithms in conjunction with the enhanced x-ray technology.● MRI: uses the magnetic properties of the hydrogen nucleus, which is excited by radiofrequency radiation transmitted by a coil, which surrounds the body part being imaged. When placed in strong magnetic fields, the nuclei of certain atoms absorb radiofrequencies beamed at them, and then emit their own radio frequency waves. This process allows readers to see very clear pictures of the inside of the body, including tissues, organs and blood vessels. MRI is a noninvasive technique that does not use ionizing radiation. MRI has become one of the primary tools used to image the brain, spinal cord, MSK (musculoskeletal) system, major blood vessels and several key organs and extremities. The images can be produced in 3-D, which significantly enhances the physician's ability to diagnose problems. MRI is also used to help view the process of surgery in real time in 3-D, which assists with a whole host of surgical procedures.

Differences between CT scans and X-Ray's: CT scans are an advanced form of x-ray technology used in detecting diseases in soft body tissues, and can actually provide images of internal organs that are impossible to detect with standard x-ray techniques. X-rays are good at finding bone fractures, and for being used as a contrasting agent for several types of exams; however, CT provides greater detail and clarity. CT scans have additional advantages of being able to produce imaging in virtually any orientation. It is a more technologically developed version of an x-ray, which is used on specific parts of the body. It also provides better images for bone structures, such as the inner ear as it can easily detect tumors in the auditory canal and cochlea. CT scans help diagnose bone fractures, bone tumors, internal injuries and bleeding and blood clots, and to monitor heart diseases and cancer.

Differences between CT scans & MRI's: MRI uses magnetic waves to produce images while CT images are produced using x-rays. CT provides more details of bony structures compared to MRI. CT scans cannot help much in seeing clearly, very fine, soft tissue details (ligaments or tendons) as in the shoulder or knee compared to MRI. MRI scans are best for imaging soft tissue. CT faster than MRI (CT takes seconds, MRI takes minutes).MRI is bad for metal objects in the body. MRI is more expensive and takes longer.

Table: American College of Radiology appropriateness criteria, relative radiation level information

Relative radiation level

Effective dose estimate range

Example examinations

None 0 Ultrasound, MRIMinimal <1 mSv Chest radiographs (CXR), hand

radiographsLow 1–5 mSv Head CT, lumbar spine radiographs

Medium 5–10 mSv Abdomen CT, barium enema,nuclear medicine bone scan

High >10 mSv Abdomen CT w/o and w/ contrast,whole body PET (glucose uptake &

metabolism)

Week 2 – Musculoskeletal

(1) Understand fracture terminology Displaced: loss of contact between fracture fragments Dislocated: loss of contact between joint surfaces Comminuted: bone fractures into 2+ fragments Angulation: bone fragments are at angles to one another Intra-articular: break crosses into joint surface; always result in some degree of

cartilage damage. Pathologic: abnormal bone; fracture through bone made weak by disease, such as a

tumor. Insufficiency: weak bone; fracture through weak bone, such as due to osteoporosis. Occult: does not appear in x-rays, but bone shows new formation (whiter) within 3-4

weeks of fracture. Open vs. closed fractures:

o Closed/simple fracture : skin is still intact. o Open/compound fracture : involves wounds that communicate with the fracture.

Stress fracture: fracture through bone due to abnormal force; NOT an insufficiency fracture.

“Greenstick” / “torus” / “buckle”: typically occurs in a young, soft bone in which the bone bends and partially breaks. It is due to mechanical failure on the tension side; that is, since the bone is not as brittle as it would be in an adult, it does not completely fracture, but rather exhibits bowing without complete disruption of the bone's cortex in the surface opposite the applied force.

What do fractures look like? - Loss of cortical integrtity - Soft tissue swelling- Deformity - Bony lucency- Effusion - Invisible (occult)- Periosteal reaction (subacute): formation of new bone in response to injury or other stimuli of the periosteum surrounding the bone.

(2) Be familiar with the cervical spine bone anatomyLateral view P-A view

Contour lines/margins:

(3) Be able to identify the following plain films:

- SALTER-HARRIS FRACTURE: involves epiphyseal/growth plate of a bone; common injury in children.

Salter-Harris fracture

Normal epiphysis/growth plate

- Distal radius fracturea) COLLE'S FRACTURE: fracture of the distal radius with dorsal/posterior displacement of the wrist and hand; aka "dinner fork" deformity. It is a dorsally-angulated fracture b/c the fracture faces the dorsal/posterior surface.

b) SMITH'S FRACTURE (opposite of Colle's): fx of distal radius w/ volar/anterior/palmar displacement of the wrist and hand. (pic at right)

Smith’s fracture vs. Colle’s fracture:

c) BARTON'S FRACTURE: comminuted (2+ fragments), intra-articular fracture of the distal radius with dislocation of the radiocarpal joint; palmar/volar is more common than dorsal/posterior.

-BOXER’S: transverse fracture through the neck of a metacarpal bone; more likely to occur from a straight punch, hence the name. In this image at right, distal 5th metacarpal fracture.

- Simple vs. comminuted fracture: see above (Colle’s vs. Barton’s)

-

Dislocation vs. displacement Dislocation fracture (aka luxation):

occurs when bones in a joint become displaced or misaligned. It is often caused by a sudden impact to the joint. The ligaments always become damaged as a result of a dislocation. A subluxation is a partial dislocation.

Displaced fracture: fracture in which the 2 ends of the bone are separated from one another, no longer in anatomical alignment.

- Hip Fracture (major kinds of femoral neck fractures) -GREENSTICK FRACTURE

- Cervical spine fracturesCT: better for bone detail, MRI: better for soft tissue and joint detail

1. AA (ATLANTO-AXIAL) DISLOCATION: Hyperextension injury, kids > adults, head slips forward on C1, usually fatal

2. JEFFERSON FRACTURE OF C1: Fracture of the anterior and posterior arches of C1 (atlas vertebra), often appearing as a 2-part or 3-part fracture. Burst fracture; caused by compressive force. Bilateral breaks in anterior and posterior archesOpen mouth view shows bilateral offset of C1 on C2. Not associated with neurologic deficit

3. HANGMAN’S FRACTURE (traumatic spondylolisthesis) of C2: Fracture of either both pedicles or pars interarticularis of C2 (axis vertebra). Hyperextension/compression fracture. Most common fracture of C2. Most common cervical spine fractureFractures through pedicles of C2, with anterior slip of C2 on C3

Teardrop fracture of inferior aspect of C2 or C3 is clue to dx of Hangman’s fracture Not associated with neurologic deficit

4. ODONTOID (DENS) FRACTURE: Fracture through the odontoid process (dens). Hyperextension injury; generally associated with anterior of C1 subluxation on C2. There are 3 types:

Type I (tip of dens): extends through the tip of the dens; usually stable. Type II (base of dens): extends through the base of the dens; most commonly

encountered fracture for this region of the axis, never stable. Type III (sub-dentate / below dens): extends through vertebral body of the

axis; can be stable or unstable.

5. FLEXION-TEARDROP FRACTUREFracture of the antero-inferior aspect of a cervical vertebral body due to flexion of the spine, along with vertical axial compression. It is usually associated with spinal cord injury, often a result of displacement of the posterior portion of the vertebral body into the central spinal canal. It’s a combination of flexion and compression, e.g. MVA (motor vehicle accident). Teardrop fragment comes from antero-inferior aspect of vertebral body. Remainder of body displaced backward into spinal canal. Facet joint and interspinous distances usually widened. Disk space may be narrowed. 70% have associated neurologic deficit.

- Pathologic fracture: fracture through bone, made weak by disease, such as by a tumor

- Radial head (proximal radius) fracture: “sail’s” sign present = anterior and posterior fat pad displacement/elevation/swelling surrounding the elbow joint

Week 3 - Abdomen Plain Films and Ultrasound

(1) Understand the diagnostic role of plain abdominal filmA. Abdominal X-ray has as much radiation as 30 chest xrays. B. Good Reasons to order

a. Cheap, Fast, available, can be highly specificC. Bad reasons to order

a. Cheap (get what you pay for), available (order because they can), can be limited. D. What it shows

a. Free fluidb. Air outside the bowel lumen

i. Intraperitoneal, retroperitoneal, abscess, pneumatosisii. Cant see pneumoperitoneum in supine position (erect or lateral decubitus is

used)c. Air inside the bowel lumen

i. Ileus (no movement), Bowel obstruction, Volvulusii. Small bowel vs colon air

1. Small bowel: Centrally located (of the abdomen), plicae circularis2. Colon: Peripherally located (of the abdomen), haustral markings.

iii. Too Much Gas Intestinal Dilation (3 cm in small bowel, 6-8 in colon)1. Think Obstruction or Ileus

a. Ileus think absent bowel sounds and think post-op or possible meds that suppress bowel activity (opioids/anti-cholinergics)

2. Next test for obstruction CT3. After that UGI/SBFT/BE

iv. Air fluid levels Look for associated signs of obstruction. d. Bowel wall thickeninge. Densities

i. Bones, appendicolith, stones, pancreatic calcification (lipase breaks down and Ca binds), AAA (pooled blood)

f. Organs.

Plain abdominal film: - Normal plain abdominal film does not exclude ileus or other pathology, and may

falsely reassure the clinician- Plain abdominal film has a limited value in the evaluation of abdominal pain- Plain abdominal films are useful for detection of:

o Kidney stones (urate stone—TLS, gout)o Pneumoperitoneum

- All other indications: use CT or sonography/US

(2) Understand the best test to order for gallbladder disease, appendicitis, kidney stones, testicular pain, and ovarian/gyn issues

a. Gallbladder disease: US (Single best for cholecystitis). Ultrasound is only 85% sensitive in detection of bile duct stones (Still test of choice).

b. Pancreas: CTc. Appendicitis:

i. CT: Single Best testii. US: for peds, poor in adults. iii. MRI for Pregnant

d. Kidney Stonesiv. Non-Contrast CT is more Sensitive (contrast: fluid will show up as bright as

bone so the whole ureter will show up white)v. US for Kidney masses (Cystic vs solid)

e. Testicular pain: US (small parts imaging: testes, breast, thyroid)f. OBGYN Issues: US

(3) Be able to identify the following on a plain x-ray of the abdomen:

Small bowel obstructiona. Dilation over 3cm. Look for valvulae

conniventes (thin circular folds of mucosa that span the entire width)

b. Causes: Adhesions, Ileus

Large bowel obstructiona. Over 6-8 cm in diameter. Look for haustra.b. Peripherally located. c. Common cause: Colorectal carcinoma and

diverticular strictures, Hernias, Volvulus.

ConstipationStool is Opaque white surrounded by black bowel gas

Free intraperitoneal airi. Emergency (Bowel Perforation)ii. Erect Position: Look for a crescent beneath the diaphragm. iii. (Below is same pt with free air highlighted in red)

Large kidney stonesThis is seen post-op or pts on MEDS, gas dilates Small and large bowel all the way to rectum

Info/Pics from other sources:-Small Bowel Obstruction

Key features: mechanical SBO - Dilated small bowel- Fighting loops- Little gas in colon, especially rectum- Disproportionate dilatation of SB

- Large Bowel Obstruction

Key features of mechanical LBO: Dilated colon until point of obstructionLittle or no air in sigmoid/rectumLittle or no gas in small bowel, if ileocecal valve remains competent

- Pneumoperitoneum (free intraperitoneal air)Signs: air beneath diaphragm, both sides of bowel wall, falciform ligament signSingle best test: abdominal & pelvic CT. (Don’t give barium enema! Will cause peritonitis.)

There’s a pic of it somewhere in the next lecture set.

Not official objectives, but these were greatly talked about in lecture…

US is very useful for biliary obstruction and choledocholithiasis (stone is common bile duct, but is only 85% sensitive in the best of hands).

PANCREAS NEEDS TO BE DONE W/ CT or MRI. Not good w/ US

increased blood flow peripheral and webby

Week 4 - Chest: Part 1

(1) Understand X-ray densities and transmission of x-raysTissues having different densities show up as differing densities on the radiograph. There are 5 fundamental radiographic densities. This is how they may appear on the fluorescent screen: air and gases appear black or radiolucent fat appears gray to black muscles and water appear grey bones and calcium appear white, or radiopaque metal appears extremely white

A tissue that is denser absorbs more x-rays than tissues that are less dense. Radiopaque (bone/calcium and metal) is a very dense tissue, and a less dense tissue (fat) is said to be radiolucent.

(2) How does an x-ray create a visible image on a radiograph?Beam from cathode tube fans out and increases in size the further away it is from the source (cathode tube). Want the area being imaged closest to film (not x-ray source/tube) in order to properly capture the area. The further away the film is to the area being imaged, the larger and more fuzzy (i.e., less clear and focused) the organ/image will be.

X-ray radiation for medical imaging is typically produced by x-ray tubes, which operate through bombarding the anode with high energy electrons emitted from a hot cathode. Image sharpness, contrast, and patient dosage are important considerations in medical radiography and these requirements determined the desired energies of the tube, the type of material used on the anode, and the method in which the power is generated to drive the tube. The photons emitted come in discrete bands of energy corresponding to the material of the anode, and the undesired bands are removed. Choice of the anode and its emitted radiation energies depends on the application and the tissues being imaged, for instance molybdenum is often used in mammography. Too high radiation energies will result in poor pictures since the radiation cannot be readily attenuated, however too low energies will increase the radiation dosage of the patient without improvements in image quality.

Sharpness of a radiographic image is strongly determined by the size of the x-ray source. This is determined by the area of the electron beam hitting the anode. A large photon source results in more blurring in the final image and is worsened by an increase in image formation distance. This blurring can be measured as a contribution to the modulation transfer function of the imaging system.

Use ionizing radiation (xrays) to create image (shadow)

PrinciplesX-ray photon fates:

Completely absorbed in pt = shows up as white (e.g., bone) Transmitted through pt; strike detector = shows up as black Scattered within pt; strike detector

X-ray absorption depends on: Beam energy (constant) Tissue density

All cardiothoracic pathology and normal anatomy is visualized (or not) by interaction of 7 different densities How is this accomplished? Differential x-ray absorption A structure is rendered visible on a radiograph by juxtaposition of two different densities

(3) Describe the term that indicates when different densities may appear the same on a radiograph, as well as being familiar with the major sources of artifact on chest x-rays.

Silhouette sign: produced when two fluid densities are contiguous and the individual outline of each is lost. Commonly used in the evaluation of chest problems. Loss of different densities when a film is too dark OVER exposure, while a film that is too white UNDER exposed.

The silhouette sign refers to loss of normal border between structures, or an intra-thoracic radio-opacity obscuring the border of the heart or aorta due to a contiguous structure. In other words it is difficult to make out the borders of a particular structure - normal or otherwise - because it is next to another dense structure, both of which will come up as white on a standard X-ray. It may occur, for example, in middle lobe disease, where the right heart margin is lost, and in right lower lobe pneumonia, where the border of the diaphragm on the right side is obscured, while the right heart margin remains distinct.

CXR localization: silhouette signo Loss of expected interface normally created by juxtaposition of two structures of different density o No boundary can be seen between two structures of similar density

Most imaging methods can create image features that do not represent a body structure or object. These are image artifacts. In many situations an artifact does not significantly affect object visibility and diagnostic accuracy. But artifacts can obscure a part of an image or may be interpreted as an anatomical feature. A variety of factors associated with each imaging method can cause image artifacts.

Differential X-ray Absorption Absence of a normal interface may indicate disease Presence of an unexpected interface may also indicate disease Presence of interfaces can be used to localize abnormalities

Cardiac radiography: Limitations Muscle, blood, pericardium, valves, arteries all same density (water) Detection of cardiac abnormalities limited to changes in heart size, shape, axis, or presence of denser matter (valve replacement,

calcification) Requires good knowledge of anatomy

Approach to the CXR: technical aspects

Inspiratory effort – 9-10 posterior ribs;Penetration – thoracic intervertebral disc space just visiblePositioning/rotation – medial clavicle heads equidistant to spinous process

(4) Understand the technical approach to reading a chest x-ray

Check the image for - Inclusion, Projection, Rotation, Inspiration, Penetration and Artifact

Inclusion: A chest X-ray should include the entire thoracic cage. Look for First ribs, costophrenic angles and the lateral edges of ribs.

Projection: PA projection is typical. X-rays pass from the posterior to the anterior of the patient - hence Posterior-Anterior (PA) projection. The image is viewed as if looking at the patient face-to-face.

Rotation: The spinous processes of the thoracic vertebrae are in the midline at the back of the chest. They should form a vertical line that lies equidistant from the medial ends of the clavicles, which are at the front of the chest. Rotation of the patient will lead to off-setting of the spinous processes so they lie nearer one clavicle than the other. Find the medial ends of the clavicles, Find the vertebral spinous processes, The spinous processes should lie half way between the medial ends of the clavicles.

Inspiration: To assess the degree of inspiration it is conventional to count ribs down to the diaphragm. The diaphragm should be intersected by the 5th to 7th anterior ribs in the mid-clavicular line. Less is a sign of incomplete inspiration.

Penetration: A well penetrated chest X-ray is one where the vertebrae are just visible behind the heart. Although X-rays are still occasionally over or under exposed, a discussion of penetration now best serves as a reminder to check behind the heart. The left hemidiaphragm should be visible to the edge of the spine. Loss of the hemidiaphragm contour or of the paravertebral tissue lines may be due to lung or mediastinal pathology.

Artifact: examples include rotation, incomplete inspiration and incorrect penetration. Other radiographic artifact includes clothing or jewelry not removed. Other common artifact to find is medical or surgical equipment like NG tubes.

Mnemonic for reading a [normal] chest x-ray: “ABCDEFGHI”A = AirwayB = BoneC = Cardiac silhouetteD = DiaphragmE = Edge of the heartF = Field of lungG = Gastric bubbleH = Hilum of lungI = Impression (diagnosis)

14 steps (total): 1. Check the patient's name. Above all else, make sure you are looking at the correct

chest x-ray first. 2. Read the date of the chest radiograph. Make special note of the date when comparing

older radiographs (always look at older radiographs if available). The date the radiograph is taken provides important context for interpreting any findings. For example, a mass that has become bigger over 3 months is more significant than one that has become bigger over 3 years.

3. Note the type of film (while this article assumes you are looking at a chest x-ray, practice noting if it is a plain film, CT, angiogram, MRI, etc.) For chest x-ray, there are several views as follows:

o The standard view of the chest is the posteroanterior radiograph, or "PA chest." Posteroanterior refers to the direction of the x-ray traversing the patient from posterior to anterior. This film is taken with the patient upright, in full inspiration (breathed in all the way), and the x-ray beam radiating horizontally 6 feet away from the film.

o The anteroposterior (AP) chest radiograph is obtained with the x-ray traversing the patient from anterior to posterior, usually obtained with a portable x-ray machine from very sick patients, those unable to stand, and infants. Because portable x-ray units tend to be less powerful than regular units, AP radiographs are generally taken at shorter distance from the film compared to PA radiographs. The farther away the x-ray source is from the film, the sharper and less magnified the image. (You can confirm this by placing your hand about 3 inches from a desk, shining a lamp above it from various distances, and observing the shadow cast. The shadow will appear sharper and less magnified if the lamp is farther away.) Since AP radigraphs are taken from shorter distances, they appear more magnified and less sharp compared to standard PA films.

o Lateral chest x-ray. The lateral chest radiograph is taken with the patient's left side of chest held against the x-ray cassette (left instead of right to make the heart appear sharper and less magnified, since the heart is closer to the left side). It is taken with the beam at 6 feet away, as in the PA view. (example pic at right)

o An oblique view is a rotated view in between the standard front view and the lateral view. It is useful in localizing lesions and eliminating superimposed structures.

o A lateral decubitus view is one taken with the patient lying down on the side. It helps to determine whether suspected fluid (pleural effusion) will layer out to the bottom, or suspected air (pneumothorax) will rise to the top. For example, if pleural fluid is suspected in the left lung, check a left lateral decubitus view (to allow the fluid to layer to the left side—you want the fluid to go the bottom and not be obstructed by the dropping mediastinum structures). If air is suspected in left lung, check a right lateral decubitus view (to allow the air to rise to the left side).Figure: Right lateral decubitus chest x-ray showing pleural effusion. The A arrow indicates "fluid layering" in the right chest. The B arrow indicates the width of the right lung. The volume of useful lung is reduced because of the collection of fluid around the lung.

4. Look for markers: 'L' for Left, 'R' for Right, 'PA' for posteroanterior, 'AP' for anteroposterior, etc. Note the position of the patient: supine (lying flat), upright, lateral, decubitus.

5. Note the technical quality of film.o Exposure: Overexposed films look darker than normal, making fine details

harder to see; underexposed films look whiter than normal, and cause appearance of areas of opacification. Look for intervertebral bodies in a properly penetrated chest x-ray. An under-penetrated chest x-ray cannot differentiate the vertebral bodies from the intervertebral spaces, while an over-penetrated film shows the intervertebral spaces very distinctly.

To assess exposure, look at the vertebral column behind the heart on the frontal view. If detailed spine and pulmonary vessels are seen behind the heart, the exposure is correct. If only the spine is visible, but not the

pulmonary vessels, the film is too dark (overexposed). If the spine is not visible, the film is too white (underexposed).

o Motion: Motion blurred areas. Finding a subtle pneumothorax is hard if there’s significant motion.

o Rotation: Rotation means that the patient was not positioned flat on the x-ray film, with one plane of the chest rotated compared to the plane of the film. It causes distortion because it can make the lungs look asymmetrical and the cardiac silhouette disoriented. Look for the right and left lung fields having nearly the same diameter, and the heads of the ribs (end of the calcified section of each rib) at the same location to the chest wall, which indicate absence of significant rotation. If there is significant rotation, the side that has been lifted appears narrower and denser (whiter) and the cardiac silhouette appears more in the opposite lung field.

6. Airway: Check to see if the airway is patent and midline. For example, in a tension pneumothorax, the airway is deviated away from the affected side. Look for the carina, where the trachea bifurcates into the R and L main stem bronchi.Figure: Left tension pneumothorax. Note the large, well-demarcated area devoid of lung markings, and deviation of the trachea (airway) and the heart away from the affected side. The bright metallic spots are snaps for EKG readings.

7. Bones: Check the bones for any fractures, lesions, or defects. Note the overall size, shape, and contour of each bone, density or mineralization (osteopenic bones look thin and less opaque), cortical thickness in comparison to medullary cavity, trabecular pattern, presence of any erosions, fractures, lytic or blastic areas. Look for lucent and sclerotic lesions. A lucent bone lesion is an area of bone with a decreased density (appearing darker); it may appear punched out compared to surrounding bone. A sclerotic bone lesion is an area of bone with an increased density (appearing whiter). At joints, look for joint spaces narrowing, widening, calcification in the cartilages, air in the joint space, abnormal fat pads, etc.Figure: Fracture of the left clavicle.

8. Cardiac silhouette: Look at the size of the cardiac silhouette (white space representing the heart, situated b/t the lungs). Normal: less than ½ the chest width.

o Look for water-bottle-shaped heart on PA plain film, suggestive of pericardial effusion. Get an ultrasound or chest CT to confirm.

Figure: Enlarged cardiac silhouette in a case of aortic dissection (blood fills the mediastinum). Note that the cardiac silhouette takes up more than half of the chest width. Characteristic of aortic dissection here is the enlarged mediastinum (labeled 1) and aortic arched (labeled 2)

9. Diaphragms: Look for a flat or raised diaphragm. A flattened diaphragm may indicate emphysema (COPD). A raised diaphragm may indicate area of airspace consolidation (as in pneumonia) making the lower lung field indistinguishable in tissue density compared to the abdomen. The right diaphragm is normally higher than the left, due to the presence of the liver below the right diaphragm. Also look at the costophrenic angle (which should be sharp) for any blunting, which may indicate effusion (as fluid settles down). It takes about 300-500 ml of fluid to blunt the costophrenic angle.

Figure: Left pleural effusion associated with left lower lobe pneumonia; note that the costophrenic angle is blunted, and the L diaphragm is raised compared to R.

10.Edges of heart; External soft tissues: Check the edges of the heart for the silhouette sign: a radioopacity obscuring the heart's border, in right middle lobe and left lingula pneumonia, for example. Also, look at the external soft tissues for any abnormalities. Note the lymph nodes, look for subcutaneous emphysema (air density below the skin), and other lesions.Figure: A) Normal chest radiograph; B) Q fever pneumonia affecting the lower and middle lobes of the right lung. Note the loss of the normal radiographic silhouette (contour) b/t the affected lung and its R heart border as well as between the affected lung and its R diaphragm border—this is called the silhouette sign.

11.Fields of the lungs: Look for symmetry, vascularity, presence of any mass, nodules, infiltration, fluid, bronchial cuffing, etc. If fluid, blood, mucous, or tumor, etc. fills the air sacs, the lungs will appear radiodense (bright), with less visible interstitial markings.Figure: R lower lobe pneumonia. Note prominent air-bronchogram sign: air visualized in the peripheral intrapulmonary bronchi, due to an infiltrate or consolidation surrounding the bronchi

12.Gastric bubble: Look for the presence of a gastric bubble, just below the heart; note whether it is obscured or absent. Assess the amount of gas and location of the gastric bubble. Normal gas bubbles may also be seen in the hepatic and splenic flexures of the colon.

13.Hila: Look for nodes and masses in the hila of both lungs. On the frontal view, most of the hilar shadows represent the left and right pulmonary arteries. The left pulmonary artery is always more superior than the right, making the left hilum higher. Look for calcified lymph nodes in the hilar, which may be caused by an old tuberculosis infection.Figure: Enlarged lymph node in left hilum, in a case of carcinoid tumor.

14. Breast implants

(5) When looking at a chest x-ray, be able to identify normal anatomic landmarks and major disease patterns, such as: Right Atrium, Right Ventricle, Left Ventricle, Diaphragms, Ribs, Trachea, Aortic Arch, Pulmonary Fissures, Costophrenic Angle (see below at chest x-ray anatomic structures to check)

Pneumonia CHF note enlarged heart CardiomegalyAir Bronchogram

Consolidated lung dense and white. Larger airways

spared low density (blacker). This phenomenon

= air bronchogram (characteristic sign of

consolidation)

Right Atrium, Right Ventricle, Left Ventricle, Diaphragms,

Ribs, Trachea,Aortic Arch, Pulmonary

Fissures, Costophrenic Angle

Pneumothorax

- Free Intraperitoneal Air

- Pneumonia: The x-ray findings of pneumonia are airspace opacity, lobar consolidation, or interstitial opacities. There is usually considerable overlap. Again, pneumonias are a space-occupying lesion without volume loss. What differentiates it from a mass? Masses are generally more well-defined. Pneumonia may have an associated parapneumonic effusion.

- Congestive Heart Failure: The earliest CXR finding of CHF is cardiomegaly, detected as an ↑ cardiothoracic ratio (>50%). In the pulmonary vasculature of the normal chest, the lower zone pulmonary veins are larger than the upper zone veins d/t gravity. In a patient with CHF, the pulmonary capillary wedge pressure rises to the 12-18 mmHg range and the upper zone veins dilate and are equal in size or larger, termed cephalization. With increasing PCWP (pulmonary capillary wedge pressure, 18-24 mmHg.), interstitial edema occurs with the appearance of Kerley lines. Increased PCWP above this level is alveolar edema, often in a classic peri-hilar bat wing pattern of density. Pleural effusions often occur, too.

- Cardiomegaly: refers to excessive heart size in proportion to the diameter of the rib cage. Heart size is usually estimated based on the cardiothoracic ratio, which compares the maximum width of the cardiac silhouette on a frontal CXR, with the maximum internal diameter of the rib cage. Cardiomegaly is usually present if the maximum width of the cardiac silhouette is >50% of the maximum internal diameter of the rib cage.

- Air Bronchogram: sign in which branching radiolucent columns of air corresponding to bronchi is seen, usually indicates air-space (alveolar) disease, as from blood, pus, mucus, cells, protein surrounding the air bronchograms; this is often seen in RDS (respiratory distress syndrome), specifically occurring due to infiltrates outlining larger air passageways. Air bronchograms occur when there is pulmonary infiltration or edema in the tissues immediately adjacent to the bronchi. Darker tubular densities can be seen when the inflammatory process involves the alveoli but has not filled the bronchi with fluid, and therefore distinguishes this disease from cases of atelectasis or pulmonary edema.

- Pneumothorax: The sx of pneumothorax can be vague and inconclusive, esp. in those with a small PSP, and confirmation with medical imaging is usually required. In contrast, tension pneumothorax is a medical emergency and may be treated before imaging - especially if there is severe hypoxia, very low blood pressure, or impaired consciousness. In tension pneumothorax, X-rays are sometimes required if there is doubt about the anatomical location of the pneumothorax.

The lung is held close to chest wall because of the negative pressure in the pleural space. Once the negative pressure is lost the lung tends to recoil due to elastic properties and becomes atelectatic. This occurs in patients with pneumothorax and pleural effusion.

- Pneumoperitoneum (free intraperitoneal air)Signs: air beneath diaphragm, both sides of bowel wall, falciform ligament sign

White arrow: evidence of free air between the abdominal wall and the liver. Black arrow: evidence of free fluid in the peritoneum.

Chest x-ray anatomic structures to check 1. Trachea/bronchi 2. Hilar structures 3. Lung zones 4. Pleura 5. Lung lobes/fissures 6. Costophrenic angles 7. Diaphragm 8. Heart 9. Mediastinum 10. Soft tissues 11. Bones

Week 5 - Chest: Part 2

(1) Understand X-ray transmission and how that is related to CT scans• X-ray source and detectors rotate around patient• Amount of radiation transmitted though body at various angles is recorded• Creates “density map” of human tissue• Table carries patient past continuously rotating x – ray tube = volumetric data acquisition

• X-ray tube & generator can make 360° revolution in 0.28 sec • Wide beam (up to 16 cm) with narrow detectors = high spatial resolution • Table carries patient past continuously rotating x – ray tube = volumetric data acquisition

CT scans are an advanced form of x-ray technology used in detecting diseases in soft body tissues, and can actually provide images of internal organs that are impossible to detect with standard x-ray techniques. X-rays are good at finding bone fractures, and for being used as a contrasting agent for several types of exams; however, CT provides greater detail and clarity. CT scans have additional advantages of being able to produce imaging in virtually any orientation. It is a more technologically developed version of an x-ray, which is used on specific parts of the body. It also provides better images for bone structures, such as the inner ear as it can easily detect tumors in the auditory canal and cochlea. CT scans help diagnose bone fractures, bone tumors, internal injuries/bleeding and blood clots, and monitor heart diseases and CA.

MRI Superconducting magnet – wire coils in liquid helium with electric current High strength magnetic field – 0.2 – 9T

o Stable magnetic field Gradient magnets

o Create variable magnetic field Radiofrequency pulse deposition of energy in pts tissues

(2) Understand the resolution differences between chest x-ray and CT scansAn Xray produces a single image in which structures are overlaid on each other. In contract a CT produces many “slices” of an image, essentially using many xrays at different angles to create images of layers throughout the body.There are several advantages that CT has over traditional 2D medical radiography (i.e. plain x-ray films). First, CT completely eliminates the superimposition of images of structures outside the area of interest. Second, because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. Finally, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referred to as multi-planar reformatted imaging. CT scans use a high level of ionizing radiation. Ionizing radiation has the capacity to break molecular bonds, and thus alter the molecular structure of the irradiated molecules.

(3) Understand how IV contrast administration effects contrastIV contrast is used to highlight blood vessels and to enhance the structure of organs like the brain, spine, liver, and kidney. Typically the contrast is contained in a special injector, which injects the contrast through a small needle taped in place (usually on the back of the hand) during a specific period in the CT exam. Once the contrast is injected into the bloodstream, it circulates throughout the body. The CT's x-ray beam is weakened as it passes through the blood vessels and organs that have "taken up" the contrast. These structures are enhanced by this process and show up as white areas on the CT images. When the test is finished, the kidneys and liver quickly eliminate the contrast from the body.IV contrast is opaque to x-rays. When given, it brightens and allows greater visualization of internal organs, arteries, veins and tissues as it courses through them. For some exams it is essential and cannot be done properly without it, while with other exams it is contraindicated, as it may cause anaphylaxis, nephropathy or negative drug-drug interactions.

4) When looking at CT scans, be able to identify normal landmarks:- Heart (Here are 4 images: superior to inferior)

- Pulmonary Arteries

- Pulmonary Fissures•Right side:

o major (oblique: yellow): separates upper from lower lobeo minor (horizontal: white): separates upper from middle lobe

•Left side:o major (oblique: blue): separates upper from lower lobe

Aorta rises in front of trachea then moves behind esophagus

ATE=>TEA

The coronal CT image on the left shows the right minor (horizontal) fissure (white arrow), right major fissure (yellow arrow), and left major (oblique) fissure. These structures are also seen on the right lateral sagittal CT image on the right. The minor fissure separates the right superior lobe from the right middle lobe. The right major fissure separates the right upper and middle lobes from the inferior lobe. The left major fissure (middle CT image) separates the left upper and lower lobes. These fissures are easy to see because this patient suffers significant pleural effusions that fill the pleural space and partially separates the lobes.

Week 6 - Abdomen: CT & Sectional Anatomy

Hounsfield Units: Relates attenuation coefficients of tissue to that of water. Low attenuation (negative) blocks only a few x-rays

-Air = -1000 -Tissue = 40-Fat = -50 -Calcium = 100-Water = 0 -Bone = 1000

Metals can cause artifacts Use CT Judiciously especially in the youth

1. Know when to order a CT scan of the abdomena. CT is very useful in the imaging of Cancer, Trauma, Vascular pathology, and

Abdominal Sxb. Intraabdominal fluid is a marker of pathology.

2. Be able to determine when to use contrast and when to order a non-contrast Abdominal CT

a. Oral and IV Contrast (IV is Iodine based)i. Water soluble Oral contrast if you suspect Perforation.

1. Don’t give them barium peritonitis!ii. IV Contrast helps with vasculature, viscera, and distinguishes cystic

from solid. b. Risk for IV Contrast

i. Allergy (Pretreat with steroids)ii. Renal insufficiency (Creatinine >2.0; nl: 0.6-1.2)

c. No Contrast for Head Trauma and Renal Stones

3. Know how to diagnose the following conditions with an Abdominal CT

a. Kidney stonesi. History of Flank Painii. (Left Ureteral Stone on image on the right)

b. Appendicitis

i. Worm like structure inferior to the cecumii. To find it, Find the ascending colon @ iliac crests and

scroll down until you reach the inferior cecum and find the worm.

c. Diverticulitis: Wall thickening and edema in the fat adjacent to the sigmoid colon (LLQ)

d. Abdominal aortic Aneurysmi. Pt typically has hypotension and distended abdomen.

Week 7 - Neuroradiology: CT scan

(1) How are skull fractures characterized on a head CT (linear vs. depressed) Linear: transverse full thickness of bone w/o being displaced downward. This is the most

common type of skull fracture. In a linear fracture, there is a break in the bone, but it does not move the bone. These patients may be observed in the hospital for a brief amount of time, and can usually resume normal activities in a few days. Usually, no interventions are necessary.

Depressed: comminuted fracture where bone is depressed inward, inc. pressure on brain. May be seen with or without a cut in the scalp. In this fracture, part of the skull is actually sunken in from the trauma. This type of skull fracture may require surgical intervention, depending on the severity, to help correct the deformity. A skull fracture is most clinically significant if the paranasal sinus or skull base is involved.- Distinguished from sutures - Sutures have undulating margins both sutures

Diastatic skull fractures: These are fractures that occur along the suture lines in the skull. The sutures are the areas between the bones in the head that fuse when we are children. In this type of fracture, the normal suture lines are widened. These fractures are more often seen in newborns and older infants.

Basilar skull fractureThis is the most serious type of skull fracture, and involves a break in the bone at the base of the skull. Patients with this type of fracture frequently have bruises around their eyes and a bruise behind their ear. They may also have clear fluid (CSF) draining from their nose or ears due to a tear in part of the covering of the brain. These patients usually require close observation in the hospital.

Intracranial hematoma (ICH)There are several types of ICH, or blood clots, in or around the brain. The different types are classified by their location in the brain. These can range from mild head injuries to quite serious and potentially life-threatening injuries.

(2) Understand the most common clinical scenarios: Subdural, Subarachnoid, Intracerebral and Epidural Bleeds- Subdural: rupture of bridging veins, usu. d/t deceleration and acceleration, or rotational forces (atrophy predisposes, so common in elderly who fall)- blood collects between arachnoid and dura matter, can’t cross falx, tentorium

CT- Crescent shaped that crosses suture lines.May contain hypodense foci due to serum, CSF or active bleeding (pic on right)

Subarachnoid:- injury of small arteries or veins on the surface of the brain- bleeds into space between pia and arachnoid mater- trauma is most common cause- also due to ruptured aneurysm- worst H/A of life- CT: Focal high density in sulci and fissures or linear hyperdensity in the cerebral sulci

Epidural Bleeds-Usually associated with a skull fracture -Lacerates a dural artery or a venous sinus (middle meningeal artery)-The blood collects between the skull and dura -On CT, a hyperdense biconvex mass -Can cross the dural reflections unlike a subdural hematoma

-Usually does not cross suture lines where the dura tightly adheres to the adjacent skull

IntracerebralThe most common cause of non-traumatic intracerebral hematoma: hypertensive hemorrhage. Other causes: Amyloid angiopathy, Ruptured vascular malformation, Coagulopathy, Hemorrhage into a tumor, Venous infarction, Drug abuse

Contusion (intracerebral hematoma): a bruise to the brain itself. A contusion causes bleeding and swelling inside of the brain around the area where the head was struck. Contusions may occur with skull fractures or other blood clots such as a subdural or epidural hematoma.

When bleeding occurs inside the brain itself (also called "intraparenchymal hemmorage"), this can sometimes occur spontaneously. When trauma is not the cause, the most common causes are long-standing high blood pressure in older adults, bleeding disorders in either children or adults, or the use of medications that cause blood thinning or certain drugs of abuse (cocaine).

Diffuse axonal injury (DAI)These injuries are fairly common and are usually caused by shaking of the brain back and forth, which can happen in car accidents, from falls, or shaken baby syndrome. Diffuse injuries can be mild, such as with a concussion, or may be very severe, as in diffuse axonal injury (DAI). In DAI, the patient is usually in a coma for a prolonged period of time, with injury to many different parts of the brain.

(3) Understand the most common cause of non-traumatic intracerebral bleedsHemorrhagic stroke, due to hypertensive hemorrhage

- 70-90% of non-traumatic primary intracerebral hemorrhages. - Vasculopathy involving deep penetrating arteries of the brain (lacunar) - Thalamus, pons, cerebellum, and basal ganglia

Blood may extend into the ventricular system. Associated with a poor prognosis

(4) Be familiar with the appearance of the following on a CT scan of the Head:Epidural Bleed, Subdural Bleed, Subarachnoid Bleed, Intracerebral Bleed, Hydrocephalus, Skull Fracture(well, all except hydrocephalus were taken care of before, so let’s git-r-done now)

Hydrocephalus - A problem with the ratio of production of CSF to its reabsorption - Communicating hydrocephalus is the most common and is due to arachnoid villi and

subarachnoid space obstruction. Meningitis is assoc w communicating hydrocephalus.- Obstructive hydrocephalus is less common but may occur as a result of the following:

aqueductal stenosis or occlusion; trapped 4th ventricle; ependymitis

Hydrocephalus Normal