Radiograph Interpretation Basics
How X-rays are made
• X-ray tube produces ionizing radiation
• Ionization can be damaging to tissues, especially
when gonads, thyroids, and eyes are irradiated
• Consider that the fetus is most radiosensitive
during organogenesis (2nd-8th week) when
ordering abdominal exams on females
• Different tissue types attenuate/absorb radiation
differently (air-dark, fluid/soft tissue-gray,
bone-white)
Chest X-rays
• Most frequently performed exam
• Provides important information about soft
tissues, bones, lung tissue, pleura and
mediastinum
• Standard patient position is PA and left lateral
(both of these place heart closest to the film)
• Upright for air-fluid levels
• 72” distance to reduce heart magnification
Normal Chest x-rays
• Costophrenic and cardiophrenic angles
• Right hemidiaphragm will be 1-2 cm higher than
left
• Compare lung size and radiolucency
• Full inspiration – should see 10 posterior ribs
with thoracic vertebrae faintly visible through
mediastinum
• Trachea in the midline
Normal Chest x-rays
• Various soft tissue densities are present
▫ Pectoral muscles overlie and extend beyond lung
fields
▫ Breast shadows are in mid chest region (females
may overlie costophrenic angles)
▫ Nipple shadows may be visible (can do chest
obliques with nipple markers to discern whether
nipple or nodule)
• Mediastinum – heart occupies large portion –
transverse diameter < ½ thorax diameter
Chest Pathologies
• Normal Chest – heart size < ½ thorax diameter
• Cardiomegaly with CHF – pulmonary edema
around hila with hilar vessels engorged. Heart >
½ thorax diameter
• Pneumothorax – presence of air in the pleural
cavity leading to complete or partial lung
collapse. Hyperradiolucent area without lung
markings. Due to obstruction, penetrating
trauma or spontaneous. If entire lung collapses,
mediastinum may shift toward affected side.
Chest Pathologies
• Atelectasis – collapse of alveoli ->diminished air
in an area of the lung. Shown as a plate-like area
of increased density usually. Caused by air or
fluid in the pleural space, bronchial obstruction,
tumor outside lung, improper placement of ET
tube
▫ ET tubes, if incorrectly placed, are likely to go into
the right primary bronchus, so it blocks the left
primary bronchus, causing its collapse
Chest Pathologies
• Pleural effusion (fluid in the pleural cavity) or
Pulmonary edema (fluid accumulation in lungs)
• Can be seen during upright cxr, also is shown on
lateral decubitus views (a must for patients who cannot
sit up or stand)
• Emphysema
▫ Barrel chest, flattened diaphragm, elongated lung
fields.
Chest Pathologies
• Pneumonia –
• Primary Lung CA – (bronchogenic carcinoma –
most common primary lung malignancy in US)
▫ If you see a chest nodule:
 Look for old films ( > 1 yr) for comparison
 Look for calcifications (calcifications generally are
benign)
 Look for irregular margins
 CT chest w/wo contrast is the next imaging step
Chest Pathologies
• Metastatic Lung CA – can have “cottonball”
effect.
• Hyaline Membrane Disease (IRDS – idiopathic
respiratory distress syndrome) – “ground glass”
appearance caused by underaeration, uninflated
alveoli. Lungs appear dense due to lack of air
▫ ET tube should be at level of clavicle
Chest Pathologies
• Histoplasmosis – fungal infections from dust of
bird droppings, seen in older, rural patients
• Sarcoidosis – may look similar to histoplasmosis
▫ 1. perihilar density – lymph nodes enlarged
▫ 2. diffuse interstitial pattern, coarse lung
markings throughout both lungs, sometimes with
small, larger widely scattered granulomatous
nodules.
Chest Pathologies
• Silicosis – a pneumoconiosis from inhaling silica
sand, leads to fibrosis
Abdomen
• KUB – taken prior to contrast exams to rule out
pathology/improper exam prep
▫ See liver, kidneys, bowel gas, abnormal masses,
calcification, and foreign bodies
Abdomen
• An acute abdominal series includes:
▫ Supine KUB – “flat plate”
▫ Upright KUB – looking for intraperitoneal air
and/or air/fluid levels
▫ Upright PA chest – also looking for free air
• And is ordered for suspected acute or emergency
conditions like bowel obstruction, perforations,
intra-abdominal masses, situs inversus
Upper GI
• Shows hiatal hernias (stomach above
diaphragm), gastric ulcers (crater fills with
barium)
• Requires patient to drink barium
Barium Enema/Lower GI
• Barium is inserted through the rectum
▫ Can shows ulcerative colitis, Crohn’s disease,
colon cancer, diverticula, polyps, etc.
▫ Fewer Barium Enemas are being done
▫ Getting colonoscopies, virtual (CT) colonoscopies
Small Bowel
• Patient drinks barium – should show from
duodenum all the way to terminal ileum
• Shows Crohns disease well
• May take up to 6 hours for the barium to
progress from mouth to cecum
IVP/IVU
• Iodinated contrast is injected intravenously and
picked up by the kidneys
• Patients who have compromised renal function
may suffer deleterious effects from the contrast
▫ If looking for renal calculi only, most places can
perform a CT –Renal Stone protocol without using
contrast
• Can show hydronephrosis, renal calculi, etc.
• VERY few of these are being done in this area
Bony Pathologies
• Osteoporosis – often an incidental finding on
other exams
• Bone metastasis
• MRSA
• Fractures
▫ Colles – distal radius fx, caused by falling on an
outstretched arm
▫ Comminuted - splintered
Bony Pathologies
• Cervical spine
▫ Lateral shows alignment
▫ Should see all 7 vertebrae in lateral C-spine film
• Lumbar spine
▫ Osteoporosis – bone is less dense
▫ Spondylolithesis – one vertebrae slips forward on
another
▫ Bone mets
▫ Multiple myeloma
Imaging modalities
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Sonography
Nuclear Medicine
Mammography
CT
MRI
Sonography
• Pros
▫ Ionizing radiation not used
▫ Relatively inexpensive
• Cons
▫ Visualization may be difficult with
 Lots of bowel gas
 Obesity/Overweight patients
Nuclear Medicine
• Pros
▫ Bone scans (osteomyelitis/bony mets/occult
fractures)
▫ VQ scans for PE if CT can’t be used
• Cons
▫ Uses radioactivity
▫ Injections/oral dosing may be inconvenient
Mammography
• Less helpful with dense breast tissue (usually
seen in younger women)
• More helpful for solid masses while breast
sonography is better for cystic masses
CT
• Pros – fast, shows many body parts well, not as
influenced by body size as other modalities
• Cons – radiation dose, obese patients may not fit
through the gantry or may exceed weight limits
(depends on facility – average around 400
pounds)
MRI
• Pros – great for soft tissue and detail
• Cons – certain patients can’t be scanned (those
with certain metals, pacemakers, etc.)
• Claustrophobic patients may be scanned under
anesthesia
• LONG!
• Not good for areas with high motion (orbits,
abdomen)
CT vs. MRI
• Most bone issues – order a CT
• For most joint issues (ligaments, tendons) –
order MRI
• Abdomen and Pelvis – order a CT
• MS – MRI
• Chest – CT
• Spines – MRI (CT okay post myelogram)
• Head exams – order CT unless…
• Tumor followup, very fine detail (pituitary) then
MRI
Contrast
• Rules of thumb
▫ Very few head CTs need contrast
 Tumor followup, MS (although MRI is better),
infections, and known mets will probably use
contrast
▫ CT Soft tissue necks always use contrast
▫ Chest CT – use contrast if cancer/staging
(otherwise unnecessary for screening, nodules,
etc)
Contrast
• Most Abd/Pelv will use oral contrast and IV
contrast
• Renal stone protocols use NO contrast
• CT Spines – don’t use contrast
• IV contrast is the ONLY way to see vessels in CT
(MRAs don’t require contrast)
• MRI spines – use contrast if they’ve had surgery
on spine before
• If you’re looking for an infection, use contrast
Contrast
• Oral contrast takes approx 2-3 hours for complete
transition if done as a work in patient before we can scan
them. They drink approx 900ml of contrast. Oral
contrast is used in CT
• Enterography is ordered to look at the small bowel and
the patient has to prep at the hospital the morning of.
• If patients are allergic to contrast they need to be
premedicated for possible reaction, recommendation of
protocol to use is in the radiology department and can be
asked for.
• If the patient has had a break through reaction (reaction
after being premed) they will not receive IV contrast
again.
Contrast info
• Prep instructions are given to office at time of scheduling, rule
of thumb IV contrast is NPO four hours prior minimum
whether CT or MR. If oral contrast is needed some offices
stock this or the patient has to go to the respective imaging
department to pick this up the day before the appointment.
• When looking for a structure that lies within the abdominal
cavity if any of that structure( such as colon) lies below the
umbilicus then a Pelvis order is also needed.
• Can scan pelvis for bony detail only if for trauma
• Biggest thing is to make sure to include the diagnosis or what
you’re looking for on the order so we can make sure the
correct protocol is used.
• If venous access is issue or allergy a VQ scan(nuc med study)
can be done instead of a PE study
Misc.
• http://www.med.yale.edu/intmed/cardio/imagi
ng/contents.html
• Questions???