2. OVERVIEW
I. Why Radiology
II. Cost
III. Radiation Dose
IV. Imaging Modalities, Physics, and Contrast Reactions
V. Organ Based Approach to Imaging
VI. How to Order an Exam
4. WHY RADIOLOGY?
Specific Question vs Fishing Expedition: Tailor your study to
answer the question.
Does my patient have gallstones?
Does my patient have a kidney stone?
Does my patient have a small bowel obstruction?
Does my patient have fibroids?
Vs
Why does my patient have this vague abdominal pain?
Why does my patient have a fever?
Why does my patient have knee pain?
5. COST
Radiographs: $30 - $80
Ultrasound: $120 - $160
CT: $300 - $2000
Nuclear scans: $120 - $240
MRI: $670 - $1,250
PET-CT: > $3,000
Current expenditures on all medical imaging: $100
billion per year
Growth rate: doubling every decade
8. RADIATION DOSE
100 mSv to each of 100 adults yields about 1 extra
malignancy
Dose from a single abdomen CT minimally – but
definitely – increases cancer risk
Age at exposure is crucial
10. RADIATION DOSE
Brenner D, Elliston C, Hall E, Berdon W. Estimated Risks of Radiation-
Induced Fatal Cancer from Pediatric CT. AJR 2001;176:289–296.
11. RADIATION DOSE
Belly exams are the big-dose ones
If you can avoid a few hundred per career, you’ll
probably avoid causing a cancer
Still - for any serious disease, failure to diagnose is still
more dangerous than the radiation.
12. WHY RADIOLOGY?
Always ask yourself:
Will the results of this test change my management of
the patient?
Is this cost effective?
Are the risks worth the benefit?
24. CONVENTIONAL RADIOGRAPHY
FLUOROSCOPY
Contrast Agents:
Barium Sulfate – Well tolerated. Aspiration rarely causes
a clinical problem. Major risk is barium peritonitis
due to spill into peritoneal cavity through bowel
perforations.
Water-soluble iodinated contrast media – No risk of
peritonitis. Aspiration causes chemical pneumonitis.
Large volumes in the GI tract draw water into the gut
and may lead to hypovolemia, shock, and death.
31. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Conventional CT
Images obtained one slice at a time
Helical/Spiral CT
Patient table moves while xray tube rotates around patient
Multidetector helical CT
Multiple detectors allowing multiple slices per rotation of
the xray tube
32. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Contrast:
Intravenous – Enhance density differences between
lesions and surrounding parenchyma, demonstrate
vascular anatomy, and characterize lesions by patterns
of contrast enhancement
Oral – Required to opacify the bowel to help
differentiate between from tumors, lymph nodes, and
hematomas
34. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Contrast Reactions:
Mild – nausea, vomiting, urticaria, injection site warmth, injection site
pain
Tx: Observation 20 – 30 minutes
Moderate – hives, vasovagal reactions, bronchospasm, mild laryngeal
edema
Tx: Diphenhydramine, beta-agonists, epinephrine, leg elevation
Severe – severe bronchospasm, severe laryngeal edema, loss of
consciousness, seizures, cardiac arrest
Tx: Life support equipment and CPR
35. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Local adverse contrast effects: venous thrombosis,
extravasation of contrast with associated pain, edema,
skin slough, or deeper tissue necrosis
Tx: elevate limb, warm compresses, consider plastic
surgery consult
36. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Contrast-induced Nephropathy
Acute renal failure within 48 hours of contrast
administration
Possibility of permanent renal damage
Risk factors: diabetes and chronic renal insufficiency
Prevention: Adequate hydration, administration of N-
acetylcysteine, use of Visipaque
Chronic dialysis patients at risk for adverse effect of
osmotic load and direct toxicity on heart; recommend
dialysis on day of contrast administration
37. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Metformin
Oral antihyperglycemic used for type 2 DM
May precipitate fatal lactic acidosis in presence of renal
impairment
FDA recommends withholding metformin for 48 hrs
following administration of IV contrast and reinstated only
after renal function has been reevaluated and found to be
normal
38. CROSS-SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Patients at risk for adverse reactions:
Reassess need for IV contrast and consider diagnostic alternatives
Previous history of adverse reaction
History of asthma or allergies: Iodine? Shellfish?
Cardiac dysfunction: CHF, arrhythmias, unstable angina, recent MI,
pulmonary HTN
Renal insufficiency
Diabetes
Sickle cell disease
Multiple Myeloma
Age over 55 yrs
39. CROSS SECTIONAL IMAGING
COMPUTED TOMOGRAPHY
Premedication regimens:
Prednisone 50 mg orally taken at 13, 7, and 1 hour prior
to contrast administration. Diphenhydramine 50 mg
orally, IV, or intramuscularly at 1 hour prior to contrast.
Use nonionic low-osmolality agent.
Methylprednisolone 32 mg orally at 12 and 2 hours
prior to contrast administration. Use of
diphenhydramine is optional. Nonionic low-osmolality
agent should be used.
40. CROSS-SECTIONAL IMAGING
MAGNETIC RESONANCE IMAGING
Based on the ability of protons in the body to absorb and
emit radio wave energy when the body is placed in a strong
magnetic field
Multiple different pulse sequences used to emphasize
different tissue characteristics
Advantages: excellent soft tissue contrast resolution,
provides images in any plane, absence of ionizing radiation
Limitations: Inability to demonstrate dense bone detail or
calcifications, long imaging times, limited spatial
resolution compared with CT, expensive
43. CROSS-SECTIONAL IMAGING
MAGNETIC RESONANCE IMAGING
Intravenous contrast: Enhance differences between lesions
and surrounding parenchyma, demonstrate vascular
anatomy, and characterize lesions by patterns of contrast
enhancement
Adverse reactions (rare): nausea, vomiting, headache,
injection site warmth, paresthesias, dizziness, itching
No nephrotoxicity
Oral contrast: Not used
44. CROSS-SECTIONAL IMAGING
MAGNETIC RESONANCE IMAGING
Nephrogenic Systemic Fibrosis (NSF)
Rare disorder affecting patients with renal impairment
after receiving intravenous MRI contrast agents
Fibrosis of skin, joints, eyes, and internal organs
Constant pain, muscle restlessness, and loss of skin
flexibility
No consistently effective therapy
Avoid MRI contrast agents if GFR < 30
46. CROSS-SECTIONAL IMAGING
ULTRASONOGRAPHY
Ultrasound transducer converts electrical energy to a
pulse of high frequency sound energy, which reflects
off of tissues, producing echoes which are used to
generate images.
Real time imaging of moving patient tissue
Doppler ultrasound permits detection of blood
velocity and direction
Highly operator dependent
48. CROSS-SECTIONAL IMAGING
NUCLEAR MEDICINE
External detection and mapping of the biodistribution of
radiotracers that have been administered to a patient.
Poor spatial resolution, but high functional resolution.
Examples: Ventilation perfusion scan, bone scan, biliary scan,
white blood cell scan, renal scan, thyroid scan, brain scan,
PET, liver spleen scan
50. NEUROLOGIC IMAGING: BRAIN
General rule: CT for acute neurologic illness (< 48 hrs); MRI for
chronic neurologic illness (> 3 days), never use plain films
If the CT or MRI suggests:
Vascular lesion MR or CT angiogram
Tumor Contrast
No infarct, but Sx of infarct Carotid doppler US or MRA or
CTA
Acute Trauma CT with no contrast
MR I inappropriate: multisystem trauma, assisted ventilation
Sedation for agitated adults and children
51. NEUROLOGIC IMAGING: BRAIN
SPECIFIC SITUATIONS
Acute Trauma: Noncontrast CT
Stroke: Noncontrast CT followed by MRI
Seizure: 1st Seizure, contrast-enhanced MR or CT
Postictal state or residual neurologic deficit, Noncontrast CT
Chronic seizure disorder, detailed MRI
Infection and Cancer: contrast-enhanced MRI
Headache: Acute headache, noncontrast CT
Chronic headache with no neurologic Sx, noncontrast MRI
Chronic headache with neurologic Sx, contrast-enhanced MRI
Dementia: noncontrast MRI
60. LIVER
Contrast-enhanced multidetector CT (MDCT):
Primary imaging method
MRI with contrast: Inability to give iodinated contrast
or need for multiple repeat examinations
US: Screening method for patients with abdominal
symptoms and suspected diffuse or focal liver disease,
assessment of hepatic vessels
61. BILIARY TREE
US: Screening for biliary obstruction
MRCP: High resolution imaging of biliary tree
62. GALLBLADDER
US: Method of choice
Cholescintigraphy: Equivocal ultrasound for detection of
acute cholecystitis
63. PANCREAS AND SPLEEN
PANCREAS: Contrast enhanced multidetector CT vs
contrast enhanced MRI
US poor visualization of pancreas
SPLEEN: Contrast enhanced CT and US
64. PHARYNX AND ESOPHAGUS
Barium Swallow/Esophagram: Swallowing disorders and
mucosal lesions
CT: Cancer staging, extent of disease
MR: Cancer staging, extent of disease, preferred for
evaluation of nasopharynx
65. STOMACH AND DUODENUM
Upper GI Series (UGI): Evaluation of mucosal surface,
largely being replaced by
endoscopy
CT: Extraluminal component of disease
66. SMALL BOWEL
Small Bowel Follow Through (SBFT): Insensitive, bowel
lumen and mucosa
details
Enteroclysis: Improved anatomic detail, shorter imaging
time
CT: Extraluminal disease
67. ADRENAL GLANDS AND KIDNEYS
ADRENAL GLANDS
CT: Modality of choice
MRI: High quality images with ability to differentiate
benign adrenal adenomas
68. ADRENAL GLANDS AND KIDNEYS
KIDNEYS
Contrast enhanced MDCT: Modality of choice
MRI: Patients who cannot tolerate iodinated IV contrast
US: Screening study to detect hydronephrosis and
demonstrate kidney size
69. PELVICALYCEAL SYSTEM AND
URETERS
Contrast enhanced MDCT: Modality of choice
MRI with or without contrast: Patients who cannot
tolerate iodinated IV contrast or with poor renal
function
72. GENITAL TRACT
FEMALE GENITAL TRACT
US: Primary imaging modality; Transvaginal vs
Transabdominal
CT/MRI: Staging and follow up of pelvic malignancies
Hysterosalpingography (HSG): Congenital anomalies
and causes of infertility
73. GENITAL TRACT
TESTES AND SCROTUM
Color US: Primary imaging method
CT/MRI: Tumor staging and locating undescended
testes
74. GENITAL TRACT
PROSTATE AND SEMINAL VESICLES
MR with endorectal coil: Local disease staging
CT/MRI: Nodal disease and distant spread
75. MUSCULOSKELETAL
Plain Radiograph: Minimum of two films at 90 degrees
to each other
CT: Examination of fine bony details or high suspicion of
fracture not seen on plain radiograph
MRI: Extent of tumor, characterization of soft tissues,
radiographically occult fractures
76. ORDERING AN EXAM
Ask for exams sequentially rather than all at once
Use your radiologists
Train your radiologists
Help your radiologists
