Use of Diagnostic Imaging in Differential Diagnosis
Reynan B. Hernandez, MD
June 21, 2011
Objectives:

To understand the role and importance of
diagnostic imaging in the present clinical setting

To develop skill in rational diagnostic approach

To demonstrate proper approach to a diagnostic
imaging procedure when discussing an imaging
study
Imaging Modalities

Diagnostic Radiography

Computed Tomography

Ultrasound

Magnetic Resonance Imaging
Diagnostic Radiography
Principles of Interpretation
Five (5) basic radiographic densities (darkest to brightest):

Air

Fat

Soft tissue

Bone

Metal





Pulmonary infections
Tumors
Pulmonary edema
Intestinal obstruction
Abnormal calcifications
Prerequisites for a Good Chest X-ray

PA View (AP View for non-ambulatory patients)

Source of X-ray at least 6 feet

Patient should be in full inspiration

Standing Position
Apicolordotic View of the thorax
Gas in bowels
Breast mammography (all views)
Diagnostic Radiography

Examinations with contrast material
Intravenous Pyelography
Intraoperative Pyelography
Intestinal tract with contrast (double contrast: barium
enema and air)
Diagnostic radiography
Diagnostic Radiography

Skeletal system

Soft tissues
Advantage: most readily available
Disadvantage: Limited diagnostic accuracy
Radiation effects
Diagnostic Radiography
Bone X-ray

Fracture

Dislocation

Bone reaction

Overlying soft tissues
CT Scan
Principles of CT Interpretation

Viewed in sequential anatomic

Slice thickness and spacing

Administration of contrast
Diagnostic Radiography
Bone X-Ray

Skull

Spine

Extremities

Thoracic cage

Pelvic bone
Skull X-Ray
AP View – Laterality, Superior and Inferior
Lateral View – Anterior and Posterior, Superior and
Inferior
T12 – Ribs
Dextroscoliosis – T12, Ribs
Osteolysis of proximal humerus
Gout
Rheumatoid arthritis – hands
Diagnostic Radiography
CT Scan

Head

Chest

Abdomen – a better picture of your intestinal
tract and other structures within the abdomen

Musculoskeletal structures
CT Scan

Head
o
o
o
o
o
CT Scan

Head
o
o
o
o
Pranchyma
Ventricles, sulci, gyri
Cranium
Mastoid
Sinuses
Hemorrhage
Infarct
Tumors
Cranial fractures
CT Scan of Head Axial
CT Scan of Head Axial with lentiform lesion – Epidural
Hematoma
Subdural Hematoma – Crescent shape and crosses the
sutures
Intraparenchymal Infarction – Thalamic Hemorrhage
Ruptured Aneurysm - Subarachnoid Hemorrhage
CT Scan of chest – prebifurcation level
Ultrasound to verify pericardial effusion
(2DEchocardiogram)
CT Scan
Abdomen

Diseases of gi tract
CT Scan of abdomen
CT Scan of abdomen axial cut, aneurysm with dissection
CT Scan of abdomen abdominal aorta ruptured aneurysm
Enlarged lithiasis
CT Scan
Virtual colonoscopy
CT angiography
Advantages: more spatial detail
Can differentiate between various soft tissue densities
Disadvantages: radiation effects
Contrast material effects
May not be able to accommodate obse patients
Ultrasound
Principles of Interpreatation
Conversion of electrical energy to sound energy sound
pulses (1-10MHZ)
High frequency: thyroid, breast, testes
Low Frequency: abdominal pelvic and obstetric
applications
Visualization is limited by bone and gas containing
structures (bowel lungs)
Optimal visualization is achieved through acoustic
windows
Endoluminal techniques obviate many of the problems of
surface scanning
Real time examination yields thousands of images within a
few minutes
Fluid containing structures contain well defined walls,
absence of internal echoes
Solid tissues demonstrate speckled pattern
Ultrasound
Obstetrics
Gynecology
Etc.
1st trimester Transvaginal ultrasound
2nd and third trimester pelvic ultrasound
Abdomen

Liver

Gallbladder

Pancreas

Kidneys

Spleen

Urinary bladder

Prostate gland
Embryo within uterus
Transabdominal approach, Cephalic Position
Ultrasound Endometrium
Space between liver and kidney – hepato-renal space ->
Morrison’s Pouch
Hepatic Steatosis Utz
Renal Cyst Ultrasound
Ultrasound Pancreas with splenoportal confluence
Celiac Artery
Superior mesenteric artery
Ultrasound Left Kidney
Nephrolithiasis – calcium oxalate
Uric acid stones – request for ultrasound
Thyroid ultrasound – isthmus connects left and right
glands, jugular vein laterally, STRAP muscles, trachea
Ultrasound advantages readily available, no radiation
Disadvantages operator dependent, technically difficult for
obese patients
MRI
Principiles of interpretation
Magnetif fileds and radio waves
Analyzes multiple tissue characteristics
Hydrogen density
T1 and t2 relaxation times of tissue
Blood flow within tissue
T1w1
Differences in t1 relaxation times
Best anatomic detail
Short TR and short TE
T2w1
Detection of edema
Pathologic lesions
Long TR and Long TE
Bright on T1
Fat blood proteinacios material
Bright on T2
Calcium gas chronic blood
Vascular imaging
Hepatic biliary tract imaging
Advantages
Soft tissue resolution
Provides images in any anatomic plane
Disadvantages
Limited ability to demonstrate dense bone detail or
calcifications
Long imaging time
Limited availability
Expensive
Contraindicated in patients with electrically, magnetically
and mechanically activated devices
Neurologic cases
Muscle and joint disorders
Tumor evaluation
Abnormalities of the heart and blood vessels
Head
Spine
Etc
MRI of enlarged pituitary gland (macroadenoma)
Conclusion
Radiography serves as the initial imaging study for
extreme, chest, spine and abdomen
Ultrasound is limited by presence of bone and gas
Ct scan provides more spatial detail than xray in the
imaging of most intracranial, head and neck, spine,
intrathoracic and intraabdominal structures
Mri is preferred over ct scan when soft tissue contrast
resolution must be highly-detailed
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