Medical Imaging and the Abdomen

Pratheep Suntharamoorthy

Learning Objectives

• Describe different diagnostic imaging techniques

• Explain the different modalities of GI imaging• Identify core anatomical features on GI

radiographs• State systematic approach to presenting an

abdominal film • Use systematic approach to present an

abdominal film

X-rays• Electrons released from a hot

cathode.

• When electrons collide with anode, they produce X-rays.

• X-rays are absorbed by bone, but pass through soft tissue.

• When X-rays used to be taken with photographic film. Now computer detection used more frequently.

• Contrast also used in X-rays.

Radiographs

Anterior Posterior

Plain films1. Black- gas

2. Dark grey- fat

3. Grey- Fluid /soft tissue

4. White- calcified structures

5. Intense bright white- metallic objects

Contrast• Most commonly used

radiological contrast is barium sulphate.

• Increases density of structure, thereby increasing amount of X-radiation absorbed.

Computed tomography• X-radiation with greater

exposure.

• Essentially breaking up a 3D structure and putting it back together as a 2D structure.

• CT can detect and differentiate a wide range of x-ray intensities by electronic detection.

CT abdomen

CT Abdomen

CT Head

A- Orbit D- External Auditory canal

B- Sphenoid sinus E- Mastoid Air cellsC- Temporal lobe F- Cerebral

Hemisphere

Anatomy

Normal Anatomy

University of Virginia Medical Education

CT Head

University of Virginia Medical Education A. Genu of the Corpus CallosumB. Anterior Horn of the Lateral VentricleC. Internal CapsuleD. ThalamusE. Pineal GlandF. Choroid PlexusG. Straight Sinus

CT Stroke

Advances in Imaging

Magnetic resonance imaging• Developed in Nottingham

• Uses magnetic properties of hydrogen

• Interaction between radio waves and hydrogen nuclei produce image.

• T1 ad T2 weighted scansNational High Magnetic Field Laboratory

MRI• T1 weighted scans: water and

fluid containing tissue are dark and fat containing tissue are bright.

MRI• T2 weighted scans: water and

fluid containing tissue are bright and fat containing tissue are dark

• Indications for MRI in abdominal pathology are malignancy, liver lesions, and MRCP.

Nuclear Imaging• Positron emission

tomography• Patient injected with a small

amount of radioactive drug.• The drug localises to a part

of the body according to metabolic properties.

• Once there it decays, due to a short half life, emitting gamma radiation.

• This gamma radiation is picked up by a gamma camera.

Abdominal Imaging

Plain films1. Black- gas

2. Dark grey- fat

3. Grey- Fluid /soft tissue

4. White- calcified structures

5. Intense bright white- metallic objects

A

B

C

D

Plain film densities

Abdominal Radiographs• Commonly taken in supine

position

• Anterio- posterior direction

• Abdominal plain films have radiation dose equivalent to 35 CXR (or 4 months background radiation)

Anterior

Posterior

Anatomy

Barium Swallow

Barium Meal

Barium follow through

Barium enema

The plain AXR lecture, Dr. Judy Holt, Derby Hospital NHS Trust

Comparison of large and small bowel

Small bowel•Valvulae conniventes

•Many loops

•Centrally placed

•3-5cm

•No solid faeces

Elsevier. Drake et al. Gray’s Anatomy for students

Large bowel•Haustra

•Fewer loops

•Peripheral distribution

•>5cm•present

Elsevier. Drake et al. Gray’s Anatomy for students

Systematic approach

• Demographics• What modality• Bowel gas pattern• Soft tissue outline• Areas of calcification• Skeletal abnormalities

Case presentation 1• 57 year old male presents with

abdominal distension and vomiting.

Remember:• Demographics• What modality• Bowel gas pattern• Soft tissue outline• Areas of calcification• Skeletal abnormalities

Case presentation 1• Demographics and Modality:

This is a plain AP radiograph of a 57 year old male.

• Bowel gas pattern: Multiple dilated loops of small bowel. No gas seen in large bowel.

• Soft tissue outline- otherwise normal

• Areas of calcification- none seen• Skeletal abnormalities- NAD• Conclusion- Findings are

consistent with small bowel obstruction.

Case presentation 2• 45 year old female patient

admitted with poor renal function.

Remember:• Demographics• What modality• Bowel gas pattern• Soft tissue outline• Areas of calcification• Skeletal abnormalities

Case presentation 2• Demographics and Modality:

This is a plain AP radiograph of a 45 year old female.

• Bowel gas pattern: No apparent distension of small or large bowel

• Soft tissue outline- otherwise normal

• Areas of calcification- Calcification seen over renal areas bilaterally

• Skeletal abnormalities- NAD• Conclusion: Findings are

consistent with nephrocalcinosis

Case presentation 3• 50 year old male with known

Crohn’s presents with an acute abdominal pain, following an ERCP.

Remember:• Demographics• What modality• Bowel gas pattern• Soft tissue outline• Areas of calcification• Skeletal abnormalities

Case presentation 3• Demographics and Modality:

This is a plain PA radiograph of a 50 year old male

• Bowel gas pattern: crescenteric appearance on the underside of diaphragm

• Soft tissue outline- otherwise normal

• Areas of calcification-NAD• Skeletal abnormalities- NAD• Conclusion: Findings are

consistent with extraluminal gas (pneumoperitoneum)

Thank you