BASIC CONCEPTS IN DIAGNOSTIC IMAGING

Dr Mohamed El Safwany, MD.

Intended learning outcome

• The student should learn at the end of this lecture Basic concepts in radiological Imaging.

Outline

• Introduction• X-Rays• Fluoroscopy• CT• MR• Innovative Modalities

Modalities Available in Radiology

• Plain Film / X-Ray/Mammography

• Fluoroscopy

• Ultrasound

• CT

• MRI

• Nuclear Medicine/Molecular Imaging

• Angiography/Interventional

X-Rays

• Discovered in 1895 and still used today

• Most widely performed imaging exam

• X Rays are emitted and detected in cassette

• Cassette can generate either a film or a digital image

• Films are kept ‘on file’ or in a digital archive

Most Useful Applications for Plain X-Rays

• Chest

• Musculoskeletal

• Abdomen: limited usefulness

Fluoroscopy

• Utilizes X-Rays

• Real-time imaging

• Utilizes image intensifier

• Involves use of contrast agents

Main Uses of Fluoroscopy

• Gastrointestinal Imaging

• Genitourinary Imaging

• Angiography

• Other– Intraoperative– Foreign body removal– Musculoskeletal

Gastrointestional Fluoroscopy

• Esophogram/Barium Swallow

• Modified Barium Swallow/Dysphgiagram

• Upper GI

• Small Bowel Series

• Enteroclysis

• Contrast Enema

• Defecography

Single Contrast vs Double Contrast

• Single Contrast– Generally uses just thin Barium– Distends lumen with high density material– Easier for patient/less mucosal detail

• Double Contrast/Air Contrast– Thick barium coats lumen– Effervescent tablets ingested to distend lumen with air– Produces ‘see-through’ images with greater mucosal

detail – Greater sensitivity for small lesions, polyps, ulcers

Single ContrastBarium Enema

Double ContrastBarium Enema

Single Contrast vs Double Contrast

Contrast Materials for GI Exams

• Barium Sulfate– Thick: used in double contrast studies– Thin: used in single and double contrast exams– Paste: mod Ba swallow and defogography

• Gastrograffin– Full stregnth: rarely used– Dilute

Gastrograffin Swallow StudyBarrium Swallow Study

Barium vs Gastrograffin

Barium Sulfate

• Most widely used

• Better images than gastrograffin

• ‘Chalky taste’

• Peritonitis may develop if perforation

• If delayed transit, may form concretions in colon

Gastrograffin

• Water soluble• Foul Taste• Poor mucosal coating

– Basically used for R/O obstruction

• Won’t cause peritonitis if perforation• May cause severe chemical pneumonitis if aspirated• Osmotic pressure draws fluid into bowel lumen

– Progressive distention in small bowel obstruction– ‘Therapeutic’ enema in constipation

Patient Factors in GI Fluoroscopy

• Ability to ingest contrast– In order to get high quality images, a relatively large

volume of contrast needs to be ingested fairly quickly

• Mobility– Multiple positions required for GI exams, particularly

double contrast exams.– Limited mobility = less diagnostic images

• Weight– Tables have weight limits– Requires maximal radiographic technique and exposure is

often suboptimal

Esophogram or Barium Swallow

• Evaluates pharynx and esophagus

• Limited evaluation of stomach

• Double or Single Contrast

• Mucosal contour and Motility

Modified Barium Swallow

• AKA Dysphagiagram and at Carle “cookie swallow”

• Performed with Speech Pathologist• Barium administered in various bolus

consistencies ranging from liquid to solid• Evaluates swallowing mechanism• Evaluates for aspiration• Performed on videotape

Modified Barium Swallow

Upper GI Exam

• Evaluates esophagus, stomach and duodenum

• Double or Single Contrast

• Can be combined with small bowel series

• Largely replaced by endoscopy and cross-sectional imaging

• Fairly insensitive

Small Bowel Series

• Patient drinks 2 cups of thin Ba

• Overhead films obtained at routine intervals

• The Ba column is followed through until it reaches the colon

• Transit time, mucosal contour, bowel loop distribution are evaluated.

• Insensitive for small masses

Small Bowel Series

Small Bowel Enteroclysis

• “Double Contrast Small Bowel Series• NGT placed at duodenal-jejunal junction• Ba injected followed by methylcellulose• See-through appearance to small bowel• Greater sensitivity for small masses and

mucosal lesions• Patient discomfort related to NGT and

diarrhea

Contrast Enemas

• Barium or Gastrograffin

• Double contrast or single contrast

• Generally less sensitive than endoscopy

• Requires bowel prep to assess for mucosal lesions

• Requires some element of patient cooperation

Single ContrastBarium Enema

Double ContrastBarium Enema

Contrast Enemas

Defecogram

• Barium paste is inserted into rectum

• Patient is asked to defecate under fluoroscopy

• Ano-rectal and pelvic floor dynamics can be assessed

• Rectocele, intussusception, pelvic floor relaxation, stress incontinence

Genitourinary Fluoroscopy

• Cystogram

• Voiding cystourethrogram

• Retrograde urethrogram

• Hysterosalpingogram

Cystogram

• Usually in adult patients

• Looking for tear or intraluminal mass

• Catheter placed and bladder filled with contrast to capacity: usually 300-500 ml.

• Spot films obtained when full

• Post void film: usually overhead

Cystogram with Intraperitoneal Rupture

Cystogram

Voiding CystourethrogramVCUG

• Usually in children with history of UTI

• Searching for vesicoureteral reflux

• In males, evaluate for urethral abnormalities: posterior urethral valves

• Same as cystogram except when full patient voids under fluoro with spot films

Retrograde UrethrogramRUG

• Male patients

• Pelvic Trauma

• Post-infectious: STD- looking for stricture

• Different techniques

• Meatus occluded and contrast injected into urethra under fluoro

Retrograde UrethrogramRUG

Hysterosalpingogram

• Used to evaluate endometrial canal and fallopian tubes

• Infertility and uterine anomalies

• Dye injected into cervical os under fluoro

• Injection continued with goal to opacify the fallopian tubes and spill contrast into peritoneum

Musculoskeletal Fluoroscopy

• Fracture/Dislocation reduction

• Hardware placement in the OR

• Flexion/Extension views of c-spine

• Arthrography– May be performed in conjunction with MRI or

CT

Techniques Relevant to MSK Radiology

• Radiography (routine and specialized views)

• CT

• MRI

• US

• Densitometry

• Interventional procedures (arthrography, percutaneous biopsy/vertebroplasty)

MRI—Sagittal Knee T1 Weighted

MSK Radiology

Vertebroplasty

Computed Tomography (CT)• Cross Sectional imaging modality

• Mobile X-ray tube that rotates around a pt

• Slices of X-ray transmission data reconstructed to generate image

• Data displayed in multiple window settings (lungs parenchyma, bone, etc.)

• Density measurements/Hounsfield Units analyze chemical component of tissue

• HU: -150-0 = fat, 0 = water, 0-20 = serous fluid, 45-75 = blood,

100-1000 = bone/calcium

CT Contrast Agents• Intravenous contrast---iodinated

Differentiate blood vessels vs. vascular internal organs

• Enteric contrast---barium

Differentiate bowel vs. intra-abdominal fluid/masses

• Rectal contrast

• Retrograde urinary bladder contrast

CT Applications• Neuro-imaging

-Acute head trauma, acute intracranial hemorrhage

-Low sensitivity for early ischemic stroke, intracranial metastatic disease, white matter degenerative disease

• Head and Neck imaging-Soft tissue of neck, paranasal sinuses, temporal

bone imaging, orbital wall imaging

CT Applications• Body Imaging

-Chest, Abdomen, Pelvis (with enteric and IV contrast)

• Pulmonary nodules, Renal Calculi (without contrast)

• Acute appendicitis (with enteric and IV contrast)

• Specialized protocols:

-Liver masses, pancreatic tissue, renal masses, adrenal masses

CT Applications• Acute Abdomen

-decrease rate of false laparotomy procedures

• Trauma Spine Imaging (cervical, thoracic, lumbar)

• Other osseous structures (pelvis, extremities)

• Vascular Imaging

-CT angiography--- i.e. coronary arteries

CTAxial, with oral contrast in stomach

CT PET PET/CT

CTA(CT Angiography)

CT Cardiac Imaging

The Power of CT

Magnetic Resonance Imaging (MRI)

• Multi-planar scanning

• Without ionizing radiation

• Images generated using powerful magnets and pulsed radio waves passing through the body

• Data from Pt’s body used to generate image

• Field strength of magnets 0.3-3.0 Tesla

MR Contrast Agents• Intravenous contrast---Gadolinium chelate-

based contrast agents

• Gadolinium is a paramagnetic lanthanide that is toxic as a free metal

• Contrast to evaluate BBB, intracranial edema and hemorrhage

• Novel agents being developed as tagged Monoclonal antibodies for Molecular Imaging

MR Applications• Neuro-imaging

-Excellent tool due to high soft tissue contrast resolution

-Abundant water content of CNS allows for imaging soft intracranial tissue

• Head and Neck imaging-Multi-planar capability allows for monitoring

extent of disease

-Differentiating subtle soft tissue boundaries of head and neck

MRIAxial, T2-Weighted

MR Applications

• Body Imaging

-Thorax: mediastinal, hilar, chest wall abnormalities

• Limited lung imaging due to artifacts

• New advances in breast imaging

• Potentials for cardiac MRI with coronary MR angiography

MRIBreast Imaging

MR Applications

• MSK Imaging

- High sensitivity for neoplastic, inflammatory, and traumatic conditions of bone and soft tissue

- T1-weighted---fluid collections and abnormalities in fatty marrow

- T2-weighted---lesions in both marrow and soft tissue

MRISagittal, T1-Weighted

Innovative Modalities• Constantly evolving face of radiology

• New contrast agents for CT and MR

• Molecular Imaging

- Imaging molecular events---enzymatic activity, receptor binding, cellular events

• Interventional Radiology and Interventional Neuroradiology

Text Book

• David Sutton’s Radiology

• Clark’s Radiographic positioning and techniques

Assignment

• Two students will be selected for assignment.

Question

• Describe importance of Hysterosalpingeogram?

Thank You

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