Imaging Procedure 1

Final Revision

Main Factors Affecting Recorded Image Detail

• kVp & mAs• Motion• Object Unsharpness• Focal Spot Size• SID (Source to Image Distance)• OID (Object to Image Distance)• Material Unsharpness

Size Distortion & OID• If source is kept constant, OID will affect

magnification• As OID , magnification • The farther the object is from the film, the

more magnification

Image Distortion• When the part to be imaged – does not lay

parallel with the IR (cassette)

• If the Central Ray is not perpendicular to the part

FOCAL SPOT ANGLE

SMALLER ANGLE – SMALLER BEAM AT PATIENT

Film Speed / Crystal size• Larger crystals or Thicker crystal layerFaster response= less detail, and less exposure (chest x-ray)• Finer crystals / thinner crystal layer

=Slower response, greater detail, more exposure (extremity)

Axial Skelton- 80 bones• Cranium-8• Facial-14• Hyoid-1• Auditory ossicles-6• Cervical vert.-7• Thoracic vert.-12• Lumbar vert.-5• Sacrum-1• Coccyx-1• Sternum-1• Ribs-24 Total-80

Anatomic Position• Upright, arms adducted,

palms forward, head and feet directed straight ahead

• Viewing Radiographs: Display x-rays so that the

patient is facing the viewer in anatomic position

R

Body Surfaces and Parts

• Posterior or dorsal• Anterior or ventral• Plantar- sole of foot• Dorsal- top of anterior surface of foot, back or

posterior aspect of hand• Palmar- palm of hand or the anterior/ventral

surface

Image Markers and Patient ID

• All films should have two markers:– Patient ID and date– Anatomic side markers

Most Useful Applications for Plain X-Rays

• Chest• Musculoskeletal• Abdomen: limited usefulness

Main Uses of Fluoroscopy

• Gastrointestinal Imaging• Genitourinary Imaging• Angiography• Other

– Intraoperative– Foreign body removal– Musculoskeletal

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

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

Techniques - Projection

•P-A (relation of x-ray beam to patient)

Techniques - Projection (continued)

• Decubitus

Rotation (continued)

Heart

Right border: Edge of (r) Atrium

3. Left border: (l) Ventricle + Atrium

4. Posterior border: Reft Ventricle

5. Anterior border: Right Ventricle

Heart (continued)

Heart

•Size:

Heart •Size of heart

•Size of individual chambers of heart

•Size of pulmonary vessels

•Evidence of stents, clips, wires and valves

•Outline of aorta and IVC and SVC

Procedure

• Apply proper compression to produce uniform breast thickness– Essential to high-quality mammograms

• Place ID markers

Routine mammography projections

Craniocaudal (CC)

Mediolateral oblique (MLO)

CT Protocolling

• Variables– Plain or contrast enhanced– Slice positioning– Slice thickness– Slice orientation– Slice spacing and overlap– Timing of imaging and contrast administration– Reconstruction algorhithm– Radiation dosimetry

CT Terminology

• Window Width– Number of Hounsfield units from black to white

• Level or Center– Hounsfield unit approximating mid-gray

CT Terminology

Clinical Applications

• Multisection CT aquires changes in the planning and staging of patient examinations. The scanning time is reduced for most examinations, requiring adjustments in the administration of intravenous contrast material. The amount of contrast material can be reduced, and different vascular phases can be better visualized. Thin-section scanning allows production of high-quality MPR images

• Couinaud’s hepatic segments divide the liver into eight segments . The hepatic veins are the longitudinal boundaries . The transverse plane is defined by the right and left portal pedicles .

Sonographic Evaluation of the Liver

• Evaluation of the hepatic structure is one of the most important procedures in sonography for many reasons. The normal , basiclly homogenerous parenchyma of the liver allows imaging of the neighboring anatomic structures in the upper abdomen.

• The appropriate transducer depends on the patient’s body habitus and size

• The average adult abdomen usually requires a 3.5MHz

Sagittal image of gallbladder

• Doppler ultrasound is used primarily to identify and evaluate blood flow in vessels• velocity and waveform information can be used to evaluate stenoses, resistance and vessel patency

Doppler Frequency Shift (fD)

where f0 is the original frequency and f is the frequency of the returning echo(from RBC)

f0

f

(RBC)

• maximum shift is obtained when = 0°• minimum shift is obtained when = 90° (recall, imaging of strongest echoes)• the shift is comparatively small and typically is between 0 - 15 kHz (audible sound)• the shift is positive when the RBC is moving towards the transducer and is negative when the RBC is moving away from the transducer

doppler frequency shift (fD) = change in frequency = (f0 - f)

Color Flow Doppler

• Color Doppler is a hybrid that combines anatomicn obtained using B-mode system with flow information obtained using pulsed Doppler analysis• colors (blue and red) are assigned dependent on motion (toward or away) from the transducer• turbulence (i.e.: variations in flow direction) can vary between green and yellow• the depth of each color varies with the velocity of flow, stationary tissues appear gray• information is provided over a large area and superimposed on a gray scale image• color Doppler can detect flow in vessels too small to see by imaging alone• spectral analysis may also be obtained using commercial color Doppler systems• modern instruments incorporate both color Doppler and spectral Doppler

• Oxygen, hydrogen, carbon, nitrogen elements

constitute 96 % of human body mass. • Oxygen is 65 % of body mass; carbon is 18.5

%, hydrogen 9.5 %, nitrogen 3.2 %.• Let us ignore all elements but Hydrogen.

T1-weighted contrast

T2-weighted contrast

Tissue Appearance

WT FAT H2O MUSC LIG BONE

T1 B D I D D

Proton Density

I I I D D

T2 I B I D D

Good Luck