Diagnostic Imaging



Diagnostic Imaging

Tuesday, May 17, 2005

8:53 PM

 

5/19/2005

 

x-ray report

o Hope to derive information from x-ray study

o The doctor owns the film not the patient unless the employer pays for the x-ray and then the business owns the films

o More convenient to send report with patient when co-managing instead of having to always send original x-rays

o Reports are good for using in research studies

o Creates a searchable database for information

o Only legal way to replace a lost or damaged film****

o Gets you paid for professional aspect of x-ray

o Any licensed healthcare practitioner can read x-rays

o Must produce a report if billing for service

Why would/would not want to read own films

o Convenience factor

• Time and money

o Liability

o Peace of mind

• Risk factor of missing something

• Send to someone better qualified

o Best interest of patient

• Send it to the specialist

Accuracy

o DACBR's, DC's, students of DC, Radiologists, Medical Doctors, Med students

o Study showed that DACBR's performed the best at 71%

o DC's were at 28.38%

o General radiologists 51.64%

o Skeletal radiologists (usually at teaching/trauma hospitals) 70.18%

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5/24/2005

 

Liability

o General practitioner

o Specialist

Behaviors

o Doctor takes and reads all films

• Falls under specialist liability

o Doctor takes but has all films read by radiologist

• Falls under general practitioner

o Pick and choose

• Falls under Specialist liability

 

 

Bone formation

o Intramembranous

• Initiated by proliferation of mesenchymal cells about a network of capillaries. Collagen fibers and ground substance join in forming a mesh-like matrix. The cells enlarge and become arranged in layers.

• Exists with us from the moment we are born until the day we die

• Ex. Building a brick wall

▪ Occiput is exception

 

o Enchondral

• Formed around primary ossification centers. Use a non-ossified matrix as a framework. Osteoblasts and osteoclasts form and become imbedded. Cell death is followed by ossification.

• Starts with mesenchyme formation

• Mesenchyme becomes cartilage which is later replaced with bone

• During this time there is an increase in blood vessel penetration

• Newborn: skeleton contains 10 primary ossification centers and non-ossified cartilage

• Apophysis does not have articular cartilage--site for muscle/tendon attachment

• All enchondral bones have the ability to lengthen.

 

ZPC: least mature portion of metaphysis or most mature part of diaphysis

"Zone of Provisional Calcification"

 

The synovial joints first form as condensations of mesenchyme. Cavitation, chondrification, synovial differentiation, and finally ossification finally complete the joint.

 

5 major regulators of bone formation

o Calcium regulators:

• Parathormone

▪ Detects low levels of circulating serum calcium

▪ 3 effects

• Cause renal tubules to become more conservative of calcium

• Stimulate conversion to D3

• Weakens bonds in boney matrix

• Osteoclasts liberates calcium

• Osteoclasts do not have parathormone receptors

• Parathormone softens bone

• 1,25-dihydroxyvitamin D (-cholecalciferol)

▪ Causes increased absorption of calcium

• Calcitonin

▪ Works in opposition to parathormone

▪ Decreases serum calcium

▪ Causes urinary loss of calcium

▪ Inhibits D3

o Maturation hormones:

• Glucocorticoids

• Insulin

• Thyroxine

• Androgen

▪ Growth site maturation role

▪ Hyper-levels cause skeletal maturation and decreased height

 

• Estrogen

▪ Growth site maturation role

 

▪ Hyper-levels cause skeletal maturation and decreased height

• Growth hormone

▪ Controls lengthening

• Exerts effect on intramembranous and enchondral

▪ Causes gigantism in prepubescent

▪ Causes acromegaly in adults

o Growth factors

• Somatomedin

• Epidermal growth factor

• Platelet-derived growth factor

o Local factors (usually in repair phenomenon)

• Prostaglandin E2

• Interleukins

o Ions 2:1 ratio (Ca:Phosphate)

• Calcium

• Phosphate

▪ Important with influx and efflux of calcium

Normal X-ray Anatomy

Basic rules for interpretation

• Plain films are a 2 dimensional gray scale image of a 3 dimensional anatomical structure

• 4 basic densities

▪ Air

▪ Fat

▪ Soft tissue

▪ Bone

• Rule of thumb for radiographs: min of 2 views that are ofset by 90 degrees for any body part

• ABCS search pattern

A-P open mouth

• Lateral masses of C-1

▪ Vertical dimensions are larger lateral than medial

• C-2

▪ Pedicles

▪ SP

▪ Lamina

o A-P lower cervical

o Lateral Cervical

• Pay close attention for assessment

o Cervical oblique

• Looking at IVF

• Know what side, what level, what structure

*go to positioning section of book and read up for Thursday

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5/26/2005

 

Know Boundaries to the IVF

Cervical obliques must be taken with a tube tilt

o LPO

• Can't see in the left IVF

• Can see well in the right IVF

• Shoot up at IVF at 15 degrees

o LAO

• Can see well in the left IVF

• Shoot down the IVF at 15 degrees

o On obliques views it is hard to see C1

Rib counting

o The larger the kyphosis the harder it is to see ribs

• They superimpose themselves

o Find the first rib and work down

Lumbar obliques

o LAO

• Key is to find out which ilium is parallel to film

▪ This shows which side scotty dog you are looking at

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5/31/2005

 

Which of the following is true with regard to Chamberlain's line?

o In C-spine

o Landmark's

• Foramen magnum

• Hard palate

o It is harder to draw than Mcgreggor's line

• Landmarks

▪ Base of occiput

o If the odontoid extends over the line it is abnormal only

• If above more than 10mm

Which of the following is true regarding Hadley's "S" curve?

Lumbar film

Assessment test

a. Can only be performed on recumbent films

i. False--

a. May be utilized for AP and oblique views

i. True

a. May be associated with protrusioacetabuli

i. False--nothing to do with lumbar spine

a. A maximum dimension is 7mm

i. False--no number attached to Hadley's

 

Notes:

The seven categories of bone disease

V-vascular (hematologic)

I-infection

C-congenital

T-trauma

A-arthritis

N-neoplasia (tumor)

E-endocrine (metabolic, nutritional)

Radiological Predictor Variables

o Analysis of the lesion

• Skeletal location

• Position within bone

• Site of origin

• Shape

• Size

• Margination

▪ If there is a sharp distinction in margin it is usually benign

• Cortical integrity

▪ No aggressive process will leave cortex alone

• Behavior of the lesion

▪ Does it cause pain, pain at night, growth spurts of lesion

• Matrix

▪ Look in the bone disease and see tissue type

• Fibrous lesions are less dangerous--usually darker

• Osteoid tumors take up calcium and are bright white

• Periosteal response

▪ Important in adult

• Periosteal lifting is very bad news

• Soft tissue changes

▪ Broad--tumor itself can push into muscle

▪ Subperiosteal bleed in kids

• Joint changes

▪ Pannus formation

o Preliminary analysis

• Clinical data: age, sex, race, history

▪ Ex. Reiter's is a 50:1 male: female ratio

▪ Ex. RA more likely in women looks like psoriasis

• Number of lesions

• Symmetry of lesions

• Systems involved

o Supplementary analysis

• Other radiologic procedures

▪ MRI, CT

• Laboratory examination

• Biopsy

Osteolytic behavior

o Geographic lesion

• Sharp margin

• Solitary

• Greater than 1cm

o Permeative lesion (aggressive)

• Multiple

• Less than 1mm

• Imperceptible transition

o Moth-eaten lesion (permeative margins connecting)

• Multiple

• 2-5mm

• Ragged margins and coalescence

▪ Scalloped margin

• Imperceptible transition

Osteoblastic behavior

o Diffuse lesion

• Obliterated corticomedullary

*see table 7.9, 7.5

 

Monostotic: one location

Polyostotic: many locations

 

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6/2/2005

 

Plain Film Weaknesses

o Ionizing radiation

• Even thought dose is relatively low

o Relatively poor resolution

o Poor spatial localization

o Soft tissues generally not seen

o Frequently fail to document fractures, even under ideal conditions.

Plain film mat be limited by:

o Poor patient positioning

o Patient motion

o Incomplete series

o Trauma patients

• Elderly may not be able to cooperate during exam

o C1-C2 region tough to evaluate

o C6-C7 region also tough to evaluate

o Lumbosacral junction tough to eval based on angle of vertebrae

Plain film proper use

o Introductory study

o Can evaluate intervertebral foramen well

o Use to rule out contraindications for advanced imaging

o Not good for central canal stenosis

Tomography

o Linear

• Move overlying structures out of the way

• Set the penetration level--number of cm's posted on the film

▪ =number of cm above the table

o Circular

o Elliptical

o Hypocycloidal

o Trispiral

Myelography

o Air was the 1st contrast agent used

o Other materials include poppy seed oil, pantopaque

• Not water soluble--had to be removed

▪ Some CSF removed as well

o In the 1940's water soluble products (very toxic)

• Produced arachnoiditis

• Tethering cord, binding cauda equina

o 1970 metrizamide non-ionic, water soluble, in use today

• Still somewhat toxic but safer

• Not as safe as pantopaque but doesn't have to be removed

Complications

o Headache is #1 complication of this study

• 60-80% people get headache

• Can linger for as long as a week

o Infections

• Pain should get progressively better after the study

• If not infection may be present

o Arterial bleeding

o Arachnoiditis

Image production

o Utilizes ionizing radiation

o Depends on displacement of contrast displacement

o Differential absorption

Proper use of Myelography

o If CT or MRI are not available

o Patient who cannot undergo MRI because of time, size, claustrophobia, other contraindications

o May be used in conjunction with CT****

• Most sensitive for disc injury

▪ In incidence of true positives

• Specificity: how of ten does the test show a true negative

• Limited by money involved to perform study

o Weaknesses

• Ionizing radiation

• Relatively poor resolution

• Soft tissues not well seen

• High rate of false negatives

• Potential complications from contrast agent

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6/7/2005

 

Cupping technique: limitation of view field using paper roll, etc.

 

Bone Scan

o One of two emitting technologies (MRI is other)

o Radionuclide used to travel to spots of focus

• Paired with glucose to cross BBB

• Use with phosphate compound to look at bone metabolism

o Normal Osteoblastic activity

• Growth plates

• Fracture sites

▪ Some are hot up to 18 months after injury

o Osteoclastic activity is not picked up by the bone scan

o Technitium used and has half life of 8 hrs

• Whenever given it is a whole body dose

• Can't localize spread of technitium

o What is seen is exaggeration of Osteoblastic activity

o Couple of phases

• Radionuclide (not contrast agent)

• 1)vascular phase

▪ Injected into vein

▪ Spread throughout body and to sites of interest

▪ After injected it takes 2-4 hours before study performed

• 2)soft tissue phase

▪ Increased blood flow areas

Computed Tomography

o Ionizing radiation

o Image based on absorption differentials

• Attenuation study

o Computer generated pictures

o Hounsfield units

• There are 16 shades of gray

o Pixels

• Volume averaging of voxels

o Voxels

• 3D box that is averaged into a pixel

o Volume averaging

o Slice thickness scout films

o Strengths

• Widely available

• Improved visualization of soft tissues

• Can provide 3D imaging

• Accurately measure a variety of structures

• Image manipulation possible

▪ Linear relationship of attenuation substances exist

▪ Change scale to look more at soft tissues or bones

• Bone window vs. Soft tissue window

• May be combined with myelography

o Weaknesses

• Higher cost

• Ionizing radiation

• Intracranial artifacts

• Artifacts secondary to metallic implants

• Dose is a consideration

o Proper use

• Very good axial imaging

• Excellent bone detail

• Some application in the neurology work-up

Helical CT

o Although MR imaging is fast becoming the dominant modality for cross-sectional musculoskeletal imaging, the availability, speed, and versatility of CT continue to make it a mainstay emergency NMS imaging

o When plain film isn't enough, CT can often delineate additional findings that lead to the correct diagnosis and triage.

o Advantages

• Extremely rapid data acquisition

• Optimization of contrast delivery

▪ Less contrast needed

• Reduced respiratory misregistration

• Much more sensitive than X-ray for fracture ID

• Multi-planar reconstruction MPR in 2D and 3D

PET Scan/SPECT

o CT is to plain film as SPECT is to bone scan

o Positron emission tomography

o Single photon emitted computed tomography

o Can allow for layering so that small fractures can be detected (pars interarticularis)

o PET

• One of first good functional brain studies

MRI

o Developed from nuclear resonance which is used to evaluate chemical composition of laboratory samples

o Raymond Damadin first produced a full body MRI in 1976

o Radiofrequency coils

• Placed on or near the area of interest

• Used to excite target tissues

• Also receives information regarding hydrogen nuclei relaxation

o Image production

• Hydrogen is a charged particle representing 80% of all the atoms in the body

• Hydrogen behaves like a small bar magnet

• They are randomly oriented and their charges cancel out

• The MR scanner can spatially locate hydrogen within the body

• In the strong magnetic field of the MR unit, the hydrogen molecules tend to align with (or less often against) the field

• Hydrogen molecules are not held static, but are induced to demonstrate precession (Wobble)

• They are aligned, but they precess or spin out of control

• A strict linear relationship exists between the frequency of precession and the MR magnetic field

• The Larmor equation forms the foundation for MR imaging

o Resonance

• Energy must be added to the system. Radiofrequency identical to the Larmor frequency is pulsed into the patient. This is the concept of Resonance. This causes the aligned hydrogen atoms to precess in phase. The RF pulse is turned off and the "excited" hydrogen atoms undergo "relaxation". This release of excess energy is in the form of radiofrequency and specialized antenna (surface coils) receive the input. Tremendous computer power is now brought to bear and an image is reconstructed.

o Imaging techniques

• Appearance of the image reflects the intensity of the emitted signal. High signal intensity appears bright and dark areas represent areas of low signal intensity.

• Intensity of the signal is determined by the quantity of mobile hydrogens and 2 magnetic relaxation times. T1 and T2

• Manipulating the repetition of administered RF pulses (repetition time, TR)

• And collection of the RF signal (Echo time, TE)

• Influences the image characteristics. Images may be described as proton density on which the image is based on the population of hydrogen T1 or T2 weighted.

• MR pulsing sequences

▪ Proton

• TR-long

• TE-short

▪ T1

• TR-short

• TE-short

▪ T2

• TR-long

• TE-long

o T1 protocols utilized

• TR's of 200-600 milliseconds

• TE's lasting approx. 25 milliseconds

• T2 images are very time consuming protocols and have long TR's and long TE's

• Hybrid images have been developed to take advantage of T2 type images with greater economy of time

o MRI strengths

• Superior resolution in 3D

• Superior tissue contrast

• Images soft tissue very well

• Non-contrast enhancement in the spinal canal

• Axial images OK

• Coronal, sagittal, etc. Images are superior

• MRA (magnetic resonance angiogram) can produce non-contrast visualization of major and minor vessels

• Measurements may be accomplished

• MR reports on the physiology as well as anatomy

• Not reliant on attenuation of ionizing radiation

• No known harmful effects

o Contraindications

• Pace makers

• Ear implants

• Misc. implanted electronic devices

• Cerebrovascular clips

• Machine shop workers

• Claustrophobia

• Orthopaedic implants (distorts Gaussian field)

o Contrast

• Non-iodinated: adverse reactions very rare

• Magnetic contrast agents

▪ Gadolinium is the most common agent

• Works as a T1 shortening agent which causes tissue containing gadolinium to appear bright white on T1

• Very useful in cases of:

• CNS tumor

• MS

• Disc herniation vs. Scar tissue

o Protocols

• 1.5 T magnet is the minimum

• Neurological s/s should be examined with MR

• Used more in extremity trauma

• Authors believe it should be used more in acute spinal injuries

• MRA for head and neck vasculature

 

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6/16/2005

 

MRA uses NO contrast medium

ABC's of Quality Control

o Anatomy-is the entire region depicted on the radiograph

o Bone-search for signs of patient motion and evaluate technique

o Cartilage-reminds us to look into the various joint spaces which may become obscured by positioning errors

o Soft tissues-helps evaluate technique and signs of injury or pathology.

ABC's for Interpretation

o Anatomy-sub-inventory

• 2TP's, 1SP, etc

o Bone-cortical and or trabecular destruction or pathology

o Cartilage-joint spaces, search for signs of arthritis, injury, and anomaly

o Soft tissues-target approach to the regional inspection of the presented soft tissues

 

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