9/11/07 - Weebly



9/11/07

-start learning normal x-ray anatomy on plain film

-osteopenia - loss of bone (a descriptive word for osteoporosis)

-generalized, regionalized, localized

-“localized” is the most serious

-osteomyelitis (infection), lytic metastasis (tumor)

-radiolucent – absorb little amount of x-rays

-an object that allows most x-rays to pass through (black on the film)

-contrast – shades of gray (high contrast = less shades of gray)

-bone – want high contrast

-chest - want low contrast (need to see rather subtle changes in attenuation)

-what controls image contrast? kVp = Kontrast (never solve a contrast pblm with mAs

-oral contrast - (barium) – to provide a separate in anatomy we normally wouldn’t discern

-contrast introduced in GI tract allowing us to separate tissues

-contrast also sometimes introduced into veins (venogram), arteries (arteriogram), lymph (lymph angiogram), lungs (bronchogram), CSF (mylogram – outline cord or cauda equina), and disc (discogram)

-differential absorption – most absorption is thickest portion of long bone is cortical bone, and interior portion is trabecular/medullary, next soft tissue (water density), then fat, then air

-metastasis – starts in one spot and migrated to another spot (usually cancer)

-bone infections often start in another tissue (like lung), and migrate to bone

-infective metastasis – starts in lungs and metastasizes to bone

-Hounsfield units – CT image made of voxels – a single hounsfield is unit to represent a single voxel

-hematopoiesis – formation of blood cells by marrow (driven by hormone erythropoietin)

-red marrow in young people, and yellow marrow (fatty) in older people

-marrow is production site (factory where RBC production takes place)

-every hollow chamber of bone has red marrow, in adolescents

-yellow marrow is degradation of red marrow factories (use it, or lose it)

-attenuating technologies (image reflects attenuation/absorption values)

- x-ray, tomogram (blurrogram – blurred around the edges), fluoroscopy, CT

9/13/07

-emission technology

-patient is emitter (MRI, and NMR ie bone scan)

-MRI releases proton, NMR releases photon

-image based upon mapping protons (MRI)

-image based upon osteoblastic bone activity (bone scan)

-two types of bone production

(1). enchondral (cartilage precursor being formed)

-long bones (enchondral growth adds length to long bone by working through a growth plate)

(2). intramembranous (direct application of new bone on old bone)

-most of skull

-happens throughout life

9/18/07

-finding 1st rib is KEY to getting reference in lower cervical region (it’s very unusual to be able to count down from C1/2 on AP view)

-cervical TP’s are small, often not seen

-black space=IVD

-C1 not perfectly inline with spinolaminar line

-obliques could be either ant or post

-LPO=left post oblique position (looking up right IVF)

-“LPO” should always be marked on rt side of film – place marker over the anatomy

-LAO=left ant oblique position – looking down left IVF

-“LAO” placed on rt side of film

-generally IVF’s orientated down and forward

-if left IVF, left-sided structures bound the hole, but some rt sided structures are visible

9/18/07[2]

-on oblique C views, the opposite side pedicle appears round (and is superimposed over the vert body)

-oblique lumbar is to see posterior elements

-scotty dog: eye=pedicle; ear=superior articular process; leg=inf art process; neck=pars interarticularis (bone b/n joint); body of dog=lamina

-in oblique lumbar images, one ilium is perpendicular and the other is parallel to film

-flat ilium always the same as the Scotty dogs

-if LPO: left ilium visible

-if LAO: rt ilium visible

-RAO: see left ilium and left pedicles

-top of iliac crest usually intersects somewhere in the body of L4

-anterior listhesis (percentage method)

-measure distance b/n ant/post sacral promontory

-draw line down back of vert body to sacrum line

-calculate % anterior translation on the sacrum

-active growth plate; ZPC (zone of provisional calcification); primary growth center; cortex, trabecular, periosteum

-ZPC – most mature layer of the growth plate

-least mature layer of the metaphysis

-between the growth plate and the metaphysis

9/20/07

Where does imaging fit in the chiropractic practice?

-OPPQRST (history/identify chief complaint)

-review of systems

-exam: orthopedic, neurologic, chiropractic

-assemble info into differential dx (listed in order of probability)

-decide what further studies are required (rule-in, rule-out, monitor known conditions)

Differential accuracy depends on history and physical exam

Quality Control

-to be able to diagnose

-to not overradiate the patient

-there is more risk to patient to not get a diagnostic film then to overdose them with x-ray

9/25/07

Quality Control

-Anatomy: is the entire region depicted on the radiograph?

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

-can you see the big white lines and small white lines?

-Cartilage: look into the various joint spaces which may become obscured by positioning errors

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

Interpretation

-Anatomy: sub-inventory

-TP, endplate, SP, lamina, vert, etc

-Bone: cortical and trabecular destruction or pathology

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

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

Diagnostic Imperatives in Radiology

-radiographs are usually only taken of the area involved, unless there is significant clinical indication to warrant full spine exposure

-imaging is for documentation not education/discovery (ie don’t take x-rays specifically for anomalies)

-in a perfect world these two items would not be mutually exclusive; however, we are required to deal with realities of cost versus benefit

-there are segments of our profession that continue to search for loopholes (beat the system)

-in the context of billing and documentation there are some appropriate uses of patient education; none of which involves the use of radiology

-improper use of billing codes or failure to document necessity for certain radiologic procedures should impede reimbursement; the worst outcome is that the behavior could be considered fraud

-a minimum of two views, at right angles to each other, must be taken for adequate initial diagnostic interpretation (helps depict a 3D object in 2D)

-single axis radiograph is not that useful and typically denied reimbursement as a diagnostic study

(except AP pelvis and frontal view of the chest)

-often the oblique view of the ankle shows the fracture most clearly

-each view has its own abilities to reveal pathologies

-decisions concerning the use of dx imaging should not be based on reimbursement

-studies obtained are based on clinical need: Rule In, Rule Out, and/or Monitor

-any film worth taking must be interpreted to reach a diagnostic conclusion

-don’t let third party payers tell you who reads the film

-no third party payer can force you to interpret the film

-the practicing chiro has control over who reads the films

-checklists limit your thinking process and are not appropriate for professional interpretation

9/25/07[2]

Liability

-individuals/institutions are held responsible based on the types, and level of service they provide

-malpractice responsibilities comparable to that of a reasonable and prudent general practitioner

2 levels of liability: general practice and Specialist

-the responsibility for proper radiologic diagnosis falls to either the general practitioner or radiologist

-the burden is placed upon whomever performs the services

-federal law: all studies must be interpreted to reach a diagnostic conclusion (Public Law 97-35 sec.978)

-it is up to the general practitioner to decide who is to provide the professional component of the imaging studies

-successful transfer of liability only occurs if it is the office policy to have all imaging studies read by a certified radiologist

-3 behaviors possible in the diagnostic imaging arena:

-general practitioner could read them all (refer none)

-could refer them all to radiologist (refer all)

-send some and read some (refer some)

-if refers all: maintain general practice level of liability

-if refer none: you will have a specialist level of liability

-if refer some: specialist level of liability

-the locality rule in some counties: level of training is a limit of liability

-can’t rely on locality rule anymore

-we have 315 hours radiology training vs radiologist who has 7-9000 hours training

-chiro radiologists are about equal with skeletal radiologists and fellows at reading x-rays

-GP chiro physicians are about equal with GP medical doctors at reading films

10/2/07

The Radiology Report

(if the x-ray is taken, it must be interpreted)

What is the role of the report?

-verbal rendition of the film study

-medico legal communication

-insurance company

-workman’s compensation boards

-attorneys (patient’s attorney)

-provides a standard for comparison

-part of the permanent patient record

-**an x-ray report is capable of replacing the lost film

-professional communication b/n physicians, attorneys, employers, workman’s comp boards, etc

-expedite treatment by highlighting indications and contraindication for treatment

Apposition=what percent of fractured surfaces are touching

Report Format

I. Stationary (template, includes who is interpreting: name of business with address & phone#)

II. Patient information - name or ID #, and Date of Birth (or age)

III. Radiology info (the series and the date the series was performed)

IV. Technique (optional) – kvp and mas, etc

V. Body (findings) – generic description of what the image contains

VI. Impressions (Conclusion) – summarize most to least important (short phrase, ie “DJD in hip”)

VII. Recommendations (when needed) – used only when we want you to read them

10/2/07[2]

Imaging Tools

-plain film

-myelography

-CT & helical computerized tomography

-MRI

-SPECT

-PET Scan

(MRI, SPECT, and PET are all sources of patient emission)

PLAIN film

-not used to look at bone density

-will not see change in density unless change is greater than 30-50%

-3-5% change (bone scan), 1-3% change to see on MR or CT

-Panorex view: bones of face (maxilla, mandible, teeth)

-panorex became affordable right after CT came along

Strengths of Plain film

-availability

-relatively low cost

-well known usage’s

-entry level diagnostic tool

-search for contraindications to further imaging

-quick assessment of gross osseous and soft tissue integrity

Weaknesses of Plain film

-ionizing radiation

-relatively poor case resolution/outcome (not talking about line-pair performance)

-not as capable as CT/MRI at revealing pathology

-poor spatial localization

-3D in 2D

-soft tissues generally not seen

-soft tissues seen best in MR

-frequently fail to document fractures, even under ideal conditions

Plain film limited by:

-poor patient positioning

-patient motion (esp. if kvp or mA is too low)

-incomplete series

-trauma patients, the elderly may not be able to cooperate during the exam

-C1-C2 & C6-C7 regions tough to evaluate

Plain film proper use

-introductory study

-can evaluate intervertebral foramen well

-use to rule out contraindications for advanced imaging

-not good for central canal stenosis

Tomography

-precursor to CT

Classic head patterns:

1. Linear

2. Circular

3. Elliptical

4. Hypocycloidal

5. Trispiral

-both tube and film move creating a “pivot point,” which can be adjusted

-tomogram=laminagram=blurrogram

-edges of image are blurred, but center of image is in focus

Myelography

-air was the 1st contrast agent used

-air was hard to control (ie air embolus headaches could arise)

-other materials include poppy seed oil, pantopaque (neither are water soluble)

-in the 1940’s water soluble products (but they were very toxic – arachnoiditis, etc)

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

Complications

-arachnoidits (less than 1%)

-infections (needle)

-arterial bleeding (large caliber needles, blind stick – can slice aa or vv – epidural hematoma)

-headache is most frequent complication

10/9/07[1]

Proper use of myelography

-if CT or MR is not available

-people who cannot undergo MRI b/c of time, size, claustrophobia, or embedded metal

-Maybe used in conjunction with CT

Arachnoiditis

-blunting of nrv root sleeves

-maybe a complication of myelography

-intradural-intramedullary lesions

-headache (most people get a headache: 8/10)

-contrast isn’t the problem, but the puncturing of the dural sleeve, and the release of a drop of blood into the CSF (CSF is highly filtered blood with all proteins taken out)

-it is believed that the proteins (from a drop of blood) entering the CSF are the causative agent

-(bring a friend with that can drive patient home – in case of severe headache)

Myelography Strengths

-relatively good availability

-good cost benefit ratio

-well known utilization

Myelography Weakness

-ionizing radiation

-relatively poor resolution

-if can’t displace contrast, then pathology is hidden from us

-soft tissues not well seen (system is designed to highlight suspended metal)

-high rate of false negatives

-potential complications from contrast agent (headaches &/or anaphylactic shock)

Radionuclide Imaging Group(ie bone scan, PET scan) & MR are both emission based technology

-energy that is mapped out come from the patient

Bone Scan

-dose of radioactive material injected into vein

-takes several hours for radioactive material to get into the skeleton

-children, puppies, kittens are the most metabolically active, and therefore the most radiosensitive

-patient emits radiation in the x-ray band

-gamma camera (aka scintilloscope) maps out the radiation

-emission pattern is isotropic (emits in 360 deg and in 3-D)

-“hot spot” = area of increased uptake (of technetium)

-bone scan is hooked up to phosphanated compounds

PET scan: linked with glucose

Computerized Tomography (CT)

-an attenuating technology that provides true 3-D imaging

-16 shades of gray

-beam passes through patient as machine rotates 360 deg

-measuring throughput (attenuated remnant beam)

-pixilated image: occurs when lost some of sensory array (in modern machines)

-helical format of imaging can be done in 5 minutes

-CT is only imaging option when patient is on life support (equipment doesn’t work in presence of high magnetic field)

-CORTEX IS WHITE

CT Strengths

-widely available

-Improved visualization of soft tissues (but not as good as MR)

-can provide 3-dimensional imaging *

-accurately measure a variety of structures

-image manipulation possible (benefit of CT over MR)

-can shift interest toward bone end or shift toward air end (digitally)

-may be combined with myelography

-normally, CSF is fluid-density and therefore should be colored similar to other soft tissues

-if CSF is white (much whiter than other ST), assume something was added to it: CT myelography

CT weaknesses

-higher cost than plain film

-ionizing radiation

-intracranial artifacts (star artifact)

-artifacts secondary to metallic implants

-dose is a consideration

10/9/07[2]

-understand how the image is produced, why info is needed, and know which tool is most appropriate based on patient presentation

CT proper use

-very good axial images

-excellent bone detail

-some application in the neurology work-up

Helical CT

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

- helical CT is faster (maybe 7 min as opposed to 20-25 min for an MR study)

-greater diagnostic yield with helical CT image

-ability to reformat the image

*This modality has several advantages:

-EXTREMELY rapid data acquisition

-optimization of contrast delivery

-reduced respiratory misregistration (only have to hold breath once)

-much more sensitive than PF in fracture identification

-multiplanar reconstruction (MPR) in 2-D and 3-D possible

-reformatted image

SPECT & PET scan – emission technologies (as opposed to attenuation-based)

-SPECT: single photon emission computerized tomography (don’t confuse with CT)

-it’s relationship to bone scan is similar to tomography’s relationship to plain film

-PET: positron emitted tomography

-more tightly linked to brain activity

-even though we’re only looking at the brain, it is a whole body dose

MRI – best tool to image CNS (ie cord)

Common problems

-spinal fracture (the more edema, the more recent the fracture)

-soft tissue injury

-skeletal survey for signs of metastasis

-post-traumatic complications (DJD, syrinx)

-peripheral entrapment

-central canal stenosis (better than CT in that MR can tell whether cord is injured)

-intracranial abnormalities

-T1: FOR FAT, ANATOMY ( SPIN-LATTICE, LONGITUDINAL RELAXATION

-CSF IS BLACK; TR 75 ms

-radiofrequency (RF) coils – greatly improved the image

-both the sender and antennae

-placed on or near area of interest

-used to excite target tissue (sender)

-also received info regarding hydrogen nuclei relaxation

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 the sum of their charges cancel out

-the MR scanner can spatially locate Hydrogen as it emits energy within the body

-in the strong magnetic field of the MR unit, the hydrogen molecules ten to align with the (or less often against) field

-the hydrogen molecules are not held static, but are induced to demonstrate precession (Wobble)

-they are aligned, but they precess or spin out of phase

10/11/07

-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

-energy must come from the patient in order to capture the mapable pattern

-in the strong magnetic field of the MR unit, the hydrogen molecules tend to align with (or against) the field

-the hydrogen molecules are not held static, but are induced to demonstrate precession (wobble)

-they are aligned, but they precess or spin out of phase

-a strict linear relationship exists b/n the frequency of precession and the MR magnetic field

-the Larmor equation forms the foundation for MR imaging

-frequency of precession = (gyro magnetic ratio) x (strength of the External field)

-*we can make hydrogen not just line up, but work together

Resonance

-Energy must be added to the system. RF 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” (when the mapping takes place). This release of excess energy is in the form of RF and specialized antenna (surface coils) receive the input. Tremendous computer power is now brought to bear and an image is reconstructed.

Imaging Techniques

-the MR image appearance is controlled by altering the timing of RF pulses sent into the patient and the returning echo

-the 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

-brightness = lots of hydrogen atoms emitting energy

-intensity of the signal is determined by the quantity of mobile hydrogens emitting at the time we listen

and two magnetic relaxation times (T1 and T2)

-manipulating the repetition of administered RF pulses (repetition time, TR)

-collection of the time emitted RF signal (Echo Time, TE)

-TR and TE influence the image characteristics. Images may be described as proton density in which the image is based on the population of hydrogen T1-weighted or T2-weighted where the specific relaxation characteristics of the various tissues will be highlighted or suppressed.

MR Pulsing sequences:

Weighting TR TE

Proton long short

T1 short short

T2 long long

T1 protocols utilized: TR ................
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