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:
- Linear
- Circular
- Elliptical
- Hypocycloidal
- 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<800 ms, TE<30 ms
-T2: FOR WATER SPIN-SPIN, TRANSVERSE RELAXATION
-CSF (&NP) IS WHITE; TR>1800 ms, TE > 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)