10/14/2016 Objectives Five shades of gray (Part Two); • Identify the appropriate imaging modality Advanced Radiographic to evaluate common musculoskeletal interpretation and treatment complaints, what to order when. for the APN • Describe the basic principles used in ordering and interpreting musculoskeletal imaging studies in musculoskeletal Christina M Kurkowski, Nurse Practitioner complaints. Conflict of Interest Nov 8 , 1895: The Birth of Radiology I hereby certify that, to the best of my knowledge, no aspect of my current • 11/8/95 Wilhelm Conrad Röntgen personal or professional situation might produces “X - rays” reasonably be expected to affect • 12/28/95 Röntgen presents: “On a significantly my views on the subject on New Kind of Rays” which I am presenting. • 2/11/96 Jones publishes: “The Discovery of a Bullet Lost in the Wrist 1901:Röntgen wins by Means of the Roentgen Rays” 1st Nobel prize in physics Learner Outcome How we make radiographs As a result of this learning activity, the participant will gain knowledge in the area of radiographic interpretation and interventions and implement appropriate changes in practice 1 10/14/2016 X - rays as Diagnostic Tool What is the best imaging test? Can See Can’t See • Plain film radiographs Bones Inside skull • MRI • Fractures • Can’t see the brain • CT Joint Width, surfaces Inside joints • US • Arthritis • Can’t see tears • Bone Scan – Osteophytes – Ligaments, • MR Arthrography tendons – Erosions • CT Arthrography – Menisci, cartilage Tips for requesting films • Consulting radiologist needs info to confirm: – Correct study was requested – Correct patient What is the cause of – Meds, allergies, status caveats musculoskeletal pain? – Cost/benefit ratio favors the patient: • Risk, dose, pain, complication, sometimes $$ • Will it alter management? If not – NO! Clinical Evaluation • DNR, religious beliefs, life expectancy….. • Old images available? Interpretation – 3 basic steps Tailored to individual joint Tailored to individual patient • First learn how each modality creates an image of internal body structures • Next, be able to accurately label normal anatomy (body structures) • Then, search for structures that don’t belong and for body structures that are abnormal in size, shape, position and/or density 2 10/14/2016 Musculoskeletal Imaging Suspected occult scaphoid Fx Variant 6: Suspected occult scaphoid fracture. Initial radiographs and repeat radiographs after 10-14 days of cast are normal. Continued Technology clinical suspicion scaphoid fracture. Next procedure. Advances in Imaging Five Shades of Gray Air Fat Soft tissue Bone Metal least opaque to most opaque most lucent to least lucent Black to White www.acr.org Five shades of gray • American College of Radiology From Black to White Appropriateness Criteria – Gas – black – few molecules to stop • Evidence–based guidelines to choose imaging beam • Relative Radiation Risk for each study – Fat – dark gray – Water – lighter than fat • Modality guidelines: CT, MRI, US, NM, PET…. but not as white as • Practice Guidelines: When (in what order) to mineral and has perform uniform appearance – Mineral/Metal - white 3 10/14/2016 One view equals no view Imaging Planes • Axial Plain Films CAN SEE Plain Films CAN’T SEE • Coronal Bones Inside skull • sagital • Fractures • Can’t see the brain Joint Width, surfaces Inside joints • Arthritis • Can’t see tears – Osteophytes – Ligaments, tendons – Erosions – Menisci, cartilage Radiographs: 2D projection of 3D patient Radiographs flatten everything Can’t tell what’s in front, what’s behind With radiographs: NEED MULTIPLE VIEWS! One view equals no view CT: Giant Leap Forward • CT: Computed Tomography(Tomo [Gr]: part, slice) • CAT: Computed Axial Tomography • 1917 Johann Radon, Austrian mathematician, proved image of a 3D object could be reconstructed from an infinite number of 2D projection images of the object. • Had to await the advent of main-frame computers in the 1970’s. For Joints – need 3 views Why CT is so Great Can see the brain • Strokes, bleeds, tumors Can see organs (lungs, liver, bowel) • Tumors, trauma, acute/chronic diseases Can see fractures otherwise missed • Cervical spine, pelvis And now with ultra-fast, multi-slice… Can scan the heart in a single beat! • Can see coronary arteries, pulmonary emboli • Hospitals have CT scanners in the ER 4 10/14/2016 What to Order When Biggest problem with CT High radiation dose …We are exposed to low levels of radiation every day, “Background Radiation” Earth: naturally occurring radionuclides; uranium 238 and Potassium 40 Atmosphere: Radon 222 (from uranium 238) – 2nd leading cause of cancer after smoking Space: cosmic rays - Airline crews, who spend a lot of time in the upper atmosphere, receive 2x typical background dose. Average background dose 2.4mSv/year Other problems with CT CT is great for assessing complex fractures. • Usually requires IV contrast • 1% patients are allergic to CT contrast & Can affect renal function • Costs more than radiographs: Knee radiographs (4 views): $154 Knee CT (no contrast): $1,200 • Can’t see structures inside joints – Knee: Menisci, Ligaments – Shoulder: Rotator Cuff, Cartilage Labrum – Spine: Disks, Spinal Cord 12 y/o girl with a trampoline injury. Radiation from Diagnostic Imaging CT - Dislocation • Average background dose ≈2.4mSv/year • Chest Radiograph ≈0.06mSv – ≈1 week of background radiation “Risks of medical imaging at effective doses below 50 mSv • Chest CT ≈7.0mSv for single procedures or 100 – ≈3 YEARS of background radiation mSv for multiple procedures over short time periods are How much radiation is too much? too low to be detectable and may be nonexistent.” ……….Who the heck knows … http://www.xrayrisk.com Lis Franc Fx/Dislocation 5 10/14/2016 CT for surgical planning Postop films CT for Surgical Planning MRI: Giant Leap Sideways • MRI doesn’t rely on X-rays to see projected shadows of patients – Unlike radiographs, tomography, CT • MRI sees tissues based upon sub - atomic characteristics – Proton nucleus of Hydrogen • MRI – “Magnetic Resonance Imaging” CT for surgical planning MRI Scanner has 2 components 6 10/14/2016 How an MRI Scanner Works Magnet: Aligns spins of protons in hydrogen nuclei – Align in direction of magnetic field, B Coil : 1)Sends RF pulse to flip spinning protons – After RF pulse is off, protons realign to B – As protons realign, resonate RF energy • 2) Measures strength of resonant RF echo – at a specific time “echo time” and at a specific “repetition time” • Steps 1&2 repeated many times / image slice Things Stuck in Magnets: ICU Bed MR Scanner is just a Tube MR Scanner is a Tube No Implanted Electronics 7 10/14/2016 No Cochlear Implants in MRI Metal Inside Patients Safety Issues Imaging Issues • No implanted electronics • Metal can affect the magnetic • No metal that can move field • OK: Orthopedic • “Susceptibility artifact” hardware • May limit diagnostic value of • OK: modern aneurysm the scan… clips • But often the scans come out • OK: modern heart valves just fine • OK: vascular stents • As long as the patient is MR • OK: IVC filters safe, radiology will try • If radiology can’t get useful images, cancel all charges No Implanted Electronics Metal Inside Patients Patient with lots of metal Is it unsafe to put this patient in the magnet? Of course not! Patient has unexplained knee pain. Metal Inside Patients Metal Inside Patients • Metal that can’t move is not a safety issue – Fillings in the teeth – Orthopedic hardware • Need to worry about metal that CAN move – Metal in/around eyes – Welding equipment, Grinding equipment, Fire guns w/o protection, People who’ve been shot – Old aneurysm clips 8 10/14/2016 Key to MRI MRI: 4 dimensional • Radiographs are flat projections Specific tissue types have specific resonant echoes Only give information in 2-D • Fluid (Hydrogen ions in water) Need 2+ projections to fully see patient – Cysts, Joint effusions, Edema (in soft tissues, in bone • CT is a stack of slices marrow) Images the patient in 3-D • Fat (Hydrogen ions in fat) • MR is a stack of slices... and more – Subcutaneous fat and Fatty yellow bone marrow Not only shows tissues in 3-D • Dense Stuff (with few Hydrogen protons) It shows the composition of the tissues – Cortical bone, Ligaments, Tendons, Menisci • T1: How Fatty, T2: How Wet MR shows more than just 3-D How We Make MR Images Comparing Sequences (knee same mid-Sag Slice) Magnetic field divides body into slices Each slice is subdivided into “voxels” • voxel: 3D pixel • voxel size = 2D pixel size X slice thickness Coil measures signal in each voxel ComputerHigh signal: White maps (“Bright”) this onto 2D slices Intermediate signal: Gray (“Iso-intense) Low signal: Black (“Dark”) MRI: Need Multiple Sequences Comparing sequences (same knee mid sag slice) T1 shows Fat best – Most normal anatomy surrounded by fat – In essence, T1 shows anatomy best T2 shows Fluid best – Most pathology contains fluid (edema) – In essence, T2 shows pathology best – Fat suppression makes fluid more conspicuous PD shows Dense stuff best – Good for meniscal and tendon tears – Used mostly for MRI of joint pain 9 10/14/2016 Limitations of MRI MRI Scans Limited Field of View (FOV) • Usually performed with patient supine • • Image resolution related to voxel size Multiplanar imaging obtained without changing position – Smaller FOV = smaller voxels • One exam = one body part – Smaller voxels = higher resolution • Average exam time 45 minutes; most patients – To maximize resolution, try to limit FOV can’t last >2 hours • Can only image inside the coil • Strict guidelines for sedation • Requires an assortment of different coils for • Optional contrast – Rad usually decides for different body parts body imaging WOW: What to Order When MRI Scans take 30-60 minutes • Should always start with radiographs • • Least expensive study Patient’s need to lie still... like a May show the answer statue...for the entire time. Needed for planning other studies • If the patient is ill the day of the • CT (MSK) scan and can’t stop coughing or • Used in ER for fracture detection (spine) Used for surgical sneezing, should reschedule.