PT 606 Unit 2 Intro to Tomogrpahic Imaging PDF

Introduction to Tomographic Imaging Kimiko Yamada, PT, DPT, OCS, ATC Types of Imaging Examinations Radiographs (x-ray radiographs) Computed tomogram (CT) Magnetic resonance image (MRI) Positron emission tomography (PET) Bone scintigraphy Dual-energy x-ray absorptiometry (DEXA or DXA)...

Introduction to Tomographic Imaging Kimiko Yamada, PT, DPT, OCS, ATC Types of Imaging Examinations Radiographs (x-ray radiographs) Computed tomogram (CT) Magnetic resonance image (MRI) Positron emission tomography (PET) Bone scintigraphy Dual-energy x-ray absorptiometry (DEXA or DXA) imaging Ultrasonography (US)  Types of Image Displays Conventional radiography Projection: converts 3D to 2D (e.g., radiography) Advanced imaging Tomographic: images a single plane of finite thickness (e.g., CT, MRI, ultrasound) 3D display: whole volume display (e.g., 3D CT)  Viewing Tomographic Images Looking at three-dimensional (3D) structures in a two-dimensional (2D) plane Always look at two views taken in orthogonal planes (90 degrees) of each other in order to re-create a perception of a three-dimensional structure  Tomography Views The spiral images are used to create tomographic views Coronal CT in three planes Almost no super- Axial CT imposition like with radiographs Sagittal CT Copyright © 2014 F. A. Davis Company www.fadavis.com MRI View Option: Oblique Slice Usually only used with the shoulder Coronal oblique of the shoulder  Tomography views Coronal Sagittal Axial Orientation of image Coronal MRI Coronal: as if you are looking at them in front of you Sagittal: as if you are looking at a patient Axial MRIm that is facing right or left Axial: as if you are looking up through them Sagittal MRI Copyright © 2014 F. A. Davis Company www.fadavis.com Tomography Views: Axial View Anterior Anterior Right Left Right Left Posterior Anterior Right Left Posterior Case courtesy of A. Prof. Frank Gaillard, radiopaedia.org, rID: 35543 CT Imaging Computed Tomography (CT) Combines radiography and computer technology X-ray beam and detector move around the patient Multiple x-ray absorption measurements made around the body  Thin slices: 0.1– 1.5 cm Takes less time because only one pass is needed Parts of a CT Gantry (x-ray tube, detectors, and data acquisition system) Operator console Computer http://www.cyberphysics.co.uk/topics/medical/CTScanner.htm  CT Scan Thin slices: 0.1–1.5 cm The spiral images are used to create tomographic views in three planes with one pass Almost no super-imposition like with radiographs Faster and lower cost than MRI  Scan Doses Exam Dose (mSv) DEXA 0.001 Extremity radiograph 0.001 Airline flight 0.02 Mammogram 0.04 Chest radiograph 0.10 Spine radiograph 1.5 Natural background 3.1/year Average US exposure 6.2/year Bone scintigraphy 6.3 Chest CT 7.0 Abdominal CT 8.0 PET/CT 25 X-ray risk: http://www.xrayrisk.com/index.php Radiation Exposure  Composition (1) Cortical bone, (2) cancellous bone, (3) muscle, (4) subcutaneous fat, (5) air  Oblique Axial ankle ankle x-ray CT radiograph  Axial cervical spine CT CT “Windows”  CT “Windowing” “Windowing” refers to the Density scale range of radiodensities Window width displayed on an image. can be Window level expanded Each digital image is only a Can be moved or contracted up and down “small window” of the total the density to control contrast data collected by the scale to control computer. brightness Humans can only see about 32 shades of gray, but a computer can see hundreds. Windowing helps us discriminate between tissues of similar densities.  Window Levels Soft tissue windows: can see gray and white matter (left image) Bone window: can see cortical and cancellous bone (right image) Note that bone always has a comparatively high radiodensity.  Window Levels (cont.) CT bone window CT soft tissue window Variations of CT  Variations of CT Imaging CT arthrogram CT myelogram CT angiogram 3D conformational CT CT arthrogram CT myelogram Contrast media: radiopaque contrast Copyright © 2014 F.A. Davis Company www.fadavis.com  CT Angiography Iodine-rich contrast material is injected into your vein at a controlled rate with an IV.  3D Reconstruction CT You can rotate the image 360 degrees. You can “subtract” bones. You can color code different bones. You can use it for 3D printing. https://www.radiologyinfo.org/en/gallery/index.cfm?image=839 Systematic Reading Patterns and Indications (for CT)  Systematic Search Pattern: Radiographs/CT A: alignment Skeletal architecture, size and contour of bone, alignment of bones to adjacent bones, number of bones B: bone density Bone density, textural abnormalities, local bone density changes C: cartilage spaces Joint space width, subchondral bone, epiphyseal plates S: soft tissues Muscles, fat pads/fat lines, periosteum, miscellaneous soft tissue findings  Indications for CT Imaging Evaluation of subtle and complex bone pathology (complex fractures and loose bodies especially) Multiple body part screen (i.e., trauma situations) Degenerative changes in the spine (i.e., measuring cross-sectional compression for cervical stenosis) Infection (i.e., cellulitis or abscess) Vascular (i.e., aneurysms) Preoperative planning Used when MRI is contraindicated MR Imaging Introduction  MRI Examination The study of hydrogen nuclei  Magnetic Resonance Imaging MRI uses the magnetic properties of the body’s tissues, rather than ionizing radiation, to produce an image. MRI forms images based on the behavior of hydrogen nuclei that are prevalent within water- and fat-containing tissues. A magnetic field and radiofrequency signals cause hydrogen nuclei to emit their own signals, which are converted into an image by a computer.  MRI Positioning Scanner Operator console Computer http://www.amerimedimaging.com/wp-content/uploads/2013/04/Closed-vs-Open-compare.jpg Magnetic Shield Magnet Gradient coils RF coils Table RF coils Gradient coils Magnet Gradient generators RF pulse generators and processors and processors Computer Film printer Copyright © 2014 F. A. Davis Company www.fadavis.com The MRI Process  Magnetic Resonance Imaging Patients positioned in the MRI scanner are exposed to a strong magnetic field and radiofrequency (RF) pulses. The magnetic field (1.5–3 Tesla) produces resonance that is characteristic for the type of tissue (spinning). The RF pulses ┴ to the magnetic field knock the protons out of alignment and the nuclei absorb energy.  The MRI Image When the RF pulses are removed, the protons realign with the magnetic field and the energy is released as an electrical signal. Each soft tissue has a different amount of water content, so it will absorb and release energy at different rates. The computer derives digital images from the different rates of energy released.  MRI Contrast and Signal Intensity Soft tissue contrast in MRI is related to differences in proton resonance within tissues. Protons within fat resonate differently from those in fluid and yield a different signal intensity.  MR Image Sagittal MR image MR Image (cont.) Coronal oblique shoulder MRI Scout image MRI Signals Contrast  MRI Signal Contrasts, Part I The energy released is detected by a receiver coil TR: repetition time (ms) is the time between two successive RF pulses TE: echo time (ms) is the time between the RF pulse and the time the signal is captured TR and TE times are displayed on the MR image  MRI Signal Contrasts, Part II Function of: 1. The concentration of protons resonating within the imaged area 2. The relaxation time of the protons back to equilibrium following the RF pulse Two types of “sequences” T1-weighted (short TR and short TE) T2-weighted (long TR and long TE)  MRI Signal Contrasts, Part III T1. Short TE T2. Long TE High signal intensity from fat High signal intensity from the remaining energy water Energy level Energy level Signal from water Signal from water (slowly realigning) Signal from fat (rapidly realigning) Signal from fat TE Echo time (TE) TE Copyright © 2014 F. A. Davis Company www.fadavis.com  MRI Signal Contrasts, Part IV Higher signal intensities are brighter on the image Fat is bright on a fat-sensitive, T1- weighted image Water is bright on a fluid-sensitive, T2- weighted image T2 = H2O  Tissue Signals Tissues Fat-sensitive Fluid-sensitive (T1-weighted) (T2-weighted) Fat and yellow bone High Intermediate marrow Cortical bone, air, Low Low ligaments, tendon, and fibrocartilage Muscle, nerves, Intermediate Intermediate hyaline cartilage Red marrow Low Low-intermediate Fluid Intermediate High  MRI Amazing soft tissue contrast Fat-sensitive, Fluid-sensitive, T1-weighted image T2-weighted image Different Types of MRI  MRI Sequences and Signals Fat-sensitive sequences Signal from fat is brightest Excellent for visualization of anatomy (anatomy defining) Can be gadolinium enhanced (contrast to enhance pathology) Includes T1-weighted, gradient echo (GRE), and proton density (PD) Fluid-sensitive sequences Signal from water is brightest Excellent for identifying pathology (fluid-sensitive) (edema/inflammation/hematoma/tumors/abnormal fluid) Can be fat saturated (suppresses fat signal to enhance fluid) Can be fluid-attenuated inversion recovery (FLAIR), susceptibility- weighted imaging (SWI) Includes T2-weighted and short tau inversion recovery (STIR)  MRI Sequences The method of reading matches anatomy- defining views with fluid-sensitive views to detect abnormal fluid This example is ankle-specific: Orthogonal plane Anatomy sequence Fluid-sensitive sequence Axial PD T2 FS Sagittal T1 T2 IR Coronal PD T2 IR Copyright © 2014 F. A. Davis Company www.fadavis.com Fat-Saturated Axial MRI T1 T2 STIR T1 FS with contrast Variations of MRI Variations of MRI MRI with contrast Similar to CT with contrast https://en.wikipedia.org  Variations of MRI (cont.) MR arthrography Sagittal MR myelography Not similar to CT myelography Systematic Reading Patterns and Indications (for MRI)  Systematic Search Pattern: MRI A: alignment Alignment and continuity of ligaments, nerves, muscles B: bone signal Alterations in bone marrow signal C: cartilage Osteochondral or articular cartilage abnormalities D: eDema Edema or signal intensity from bony and soft tissue S: soft tissue and synovial tissue Abnormalities in synovium, fat pads, bursa  General Indications for MRI Advanced imaging of soft tissue, such as muscle, cartilage, ligament, tendon, meniscus, vessel, nerve, fat, and disc Imaging for fluid, hematoma, cysts, infection, and so on Tomographic imaging for avascular necrosis and loose bodies Advanced imaging for tumors Preoperative planning Questions? Imaging Evaluation of Fractures Kimiko Yamada, PT, DPT, OCS, ATC Photo Credit: By Grant Cochrane/FreeDigitalP hotos.net  Fracture Evaluation We will cover: Types of imaging used in musculoskeletal (MSK) trauma Focus on finding fractures in imaging Elements of fracture description in adults Elements of fracture description in children  Fractures “A fracture is a break in the structural continuity of bone” A bone fracture pattern can be predicted by the: 1. Viscoelastic properties of the bone 2. Biomechanics of the load on the bone  Imaging for Musculoskeletal Trauma X-ray is the usual first-line imaging for most fractures and dislocations. CT is used for complex injuries and injuries of multiple areas of the body. MRI is used for soft tissue trauma injury visualization. FAST (focused abdominal ultrasound for trauma) is used to identify free fluid in the peritoneal cavity. Radiographic Signs of Fractures  Radiographic Signs of Fractures Discontinuity of the bone structure (cortical disruption), smooth contour, or shape of the bone Malalignment or displacement of bone Lucent line Linear region of sclerosis Fragment avulsion Double density Disruption of one area of a ring means that there is another Soft tissue swelling Lipohemarthrosis (fat–blood interface [FBI] sign) Abnormal or displaced fat pad  Lipohemarthrosis Lipohemarthrosis (white arrows/asterisk) results from intra-articular fracture Black asterisk is edema/fluid Results from intra-articular fracture with escape of fat and blood from the bone marrow into the joint; most often seen in the knee  Abnormally Displaced Fat Pad Fat pad displacement by joint edema: fat pad sign or sail sign because it looks like a sail Copyright © 2014 F. A. Davis Company www.fadavis.com Elements of Fracture Description Part 1  Fractures Eponyms are sometimes used to describe fractures but should be avoided because they are too vague and can lead to misunderstanding/misinterpretation. For a list of commonly used eponyms, see pages 108–111 (McKinnis text).  Elements of Fracture Description One commonly used terminology describes whether the fracture was exposed to the environment outside of the body/skin. Closed Open Not exposed Exposed Copyright © 2014 F. A. Davis Company www.fadavis.com  Signs of an Open Fracture Disruption of the skin Bone fragment may or may not be protruding through skin or missing bone fragments Gas in soft tissues Intra-articular gas Foreign body fragments in wound Gas in Joint or in Soft Tissue Egol KA, Gardner MJ (Eds.). Let’s discuss management of common fractures. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2016, pp. 135–152.  Seven Elements of Fracture Description, Part I 1. Anatomic site 2. Type: complete/incomplete/comminuted/ number of pieces 3. Alignment or angulation 4. Direction of fracture line(s) 5. Special features (i.e., impaction or avulsion) 6. Associated abnormalities (i.e., joint dislocation) 7. Secondary to abnormal stresses (i.e., stress fractures or pathological fractures)  Seven Elements of Fracture Description, Part II Anatomic site Proximal or distal end Intra- or extra-articular Proximal, middle, or distal third of the shaft (for long bones) Copyright © 2014 F. A. Davis Company www.fadavis.com  Seven Elements of Fracture Description, Part III Type A. Incomplete: a portion of the cortex is intact B. Complete: fracture into two fragments C. Comminuted: more than two fragments A B C C C Copyright © 2014 F. A. Davis Company www.fadavis.com  Seven Elements of Fracture Description, Part IV Type (cont.) D. Number of fragments Neer II CS. Displaced proximal humeral fractures. Part I. Classification and evaluation. Journal of Bone and Joint Surgery, American Volume. 1970;52:1077–1089.  Seven Elements of Fracture Description, Part V Alignment/angulation descriptors Direction or position of distal displacement Copyright © 2014 F. A. Davis Company www.fadavis.com  Seven Elements of Fracture Description, Part VI Alignment descriptors Direction of apex of the angle formed by the fracture fragments (i.e., volar apex or dorsal apex) Amount of displacement (i.e., one cortex width, one-half shaft width, or full shaft width) Volar apex Dorsal apex Copyright © 2014 F. A. Davis Company www.fadavis.com Journal of the American Academy of Orthopaedic Surgeons. 2011;19:623–633.  Seven Elements of Fracture Description, Part VII Direction of fracture line(s) Described in reference to the long axis of the shaft Copyright © 2014 F. A. Davis Company www.fadavis.com Elements of Fracture Description Part 2  Seven Elements of Fracture Description, Part VIII Special features Impaction Depression: one bone surface driven into the other Compression: both surfaces forced together Avulsion: tensile loading on bone; pulling off attachment site for muscles, tendons, and ligaments  Seven Elements of Fracture Description, Part IX Associated abnormalities Dislocation and subluxations associated with fractures May need further imaging for specific diagnosis of soft tissue involvement Case courtesy of Dr. Sajoscha Sorrentino, radiopaedia.org, rID: 14836  Seven Elements of Fracture Description, Part X Fractures secondary to abnormal stresses Stress fractures Pathologic fractures Periprosthetic fractures Bone graft fractures  Seven Elements of Fracture Description, Part XI Stress fractures Anterior-posterior (AP) Lateral Korsh J, Matijakovich D, Gatt C. Adolescent shin pain. Pediatric Annals. 2017;46(1):e29–e32.  Seven Elements of Fracture Description, Part XII Fractures secondary to abnormal stresses Pathological fractures AP Lateral Copyright © 2014 F. A. Davis Company www.fadavis.com  Seven Elements of Fracture Description, Part XIII Fractures secondary to abnormal stresses (cont.) Periprosthetic fractures AP Lateral Pike J, Davidson D, Garbuz D, et al. Principles of treatment for periprosthetic femoral shaft fractures around well- fixed total hip arthroplasty. Journal of the American Academy of Orthopaedic Surgeons. 2009;17:677–688.  Seven Elements of Fracture Description, Part XIV Fractures secondary to abnormal stresses (cont.) Bone graft fractures Fractures through allografts usually occur spontaneously two or three years after implantation AP Lateral AP Latera l Elements of Fracture Description: Pediatrics  Fractures in Children Difficult to assess because the following may be mistaken for fractures: Growth plates Dense growth lines Secondary centers of ossification Large nutrient foramina Cartilage model not event on a radiograph  Seven Elements of Fracture Description for Children (Similar to Adults) 1. Anatomic site 2. Type: complete or incomplete 3. Alignment 4. Direction of fracture line(s) 5. Special features (i.e., impaction or avulsion) 6. Associated abnormalities (i.e., joint dislocation) 7. Secondary to abnormal stresses (i.e., stress fractures or pathological fractures)  Seven Elements of Fracture Description for Children (Unique Aspects) Anatomic site Diaphyseal: at central shaft Metaphyseal: at expanding end of bone Physeal: at epiphyseal growth plate Epiphyseal: at epiphysis/end of bone Copyright © 2014 F. A. Davis Company www.fadavis.com Pelvic Development/Growth Plates Not fractures! Hand Development/Growth Plates 3 years old 4 years old 8 years old 10 years old https://radiopaedia.org/cases/carpal-ossification  Seven Elements of Fracture Description for Children (Unique Aspects), Part I Type A. Incomplete: a portion of the cortex is intact B. Complete: fracture into two fragments C. Comminuted: more than two fragments A B C C C Copyright © 2014 F. A. Davis Company www.fadavis.com  Seven Elements of Fracture Description for Children (Unique Aspects), Part II Type (cont.) D. Additional incomplete fracture descriptors Copyright © 2014 F. A. Davis Company www.fadavis.com  Seven Elements of Fracture Description for Children (Unique Aspects), Part III Epiphyseal fractures 15–20% of pediatric imaging Type II is most common Salter Harris classification of epiphyseal fractures Copyright © 2014 F. A. Davis Company www.fadavis.com Conclusion CSM 2017, San Antonio, TX