other imaging modalities 2 Flashcards

Question

MRI for TMJ

Answer 1

internal derangement (clicks/cracks/limitation) US is alternative but controvesial (only if pt not suitable for MRI) KEY * T1W scan fat is always white, bone is black and fluid is black – good for anatomy * T2W scan fat is white, fluid is white, bone is black – good for pathology So CSF can determine

Answer 2

Disc is visualised on MRI (only one that can see properly) Can determine if with or without reduction and which direction the disc moves in relation to the condyle. * 2 views to determine displacement (medial and/or lateral) Need to view in para-sagittal (along short axis of condyle) and para-coronal (along long axis of condyle) * Need dedicated TMJ MRI, not a typically head or neck view

Answer 3

T1W parasagittal view (fat is white) Usually healthy articular disc – bow tie shape, usually sits at 12 to 10 o’clock First is normal healthy TMJ joint and articular disc Image the pt closed and open – 2nd image is open – codylar head has translated forward (normal again) 3rd -abnormal, advanced osteoarthritic appearance – thinning of cortical bone on superior surface (not equal thickness all way round), loss of joint space, fatty marrow is no longer bright white in condylar head – suggested inflammation and degeration. Disc isn’t in normal position – sitting anteriorly beneath articular eminence, shape is smaller and no longer bow tie (shrivelled and desiccated) – long standing articular inflammatory reaction **Anterior disc displacement without reduction **

Answer 4

Supplement MRI with CBCT – see bone in more detail See osseous changes more detail Left image is right degenerative TMJ, right image is left healthy TMJ Degenerative - irregularities, no smooth outlines, osteophyte at edge (beak) – all degenerative change from osteoarthritis – early stage

Answer 5

initially US and noticed discrepanacy in floor of mouth OPT done and noticed left condyle was large compared to right, chin point deviation CBCT to get more detail * Left side is bigger than pt right * Condylar head not sitting in joint space, reaching towards anterior aspect of articular eminence (parasagittal view) * See subtle change in density in condylar head Either condylar hyperplasia or osteoblastoma or fibrous dysplasia Biopsy after MRI * Condylar hyperplasia – had distraction osteogenesis

Answer 6

E.g Condylar hyperplasia – is joint undergoing active growth? 99mTc used **Check for activity of joint compared to normal ** High sensitivity, low specificity (cannot tell why – tumor, infection, hyperplasia) Only used as screening method to see if there is more activity Not really used due to increased radiation exposure

Answer 7

Following examination and history taking: Cross-sectional imaging with contrast (depending on type of tumor) * CT (SCC) * MRI Extensive imaging as assessing distant metastases – e.g. suspect in tongue do head, neck and thorax Ultrasound guided biopsy of cervical lymphadenopathy PET/CT – if cannot find primary tumour DPT for Dental assessment prior to radiotherapy

Answer 8

tumors light up with contrast Darker areas are geniohyoid and mylohyoid See cervical lymph node in level 1b (circle), enlarged – likely local metastatic spread

Answer 9

Better definition of tumour compared to CT * See lingual septum is getting encroached on by tumour * Could change tx plan as getting to contralateral side but takes longer and more contraindications for MRI

Answer 10

MRI * no radiation dose to the patient * scan takes longer * More contraindications for MRI: Pacemakers, cochlear implants, metal in tattoo (heatup), Claustrophobic CT * only contraindication is allergy to iodine-based contrast - rare but MRI better for assessing (better definition) * perineural spread * Bone invasion via bone marrow changes * soft tissue characteristics of lesion

Answer 11

US Benign – smooth, lobulated – able to draw round **Here cannot draw round - MALIGNANT** Check masses relationship with CCA and internal jugular vein for level 2 and 3 of neck – here encased Extracapsular spread here – prognostic 50% worse Pt went on to have CT found oropharyngeal base of tongue tumor and metastatic spread through perineural invasion to both sides neck and intracranial spread Necrotic cystic lump further down neck also found –US biopsy non necrotic area to assess

Answer 12

Positron Emission Tomography Radioactive fluorine labelled glucose injected (18 – FDG) * Goes to metabolically active tissues * Doesn’t give anatomical detail so overlaid onto CT or MRI * Good for looking for unknown primary tumours * Useful for follow-up and recurrence Goes to any metabolic active tissue – not allowed to talk or drink or swallow

other imaging modalities 2 Flashcards

(36 cards)