Which Scan Do I Order?

Which Scan Do I Order?
GP14 Stream Workshop
Dr Jacqueline Pearce, MBBS FRANZCR
I-MED Radiology Network
Which Modality Will Give Me the Answer?
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MRI
CT
US
Plain x-ray
Bone scan/SPECT CT
A combination of the above
None of the above
– wait and see for a period of time
– may require clinical judgement only
GENERAL CONSIDERATIONS
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Patient contraindications
Radiation dose
Availability*
Cost*
* beware of decision making traps!
MRI Contraindications
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Some aneurysm clips
Endovascular stent grafts
Recent coronary stents (6 weeks)
Metal in eyes
Bullets
Pacemakers
Some ossicular implants
Some mechanical heart valves
Claustrophobia (almost always fine with sedation)
• Joint replacements & other bony metalware OK!
Contrast Contraindications: Allergy
• Urticaria, angioneurotic oedema, bronchospasm,
anaphylaxis, death
• Iodinated CT contrast
– 0.5-3.0% mild reactions
– 0.004% severe (1 in 25,000 doses)
• Gadolinium MR contrast
– 0.5% immediate reactions
– 1 death per 5.26 million doses over 10y
Contrast Contraindications: Renal Function
• C+ CT & MRI requires adequate renal function
– eGFR >60 but there is some discretion depending on
patient background and degree of need for the test
• Is renal function acutely declining or just recovering?
• Could a non-contrast test give reasonable information or
would it be useless?
• Could another test be performed instead?
– Check UEC if patient older than 70y, diabetic, history
of renal impairment etc.
Radiation Dose
• Radiation dose from CT should always be considered but
should not prevent you from performing the correct test
for the clinical indication
• Choose MRI/US vs. CT where it will give you the answer
in:
– Children, young adults, pregnant women
– Multiple examinations
– Low-dose CT partially mitigates but does not mean you can
disregard radiation exposure as an issue
Radiation Dose Lists Should Not be Used
to Impact Decisions or Advise Patients
• Depends on individual scanner, patient size and
scanning protocols used!
• Huge variability and potentially wildly inaccurate
• In reality the actual dose of a particular scan should be
irrelevant as you should always choose the lowest dose
scan option that will give you the answer you need
• If that happens to be a CT then it is appropriate to order
one!
– eg. CT KUB in a young person – there is no appropriate
substitute to prove the presence/site of a ureteric calculus
Radiation Dose
• One important exception is when a pregnant
woman has a pressing need for imaging requiring
radiation
– Relative dose and risks to foetus and mother
considered specifically
– eg. For ?PE: CTPA 1&2nd trimesters; V/Q 3rd trimester
• Ensure you send to a site with a modern low dose
CT scanner
Cost and Availability
• Waiting times usually not a problem
• Cost: now many fully and partially licensed MRI scanners
around
• Widely available bulk billing for specific rebatable
indications with no out-of-pocket costs for patients on all
modalities
BUT…
• whether an examination is bulk billed or not should not
be the primary determinant of whether to order it!
Don’t Order the Wrong Test Because:
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The patient requests it
It is bulk billed or cheaper than the alternative
The patient has claustrophobia
The availability is thought to be sooner
Geographic access is more convenient
The Wrong Test:
• Is unlikely to give you the right or complete answer for
the clinical problem
• Results in delays in diagnosis
– At best inconvenient and time wasting for Px/Ref/Rad
– At worst dangerous for the patient
• May unnecessarily irradiate the patient
• May cost a lesser amount initially but the correct test still
usually has to be performed, ultimately leading to higher
cost to the patient and Medicare in the long run
For Example………
• A (bulk billed) knee ultrasound will not give you any
useful information about the menisci, cruciates or
articular cartilage
• If the patient does not have an acute knee injury they
may not qualify for a Medicare rebated MRI but the best
test to assess these structures is still an MRI
SPECIFIC CONSIDERATIONS:
Let’s look at particular regions (MSK)
There are some general choice of modality
guidelines to be aware of, but the best test
to order depends on:
• The region of interest!
• The likely pathology!
Large Joints: MRI best all round test.
US useful for some indications
• Shoulder, elbow, wrist, hip, knee, ankle = MRI is the best
all round test
• Detailed assessment of bone, ligaments, tendons,
menisci, muscles etc.
• Detailed objective imaging that can be viewed by
specialists etc. (US relies on report/sonographer/radiologist
skill and can only be checked by performing another scan)
US Can’t Tell You About:
• Bone contusion or subcortical fracturing
• State of articular cartilage (eg. Osteochondral
lesions, post traumatic degeneration/wear)
• Can’t see acetabular/glenoid labrums
• Cant see cruciates/menisci
• Can’t see all of the ankle/elbow/wrist ligaments
• Insensitive for low-intermediate grade muscle
sprains
Small Joints: Ultrasound is Best!
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Fingers and toes
Tendons, lumps, capsular & ligamentous injuries
Dynamic assessments e.g. triggering
Tenosynovitis, ganglia, small tumours
Morton’s neuroma, intermetatarsal bursitis, plantar
fasciitis
• Requires careful assessment, high quality equipment,
good knowledge of anatomy: trusted radiologist!
• MRI often used for thumb, plantar plate injuries etc. but
spatial resolution can limit detailed analysis esp. on 1.5T
scanners or if patient moves
Ultrasound: Tenosynovitis finger
SHOULDER
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Plain films
– AC/GH degeneration, acromion type, calcifications
US
– Useful to screen for rotator cuff tears, biceps tendinosis & bursitis
– Gives dynamic info: range of motion and impingement
– Localize regions of tenderness to anatomical structures
– Can’t see labrum, GHJ, IAB, limited ACJ
– Less accurate than MRI for size and extent of rotator cuff tears
– Can be difficult to distinguish areas of tendinosis from partial thickness tears
– Very limited bony detail
– Difficult in obese people
MRI
– Best test, most reliable for all parts of shoulder
CT – orthopaedic pre-op assessment only
Ultrasound: Spinoglenoid ganglion
MRI: Spinoglenoid ganglion with labral tear
ELBOW
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Plain XRAY
– ?#
– OA screening
US
– Good to assess CEO/CFO tendinosis and hypervascularity
– Joint effusion
– Ulnar and PIN nerve entrapments (sometimes)
– Limited bony detail
– Small or partial thickness tears can still be missed
– Cannot assess ligaments
MRI
– Best all round test
Ultrasound: CEO tendinosis
WRIST
• XRAY
• US
– Good for tendons e.g.. De Quervain’s
– Ganglia, other lumps
– Median nerve at carpal tunnel
• MRI
– Only way to assess TFCC, intrinsic and extrinsic ligaments
– Good for tendons
– Bony changes e.g. scaphoid fracture
• CT
– Fracture characterisation
X-Ray: carpal fracture
CT: fracture triquetral
MRI: scaphoid fracture
HIP
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Plain X-Ray
– Screening for OA, useful with MRI
– Screening for DDH, Perthes, SUFE etc.
– Review of prostheses
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MRI
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The only test for evaluation of labrum and extent of OA/FAI
Early AVN
Occult/stress fractures/transient osteoporosis
Best look at gluteus tendons
Hamstring origin
Iliopsoas, piriformis etc.
US
– OK for trochanteric bursitis
– Average for gluteus tendinosis & tears
• CT
– No more information than a plain film!
– Orthopaedic Pre-op assessment only!
X-Ray: L hip pain 43y M
MRI: transient osteoporosis with stress microfracturing
KNEE
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Plain XRAY
– OA screening
– Weight bearing, alignment, PFJ views
MRI
– Best test for all!
– OA, meniscal tears, cruciates, collateral ligs, extensor
US
– Limited role for patellar/quads tendons ? Tendinosis
– ?prepatellar bursitis
– Baker’s cyst/effusion
– Basic assessment of MCL/LCL sprains
– Cannot see menisci, cruciates, articular cartilage
CT
– Orthopaedic pre-op assessment only! (eg. patellar maltracking)
ANKLE
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Plain films
– ? # screening in acute trauma
US
– Good for tendon tears/tenosynovitis
– Limited assessment of ligaments
• Can only see ATFL, Ant Tib-Fib Syndesmosis, CFL
• Acute oedema/haematoma makes extent/grade of sprains hard to assess
• ? Joint effusion
MRI
– Best test for assessment of all ligaments
– Bony contusions
– Talar dome osteochondral lesions
– Sinus tarsi, spring ligament, achilles, plantar fascia
– Impingement syndromes
CT
– Pre and post-op assessments only!
CERVICAL SPINE
• Neck pain PLUS symptoms & signs of radiculopathy
• Arm pain, paraesthesias, weakness, wasting
• MRI first choice: rebatable scan!
• CT only if MRI contraindicated
• CT
• Pre/post-operative assessments of bony fusion
• Acute traumatic fracture assessment
• Plain X-Ray
• Basic screen for neck pain only
• Standing AP for scoliosis
• Flexion and extension for instability
X-Ray:Cervical degenerative change
CT: cervical radiculopathic and cord symptoms
Cervical MRI: epidural haematoma & intradural tumour
Cervical spine L: CT axials
R: MRI axials
THORACIC SPINE: pain +/- radiculopathy
• MRI: assess osteoporotic fractures
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Ensure no underlying tumour, infection
New or old
Disc disease
Cord pathology
• CT:
– Characterisation of acute traumatic fractures
– Generally poor for other indications
• Plain films:
– AP erect for scoliosis assessment
– Lateral for ?Osteoporotic crush fractures +/- old films
– Review previously documented fractures
LUMBAR SPINE
• Back pain with radiculopathy, all ages
– MRI is the best test
– CT a reasonable alternative but NOTE significant radiation dose to pelvis
• Don’t order CT lumbar spine in young people
• Back pain in young people WITHOUT radiculopathy
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MRI is modality of choice
Muscular
Discogenic
Pars defects with stress fractures
Spondylolisthesis
Congential predisposition to premature degeneration
CT may be used characterise pars defects or other bony lesions seen on
MRI as part of specialist work-up
When Should I Order a Bone Scan?
• Back (or other bone) pain in Px with red flags or risk for skeletal
metastatic disease
– Start with plain films!
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Review of known skeletal metastatic disease: restaging
?stress fracture with negative plain films (also MRI)
Differentiate cellulitis from osteomyelitis (also MRI)
Differentiate osteomyelitis from avascular necrosis (also MRI)
Evaluate prostheses for loosening, fracture, OM
Work up of focal bony lesions seen on other modalities
A FEW COMMENTS ON IMAGE GUIDED
THERAPEUTIC INJECTIONS
CT Guided Lumbar Spine Injections
• Trans-laminar epidural
– Canal stenosis: bilateral leg symptoms
– Post-op
• Trans-foraminal nerve root
– Unilateral sciatica
• Facet joint
– Often bilateral or multilevel but usually staged
• Choose ONE level per procedure!
• Be precise about what procedure you want!
CT Guided Cervical Injections
• Facet joints
– Try to do one level at a time as often diagnostic as
well as therapeutic
• Cervical nerve roots from specialist referral only
– Risk of death from stroke, cord haemorrhage
– Requires neurologist/neurosurgeon supervision
– Must have planning MRI before procedure
MSK Therapeutic Injections: HOW?
• US
– Shoulder BURSA, biceps; elbow:CEO/CFO; wrist,
hands, trochanteric BURSA, gluteus tendons, knee,
ankle joint, tendons, some small joints foot
• Fluoroscopy
– Hip JOINT! Requires contrast
– Shoulder JOINT! (hydrodilatation) Requires contrast
• CT
– Sacroiliac joints
– Subtalar and other small joints foot (also US)
Vascular Imaging
• CTA
– first line for thoracic and abdominal aorta aneurysm
assessment, atheroscerlotic disease
– Excellent for renal and peripheral arteries but need good renal
function
– Problem solve for carotids and cerebral vessels
• MRA
– first line for intracranial imaging
– OK renal aa, no good aorta or peripheral arteries
• Doppler US
– first line for peripheral arteries, renal aa, carotid aa
– Limited review aorta
– No good for central great vessels
Intracranial MRA: L ICA aneurysm
CTA infra-renal aortic aneurysm
CTA renal artery stenosis
Doppler carotid ultrasound
Investigation of Headache
• MRI Brain +/- MRA, MRV
– Investigation of choice for headache with red flags
• CT Brain
– Acute trauma for haemorrhage and skull fracture
– Never plain X-ray skull!
• CT paranasal sinuses but can often see sinus
pathology on standard MRI brain
MRI BRAIN: acute sphenoid sinusitis
25y F
MRI SS sinus thrombosis
SSS & R transverse sinus thrombosis
19y M
Ct head bilateral acute on chronic subdurals
Investigation of Seizures
• MRI brain is the investigation of choice
• No role for CT unless they occur in the setting of
acute head trauma!
MRI Brain: seizures post surgery for MTS
If you’re not sure which is the right test…..
• A quick phone call to your local radiologist will
save a lot of time and angst!
• We are always happy to provide advice over the
phone
FRONTIERS IN BREAST IMAGING
Breast Tomosynthesis
• Higher sensitivity specificity than standard mammography
• 2 view BT slightly higher dose than standard DM, but less work up
views
• At present used in addition to standard views so roughly double
the radiation exposure for the test
– In future may be used without standard views
– MALMO 2014 study looked at single view tomo with reduced
compression cf. standard DM
– increased cancer detection by 40%
– 65 CA detected: 46 both BT/DM; 18 only BT; 1 only DM
9mm spiculated breast cancer:
L: standard mammo R: tomosynthesis
Breast MRI
• To identify early breast cancer in women with a high risk
of breast cancer
– e.g. a past history of breast cancer in a young woman
– a strong family history of breast cancer
– a known genetic mutation
• To determine the extent of breast cancer that has already
been diagnosed on mammography or ultrasound
followed by a biopsy
• To determine whether an artificial breast implant in one
or both breasts is intact
Breast MRI
• Medicare rebate for women < 50y old who have
no symptoms or signs but are high risk for breast
cancer either through family history or genetic
predisposition (BRCA1/2)
• Must be a specialist referral
Medicare Rebate for Breast MRI
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Three or more first or second degree relatives, on the same side of the family, who have
been diagnosed with breast or ovarian cancer;
Two or more first or second degree relatives, on the same side of the family, who have
been diagnosed with breast or ovarian cancer; Two or more first or second degree
relatives, on the same side of the family, who have been diagnosed with breast or ovarian
cancer, if any of the following applies to at least one of the relatives:
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has been diagnosed with bilateral cancer;
had onset of breast cancer before 40 years of age;
had onset of ovarian cancer before 50 years of age;
has been diagnosed with breast and ovarian cancer, at the same time or at different times;
has Ashkenazi Jewish ancestry;
is a male relative who has been diagnosed with breast cancer;
One first or second degree relative diagnosed with breast cancer at 45 years or younger,
plus another first or second relative on the same side of the family with bone or soft
tissue sarcoma at age 45 years or younger;
Genetic testing has identified the presence of a high risk breast cancer gene mutation.
These requirements were based on the National Breast and Ovarian Cancer Centre’s
(NBOCC) clinical practice guidelines on familial aspects of breast and ovarian cancer
(2006).
Breast MRI: The Issues
• Too sensitive leading to significant number of false
positives
• Lacks specificity – not good differentiation of benign from
malignant
• Still requires correlative imaging and/or biopsy
• Lesions found only on MRI are often very small and deep
how to biopsy? >> MRI guided biopsy unavailable
• Costly cf. mammography/US
• Time consuming to report >> delayed results
• Subspecialist training needed for radiologists to report
Breast MRI: Left invasive lobular carcinoma
What to Say if Your Patient Asks About….
• Prostate MRI
• CT Colonography
Prostate MRI
• NO Medicare rebate for any current indication
• A rapidly evolving field, but MRI is not YET being used
either as a screening tool or as a primary investigation
for an elevated PSA
• Referrals from urologists only at this stage
Prostate MRI
• Currently accepted indications:
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Local staging of biopsy proven cancer (ECS, SVI, nodes)
Radiotherapy planning in biopsy proven cancer
Detection of local recurrence post treatment
Monitoring biopsy proven lower grade tumours where the
patient/urologist have elected not to proceed with surgery
– Negative biopsy with a rising PSA
MRI extensive prostate cancer with:
Extracapsular Spread
Seminal Vesical Invasion
Lymphadenopathy
CT Colonography
Medicare rebatable indications are ONLY:
• Exclusion of colorectal neoplasia in symptomatic or high
risk patients when:
– There has been a failed or incomplete colonoscopy
within 3 months of request
– There is a contraindication to colonoscopy such as:
• Suspected perforation
• High grade obstruction that will not allow passage
of scope
CT Colonography
• Therefore usually ordered by endoscopist only
• Not used as first line screening
• C+ standard CT abdomen not sensitive for
screening
• To exclude polyps or neoplasia refer for a scope!
CT Colonography: adenomatous polyp
Thank you