Transcript Role of MRI in diagnosis of benign and - Learning

Role of MRI in diagnosis of benign
and malignant bone and soft tissue
tumours
John-Henry Corbett
Department of Radiology
University of the Free State
05/2011
• Conventional radiographs remain the initial
imaging examination for bone and some soft
tissue tumours
• XR is invariably the most diagnostic
– Best for establishing a differential diagnosis
– Best in assesing activity of the lesion
• Benign vs malignant
• Other imaging modalities ( eg. MRI ) are
superior in staging musculoskeletal neoplasms
• Major advantages of MRI for musculoskeletal imaging
– Excellent soft tissue contrast resolution
– Multiplanar imaging capabilities
– Various available contrast agents
• Powerful imaging modality for abnormalities of
– Fat, muscles, nerves, bone and bone marrow
• Effective for use in
– Neoplasms of tissues mentioned above
– Response of neoplasms to neoadjuvant / posoperative
chemotherapy and/or radiotherapy
– Residual and/or recurrent tumour after surgery
– Congenital and developmental musculoskeletal
abnormalities
– Traumatic lesions
– Haemorrhage
– Ischaemia / infarction of bone marrow / muscles / fat
– Infectious and non-infectious inflammatory diseases
• Longitudinal bone growth occurs by enchondral bone
formation
– A calcified cartilaginous matrix at the growth/physeal plate is
remodelled into bone
• Physeal plate contains four parallel zones perpendicular to the
long axis of the bone
•Active cartilage cell division and maturation in
the proliferating and hypertrophic zones
•Ostoid matrix formation and mineralization
occurs in the ossification zone
•Resting, Proliferating and Hypertrophic zones
•Radiolucent on XR / CT
•High signal on T2WI
•Ossification zone
•Mineralized bone on XR / CT
•Low signal on T2WI
• Axial bone growth occurs directly from the
periosteum
– E.g.: Diameter of long bones, facial bones
• Outer fibrous layer and inner cellular layer
(cambrium – osteoblastic activity)
• Periosteum is loosely attached to the cortex of
bones in children and firmly in adults
• Periosteum is low signal on T1WI & T2WI
• Reactivation of periosteum in adults
– Trauma, infection or neoplasm
• MRI can demonstrate periosteal elevation as well
as subperiosteal abnormalities such as tumour,
pus or haemorrhage
• MRI signal in medullary portion of bone
– Red (hematopoietic) marrow
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40% fat , 40% water & 20% protein
Intermediate T1WI signal – lower than subcut fat
Intermediate T2WI signal – similar to muscle
Predominant marrow in early childhood
Adults : Spine, flat bones, skull, proximal femur &
humerus
– Yellow (hematopoietically inactive) marrow
• 80% fat, 15% water & 5% protein
• Similar signal to subcutaneous fat on T1WI & T2WI
• Later in childhood – progressive conversion of red to
yellow marrow
– Hands and feet
– Distal long bones : diaphyseal regions in the first decade
• Most pathological processes increase the T1
and T2 relaxation coefficients of involved
tissue
• Leads to ↓T1 signal and ↑T2 signal compared
to surrounding normal tissue
– Includes : ischaemia, infarction, inflammation,
neoplasm
– Haemorrhage : variable appearance according to
age
Imaging evaluation of bone and soft
tissue tumours
• On XR most bone tumours are radiolucent
• Osteolytic lesions may not be visible on XR
until there is 30-50% loss of mineralization
• MRI can detect marrow based tumours before
they are evident on XR
• MRI can also further characterize lesions with
regards to extent and soft tissue extension
• Features used to characterize bone and other tumours
on XR
– Lesion location
• Epiphyseal / metaphyseal / diaphyseal
• Cortical / intramedullary / eccentric / central
– Lesion size
– Lesion density
• Radiolucent / sclerotic / presence of matrix mineralization
– Margins
• Well defined geographic ± sclerotic borders / poorly defined
• Moth eaten / permeative radiolucent patterns
– Presence of cortical destruction
• ± Extra osseous tumour extension
– Presence of periosteal reaction
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Interrupted vs non-interrupted pattern
Lamellated / onion skin appearance
Perpendicular-, sunburst pattern
Codman triangles
• Features used to characterize bone and soft
tissue tumours on MRI
– Lesion location
– Lesion size
– Margins
• Well-defined geographic ± low signal margins vs poorly
defined
– Signal of the lesion on
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T1WI
PDWI with and/or without fat saturation
T2WI with and/or without fat saturation
STIR images
– Enhancement after IV Gadolineum based contrast
– Presence of cortical destruction
• T1WI
– Good contrast for identification of marrow , cortical and
soft-tissue involvemement
– Differentiation between fat (↑) and tumour (↓)
– Definition of muscle plains and anatomic compartments
– Longitudinal extent of the tumour can be seen on coronal
or sagital T1WI
• Gadolinium enhanced T1WI
– Better characterize osseous & soft tissue involvement
– Non-enhancing regions of tumour regarded as tumour
necrosis
– Useful for differentiating
• Peritumoural oedema from underlying tumour
• Recurrent tumour from scar / fibrosis
– Dynamic contrast enhanced imaging has been used to
determine response to chemotherapy
• Good response shows reduced enhancement
• Short time intervals should be used (similar in late phase
enhancement)
• T2WI
– Distinguish muscle from tumour
– Increase diagnostic specificity of marrow
infiltration
• Seen as low signal on T1WI
• Proton density- / T2WI- with fatsat or STIR
– Lesion iso-intense to adjacent tissue
• T1WI, T2WI and T2WI fatsat / STIR
– Axial images to delineate the relationship of the
tumour to adjacent neurovascular structures and
compartments
• MR spectroscopy not routinely used
• Not possible to distinguish benign from
malignant lesions of bone and soft tissue on
MRI signal characteristics alone
• Malignant lesions tend to be more extensive
– Involvement of cortex, marrow and soft tissues
– Involvement of the neurovascular bundle
• Perform MRI prior to biopsies to avoid
postsurgical inflammation and oedema
– Prolong T2 relaxation time of uninvolved tissues
• Muscle oedema is non-specific
– Associated with trauma, infection & vascular
insults
• On T1WI ↑ signal in surrounding muscles can
be seen in atrophy with fatty infiltration or
neuromuscular disorders
– Not to be mistaken for tumour
• Marrow inhomogeneity
– Red to yellow marrow conversion
– Especially middle aged obese women with
smoking history / immature skeleton
– Metaphyseal or diaphyseal low signal intensity
(red marrow)
• No extension over physeal scar
– ↑Signal intensity on STIR images
T1WI : Normal ↓ signal metadiaphyseal red marrow.
Epihyseal region is uniformly
yellow marrow
STIR : ↑ signal red marrow
This finding of marrow inhomogeneity is
considered a normal variant.
Coronal T1WI
Coronal STIR
Red marrow heterogeneity in the femoral dyaphysis with no
extension across the physeal scar
• Staging of bone / soft tissue tumours
– MRI is the imaging modality of choice
• Should be used with conventional XR
– MRI is accurate in determining
• Local extent of the tumour – intra /extra osseus
• Skip metastases
• Involvement of muscle compartments, joints and
neurovascular bundles
• Local lymphadenopathy
– Enneking staging system for bone and soft tissue
tumours is most widely used
• Based on tumour grade, site and metastases
• Histologic, radiologic and clinical criteria
• Benign lesion are considered grade 0 (G0)
• Malignant lesions are either
– Low grade (G1)
– High grade (G2)
• Site and extent of tumours
– T0 : benign tumours confined in a true capsule and
anatomic compartment of origin
– T1 : aggressive benign or malignant lesion confined to
its anatomic compartment
– T2 : spread beyond the anatomic compartment of
origin
• Metastatic disease
– M0 : no metastatic disease
– M1 : regional or distant metastases
Benign
1
Latent
G0
T0
M0
2
Active
G0
T0
M0
3
Aggressive
G0
T0
M0-1
Ia
Low grade
Intra compartmental
G1
T1
M0
Ib
Low grade
Extra compartmental
G1
T2
M0
IIa
High grade
Intra compartmental
G2
T1
M0
IIb
Low grade
Extra compartmental
G2
T2
M0
IIIa
Low or high grade
Intra compartmental + metasteses
G1-2 T1
M1
IIIb
Low or high grade
Extra compartmental + metasteses
G1-2 T2
M1
Malignant
• Important points in reporting on bone tumours
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What is the total intraosseous extent of the tumour
Is there involvement of the growth plate
Are there any “skip” metastases
Is the adjacent joint involved
What is the relationship to the neurovascular bundle
• Important points in reporting on soft tissue
tumours
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Anatomical location of the tumour
Its relationship to the adjacent bone
Its relationship to the neurovascular bundle
Provisional diagnosis
• Neoplastic or non-neoplastic
• Benign or malignant
• Suggested series for bone tumours ( 3 )
– Longitudinal T1WI
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Covering the whole lesion
Include the adjacent joint
Intraosseous extent and relationship to the growth plate
Extremity coil if possible
– Coronal T1WI
• Body coil
• Include the whole bone
• Evaluation for skip metastases
– Axial T2WI with FATSAT
• Relationship to the neurovascular bundle
• Extremity coil if possible
• Include the whole lesion
• Suggested series for soft tissue tumours ( 4 )
– Longitudinal T1WI
– Longitudinal STIR
– Coronal T1WI
– Axial T2WI with FATSAT
• Longitudinal T2WI
– Adds nothing to intraosseous staging
– Both tumour (osteosarcoma) and marrow are
relatively high signal
• Standard enhanced T1WI
– Have not been shown to be of value in evaluating
primary bone tumours
• Axial T1WI
– Adds nothing to extraosseous staging
– Tumour mostly isointense to muscle
Coronal T1W SE image of the distal
femur in a patient with
osteosarcoma showing intraosseous
extent.
Sagittal T1W SE image of the whole femur in a
patient with distal femoral osteosarcoma. A
region of reduced signal intensity in the
mid-diaphysis proved to be a ‘skip’ metastasis.
Axial dual-echo T2 FSE sequence with fat saturation in a patient with distal femoral
osteosarcoma. The relationship between extraosseous tumour and the neurovascular bundle
is best demonstrated on the proton density image (right) since the neurovascular bundle is
isointense to muscle on the T2W sequence (left). Peritumoural oedema is also clearly
distinguished from fat by the addition of fat saturation.
WHO classification of soft tissue
tumours
WHO classification of
bone tumours
Incidence of soft tissue tumours
Incidence of soft tissue tumours
References
• Aisen AM, Martel W, Braunstein EM et al. MRI and CT
evaluation of bone and soft-tissue tumors. American
Journal of Roengenology 1986; 146:749-756.
• Kransdorf MJ & Murphey MD. Radiologic evaluation of softtissue masses: a current perspective. American Journal of
Roengenology 2000; 175: 575-587.
• Meyers SP. MRI of bone and soft-tissue tumours and
tumour-like lesions. Thieme; 2008.
• Saifuddin A, Twinn P, Emanuel R & Cannon SR. An audit of
MRI for bone and soft-tissue tumours at referral centres.
Clinical Radiology 2000; 55:537-541.
• Stoller DW. MRI in orthopaedics and sports medicine. 3rd Ed.
Lippincott, Williams & Wilkins; 2006.