Osseous Tumor Reporting and Data System (OT-RADS) is a reporting and communication tool designed to reliably identify benign and malignant bone tumors and to communicate them in a standardized way, using BI-RADS as an example 1-3.
On this page:
History and etymology
The Osseous Tumor Reporting and Data System has been developed and validated by a group of radiologists and orthopedic surgeons from UT Southwestern Medical Center in Dallas around the American Radiologist Avneesh Chhabra and has been published in the Journal of Computer Assisted Tomography in 2021 1.
Usage
The reliability of the OT-RADS system was validated by the above study group mainly based on a "complete MR imaging study" with the following predefined requirements 1:
full tumor coverage in each of the following sequences in at least one plane
T1 weighted imaging (T1)
fluid sensitive imaging (T2FS/STIR)
postcontrast fat-saturated T1 weighted imaging (T1FS C+)
An additional complementary set of MRI sequences is considered sufficient if acquired within two weeks of the initial incomplete imaging set 1.
The following are considered optional supplemental imaging features for the diagnosis 1,3:
diffusion-weighted imaging (DWI) with the apparent diffusion coefficient (ADC)
corresponding radiographic imaging features (if available)
Assessment categories
The assessment categories were created using the BI-RADS system as an example and based on the WHO classification of bone tumors. The assignment of categories in the OT-RADS seems to be based more on the typical MRI appearance of representative lesions with lesion-specific predefined imaging criteria than on generalized MRI signal characteristics 2,3 with some exceptions, such as about appearance on diffusion imaging and post-contrast enhancement.
OT-RADS 0
interpretation: incomplete imaging (see above)
probability of malignancy: not applicable
management: additional imaging or prior imaging examinations required
imaging criteria: not applicable
OT-RADS 1
interpretation: no bone tumor/lesion
probability of malignancy: substantially 0%
management: no further imaging follow-up is required
imaging criteria: normal bone anatomy
OT-RADS 2
interpretation: definitely benign bone lesion
probability of malignancy: substantially 0%
management: imaging follow-up as per recommendations of the clinical team
-
representative lesions:
intraosseous lipoma: uniform typical fat signal on all sequences and no enhancement
classic aneurysmal bone cyst: fluid-fluid levels and no solid component
non-ossifying fibroma: subcortical location, mixed signal intensity
osteoid osteoma: with well-defined nidus (<1.5 cm)
small enchondroma: <4-5 cm, endosteal scalloping <50%, no bone marrow edema or periosteal edema
classic hemangioma of bone: T1 signal hyperintensity
osteochondroma: exostosis, cartilage cap ≤1.5 cm
-
enhancement patterns:
no enhancement
thin or septal enhancement
nidus-like enhancement (osteoid osteoma)
variable enhancement
-
diffusion-weighted imaging:
moderate to marked hyperintensity in both DWI and ADC images
mean ADC values: >1.5-3.0 x 10-3 mm2/s with exception of fat-containing tumors
OT-RADS 3
interpretation: probably benign bone lesion
probability of malignancy: ≤2%
-
management:
imaging follow-up in 3 months, 6 months, 1 year and 2 years or <2 years
follow-up might be shorter in the setting of lesion regression or resolution
-
representative lesions:
Langerhans cell histiocytosis: in children and young adults
intraosseous myxoma
synovial chondromatosis with involvement of bone
enchondroma protuberans: in hands and feet
enhancement patterns: usually variable enhancement
-
diffusion-weighted imaging:
moderate to marked hyperintensity in both DWI and ADC images
mean ADC values: >1.2-2.0 x 10-3 mm2/s with caution in myxoid lesions and giant cell tumor of bone
OT-RADS 4
interpretation: indeterminate or suspicious for malignancy
probability of malignancy: >2% and <50%
-
management:
histology or short-term follow-up in 4-6 weeks
imaging follow-up as per OT-RADS 3 category in the setting of negative or indeterminate histology
MR imaging criteria: mixed intensity, solid appearance, up to 5 cm in length
-
representative lesions:
enchondroma with deep endosteal scalloping (>50% of cortex)
enhancement patterns: variable
-
diffusion-weighted imaging:
moderate to marked hyperintensity on DWI and mild-to-moderate hyperintensity on ADC images
mean ADC values: >1.1-1.2 x 10-3 mm2/s with caution in myxoid lesions and giant cell tumor of bone
OT-RADS 5
interpretation: highly suspicious for malignancy
probability of malignancy: ≥50%
management: histology required
MR imaging criteria: mixed intensity, solid appearance
-
representative lesions:
enhancement patterns: variable
-
diffusion-weighted imaging:
diffusion restriction
mean ADC values: <1.1-1.2 x 10-3 mm2/s with caution in myxoid lesions and giant cell tumor of bone
OT-RADS 6
interpretation: histologically proven malignancy or known tumor recurrence
probability of malignancy: not applicable / proven
management: surgical excision and/or treatment as clinically appropriate
imaging criteria: solid nodule or residual mass in tumor bed with pre-interventional imaging features