Solitary bone tumor imaging reporting and data system (BTI-RADS)

Solitary bone tumor imaging reporting and data system (BTI-RADS) is a reporting and communication tool designed to stratify benign and malignant bone lesions and to communicate them in a systematic and standardized way ^1,2.

History and etymology

The solitary bone tumor imaging reporting and data system was developed and clinically tested by a group of radiologists in Nancy, France around the Brasilian radiologist Guilherme Jaquet Ribeiro and has been published as the first reporting and data system for bone lesions in the Journal of European Radiology in 2021 ^1,2.

Usage

The BTI-RADS system is based on different CT and MR imaging features as well as basic clinical data and was clinically tested by the above study group with a fair interobserver agreement ¹. The following features are required for the assessment and evaluated by the respective imaging modality or clinically ¹:

Clinical data

• age (18-50 years / >50 years)

• anatomical tumor localization (hand and feet, pelvic bones)

CT features

• transverse bone location (subperiosteal or cortical, intramedullary)

• modified Lodwick-Madewell grade (grade 1, grade 3)

• aggressive periosteal reaction

• metastatic disease

MR features

• lesion size (<15 mm, ≥60 mm)

• lesion shape (round or oval, irregular)

• contrast enhancement (none)

• soft tissue invasion (absent, present)

Assessment categories

The assessment categories range from 1 to 4 and are based on clinical and imaging features classified as predefined benign indicators, minor malignant indicators and major malignant indicators as well as typical imaging characteristics of bony "do not touch" lesions for the benign assessment categories ^1,2.

BTI-RADS 1

• interpretation: benign

• imaging and clinical criteria:

  • ≥2 benign and ≤1 minor malignant indicator and

  • imaging features of a typical "do not touch" lesion

BTI-RADS 2

• interpretation: likely benign

• imaging and clinical criteria:

  • ≥2 benign and ≤1 minor malignant indicator and

  • no imaging features of a typical "do not touch" lesion

BTI-RADS 3

• interpretation: suspicious for malignancy

• imaging and clinical criteria:

  • ≤1 benign indicator or

  • <3 minor malignant indicator

BTI-RADS 4

• interpretation: likely malignant

• imaging and clinical criteria:

  • ≥3 minor malignant indicators or

  • any major malignant indicator

Benign indicators

The following characteristics have been considered benign indicators ¹:

• lesion size <15 mm

• round or oval shape

• no contrast enhancement (MRI)

• no soft tissue invasion (MRI)

• cortical or subperiosteal location

• Lowick-Madewell grade 1

• anatomical region: hand and foot

Minor malignant indicators

The following characteristics have been considered minor malignant indicators ¹:

• lesion size ≥60 mm

• age >50 years

• irregular shape

• soft tissue invasion (MRI)

• intramedullary centered location

• anatomical region: pelvic bones

Major malignant indicators

The following characteristics have been considered major malignant indicators ¹:

• Lowick-Madewell grade 3

• aggressive periosteal reaction

• suspicion for metastases

"Do not touch" lesions

The following "do not touch” lesions have been considered by the study group for lesion categorization ^1,2 by their corresponding established imaging characteristics ^1-9:

• geode (subchondral cysts and synovial herniations)

  • lytic well-defined periarticular subchondral lesion

  • fluid-like signal

  • no central enhancement

• enostosis

  • small (<1 cm) round or oval spiculated areas of densely compacted bone within cancellous bone

• non-ossifying fibroma

  • well-defined lucent cortical defects located in the metaphysis or the diametaphyseal junction

  • no adjacent bone marrow edema or abnormalities

  • no adjacent soft tissue mass

• simple bone cyst

  • well-define lucent intramedullary lesions

  • commonly metaphyseal location

  • narrow transition zone, sclerotic margins

  • "fallen fragment sign" in the setting of pathologic fracture

• bone infarction

  • central medullary bone lesion with a geographical shape and fatty content

• subperiosteal hematoma

  • eccentric lens-shaped subperiosteal lesion

  • presence of a“ghost native cortex”

  • no soft tissue or bone evasion, no periosteal reaction, no peritumoral edema

See also

• Bone Reporting and Data System (Bone-RADS)

• Osseous Tumor Reporting and Data System (OT-RADS)

• Reporting and Data Systems (RADS): list of all RADS