Quantitative Bone SPECT/CT of Central Cartilaginous Bone Tumors: Relationship between SUVmax and Radiodensity in Hounsfield Unit

Abstract

(1) Background: it is challenging to determine the accurate grades of cartilaginous bone tumors. Using bone single photon emission computed tomography (SPECT)/computed tomography (CT), maximum standardized uptake value (SUVmax) was found to be significantly associated with different grades of cartilaginous bone tumor. The inquiry focused on the effect of the tumor matrix on SUVmax. (2) Methods: a total of 65 patients from 2017 to 2022 with central cartilaginous bone tumors, including enchondromas and low-to-intermediate grade chondrosarcomas, who had undergone bone SPECT/CT were retrospectively enrolled. The SUVmax was recorded and any aggressive CT findings of cartilaginous bone tumor and Hounsfield units (HU) of the chondroid matrix as mean, minimum, maximum, and standard deviation (SD) were reviewed on CT scans. Pearson's correlation analysis was performed to determine the relationship between CT features and SUVmax. Subgroup analysis was also performed between the benign group (enchondroma) and the malignant group (grade 1 and 2 chondrosarcoma) for comparison of HU values and SUVmax. (3) Results: a significant negative correlation between SUVmax and HU measurements, including HUmax, HUmean, and HU_SD, was found. The subgroup analysis showed significantly higher SUVmax in the malignant group, with more frequent CT aggressive features, and significantly lower HU_SD in the malignant group than in the benign group. (4) Conclusions: it was observed that higher SUVmax and lower HU_SD were associated with a higher probability of having a low-to-intermediate chondrosarcoma with aggressive features and a less calcified tumor matrix.

Keywords: SUVmax; bone SPECT/CT; cartilaginous bone tumor; chondroid matrix mineralization; correlation; hounsfield units.

Figure 1

Radiodensity measurement in a patient with ACT in the distal femur. (A) Axial CT image shows a lobulated mass containing chondroid matrix mineralization and focal deep endosteal scalloping ≥ 2/3 of the normal cortical thickness (arrow). (B) Mean (±SD) attenuation of this lesion was measured using the freehand ROI tool (green line) and HU values were found to be 435.49 ± 335.30 [−111 to 1501]. (C) Fused SPECT/CT image shows the radioactive uptake with SUVmax of this lesion which was calculated to be 23.71.

Figure 2

Extensive endosteal scalloping ≥ 2/3 of the lesion length in a patient with ACT in the distal femur. (A) An axial CT image shows a lobulated mass containing chondroid matrix mineralization and focal endosteal scalloping (arrow). (B) A sagittal T2-weighted image shows a lobulated mass with heterogeneously increased signal intensity and extensive endosteal scalloping ≥ 2/3 of the lesion length (arrows).

Figure 3

Expansile cortical remodeling in a patient with CS2 in the proximal femur. (A) An axial CT image shows a lobulated mass containing chondroid matrix mineralization and expansile cortical remodeling (arrows). (B) A plain radiograph shows a lobulated mass with expansile cortical remodeling (arrows) with cortical thickening (arrowhead).

Figure 4

Cortical destruction with small extraosseous soft tissue extension in a patient with CS2 in the scapula. (A) An axial CT image shows a lobulated mass containing chondroid matrix mineralization and focal cortical destruction (arrow). (B) An axial T1-weighted fat-suppressed enhanced MRI shows a lobulated mass with extraosseous soft tissue extension (arrowhead).

Figure 5

The relationship between SUVmax and radiodensity. (A) HUmax, (B) HUmin, (C) HUmean, and (D) HU_SD. r = Pearson’s correlation; r² = goodness-of-fit of linear regression.

Figure 6

Comparison of SUVmax and radiodensity in HU measurements between ACT (A–C) and enchondroma (D–F). (A) A coronal T1-weighted fat-suppressed enhanced MRI shows a lobulated mass with septal enhancement with pathology of ACT. (B) A fused SPECT/CT image shows the radioactive uptake with SUVmax of this lesion which was calculated to be 23.61. (C) The radiodensity in HU measurement of this lesion was found to be 376.14 ± 270.35 [−163 to 1458]. (D) A coronal T1-weighted fat-suppressed enhanced MRI shows a lobulated mass with faint septal enhancement with pathology of enchondroma. (E) A fused SPECT/CT image shows the radioactive uptake with SUVmax of this lesion which was calculated to be 11.5. (F) The radiodensity in HU measurement of this lesion was found to be 724.05 ± 653.68 [−463 to 2689].