Quantification of tumor burden in multiple myeloma by atlas-based semi-automatic segmentation of WB-DWI

Abstract

Background: Whole-body diffusion weighted imaging (WB-DWI) has proven value to detect multiple myeloma (MM) lesions. However, the large volume of imaging data and the presence of numerous lesions makes the reading process challenging. The aim of the current study was to develop a semi-automatic lesion segmentation algorithm for WB-DWI images in MM patients and to evaluate this smart-algorithm (SA) performance by comparing it to the manual segmentations performed by radiologists. Methods: An atlas-based segmentation was developed to remove the high-signal intensity normal tissues on WB-DWI and to restrict the lesion area to the skeleton. Then, an outlier threshold-based segmentation was applied to WB-DWI images, and the segmented area's signal intensity was compared to the average signal intensity of a lowfat muscle on T1-weighted images. This method was validated in 22 whole-body DWI images of patients diagnosed with MM. Dice similarity coefficient (DSC), sensitivity and positive predictive value (PPV) were computed to evaluate the SA performance against the gold standard (GS) and to compare with the radiologists. A nonparametric Wilcoxon test was also performed. Apparent diffusion coefficient (ADC) histogram metrics and lesion volume were extracted for the GS segmentation and for the correctly identified lesions by SA and their correlation was assessed. Results: The mean inter-radiologists DSC was 0.323 ± 0.268. The SA vs GS achieved a DSC of 0.274 ± 0.227, sensitivity of 0.764 ± 0.276 and PPV 0.217 ± 0.207. Its distribution was not significantly different from the mean DSC of inter-radiologist segmentation (p = 0.108, Wilcoxon test). ADC and lesion volume intraclass correlation coefficient (ICC) of the GS and of the correctly identified lesions by the SA was 0.996 for the median and 0.894 for the lesion volume (p < 0.001). The duration of the lesion volume segmentation by the SA was, on average, 10.22 ± 0.86 min, per patient. Conclusions: The SA provides equally reproducible segmentation results when compared to the manual segmentation of radiologists. Thus, the proposed method offers robust and efficient segmentation of MM lesions on WB-DWI. This method may aid accurate assessment of tumor burden and therefore provide insights to treatment response assessment.

Correlations between apparent diffusion coefficient values of WB-DWI and clinical parameters in multiple myeloma

“…WB-DWI, with its advantages of large imaging range and no radiation, especially the ADC value which can be used to quantify the diffusion of water molecules in tissues, has become an alternative method for the detection of bone disease in MM patients [ 5 , 18 ]. Limitations of WB-DWI include possible difficulties in focus segmentation in patients with multiple bone marrow diseases [ 5 ]. WB-DWI is also not satisfactory for distal extremity and extramedullary lesions.…”

“…Although conventional MR imaging analysis has been used for many years to assess the disease burden [ 4 ], it cannot fully explain the clinical features of MM intramedullary lesions. Whole-body diffusion-weighted imaging (WB-DWI) is a clinically applicable MRI method that adopts the short tau inversion recovery (STIR) sequence to suppress background signals [ 5 ]. However, a fundamental limitation of DWI is the lack of relationship between imaging indicators and clinical or even genetic characteristics.…”

Correlations Between Apparent Diffusion Coefficient Values of WB-DWI&nbsp;and Clinical Parameters in Multiple Myeloma

“…WB-DWI, with its advantages of large imaging range and no radiation, especially the ADC value which can be used to quantify the diffusion of water molecules in tissues, has become an alternative method for the detection of bone disease in MM patients. [5,10] Limitations of WB-DWI include possible di culties in focus segmentation in patients with multiple bone marrow diseases. [5] WB-DWI is also not satisfactory for distal extremity and extramedullary lesions.…”

“…[5,10] Limitations of WB-DWI include possible di culties in focus segmentation in patients with multiple bone marrow diseases. [5] WB-DWI is also not satisfactory for distal extremity and extramedullary lesions. However, WB-DWI has been shown to produce good consistency in the detection of bone marrow and extraosseous metastasis (κ = 0.887, agreement = 94.44%, p= 0.001).…”

“…Whole-body diffusion-weighted imaging (WB-DWI) is a clinically applicable MRI method that adopts the short tau inversion recovery (STIR) sequence to suppress background signals. [5] However, a fundamental limitation of DWI is the lack of relationship between imaging indicators and clinical or even genetic characteristics. However, the apparent diffusion coe cient (ADC) values may be helpful in overcoming these limitations.…”