Comparison of reduced field-of-view DWI and conventional DWI techniques for the assessment of lumbar bone marrow infiltration in patients with acute leukemia.

Objectives: To compare the imaging quality, apparent diffusion coefficient (ADC), and the value of assessing bone marrow infiltration between reduced field-of-view diffusion-weighted imaging (r-FOV DWI) and conventional DWI in the lumbar spine of acute leukemia (AL).

Methods: Patients with newly diagnosed AL were recruited and underwent both r-FOV DWI and conventional DWI in the lumbar spine. Two radiologists evaluated image quality scores using 5-Likert-type scales qualitatively and measured signal-to-noise ratio (SNR), contrast-to-noise (CNR), signal intensity ratio (SIR), and ADC quantitatively. Patients were divided into hypo- and normocellular group, moderately hypercellular group, and severely hypercellular group according to bone marrow cellularity (BMC) obtained from bone marrow biopsies. The image quality parameters and ADC value between the two sequences were compared. One-way analysis of variance followed by LSD test was used for the comparisons of the ADC values among the three groups. The performance of ADC obtained with r-FOV DWI (ADC) and conventional DWI(ADC) in evaluating BMC and their correlations with BMC and white blood cells (WBC) were analyzed and compared.

Results: 71 AL patients (hypo- and normocellular: n=20; moderately hypercellular: n=19; severely hypercellular: n=32) were evaluated. The image quality scores, CNR, SIR, and ADC value of r-FOV DWI were significantly higher than those of conventional DWI (all <0.05), and the SNR of r-FOV DWI was significantly lower (<0.001). ADC showed statistical differences in all pairwise comparisons among the three groups (all <0.05), while ADC showed significant difference only between hypo- and normocellular group and severely hypercellular group (=0.014). The performance of ADC in evaluating BMC (Z=2.380, =0.017) and its correlations with BMC (Z=-2.008, = 0.045) and WBC (Z=-2.022, = 0.043) were significantly higher than those of ADC.

Conclusion: Compared with conventional DWI, r-FOV DWI provides superior image quality of the lumbar spine in AL patients, thus yielding better performance in assessing bone marrow infiltration.