Patient population: in this retrospective analysis we enrolled all the patients with plasma cell dyscrasia which underwent WBMRI between September 2013 and October 2016.
Our study population included 23 patients,
16 females and 7 males,
with an average age of 57 years (range 30-82).
Four patients were classified as MGUS,
5 as SMM,
11 as MM and 3 as P according to IMWG.
MRI imaging: all examinations were performed on a 1,5T MRI scanner (Ingenia,
Philips Medical System).
All participants were scanned supine with arms by their sides.
We obtained a whole body study by acquiring contiguous body regions from head to feet. The sequence protocol included:
-
Coronal T1-weighted turbo spin-echo (TSE) sequences [repetition time (TR),
522 ms; echo time (TE),
17 ms; section thickness (ST),
6 mm; 30 sections per block; field of view (FOV),
510x392x285 mm].
-
Coronal T2-weighted short-tau inversion recovery (STIR) sequences [TR,
4371 ms; TE,
55 ms; ST,
6 mm; 30 sections per block; FOV,
530x209x265 mm] (Fig. 1).
-
Axial diffusion weighted (DW) sequences [b-Values of 0 and 800 s/mm2; ST,
5 mm; 46 sections per block; FOV,
510x392x211 mm].
Multiplanar reconstruction images were then reformatted (Fig. 2).
DWI images were fused with T1-weighted images in order to allow an easier anatomical localisation (Fig. 3 - Fig. 4).
We also performed sagittal T1-weighted TSE sequences [TR,
514 ms; TE,
16 ms; ST,
4 mm] and sagittal T2-weighted STIR sequences [TR,
2500 ms; TE,
70 ms; ST,
4 mm] of the spine in order evaluate the rate of bone marrow infiltration.
Image evaluation: two radiologists,
with 7 and 4 years of experience respectively,
evaluated the MR images on a workstation (Carestream Vue PACS Version 11.4,
Carestream Health,
Rochester,
NY,
USA).
For each patient,
the presence and absence of diffuse bone marrow infiltration and focal lesions were evaluated using the following criteria:
Diffuse bone marrow infiltration
-
No involvement: bone marrow with a hyperintense signal compared to the intervertebral disk on T1-weighted images and a hypointense signal compared to paravertebral muscle tissue on STIR images.
-
Low grade infiltration: “salt-and-pepper” pattern with no focal lesions detectable but patchy aspect of bone marrow at T1-weighted images reflecting innumerable small bone marrow areas of infiltration intermingled with focal fat islets.
-
Moderate infiltration: bone marrow with low signal intensity on T1- weighted images associated with an increased signal intensity on STIR images.
-
Severe infiltration: bone marrow appears hypo or isointense on T1-weighted images compared to the intervertebral disk and hyperintense on STIR images (Fig. 5).
Focal lesions
Localised area of 5 mm or greater in diameter with low signal intensity in T1-weighted,
high signal intensity in STIR images and restricted diffusion.
Moreover,
among all the bone lesions,
we included for the qualitative analysis the greatest lesion in diameter for each bone segment.
We considered ribs,
cervical,
dorsal and lumbar spine as single units and chose the greatest lesion in each unit. A total of 94 lesions were analysed and rated with a qualitative score (from 1 to 3) in order to assess the conspicuity of each lesion in T1-weighted,
STIR and DWI images (Fig. 6).
The findings were compared with the clinical stage and the results were analysed with chi-square test and ANOVA.