Patient’s selection and preparation
We enrolled in this prospective study 32 patients with newly diagnosed lymphoma of different types over a period from May 2018 to January 2020, (27 males and 5 females) with age ranged from 16 to 60 years. All patients underwent routine evaluation include history, physical examination, and blood sugar test.
Exclusion criteria were contraindications to MRI, previous diagnosis of malignancy, patients with renal function impairment (serum creatinine > 2 mg/dL), patients with blood glucose level > 160 mg/dL, and patients received chemotherapy prior to the initial staging or in between the two techniques.
Patients underwent 18F-FDG PET/CT and WB-MRI-/DWIBS within 10 days of diagnosis and before starting the treatment. Staging was based on Ann Arbor staging system considering patients symptoms and bone marrow Biopsy (BMB).
18F-FDG-PET/CT protocol
18F-FDG-PET/CT is obtained using PET/CT scanner (Discovery STE; GE Healthcare, Boston, USA). Patient was fasted for at least 6 h before the examination. A dose of 5.5 MBq/kg 18F-FDG was injected intravenously 60 min before the scan, patients were asked to rest in a quiet room devoid of distraction to minimize physiological uptake of FDG. Diagnostic CT was performed using the following diameters, 120 kV, 350 mAs, 0.5 s tube rotation, slice thickness 5 mm, 8 mm table feed, and 3 mm incremental reconstruction. A PET emission scan was performed over several bed positions from 5 to 7 for 2 min per bed position with axial field of view of 21.6 cm per bed position and in-plane spatial resolution of 2 mm covering the same field of view as with CT. Reconstructed trans-axial PET and CT images were fused. These are then reformed into coronal and sagittal images, and data were generated.
The maximum SUV in the volume of interest was considered as the SUV max for the purpose of analysis.
The PET/CT images were interpreted by two experienced radiology consultants (more than 5 years of experience) with inter-observer agreement.
Reports were compared to those of DWIBS. The readers were blinded to other modality results.
WB-MR/DWIBS protocol
All examinations were performed using a 1.5-T MR scanner (Achieva Philips Medical SSystem, Netherlands) Q-body coil with the patient positioned feet first to cover head, neck, and trunk. Sequences used were T1-weighted Turbo Spin Echo (TSE) and T2-weighted short T1 Inversion Recovery (STIR) in coronal orientation to encompass all anatomical districts from head to the mid-thigh.
Coronal T1-weighted and STIR and axial DWIBS sequences were performed by the following parameters. In coronal T1-weighted sequence, single-shot turbo spin echo, TR/TE shortest, slice thickness 6 mm, gap 1 mm, number of slices for station 39, FOV 350 × 265, acquisition matrix 208 × 287, reconstruction matrix 512, acquisition voxel size 1.27 × 1.85 × 6.00, reconstructed voxel size 1.04 × 1.04 × 6.00, number of acquisitions 1, acquisition time/sequence 63 s. In coronal STIR, the following parameters were used: single-shot turbo spin echo, TR/TE shortest, inversion time 165 ms, slice thickness 6 mm, gab 1 mm, number of slices for station 39, FOV 350 × 265, acquisition matrix 336 × 121, reconstruction matrix 512, acquisition voxel size 1.58 × 2.18 × 6.00, reconstructed voxel size 1.04 × 1.04 × 6.00, number of acquisition 2, acquisition time/sequence 62 s. Both T1W and STIR images were acquired in free breathing. DWIBS sequence were acquired in the axial plane, in free breathing and with the folowing parameters: single-shot EPI, TR/TE shortest ,inversion time 180 ms, slice thickness 6 mm, gap 0mm , number of slices for station 44, FOV 530 × 303, acquisition matrix 108 × 61, reconstructed voxel size 1.5 × 1.50 × 600, half-scan factor 0.627, EPI factor 61, b values 0–1000 s/mm2, number of acquisition 2, acquisition time/sequence 3 min, and 29 s.
DWIBS images were reconstructed on radial (for a volumetric view) and on coronal planes, with slice thickness 4 mm, gap 1 mm, number of images 44. The reconstructed images were merged and a coronal whole-body/DWIBS images were obtained.
ADC maps were automatically generated from DW images by the MR software.
The WB-MR/DWIBS images were interpreted by two experienced radiology consultants (more than 5 years of experience) with inter-observer agreement.
Reports were compared to those of PET/CT. The readers were blinded to other modality results.
Images analysis for both modalities
For standardized comparison of the WB-MR/DWIBS and PET/CT findings, anatomical regional nodal distribution was performed into 6 nodal basins cervical, axillary, mediastinal, abdominal, pelvic, inguinal, and femoral.
Standard of reference
Histopathologically proven data as well as follow-up period of 10 months.
WB-MR/DWIBS image analysis
Visual analysis
Lymph-nodes larger than 10 mm in coronal short axis on T1WI or STIR sequences have been considered positive. In extra nodal assessment, any areas with altered signal in T1WI or STIR images showing signal intensity in DWIBS higher than surrounding tissues were considered positive for lymphoma infiltration. Signal intensity of the lesion should be equal or higher than the signal intensity from the organ with highest intensity in each station as follows: in the neck, we compared with the brain; in the chest, we compare with the bone marrow; in the abdominal region with the kidney; and in the inguinal region, with the bone marrow. A diffusely enlarged spleen (> 13 cm) without focal lesions was also considered positive.
Bone marrow infiltration was divided into focal or diffuse involvement. Focal disease was diagnosed. If there is patchy lesion with signal intensity higher than the surrounding bone marrow, the diffuse involvement was defined as wide-spread DWI signal intensity, similar to or higher than the spleen, corresponding to a hypo-intense signal in T1WI and hyper-intense signal in T2W-STIR images.
Semi-quantitative analysis
For each lymph node region and organ recorded as positive on DWI, the lesion showing the lowest signal intensity on ADC maps was identified.
18F-FDG PET/CT images analysis
Visual analysis
Any focus of elevated FDG metabolism in comparison with the liver and mediastinum, and not located in areas of normal FDG uptake, was considered positive.
PET/CT images were assessed for lymphomatous infiltration using a 5-point grading system in which the lesion uptake was compared to the liver uptake as follows: score 0 (no uptake), score 1 (lesion uptake <liver uptake), score 2 (lesion uptake = liver uptake), score 3 (lesion uptake > liver uptake), score 4 (intensive lesion uptake that is significantly higher than liver).
Score 0 = the lesion is definitely negative, score 1 = it is probably negative, score 2 = the lesion is equivocal, score 3 = the lesion is probably positive, and score 4 = the lesion is definitely positive.
Quantitative analysis
18F-FDG PET/CT was measured by SUV max, a region of interest was manually placed on each lesion of abnormal uptake and it was calculated.