Functional Imaging

DW-MRI was performed on a 1.5 Tesla Philips Achieva scanner as described previously ⁹. Briefly, the protocol included scanning from vertex to toes in 7-9 slabs depending on patient height. Each slab constituted 50 slices 5 mm thick, field of view 450 mm, matrix 112x79, repetition time 7500 ms, time to echo 69.9 ms, number of acquisitions 2, with a "Q" body coil, b=0 and 800 s/mm². A coronal whole body T₁ turbo-spin echo image was obtained as a localizer. Asplenia was excluded using coronal T₁ weighted whole body survey images. Next, the spleen signal was assessed on inverted greyscale b800 DWI and exponential ADC (eADC) maps by two experienced investigators in consensus read. Absence of spleen signal was defined as (1) significant signal loss on the DWI (b800) image with isointensity to fat tissue, and (2) lack of spleen visualization on the corresponding EADC map. ADC values were not considered for this study.

For anti-CD66 antibody scintigraphy, the murine anti-CD66 monoclonal antibody BW 250/183 (anti- Granulocyte®, Scintec Diagnostics, Zug, Switzerland) was labelled with 99mTc. Planar whole body imaging using a dual-head γ-camera (Symbia Intevo, Siemens Healthineers, Erlangen, Germany) was performed 4 h and 24 h after iv injection of 650-700 MBq of the radiolabeled antibody. Low-energy, high-resolution collimators were used. A 15% energy window was centered over the 140-keV photopeak of 99mTc. After the acquisition of the 24h-planar scans, an additional SPECT/CT emission/transmission study of the abdomen was performed (Symbia Intevo, Siemens Healthineers, 180-degree acquisition per detector, 256 x 256 matrix, 3-degree steps, and 20 s/frame; CT: 110 kV, 35 mAs). Images were reconstructed using an iterative ordered subsets expectation maximization algorithm (Flash 3D: 6 subsets, 6 iterations), both with and without CT-based attenuation correction.