Page 51 - 89Zr-Immuno-PET:Towards a Clinical Tool to Guide Antibody-based Therapy in Cancer

Immuno-PET with 89Zr-cMab U36 in head and neck cancer
Imaging studies
All patients were examined by palpation, CT and/or MRI, and 89Zr-cMAb U36 PET (immuno-PET), whereas six patients were also examined by FDG-PET. The latter procedure was indicated for the detection of unknown primary tumors and/ or for screening of distant metastases.
Preoperative palpation was performed in all patients by the same experienced head and neck surgeon. CT, MRI, FDG-PET, and immuno-PET were 3 performed in 17, 15, 6, and 20 patients, respectively. In all patients diagnostic examinations and surgery were done within a 3-week period. CT scans were
obtained with a third-generation Siemens Somaton Volume Zoom (Siemens AG,
Erlangen, Germany). After contrast administration, axial scans with a slice
thickness of 3 mm and increment of 3 mm were obtained. MRI examinations were
done on a 1.5 T imaging system (Vision-system, Siemens AG, Erlangen, Germany)
using a dedicated neck coil. Axial T2-weighed spin-echo, short-term inversion
recovery, and pre- and post-gadolinium-diethylenetriaminepentaacetic acid (Magnevist, Schering AG, Germany) T1-weighed spin-echo MRI examinations
were made. Slice thickness varied, depending on the MRI pulse sequence used,
from 4 to 7 mm, with an interslice gap of 10%. Criteria for the optimal assessment
of cervical lymph node metastases by CT or MRI, as defined by our Institute, were
used (14). At CT and MRI, lymph nodes were considered malignant if nodes with
necrosis were depicted, or if the minimal diameter in the axial plane of the node
was ≥11 mm for nodes located in level II (subdigastric) and >10 mm for nodes in
other levels. In routine diagnostic work-up, patients with enlarged lymph nodes of
4–11 mm (n = 14) went for additional diagnosis by ultrasound-guided fine-needle
aspiration cytology.
PET scans were performed using a dedicated full-ring PET scanner (ECAT EXACT HR+, CTI/Siemens, Knoxville, TN). In case of immuno-PET scanning, whole body scans were made consisting of approximately seven bed positions covering the patient from base of the skull to the pelvis. At each bed position, a 3-minute transmission scan, acquired using three germanium-68 rod sources, and a 7-minute emission scan in three-dimensional mode were acquired. Whole body scans were performed starting within 1 hour and at 24, 72, and/or 144 hours after i.v. injection of 89Zr-cMAb U36. All scans were normalized and corrected for randoms, scatter, attenuation, and decay. Reconstructions were performed using an attenuation and normalization weighted ordered subset expectation maximization (OSEM) algorithm (ECAT software version 7.2, CTI/Siemens) with
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