Registration of emission and transmission whole-body scintillation-camera images.

UNLABELLED: In this work, a method for registration of whole-body (WB) scintillation-camera images is presented. The primary motive for the development is to perform activity quantification using the conjugate view method on an image basis. Accurate image registration is required for sequential anterior and posterior scans, for serial emission images for analysis of the biokinetics, and for transmission and emission images for a pixel-based attenuation correction. METHODS: Registration is performed by maximization of the mutual information. The spatial transformation has been tailored for the registration of WB images and is composed of global and local transformations, including rigid, projective, and curved transformations. A coarse registration is first performed using cross-correlation and direct pixel scaling. Optimization is then performed in a sequence, beginning with the 2 legs independently, followed by the upper body and head. Evaluation is performed for clinical images of an (131)I-labeled monoclonal antibody and for Monte Carlo-simulated images. An anthropomorphic WB computer phantom, which has been especially modified to match the patient position during WB scanning, is used for the simulations. RESULTS: For simulated images, registration errors are within 1 pixel (<3.6 mm) for a sufficient image count level. Separate evaluation of the influence of noise shows that the errors increase below a total image count of approximately 10(5) (signal-to-noise ratio, approximately 4). For clinical evaluations, the deviations between point markers are 9 +/- 5 mm. CONCLUSION: An automatic registration method for WB images has been developed, which is applicable to emission-emission and transmission-emission registration. This method has been applied in more than 50 clinical studies and has shown to be robust and reliable.

Radioimmunotherapy using 131I-labeled anti-CD22 monoclonal antibody (LL2) in patients with previously treated B-cell lymphomas.

Experience in using rapidly internalizing antibodies, such as the anti-CD22 antibody, for radioimmunotherapy of B-cell lymphomas is still limited. The present study was conducted to assess the efficacy and toxicity of a 131I-labeled anti-CD22 monoclonal antibody (mAb), LL2, in patients with B-cell lymphomas failing first- or second-line chemotherapy. Eligible patients were required to have measurable disease, less than 25% B cells in unseparated bone marrow, and an uptake of 99mTc-labeled LL2Fab' in at least one lymphoma lesion on immunoscintigram. Eight of nine patients examined with immunoscintigraphy were unequivocally found to have an uptake, and therapy with 131I-labeled anti-CD22 [1330 MBq/m2 (36 mCi/m2)] preceded by 20 mg of naked anti-CD22 mAb was administered. Three patients achieved partial remission (duration, 12, 3, and 2 months), and one patient with progressive lymphoma showed stable disease for 17 months. Four patients exhibited progressive disease. The toxicity was hematological. Patients with subnormal counts of neutrophils or platelets before therapy seemed to be more at risk for hematological side effects. Radioimmunotherapy in patients with B-cell lymphomas using 131I-labeled mouse anti-CD22 can induce objective remission in patients with aggressive as well as indolent lymphomas who have failed prior chemotherapy.

High resolution pinhole SPECT for tumor imaging.

High-resolution, non-invasive, 3D-imaging techniques would greatly benefit the investigation of the localization properties of tumor-specific radiopharmaceuticals in laboratory animals. The present study reports how pinhole SPECT can be applied to tumor localization studies in small laboratory animals to provide high resolution SPECT images in vivo. Pinhole SPECT was performed using a rotating scintillation camera, equipped with a pinhole collimator. The sensitivity of a 2 mm diameter collimator at 45 mm from the source is 90 cps/MBq for 99mTc. The planar spatial resolution at a 45 mm distance is 2.2 mm. The transaxial spatial resolution, with a distance of 45 mm between the collimator aperture and the axis of rotation, is 3.1 mm. For SPECT imaging, spatial linearity is preserved across the usable field-of-view. The major advantage of the high resolution properties of pinhole tomography is demonstrated by the enhanced lesion-to-normal-brain uptake ratio achieved on tomographic slices as compared to planar images. For example, 201Tl tumor-to-normal-brain uptake ratios of 1.1 to 1.3 observed on planar images, corresponded to ratios ranging from 3.2 to 3.7 on the SPECT slices. Examples of the activity distributions of two radiopharmaceuticals in tumor and in normal brain for sagittal and coronal images are given. In all cases, tumors are clearly delineated on the pinhole SPECT slices. The present study shows that pinhole SPECT performed with standard SPECT instrumentation can give high spatial resolution images, with a FWHM approximately 3 mm and a sensitivity approximately 100 cps/MBq for 99mTc.