Research Report 2001-2002

Research activities of this group are primarily focused on the development and evaluation of instrumentation and data acquisition techniques; Monte Carlo simulation, image reconstruction and correction algorithms; as well as tracer kinetic and dynamic modeling approaches for positron emission tomography (PET) and single photon emission computed tomography (SPECT), the main radiotracer imaging modalities in nuclear medicine. For most of the phase of this report, the research group was particularly concerned in medical research applied to PET. Given the intrinsic mathematical/statistical model resemblance in many of the algorithms and methods under investigation (discrete iterative image reconstruction, tracer kinetic models, Monte Carlo simulation, etc.) and increased involvement in multidisciplinary research studies, particularly in the newly evolving area of small animal imaging, the group started to broaden their efforts on SPECT research and, most recently, on optical and multi-modality imaging approaches.

This group.s primary, clinically employed, tomograph is the high-resolution whole-body PET scanner ECAT EXACT HR+ (CTI, Siemens). A number of research studies have been performed to evaluate the system.s physical performance under diverse protocols and to validate improved or newly developed correction and reconstruction algorithms [6,7,20]. In addition to experimentally acquired data, Monte Carlo (MC) simulations have been performed, too, to propose enhancements in scanner design and clinical acquisition protocols and to investigate aspects such as scatter radiation which cannot be accessed analytically [11-13]. The development of an application-specific MC simulation tool has helped to design a scheme for a submillimeter spatial resolution dual-modality SPECT-OT (optical tomograph) scanner, the first of its kind [10,14].

The mathematics of image reconstruction plays a crucial role in achievable image, and such diagnostic, quality. There have been several individual research studies carried out aimed at improving and accelerating image reconstruction techniques [1,9,16,19]. Further studies have been performed to improve image quality by incorporating scanner characteristics into the reconstruction algorithm resulting in increased spatial resolution within reconstructed images. In order to correct for the effects of inevitable photon attenuation and scattering in tissue, several methods have been studied and developed. An existing clinical tool for 3D scatter correction of PET data has been significantly optimized in terms if computational performance using a novel numerical approach [20]. The value of PET in oncology has been extensively studied by the use of image matching techniques to fuse 3D activity distributions with anatomical data such those from CT or MRI. One particular approach has been found to produce highly accurate matches of brain data without user interaction that is based on mutual information [5].

In clinical studies at DKFZ, PET has been used primarily for detecting and quantifying physiological and metabolic processes in vivo. Prime objectives are to track and quantify physiological and metabolic processes in vivo and to evaluate quantitatively bio-distributions and metabolism rates of labeled pharmaceuticals and such to differentiate and characterize the growth behavior of tumor tissue [3,18]. Group-specific aims are focused on the development of dedicated tracer-specific pharmacokinetic models as well as on consequently implementing kinetic analysis tools within optimized parametric image reconstruction strategies [2,4,11-13]. Major aims are to not only calculate regional tracer concentrations but more distinctively to obtain true metabolism-specific turnover rates, absolute local receptor concentrations, or tissue perfusion as well as to derive spatial-temporal distributions here of. Besides efforts to develop and evaluate pharmacokinetic models - partly also by means of Monte Carlo based methods, research activities were established to search for alternatives of measuring arterial blood input curves.

[1] Bowsher JE*, Tornai MP*, Peter J, Kroll A*, Gilland DR*, Gonzalez-Trotter D*, Jaszczak RJ*: Modeling the axial extension of a transmission line source within interative reconstruction via multiple transmission sources. IEEE Transactions on Medical Imaging, 21 (2002) 200-215.
[2] Brix G*, Bellemann ME*, Hauser H, Doll J: Recovery-Koeffizienten zur Quantifizierung der arteriellen Inputfunktion aus dynamischen PET-Messungen: experimentelle und theoretische Bestimmung. Nuklearmedizin, 41 (2002) 184-190.
[3] Brix G*, Henze M, Knopp M, Lucht R*, Doll J, Junkermann H*, Hawighorst H, Haberkorn U: Comparison of pharmacokinetic MRI and 18F fluorodeoxyglucose PET in the diagnosis of breast cancer: initial experience. European Radiology, 11 (2001) 2058-2070.
[4] Brix G*, Ziegler I*, Bellemann ME*, Doll J, Schosser R*, Lucht R*, Krieter H*, Nosske D*, Haberkorn U: Quantification of (18F)FDG uptake in the normal liver using dynamic PET: Impact and modeling of the dual hepatic blood supply. Journal of Nuclear Medicine, 42 (2001) 1265-1273.
[5] Doll J, Brückner TC, Bendl R, Henze M, Hipp P, Brix G*, Semmler W: Interaktionsfreie Überlagerung von CT-und PET-Volumendaten des Schädels durch Maximierung der mutual information. Proc. DGMP, (2001) 433-434.
[6] Doll J, Werling A, Bublitz O, Hauser H, Semmler W, Brix G*: Auswirkung von Aktivitäts- und Dichteverteilungen außerhalb des Gesichtsfeldes auf die Genauigkeit von 3D-PET-Messungen. Proc. DGMP, (2001) 345-346.
[7] Doll J, Saffrich R., Peter J., Hauser H, Brix G, Semmler W: Auswirkungen zusätzlicher Bleiabschirmungen bei PET-Messungen im 3D- und 2D-Modus auf den Einfluss externer Aktivitäten. Proc. DGMP (2002).
[8] Haberkorn U, Bellemann ME*, Brix G*, Kamencic H*, Morr I, Traut U*, Altmann A, Doll J, Blatter J*, Kinscherf R*: Apoptosis and changes in glucose metabolism after treatment of mottis hepatoma with gemcitabine. European Journal of Nuclear Medicine, 28 (2001) 418-425.
[9] Metzler SD*, Bowsher JE*, Tornai MP*, Pieper BC*, Peter J, Jaszczak RJ*: SPECT breast imaging combining horizontal and vertical axes of rotation. IEEE Transactions on Nuclear Science, 49 (2002) 31-36.
[10] Peter J, Bock M: Design Study of A Novel Dual-Modality Emission Micro-Imaging Tomograph for Radiopharmaceutical and Bioluminescent/Fluorescent Molecular Approaches. Proc. IEEE/NIH/NIBIB Int. Symp. on Biomedical Imaging, Washington, D.C., USA, (2002) 255-59.
[11] Peter J, Doll J, Saffrich J, Semmler, W: Der Einfluss von Akquisitions- und Rekonstruktionsparametern auf die Güte tracerkinetischer Modelle in der Emissionstomographie - Eine Monte Carlo Simulationsstudie. Proc. DGMP (2002).
[12] Peter J, Doll J, Semmler, W: Design und Anwendung hybrider Phantome zur Modellierung nichtstatischer Geometrien und dynamischer Aktivitätsverteilungen in PET und SPECT Monte Carlo Simulationen. Proc. DGN (2002).
[13] Peter J, Henze M, Semmler, W: Monte Carlo Simulation of Tracer-Kinetic PET and SPECT Studies Using Dynamic Hybrid Phantoms. J Nuc Med 43 (2002) 146.
[14] Peter J, Saffrich R, Semmler W: Simultaneous Simulation of Isotopic and Optical Photons for Micro-Tomographic Imaging Approaches. Eur. J. of Nuclear Medicine, 29 (2002) 116.
[15] Peter J: Modellierung und Simulation der Kinetik radiopharmazeutischer Verteilungen mittels anthropomorphischer Phantome. RöFo - Proc. DRG, (2002) 261.
[16] Pieper BC*, Bowsher JE*, Tornai MP*, Peter J, Greer K*, Jaszczak RJ*: Breast-tumor imaging using a tiltable head SPECT camera. IEEE Transactions on Nuclear Science, 48 (2001) 1477-1482.
[17] Saffrich R, Semmler W, Doll J, Peter J: Analytisches Mausphantom unter Verwendung superquadratischer Körper zur Simulation von Kleintiertomographen. Proc. DGMP, (2002) (DGMP Poster Award).
[18] Schumacher J, Kaul S, Klivenyi G, Junkermann H, Magener A, Henze M, Doll J, Haberkorn U, Amelung F, Bastert G: Immunoscintigraphy with Positron Emission Tomography: Gallium-68 Chelate Imaging of Breast Cancer Pretargeted with Bispecific Anti-MUC1/Anti-Ga. Cancer Res. 61 (2001) 3712-3717.
[19] Tornai MP*, Bowsher JE*, Archer CN*, Peter J, MacDonald LR*, Patt BE*, Iwanczyk JS*: A compact dedicated device for dual modality radionuclide imaging of the breast with an application specific emission and transmission tomograph (AETT). Proc. RSNA, (2001) 555.
[20] Werling A, Doll J, Bublitz O, Brix G*, Semmler W: Evaluierung einer iterativen, simulationsbasierten Streukorrektur für 3D-PET mittels Phantommessungen. Proc: DGMP, (2001) 337-338.
[21] Werling A, Bublitz O, Doll J, Adam LE*, Brix G*: Fast implementation of the single scatter simulation algorithm and its use in iterative image reconstruction on PET data. Physics in Medicine & Biology 47 (2002) 2947-2960.

Author: Jörg Peter
2003/01/23