Ms. Ahlam Issa –PhD candidate

Ms. Ahlam Issa –PhD candidate

PGSB Returner Fellows
PET Physics Group, Institute of Neuroscience and Medicine (INM-4). FZJ, Arab American University Palestine (AAUP), Al-Quds university Palestinian & Ministry of Health

Field of research: Medical Imging Phyiscs 

Area of specialization: Specialist in Positron Emission Tomography (PET)

Research cluster affiliation: Neuroscience Research Cluster for the investigation of psychiatric disorders

German affiliation(s): PET Physics Group, Institute of Neuroscience and Medicine (INM-4),  Forschungszentrum Jülich GmbH. 

Group leader: Dr. Christoph Lerche

Host Palestinian university: Arab American University Palestine (AAUP), Al-Quds university & Palestinian Ministry of Health

Research project title(s): Development & Evaluation of the next generation Brain PET as an  insert of a  7T MRI

Science case: why does your research need to be done? What is the possible benefit? The PET is determined as an effective functional imaging tool. Thus, the ability of PET to measure neuroreceptor densities and also changes in their occupancy is induced either by exogenous occupancy studies (pharmacological challenges). Since the late seventies, functional PET studies have contributed significantly to the understanding of cerebrovascular diseases, dementia, movement disorders, epilepsy, schizophrenia, addictive disorders, depression, anxiety disorders, brain tumors, and last but not least understanding the healthy brain. Moreover, dynamic PET together with fast blood and plasma analyses and subsequent kinetic modeling allows for collecting highly quantitative data on physiologically relevant parameters and metabolically active substances. However, quantitation precision and accuracy of state-of-the-art PET imaging devices are currently limited and the reasons for this are manifold. Thus, the data corrections in the PET data acquisition system (DAQ) are a fundamental part of the PET improving modality. 

The data corrections are the challenges for increasing the accuracy of the results images. One of the most relevant sources of errors in PET imaging is count losses caused by the dead time (DT) of the scintillation detectors and the DAQ. The DT losses have to correct to improve the accuracy of the quantitive images of the PET. However, the DTC for the 3T MR-BrainPET insert is the main task that I was working on during my Ph.D. time. The implementation of the new dead time correction (DTC) method was done by using a block-pairwise DTC method, which uses the delayed random coincidence count rates to estimate the dead time in the individual scans and planes (i.e., scintillation pixel rings). That method presents promising results of the quantitative image. The phantom measurements have shown consistent results of the block-pairwise DTC method compared with the current DTC in the 3T MR-BrainPET insert (Global DTC). Thus, during the PhD works the block-pairwise DTC method has been determined to be a sufficient DTC method. The first part of patients' measurements has been evaluated by the block-pairwise DTC, those measurements include the [11C]-ABP688, O-(2-[18F] fluoroethyl)-L-tyrosine (18F-FET) measurements, and the [15O] water. Therefore, one motivated task is to continue in the evaluation of other patients' measurements by the block-pairwise DTC method. Thus, can find the ground truth in the correction of the PET quantitative images.

Short summary of main expected outputs/ results: Several studies have been done by using multimodal, and many are expected to be approved as soon as possible. Such as the [11C]-ABP688 and [11C]-Flumazenil. During the PhD, we found that an insufficient DTC method has an important effect on the [11C]-ABP688 measurements, it results in data corruption and deviating of data on that time, with a knee shape, while the ideal correct correction values should have consistent results shape (smoothly stability). This effect has to study more carefully in other patients’ studies, for the sake of improving the quantitative accuracy of the PET images. The [11C]-Flumazenil measurements were performed on 2015, it was corrected by the inefficient DTC method. The effect of the DTC has to study for those studies to find a solution to the data deviation and bias.  This work will be a part of cooperating with the MEG group. The observed inaccuracies of the DTC method can lead to relevant quantitation errors in human studies, the [11C]-Flumazenil study whose data were utilized here was performed with a bolus-infusion protocol, so that the BPND is determined after 70 min, in this period should study the effect of the global DTC compared to the block-pairwise DTC. One of the expected studies which will take place soon in the multimodal studies works is a depression study.

Expected future impact, including directly in the Palestinian (research) community:

  • A current project within the PGSB framework, which aims at improving the dead time correction for dedicated brain PET scanners. Within the neuroscience research cluster for the investigation of psychiatric disorders cluster activity, we aim at reaching a quantitation accuracy of 1% for the newly built PET insert. Moreover, many aspects of methodological development and system development for PET and combined PET/MR imaging can be addressed via Monte Carlo simulations, where experimental verification can be done at the institutes with the corresponding instrumentation. This enables an ideal scenario for a distributed development within the proposed cluster.
  • Cooperation with the Palestinian partners, As a member of the neuroscience research cluster for the investigation of psychiatric disorders and under the PGSB framework, we had an agreement with the Palestinian Ministry of Health. Moreover, agreements of scientific cooperation and hosting with two of Palestinian universities, the Arab American University Palestine AAUP, and  Al-Quds university. 

Your future plans: Part of the Postdoc activity in Palestine and under of PGSB framework is the agreement with two Palestinian universities, Al-Quds university, and the Arab American University Palestine AAUP. The scientific cooperation and hosting activities:

All those activities are going under the neuroscience research cluster for the investigation of psychiatric disorders framework to active the following specific aims: 

  • Secure training opportunities for Palestinian students and researchers with colleagues from Forschungszentrum Jülich and RWTH Aachen. 
  • Imaging hemodynamic, molecular, metabolic, and electrophysiological brain states to serve as fingerprints and early diagnosis for psychiatric disorders. 
  • Development of advanced machine and deep learning data analysis tools which will enable us to further decode and understand the information flow in the living human brain from multimodal recordings.
  • Advance imaging methodology as combined PET-MRI-EEG and Ultra-High Filed (UHF) MRI combined with PET. 

Future vision for the PGSB/research in Palestine or general: Currently, the combination of magnetic response imaging (MRI) and positron emission tomography (PET) as a hybrid imaging modality with in vivo molecular information provided by Positron Emission Tomography (PET) has tremendous potential, especially in basic research. That approach in the next scientific research level is highly recommended to the Palestinian partners.

Lectures you have given/are giving/will give:

Recently attended conferences: 

  • The INM & IBI Retreat 2019, FZJ.
  • European Association of Nuclear Medicine (EANM'20). October 22 – 30, 2020. Virtual Abstracts, Vienna. 
  • 2020 IEEE NSS MIC, Boston - 31/10/2020-7/11/2020. Virtual.  
  • The INM & IBI Retreat 2021, FZJ, taking place virtually
  • Virtual 2021 IEEE Nuclear Science Symposium and Medical Imaging Conference28th International Symposium on Room Temperature Semiconductor X-Ray & Gamma-Ray Detectors. 
  • Accepted abstract in 2022 IEEE Nuclear Science Symposium and Medical Imaging Conference


  • Issa, A.S.M., Scheins, J.J., Tellmann, L., Montes, A.L., Herraiz, J.L., Brambilla, C.R., Herzog, H., Neuner, I., Shah, N.J. and Lerche, C.W., 2022. A detector block-pairwise dead time correction method for improved quantitation with a dedicated BrainPET scanner. Physics in Medicine & Biology.
  • Brambilla, C.R., Scheins, J., Issa, A., Tellmann, L., Herzog, H., Rota Kops, E., Shah, N.J., Neuner, I. and Lerche, C.W., 2021. Bias evaluation and reduction in 3D OP-OSEM reconstruction in dynamic equilibrium PET studies with 11C-labeled for binding potential analysis. PloS one, 16(1), p.e0245580.
  • Li, C., Scheins, J., Tellmann, L., Issa, A., Wei, L., Shah, N.J. and Lerche, C., 2023. Fast 3D kernel computation method for positron range correction in PET. Physics in Medicine & Biology, 68(2), p.025004.
  • Régio Brambilla, C., Scheins, J., Tellmann, L., Issa, A., Herzog, H., Shah, N.J., Neuner, I. and Lerche, C.W., 2023. Impact of framing scheme optimization and smoking status on binding potential analysis in dynamic PET with [11C] ABP688. EJNMMI research, 13(1), p.11.
  • Evaluation of Radiation Doses in Pediatric Patients Undergoing Conventional Chest X-ray Examination, Health Physics: February 2021.
  • Issa, A.S.M., Scheins, J.J., Lutz Tellmann, Cláudia Régio Brambilla, Philipp Lohmann, Elena Rota-Kops, Hans Herzog, Irene Neuner, N. Jon Shah, and Christoph Lerche, as Impact of Improved Dead Time Correction on the Quantification Accuracy of a Dedicated BrainPET Scanner.

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