الفهرس 
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Abstract
Brain imaging is a process which allows scientists and physicians to view and monitor areas of the brain which allow diagnosis and following up different abnormalities in the brain. The measurement of regional cerebral blood flow (rCBF) by single photon emission computed tomography (SPECT) represents the most commonly available and widely applied functional brain imaging technique used in clinical practice. Brain SPECT is now commonly used in diagnosis, prognosis assessment, evaluation of response to therapy, detection of benign or malignant viable tissue and choice of medical or surgical therapy, especially in head injury, malignant brain tumors, cerebrovascular disease, movement disorders, dementia, and epilepsy. The search continues for an optimal brain radiopharmaceutical of high brain uptake and good in-vivo and in-vitro stability as a reliable first step for functional brain imaging.
The selection of proper isotope to be used in preparation of such radiopharmaceutical is important because it should have suitable short half life to avoid unwarranted harmful exposure to radiation and suitable photon energy within the range of gamma camera. The two most proper isotopes that fulfill these two precautions are 123I and 99mTc. The selection of either of them depends on the structure of the compound to be labeled.
This thesis aimed to prepare radiopharmaceutical compounds effective and specialized for use in nuclear imaging of brain, and the compounds of ropinirole, itopride and prochlorperazine have been selected because of their high ability to access to the brain and bind to the dopamine receptor, labelling of these compounds using 99mTc or 125I radioisotope, and then study the biodistribution of labelled compounds in Swiss albino mice to ensure efficient access to brain.
This thesis consists of two chapters:
Chapter I:
Preparation and biological evaluation of 99mTc-ropinirole and 99mTc-itopride as radiopharmaceutical models for brain imaging.
Chapter II:
Preparation and biological evaluation of 125I-prochlorperazine as radiopharmaceutical model for brain imaging
Following is a brief description of contents of each chapter:
Chapter I
Preparation and biological evaluation of 99mTc-ropinirole and 99mTc-itopride as radiopharmaceutical models for brain imaging
This chapter includes the factors affecting the labelling of ropinirole and itopride with 99mTc, using the direct labelling technique, and the determination of the radiochemical purity of the produced complexes.
Also in this chapter, the biodistribution of99mTc-ropinirole, and 99mTc-itopride complexes in Swiss albino mice have been studied. In addition to, the dopamine receptor blocking study.
Labeling process:
In an evacuated vial under N2 gas, ropinirole and itopride was labeled with technicium-99m by direct method. Factors (pH of reaction medium, reducing agent amount, ligand amount, temperature and reaction time) affecting the radiochemical yield percent of 99mTc-ligand complex in addition to the radiotracer stability were studied. In the process of labeling, trials and errors were performed for each factor under investigations till optimum value was obtained. The experiment was repeated with all factors kept at optimum values except the factor under study, till the optimal conditions are achieved with all reaction variables.
The results can be summarized in the following points:
Ropinirole was labelled with 99mTc and gave maximum radiochemical yield of 92.3% at 300 μg ropinirole, 20 μg SnCl2.2H2O, at pH 7 and 15 min reaction time at room temperature. 99mTc-ropinirole was stable for a time up to 6 hours.
By tracing the biological distribution of 99mTc-ropinirole into the mice body organs showed the following:
The 99mTc-ropinirole showed brain uptake of 4.8 %ID/g organ at 30min post injection that reached 2.3 %ID/g brain at 120min. Comparing to the currently used radiopharmaceuticals for brain imaging such as 99mTc-ECD, 99mTc-HMPAO and 123IMP which has maximum brain uptake of 4.7, 2.25 and 1.14%ID/g, respectively, it show higher brain uptake with more in-vivo and in-vitro stability.
The high accumulation of radiolabeled compound percent was clearly seen in intestine and liver 19.9 and 24.8% ID/gram organs, respectively, that indicate that the complex excretion was done through hepatobiliary system.
Blocking study of dopamine receptor showed that the formed complex is selective for dopamine receptor as the radiolabeled compound percent dropped to 0.26% ID/gram organ at 1 mg of unlabelled ropinirole.
Itopride was labelled with 99mTc using two reducing agents
Stannous chloride: where maximum radiochemical yield of 76% was at 500 μg itopride, 30 μg SnCl2.2H2O, at pH 5 and 30 min reaction time at room temperature.
Sodium borohydride: where maximum radiochemical yield of 98% was at 150 μg itopride, 45 mg NaBH4, at pH 9 and 30 min reaction time at 60oC temperature. 99mTc-itopride was stable for a time up to 6 hours.
By tracing the biological distribution of 99mTc-itopride into the mice body organs showed the following:
The 99mTc-itopride showed brain uptake of 1.2%ID/g organ at 15 min post injection that reached 0.2%ID/g brain at 120min, respectively, indicating that 99mTc-itopride has low brain uptake, but it is more than the commercially available radiopharmaceutical agent for brain imaging 123IMP which has 1.14%ID/g maximum brain uptake.
The high accumulation of radiolabeled compound percent in the kidney (21.6% ID/gram organs), indicate that the complex excretion takes place through kidneys.
Blocking study of dopamine receptor showed that the formed complex is selective for dopamine receptor as the radiolabeled compound percent dropped to 0.16 % ID/gram organs at 1 mg of unlabelled itopride.
Chapter II
Preparation and biological evaluation of 125I-prochlorperazine as radiopharmaceutical model for brain imaging
This chapter includes the factors affecting the labelling of prochlorperazine with 125I, using the direct electrophilic labelling technique, and the determination of the radiochemical purity of the produced complexes.
Also in this chapter, the biodistribution of 125I- prochlorperazine complex in Swiss albino mice have been studied. In addition to, the dopamine receptor blocking study.
Labeling process:
prochlorperazine was labeled with 125I in presence of Chloramine-T oxidizing agent (CAT). The pH of the reaction mixture was adjusted to the optimum then left at different temperatures for 1-90min. At the end of the reaction time, sodium thiosulfate was added to quench the reaction by reducing iodine to iodide (I-). In the process of labeling, trials and errors were performed for each factor under investigations till optimum value was obtained. The experiment was repeated with all factors kept at optimum values except the factor under study, till the optimal conditions are achieved with all reaction variables.
The results can be summarized in the following points:
Prochlorperazine was labelled with 125I and gave maximum radiochemical yield of 97% at 150 μg prochlorperazine, 30 μg CAT, at pH 4 and 30 min reaction time at room temperature. 125I-prochlorperazine was stable for a time up to 24 hours.
Tracing the biological distribution of 125I-prochlorperazine into the mice body organs showed the following:
The 125I-prochlorperazine showed brain uptake of 2.84%ID/g organ at 15 min post injection that reached 1.49%ID/g brain at 120min.
The high accumulation of radiolabeled compound percent was clearly seen in kidney 19.8 % ID/gram organs for125I-prochlorperazine, which indicates that the complex excretion was done through kidneys.
Blocking study of dopamine receptor for 125I-prochlorperazine shows that the formed complex is selective for dopamine receptor as the radiolabeled compound percent dropped to 0.27 % ID/gram organs at 1 mg of unlabelled prochlorperazine.
The obtained results showed that:
The three ligands under study, 99mTc-ropinirole, 99mTc-itopride and 125I-prochlorperazine can be used as novel radiopharmaceutical drugs for brain imaging due to its high in vitro and in vivo stability compared to that of commercially available radiopharmaceutical drugs for that purpose.
At the end of this study, we can conclude that the choosing the suitable radioisotope in the radiolabeling of the pharmaceutical drugs and obtaining the high radiochemical yield depends on the adjustment of different conditions and parameters for the reaction.