18F-FLT Positron Emission Tomography/Computed Tomography Imaging in Pancreatic Cancer: Determination of Tumor Proliferative Activity and Comparison with Glycolytic Activity as Measured by 18F-FDG Positron Emission Tomography/Computed Tomography Imaging

OBJECTIVE: This phase-I imaging study examined the imaging characteristic of 3’-deoxy-3’-((18)F)-fluorothymidine ((18)F-FLT) positron emission tomography (PET) in patients with pancreatic cancer and comparisons were made with ((18)F)-fluorodeoxyglucose ((18)F-FDG). The ultimate aim was to develop a molecular imaging tool that could better define the biologic characteristics of pancreas cancer, and to identify the patients who could potentially benefit from surgical resection who were deemed inoperable by conventional means of staging. METHODS: Six patients with newly diagnosed pancreatic cancer underwent a combined FLT and FDG computed tomography (CT) PET/CT imaging protocol. The FLT PET/CT scan was performed within 1 week of FDG PET/CT imaging. Tumor uptake of a tracer was determined and compared using various techniques; statistical thresholding (z score=2.5), and fixed standardized uptake value (SUV) thresholds of 1.4 and 2.5, and applying a threshold of 40% of maximum SUV (SUV(max)) and mean SUV (SUV(mean)). The correlation of functional tumor volumes (FTV) between (18)F-FDG and (18)F-FLT was assessed using linear regression analysis. RESULTS: It was found that there is a correlation in FTV due to metabolic and proliferation activity when using a threshold of SUV 2.5 for FDG and 1.4 for FLT (r=0.698, p=ns), but a better correlation was obtained when using SUV of 2.5 for both tracers (r=0.698, p=ns). The z score thresholding (z=2.5) method showed lower correlation between the FTVs (r=0.698, p=ns) of FDG and FLT PET. CONCLUSION: Different tumor segmentation techniques yielded varying degrees of correlation in FTV between FLT and FDG-PET images. FLT imaging may have a different meaning in determining tumor biology and prognosis

90Y-DOTA-CHS Microspheres for Live Radiomicrosphere Therapy: Preliminary In Vivo Lung Radiochemical Stability Studies

Chitosan (CHS) is used to prepare microspheres of 31 ± 8 µm size. Surface modification with p-SCN-Bn-DOTA was performed. A maximum 90Y capacity was found to be 12.1 ± 4.4 µCi/particle. The best obtained labeling yield was 87.7 ± 0.6%. More than 90% in vitro stability was found. Particle in vitro degradation half-life in PBS was found to be greater than 21 days. In vivo studies with 90Y-DOTA-CHS showed more than 95% of the injected activity (decay corrected) in the lungs 24 hours after tail vein administration. 90Y-DOTA-CHS in vivo label stability was superior to resin microspheres. The addition of p-SCN-Bn-DOTA served as a radioprotectant for bone marrow as the 5% 90Y released, during the first 24 hours, was quickly eliminated via urine

68Ga-NOTA-CHSg and 99mTc-CHSg Labeled Microspheres for Lung Perfusion and Liver Radiomicrospheres Therapy Planning

Fast biodegradable (12 h \u3c half-life \u3c 48 h) radioactive labeled microspheres are needed for PET and SPECT lung perfusion and radiomicrosphere therapy planning. An emulsion method was used to create 30.1 ±4.8 μm size range microspheres with biodegradable Chitosan glycol (CHSg). Microspheres were characterized and labeled with or as an alternative to MAA in perfusion PET and SPECT studies. Surface decoration of CHSg microspheres with p-SCN-Bn-NOTA was performed to increase   in vivo stability. was labeled directly to the CHSg microspheres. Labeling yield and in vitro radiochemical stability were evaluated. In vitro CHSg microsphere degradation half-life was ~24 hours in porcine blood. Labeled microspheres were injected into Sprague Dawley rats and biodistribution was determined after 2 and 4 hours. Both -CHSg and -NOTA-CHSg were quickly allocated in the lungs after injection. -CHSg showed 91.6 ± 6.5% and 83.2 ± 4.1% of the decay corrected injected activity remaining in the lungs after 2 and 4 hours, respectively. For the obtained -NOTA-CHSg microspheres, lung allocation was very high with 98.9 ± 0.2% and 95.6 ± 0.9% after 2 and 4 hours, respectively. The addition of p-SCN-Bn-NOTA acts as a radioprotectant eliminating the released activity from the lungs to the bladder protecting the other organs

Post traumatic brain perfusion SPECT analysis using reconstructed ROI maps of radioactive microsphere derived cerebral blood flow and statistical parametric mapping

Background Assessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets. Methods The focal effects of moderate traumatic brain injury (TBI) on cerebral blood flow (CBF) by SPECT cerebral blood perfusion (CBP) imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM). Results A significant area of hypoperfusion (P \u3c 0.01) was found as a response to the TBI. Statistical mapping of the reference microsphere CBF data confirms a focal decrease found with SPECT and SPM. Conclusion The suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques

Dynamic lung tumor phantom coupled with chest motion

Motion artifacts have always been a non-desired effect in the field of Medical Imaging. Thus new technologies are being investigated to ameliorate the damaging effects of image blurring caused by motion. The development of these new technologies requires the use of phantoms as a means of precise, repeatable and controllable source of motion for testing initial algorithms and prototypes. The objective of this project was to design a dynamic lung tumor phantom coupled with chest motion. The phantom consists of a pair of linear actuators. The complete design, excluding the actuators was built in house out of acrylic materials with low attenuation factors, making it ideal for PET studies. The linear actuator is a stepper motor coupled to a lead screw which translates rotational motion into linear displacement at a rate of 0.0254 mm/step. The system is driven by a PIC microcontroller that allows the user to select different tumor motion parameters, and is capable of performing 3D motion. The phantom is capable of providing lung tumor and chest position with an accuracy of 1.3 m in the axis of motion, with a displacement of up to 52 mm and maximum velocity of 21.59 mm/second. The design has proven to be suitable for simulating lung tumor motion in PET studies, as well as testing motion tracking algorithms. However it can also be used in studies dealing with gated radiotherapy