Mike Georgiou

ACE inhibition scintigraphy in the management of hypertension in children

Abstract Angiotensin converting enzyme (ACE) inhibition scintirenography was performed to help establish the diagnosis and plan treatment of renovascular hypertension (RVH) in 57 hypertensive pediatric patients, 33 infants and 24 children older than 1 year. In 16 of 33 hypertensive infants, ACE inhibition scintirenography established the diagnosis of RVH from renal ischemia (due to aortic or renal arterial thrombi). Two scintigraphic criteria were used for the diagnosis of RVH: criterion I, ischemic and damaged kidney (a non-functioning kidney on or off ACE inhibition) and criterion II, ischemic but not damaged kidney (ACE inhibition induced deterioration of function of the kidney). When criterion I was present and the contralateral kidney was normal, ACE inhibitors could be used for treatment of hypertension without deterioration of renal function; kidneys satisfying criterion I eventually involuted or manifested growth arrest and frequently caused persistent RVH, even after resolution of the thrombus, requiring nephrectomy. When criterion II was present bilaterally, or it was associated with criterion I contralaterally, the use of antihypertensive drugs other than ACE inhibitors was necessary in order to prevent renal insufficiency or failure from ACE inhibitors. However, kidneys with criterion II showed normal growth and, following retraction or dissolution of the aortic thrombus, hypertension resolved. In 2 of 24 hypertensive children older than 1 year, the test was diagnostic of branch renal artery stenosis; RVH was cured by selective angioplasty. ACE inhibition scintirenography is useful in the evaluation and planning of treatment in children with hypertension and may predict the outcome of therapy and ultimate renal function.

Quantitation of Metabolic Change in Serial FDG-PET Brain Scans of Pediatric Patients with Traumatic Brain Injury

The aim of this research was to develop a method to quantitate the changes in regional brain metabolism on serial FDG-PET scans in children with Traumatic Brain Injury (TBI) in order to determine their response to treatment with psycho stimulant medication. Methods: A Fusion-Based Image Subtraction (FBIS) technique was developed in order to calculate the differences in metabolism between baseline and follow-up scans. The FDG-PET brain images were count normalized to account for differences in the injected activity. Image registration was then performed using a 3D normalized mutual information algorithm and subsequently the fused images were subtracted on a pixel by pixel basis. FBIS extracted areas of increased or decreased metabolism were then compared to a database of normal subjects using NeuroQ (Syntermed, Inc.) and analyzed for statistical significance in cluster areas defined by a standard brain template. Results: Validation of the technique was performed using images from 15 pediatric cases with severe TBI who had baseline (pre-treatment) and follow-up (post-treatment) scans. The FBIS technique was found to be accurate in detecting and localizing the statistically significant changes in regional cerebral metabolism and provided useful data that could be applied clinically. Conclusions: The developed FBIS method identified and quantified areas of regional brain metabolic change thus providing a way to evaluate the effects of pharmacologic treatment in children with TBI. This quantitative technique could be used as an adjunct tool to enhance the interpretation of FDG-PET brain images and aid the referring clinician to assess the response to pharmacologic treatment.

A Respiratory Gating System for PET Imaging of Lung Cancer

The accurate characterization of lesions in FDG-PET imaging of lung cancer in terms of their size, shape, location and quantitation, can be significantly affected by motion of the lungs during respiration. The objective of this research was to develop a system to acquire and process the patient’s breathing signal and use it to “gate” the acquisition of FDG-PET images in order to reduce the effects of respiratory motion. Methods: A high-resolution CCD laser system that senses the displacement of the chest or abdomen during the patient’s breathing cycle was employed. The displacement information was appropriately processed to reconstruct the respiratory signal, which in turn was used to trigger the gated acquisition of FDG-PET images in a synchronized fashion from inspiration to expiration. The system was attached to a custom designed mechanical assembly with robotic movements and was tested on a Philips C-PET and a Philips Gemini PET/CT scanner. A motorized oscillating phantom and a ventilator supplied lung simulator were developed for testing and validating the system with positron emitting sources simulating lung lesions at variable speeds of breathing and motion displacement. Results: There was a significant reduction in the effects of respiratory motion with the proposed respiratory gating system. Improved accuracy was noted in determining the spatial location, obtaining the size, and recovering the actual counts of simulated lung lesions with gated vs. non-gated phantom experiments. The reliable operation of the respiratory gating system was also validated in 3 patient studies. Conclusions: A system was developed that enables respiratory-gated acquisition in FDG-PET imaging in order to reduce the effects of respiratory motion, which can affect lung lesions. Phantom experiments and limited clinical applications demonstrated the reliable performance of the system and improved accuracy in the characterization of lung lesions.

Multivendor nuclear medicine PACS provide fully digital clinical operation at the University of Miami/Jackson Memorial Hospital

In an effort to improve patient care while considering cost-effectiveness, we developed a Picture Archiving and Communication System (PACS), which combines imaging cameras, computers and other peripheral equipment from multiple nuclear medicine vectors. The PACS provides fully-digital clinical operation which includes acquisition and automatic organization of patient data, distribution of the data to all networked units inside the department and other remote locations, digital analysis and quantitation of images, digital diagnostic reading of image studies and permanent data archival with the ability for fast retrieval. The PACS enabled us to significantly reduce the amount of film used, and we are currently proceeding with implementing a film-less laboratory. Hard copies are produced on paper or transparent sheets for non-digitally connected parts of the hospital. The PACS provides full-digital operation which is faster, more reliable, better organized and managed, and overall more efficient than a conventional film-based operation. In this paper, the integration of the various PACS components from multiple vendors is reviewed, and the impact of PACS, with its advantages and limitations on our clinical operation is analyzed.