Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-12-01
2003-12-30
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S431000, C250S363100, C250S370090
Reexamination Certificate
active
06671541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to medical diagnostic and screening apparatus and methods. Particularly, the present invention relates to non-invasive medical diagnostic and screening systems. Still more particularly, the present invention relates to non-invasive imaging and functional analysis systems for evaluating cardiac and cardiovascular health.
2. Related Art
Cardiac imaging and functional analysis is the largest single nuclear medical imaging application and represents the area of greatest unmet need in the prior art. This need is exemplified by the fact that historically, for 30%-50% of those stricken with coronary occlusive (artery) disease, the first symptom of the disease is death. This outcome has motivated considerable interest in developing diagnostic methods and apparatus to detect the condition of coronary occlusive disease prior to the onset of fatal symptoms, and further to assist in the development and implementation of preventive measures.
First-Pass RNA
First-Pass Radionucleide Angiography (RNA) provides the clinician with patient information for improved patient management that is either difficult and/or costly to obtain using other technologies. The First-Pass RNA can provide unique qualitative and quantitative information about cardiac function such as regional ventricular wall motion just at the peak of maximum exercise stress, left and right ventricular ejection fraction, regional contractivity, and left to right shunt quantitation. Concurrently, improvements in software analysis of the diagnostic tests are being developed and implemented on a regular basis. However, medical instrument improvements have not kept pace with detector hardware enhancements such as pixellated scintillation crystals, and position-sensitive photomultipliers. Presently, the nuclear medicine health care sector can perform a first—pass RNA diagnostic protocol using the commercially available dedicated cardiac imager multicrystal scanner model SIM400 from Picker International or a single crystal Anger gamma camera. The single crystal Anger camera has numerous disadvantages when used for first-pass RNA related to its low count rate capability including pulse-pileup and low count density. A low-count density image limits the ability to define changes in wall motion. Improvements in defining wall motion are attained using the multicrystal high rate camera. Other factors influencing the image quality are the intrinsic system resolution, count density, and the target-to-nontarget ratio.
The SIM400 scanner uses a 2.54 cm thick Na1(TI) crystal divided into 400 detector elements in a 20×20 matrix. Surrounding each detector element is reflective material. Every second row is partially cut through the crystal to create a scintillation bridge between two adjacent elements. The scintillation light is detected by
115¾″ diameter bialkali tubes and each photomultiplier tube (PMT) detects scintillation from two optically decoupled detector elements. Variations in pulse output from adjacent PMTs viewing the doublet detector element provides the photon spatial information. This scenario provides for improved count rate capability but limits spatial resolution.
In practice, clinical interpretations of the SIM400 scanner treadmill stress acquisitions are more difficult to analyze. Patient motion during peak stress acquisition can cause image artifacts that can trigger an incorrect diagnosis. To counteract this problem Picker International uses an Am-241 source placed on the patients' chest. Dual energy windows are utilized during treadmill stress acquisitions and the Am-241 energy window is used to correct for patient motion. Unfortunately, this method only corrects for up/down/side planar motion, i.e., motion in a plane, and motion in any direction outside the defined plane is uncorrected. If the patient rotates along the z-axis, the planar patient correction can magnify image artifacts. The solution of using an array of fast compact photomultiplier tubes (PMTs) to obtain compact application-specific highrate gamma cameras is described in literature. However, the prior art instruments were slow, designed primarily for relatively low rate (up to 5 kHz) breast imagers. The array concept was conceived and first tested in a small laboratory prototype by Dr. Roberto Pani and his group in University “La Sapienza” in Rome, Italy. At the time of this application, there are three companies in US that are developing products based on this mature and reliable concept: Gamma Medica Instruments (www.gammamedica.com), Dilon Technologies (www.dilon.com), and PEM Technologies, Bethesda, Md. Initially, imaging of breast cancers was emphasized, taking advantage of the small size of the cameras that allows flexibility in positioning the detector for better localization and visualization of breast lesions. One company, Digirad (www.digirad.com), produces heart imagers based on not yet technically mature and expensive solid state technology (CsI(T1) scintillator and PIN diode arrays). The only high count-rate dedicated heart imager (developed by Proportional Technologies, Inc. Houston) is based on a high pressure wire chamber concept and therefore has its energy range practically limited to less than 100 keV. Also, its rate capability is in fact limited by the physical nature of radiation interaction with a gas detector medium in a two-step process.
Positron Imaging
At the present time, essentially all nuclear cardiac imaging is limited to single-photon tomography for myocardial perfusion determination. This examination is more accurately performed by positron imaging. Prior to cardiac revascularization there is a great need to determine the viability of hypoperfused myocardium. This is accurately determined only by positron imaging. The capability to image the annihilation radiation from positron tracers will greatly increase the usefulness of a cardiac gamma camera. From the list of the presently available detection technologies of: crystal scintillators with photomultipliers, scintillators with PIN photodiodes, scintillators with avalanche photodiodes (APDS), gas filled detectors, Cadmium Zinc Telluride (CdZnTe) and other solid state detection materials, only the first solution is viable at this time from the technical and economical point of view and can be used for positron imaging as well as single gamma imaging. The detection efficiency and excellent signal to noise ratio, good energy resolution, and above all the unmatched speed of operation of fast scintillator/compact photomultiplier combination makes it the solution of choice for a combined single gamma/positron imager. The easily implemented modular structure with segmented fast readout adds to the list of main advantages of this preferred solution. However, it is possible that further development of some of the other detection technologies can lead to another option for the screening and diagnostic instruments and procedures described in this disclosure.
Coronary Artery Disease (CAD) Screening
There are two screening strategies to reduce morbidity and mortality from CAD. The first involves screening for modifiable cardiac risk factors, such as hypertension, elevated serum cholesterol, cigarette smoking, physical inactivity, and diet. The second strategy is early detection of asymptomatic CAD. The principal tests for detecting asymptomatic CAD include resting and exercise ECGs, which can provide evidence of previous silent myocardial infarctions and silent or inducible myocardial ischemia. Another principal test is computed tomography (CT) calcification scoring, which can provide visual evidence of plaques in the coronary arteries. Thallium201 scintigraphy, exercise echocardiography, and ambulatory ECG (Holter monitoring) are less commonly used for screening purposes. Neither of these strategies has produced a solution to the high incidence of previously asymptomatic CAD deaths.
Need for Solutions
In summary, nuclear cardiology equipment has evolved in recent years in the direc
Bishop Harry
Majewski Stanislaw
Umeno Marc M.
Keller Paul V.
Lateef Marvin M.
NeoMed Technologies, Inc.
Pass Barry
LandOfFree
Cardiovascular imaging and functional analysis system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cardiovascular imaging and functional analysis system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cardiovascular imaging and functional analysis system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3097515