They were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in Many of the early Crookes tubes invented around undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below.
Current guidelines from the American Heart Association recommend against routine stress testing for screening asymptomatic adults. Pre-operative assessment of persons scheduled to undergo 'high-risk" non-cardiac surgery, where an imaging stress test or invasive coronary angiography is being deferred unless absolutely necessary.
Pre-operative assessment for planned non-coronary cardiac surgeries including valvular heart disease, congenital heart disease, and pericardial disease, in lieu of cardiac catheterilzation as the initial imaging study, in persons with low or intermediate pretest risk of obstructive CAD.
Detection and delineation of suspected coronary anomalies in young persons less than 30 years of age with suggestive symptoms e. Aetna considers CT angiography of cardiac morphology for pulmonary vein mapping medically necessary for the following indications: Evaluation of persons needing biventricular pacemakers to accurately identify the coronary veins for lead placement.
Evaluation of the pulmonary veins in persons undergoing pulmonary vein isolation procedures for atrial fibrillation pre- and post-ablation procedure. Anomalous pulmonary venous drainage; Evaluation of other complex congenital heart diseases; Evaluation of sinus venosum atrial-septal defect; Kawasaki's disease; Person scheduled or being evaluated for surgical repair of tetralogy of Fallot or other congenital heart diseases; Pulmonary outflow tract obstruction; Suspected or known Marfan's syndrome; Evaluation of suspected native or prosthetic cardiac valve dysfunction when echocardiographic imaging is inconclusive or there is suspicion for paravalvular abscess formation.
Aetna considers cardiac CT angiography experimental and investigational for persons with any of the following contraindications to the procedure because its effectiveness for indications other than the ones listed above has not been established: Persons with extensive coronary calcification by plain film or with prior Agatston score greater than Repeat calcium scoring is considered medically necessary only if the following criteria are met: Otherwise, serial or repeat calcium scoring is considered experimental and investigational.
Aetna considers calcium scoring by means of low-dose CT angiography medically necessary for persons who meet criteria for diagnostic cardiac CT angiography to assess whether an adequate image of the coronary arteries can be obtained.
Background Cardiac CT Angiography Coronary computed tomography angiography CCTA is a noninvasive imaging modality designed to be an alternative to invasive cardiac angiography cardiac catheterization for diagnosing CAD by visualizing the blood flow in arterial and venous vessels.
The gold standard for diagnosing coronary artery stenosis is cardiac catheterization. Beta-blockers and sublingual nitrates may be administered prior to the scan in order to lower the heart rate, avoid arrhythmia and dilate the coronary arteries.
In order to allow for an improved image quality and contrast media dose reduction, the CCTA is usually ECG-triggered to adapt the scan sequence to the person's heartbeat Bell et al.
In addition to being a non-invasive alternative to conventional invasive coronary angiography for evaluating coronary artery disease, CCTA has emerged as the gold-standard for the detection of coronary artery anomalies Ramjattan and Makaryus, The performance of cardiac CTA has been improved by increasing the number of slices that can be acquired simultaneously by increasing the number of detector rows AHTA, As the number of slices that can be acquired simultaneously increases, the scan time is shortened, spatial resolution is increased, and reconstruction artifacts are significantly reduced.
Initial cardiac CT imaging was conducted with 4-slice detector CT. Scanning times were reduced from 40 seconds down to 20 seconds with slice detector CT. With the advent of slice detector CT, scanning times were reduced to a 10 second breath-hold. Given its high negative predictive value, cardiac CTA has been shown to be most useful for evaluating persons at low to intermediate risk of coronary artery disease.
This would include evaluation of asymptomatic low- to intermediate-risk persons with an equivocal exercise or pharmacologic stress test, and evaluation of low- to intermediate-risk persons with chest pain.
Cardiac CTA is also a useful alternative to invasive coronary angiography for pre-operative evaluation of persons undergoing non-coronary cardiac surgery or high-risk non-cardiac surgery, where invasive coronary angiography would otherwise be indicated. Einstein and colleagues ascertained the lifetime attributable risk LAR of cancer incidence associated with radiation exposure from a slice computed tomography coronary angiography CTCA study and evaluated the influence of age, sex, and scan protocol on cancer risk.
Organ doses from slice CTCA to standardized phantom computational model male and female patients were estimated using Monte Carlo simulation methods, using standard spiral CT protocols.
Main outcome measures were whole-body and organ LARs of cancer incidence. Organ doses ranged from 42 to 91 mSv for the lungs and 50 to 80 mSv for the female breast.
Lifetime cancer risk estimates for standard cardiac scans varied from 1 in for a year old woman to 1 in 3, for an year old man. Use of simulated electrocardiographically controlled tube current modulation ECTCM decreased these risk estimates to 1 in and 1 in 5, respectively.
Estimated cancer risks using ECTCM for a year old woman and a year old man were 1 in and 1 inrespectively. A combined scan of the heart and aorta had higher LARs, up to 1 in for a year old woman. The highest organ LARs were for lung cancer and, in younger women, breast cancer.
The authors concluded that these estimates derived from simulation models suggested that use of slice CTCA is associated with a non-negligible LAR of cancer.MONTE CARLO IN RADIATION THERAPY. The Monte Carlo techniques have been used in various branches of radiation therapy,[8,9] from simulation of radiation therapy equipments and sources to dose calculation in various geometries.[10–18] For simulation of the photon and electron particles one has to apply the physics of transport for .
There are no proven relationships between coronary artery calcification and the probability of plaque rupture. Some advocates have argued that EBCT scores could be an effective substitute for standard risk factors in predicting the risk of coronary artery disease.
Hypothesis-1 proposes that exposure to medical radiation is a highly important cause (probably the principal cause) of cancer-mortality in the United States during the Twentieth Century even though medical radiation is only rarely mentioned in lists of "risk factors" for Cancer.
Arabic Course Descriptions. Two one-hour language laboratory periods weekly are required in each four-hour course, one of which is a concurrent lab class enrollment.
The Module Directory provides information on all taught modules offered by Queen Mary during the academic year The modules are listed alphabetically, and you can search and sort the list by title, key words, academic school, module code and/or semester.
Europe/Rome Artificial intelligence (AI) is undergoing an explosive phase — machines can now accomplish complex specific tasks at a level that exceeds human skills.
At the basis of this performance is the ability to understand the sensory input from the external world and to associate it with effective strategies to achieve the desired goal.