Only the second purchase 3ml careprost fast delivery, nonarrhythmic beat was used for reconstruction of images (Panel B) order careprost 3 ml with mastercard. Physicists provide the basis for radiation dosimetry with the defnition of the funda- Bone marrow 0 cheap careprost 3ml otc. Measurements are T The efective dose is the pragmatic weighted sum of performed with a 100 mm long pencil ionization cham- equivalent organ doses cheap careprost 3 ml with amex, where the tissue weighting fac- ber (Fig. A disadvantage is that they may not be updated for new types of scanners, only provide dose 7. Clearly, female breast tissue and lung tissue cations do not require special user skills, it is sufcient to receive the highest doses. The 2007 recommendations of the international commission on radiological Recommended Reading protection. Reassure the patient that the examination will be short and uncomplicated – consider oral beta 8. Plan scan range, and adjust scan and contrast Abstract agent parameters individually 6. Administer nitroglycerin sublingually In this chapter, the examination- and reconstruction- 7. Repeat beta blocker injection if necessary patients with nitroglycerin as well as with oral and/or 9. Inject the contrast agent – adjust scan delay intravenous beta blockers is explained. How to avoid individually pitfalls during scanning and reconstruction is the ﬁnal 10. This of cardiac catheter examination (which is ofen per- approach, however, requires calculating or estimating the formed with intracoronary nitroglycerin administra- score during the examination and may reduce workfow. The onset of action of sublingual nitroglycerin In our experience, neither image quality nor diagnostic spray (Fig. Patients should what higher calcium scores, and patients with atypical be given two to three sprays of sublingual nitroglyc- angina pectoris and a 20–70 % pretest likelihood of coro- erin (corresponding to a dose of about 0. Complications of nitroglycerin administration include Terefore, on our 64-row scanner, we did not routinely tachycardia and hypotension (which may cause head- perform calcium scanning in patients with low-to-inter- aches). Relevant refex tachycardia is rare, and this mediate pretest likelihood of coronary artery disease. All intravenous beta blockers should be injected slowly, and the examiner Once the patient has been placed on the table in the must wait and see how the patient reacts to the initial supine position with the arms above the head (Fig. Examining the patient feet-ﬁrst (Panel A) has the advantage of providing better access to the patient than with head-ﬁrst positioning. The arms are comfortably placed above the head to improve penetration of the chest by the X-rays, thereby reducing artifacts and radiation exposure. The patient is placed in an oﬀset position, slightly to the right side of the table (arrows, Panel B), to ensure that the heart is as close as possible to the center of the scan ﬁeld. However, heart rate reduc- cranially, and therefore the caudal portions of the heart were tion using beta blockade should be considered missed. Oblique coronal maximum-intensity projection in the left ventricular outﬂow tract view. Another important efect of beta blockers is esmolol is approximately 2–5 min, and the half-life is the reduction of heart rate variability, which signifcantly only 9–10 min. Up to a threshold of about 65 beats per min, beta blockade and adding intravenous beta blockers if good image quality can almost always be achieved and 74 Chapter 8 ● Examination and Reconstruction A 8 ⊡ Fig. A typical anterior scanogram (Panel A) with a too-high electrode (arrow) on the left side of the chest, which can lead to artifacts over the cardiac structures. Such artifacts can be easily avoided by lower place- ment of the electrode (arrowhead in Panels B and C). The typical anatomic scan range for patients with suspected or known coronary artery disease is indicated by the yellow lines and extends from above the left atrium to immediately below the heart (Panel B ). Because of the high eﬀective dose, the scan range should be as short as reasonably achievable. Curved multiplanar reformation of the right coro- that avoids the contraindications of beta blockers (Chap. Nitroglycerin administration leads to a relevant increase has been shown very efective in achieving target heart in the coronary diameter (on average 12–21 %), which also rates, either alone or in combination with beta blockers. Sublingual nitroglycerin (Panel A) increases coronary ves- sel diameters and facilitate comparison of the ﬁndings to ⊡ Fig. Oral (Panel B, metoprolol or The patient (90 kg) had an initial heart rate of 80–92 beats per min atenolol) and/or intravenous beta blockade (Panels C and D , during breath-hold training (Panel A). An initial dose of 10 mg esmolol or metoprolol) is important to reduce heart rate in order metoprolol (equivalent to approximately 100 mg esmolol) reduced to improve image quality and increase diagnostic accuracy as the heart rate to 60–67 beats per min (Panel B). After a second much as possible injection of 10 mg metoprolol, the patient’s heart rate was ade- quately reduced to 50–55 beats per min during the ﬁnal breath- In general, beta blockers should be administered in hold training period (Panel C). Following contrast injection, the accordance with local practice and guidelines where heart rate remained stable at 55 beats per min. Note that atropine must be available as an anti- dose of intravenous beta blockers might have been reduced if oral dote whenever beta blockers are given. Complications of beta blockers had been administered before the patient entered beta blockers are bradycardia, hypotension, and acute the scanner room 76 Chapter 8 ● Examination and Reconstruction asthmatic episodes. The foremost measure to alleviate highlight the importance of taking into account clinical the initial symptoms of bradycardia and hypotension is information about previous treatments and diagnostic to elevate the patient’s legs and administer saline intra- tests to tailor the examination to the individual patient’s venously. Nevertheless, T e scan feld of view (axial extension of the radiated serious complications of beta blockers are very rare and, area) should be as small as possible to reduce the radia- in patients with high heart rates, should not prevent us tion exposure and, most important, to increase the spa- from making use of the positive efects of beta blockers tial resolution (since small focus spots are used). We use, in terms of improved image quality and diagnostic accu- for instance, 320-mm scan felds of view (medium size) racy at a markedly decreased efective dose. In case of for coronary imaging, which reduces radiation exposure an insufcient efect of beta blockade, intravenous con- by 20–25 % when compared with large scan felds of view scious sedation (e. The scan feld of view needs to be diferenti- is a very efective alternative to slow heart rate and may ated from the smaller reconstruction feld of view, which improve image quality in selected patients. If the scanner allows the 8 determination of this reconstruction feld of view dur- 8. As 1 cm of a retrospective helical scan is equal to an efective dose of 1–2 mSv, every efort should be made to limit the scan 8. For imaging of the ascending aorta or the aortic and/or pulmonic valve, the start of the Temporal resolution can be improved by testing the scan range needs to be extended above the aortic arch patient’s heart rate before the examination using the (Fig. This scan range is also sufcient for patients same breathing instructions (“Please breathe in and who have undergone sole venous coronary bypass graf- then hold your breath”) as during the actual scan ing, whereas in patients with lef or right internal mam- (Fig. The information on the individual patient’s mary artery grafs, the scan should start approximately heart rate range during the trial breath-hold can be in the middle of the clavicle (Fig. Tese diferent scan lengths parameters such as pitch and gantry rotation time to ⊡Fig. We then perform a single axial scan at the level of the largest diameter of the heart (Panel B ), which is indicated by a yellow line in Panel A.
Impact of retro- a potential marker for cerebral events during cardiopulmo- grade cerebral perfusion on S100β release during hypother- nary bypass order 3ml careprost otc. Ann Thorac Surg value of S-100β and neuron-specific enolase serum levels for 1999; 68: 2202–2208 3ml careprost sale. Ann Thorac Surg 2001; 71: Protein S-100beta in brain and serum after deep hypother- 1512–1517 order 3ml careprost fast delivery. S100B as a pre- analysis of serum concentrations of protein S-100B and glial dictor of size and outcome of stroke after cardiac surgery purchase careprost 3ml free shipping. Lund malignant course of infarction in patients with acute middle University, Sweden, 2001. Elevated as a surrogate marker for successful clot lysis in hyper- serum levels of S-100 after deep hypothermic arrest correlate acute middle cerebral artery occlusion. S-100β release in hypo- value of S-100β and neuron-specific enolase serum levels for thermic circulatory arrest and coronary artery surgery. Ann Thorac Surg blood after cardiac surgery is a powerful predictor of late 1999; 68: 1225–1229. Serial measurement of with neurologic complications after aortic operation using serum S-100B protein as a marker of cerebral damage after circulatory arrest. Role of neurobio- after out-of-hospital cardiac arrest: prediction by cere- chemical markers of damage to neuronal and glial brain brospinal fluid enzyme analysis. Time course of psychological changes after cardiopulmonary bypass for serum neuron-specific enolase: a predictor of neurological coronary artery bypass grafting. Release of brain- ship between serum S-100β protein and neuropsychologi- specific creatine kinase and neuron-specific enolase into cal dysfunction after cardiopulmonary bypass? J Thoracic cerebrospinal fluid after hypothermic and normothermic Cardiovasc Surg 2000; 119: 132–137. Ann Thorac Surg 2000; 69: in cerebrospinal fluid during thoracoabdominal aortic 750–754. Biochemical enolase is a molecular marker for peripheral and central markers for brain damage after cardiac surgery – time neuroendocrine cells. Neuron-specific eno- tials for identifying adverse neurological outcome after lase concentrations in serum and cerebrospinal fluid in thoracic and thoracoabdominal aortic aneurysm surgery. Neurone- lary acidic protein in serum after traumatic brain injury specific enolase and Sangtec 100 assays during cardiac and multiple trauma. Finding severely obstructive disease is score will have (silent) obstructive coronary artery dis- rare, and the overall prognosis of asymptomatic patients ease. In these patients a low threshold to ischemia detec- without detectable coronary calcium is excellent (<1 % tion seems reasonable. Exercise electrocardiography has a high most useful to exclude coronary artery disease in patients specifcity but a low sensitivity, using invasive angiogra- with a low-to-intermediate pretest likelihood of disease. Just as moderate obstructive disease to assess hemodynamic there are patients who are unsuitable to undergo stress signifcance. Methods to assess functional signifcance of coro- nary stenosis by computed tomography are under 4. Whether the technique should be used as the initial A simple calcium scan may allow exclusion of severe test in low-to-intermediate risk patients followed by disease in a substantial number of patients and is associ- functional testing in patients with obstructive disease or ated with excellent outcome. However, because of the secondary to functional tests that cannot be performed potentially devastating consequences and the possibly 35 4 4. The applicability of these results and limited to exclude an acute coronary syndrome with a high nega- low risk patients. No clinical beneft was demonstrated tive predictive value, whereas the positive predictive and cost-efectiveness will be afected by local logistics value appears to be somewhat lower in acute patients. Routine performance of a so-called cance of lesions, which may be unpredictable in the pres- 4 triple rule-out scan for exclusion of myocardial infarc- ence of collateral perfusion of the myocardium. Terefore, tion, pulmonary embolism, and aortic dissection has complementary functional information will ofen be needed been investigated, but shows limited beneft. In-stent resteno- suspected of an acute coronary syndrome to simultane- sis in an (unprotected) lef main stent may have serious ously image the pulmonary arteries, may negatively afect consequences. Because stress testing is considered less the interpretability of the coronary arteries (Chap. As subclinical occlusion may exist for needs to be excluded, even when concrete symptoms of years, because of competitive antegrade or collateral ischemia are absent. Conventional coronary angiogra- fow, assessment of the signifcance of an occluded graf phy is routinely performed in patients scheduled for late afer revascularization requires some kind of func- (noncoronary) cardiac surgery, such as valve surgery. Information on the angula- After Coronary Revascularization tion of vessels or the presence and location of plaques at ostial or bifurcation sites is useful in complex coronary Follow-up of patients afer revascularization is more com- procedures. Short occlusion (arrow) with moderate amounts of calcium in the left anterior descending coronary artery. Panel A is a volume-rendered reconstruction, Panels B and C are curved multiplanar reformations and maximum-intensity projections suitability, select the optimal device size, predict List 4. In addition, imaging of the chronic total occlusion peripheral vasculature is important to select the most optimal vascular access (Chap. When an acceptable echocardiographic window is available, echocardiogra- phy is the frst choice for functional imaging of the heart. Assessment of an area of subendocardial scarring will be difcult to rec- coronary artery disease by cardiac computed tomography: a scien- ognize based on these attenuation values. Acta Radiol outperforms calcium imaging in the triage of acute coronary 52:378–384 syndrome. Eur force on the management of stable angina pectoris of the European Radiol 16:818–826 Society of Cardiology. J Cardiovasc Comput tector computed tomography viability imaging afer myocardial Tomogr 4:407. Ann Intern Med 154: embolism and acute aortic syndrome occurring outside of the feld 413–420 5 Clinical Indications M. However, patients with a likelihood of less than patients with inconclusive fndings in previous stress 20 % may not beneﬁt from noninvasive testing because of the very tests and those presenting with atypical angina. Modiﬁed from Diamond and Forrester New Engl J Med 1979 b Only one of the three characteristics of angina pectoris is present (either retrosternal localization of pain, pain precipitated by exercise or decreased at rest, or on nitrate medication) c Only two of the three characteristics of angina pectoris are present d All of the three characteristics of angina pectoris are present (<20 %; e. Interestingly, Hofmann may also be helpful in increasing the cost-efectiveness et al. Modiﬁed from Diamond and Forrester New Engl J Med 1979 b Only one of the three characteristics of angina pectoris is present (either retrosternal localization of pain, pain precipitated by exercise or decreased at rest, or on nitrate medication) c Only two of the three characteristics of angina pectoris are present d All of the three characteristics of angina pectoris are present Please note that 1. Modiﬁed from Diamond and Forrester New Engl J Med 1979 b Only one of the three characteristics of angina pectoris is present (either retrosternal localization of pain, pain precipitated by exercise or decreased at rest, or on nitrate medication) c Only two of the three characteristics of angina pectoris are present d All of the three characteristics of angina pectoris are present Please note that 1. In only rare cases there is a clinical indication for cardiac function analysis alone. Tus, the technical approach may higher overall radiation exposure, downstream utiliza- better individually focus on two of the vascular beds tion, and invasive testing. However, the available evi- for follow-up of coronary aneurysms; however, in young dence (Chaps. Also, involve radiation exposure, and there is no need for con- because such stents represent 70–80 % of all implanted trast agent administration.
A distribution that has the central location to the right and a tail off to the left is said to be "negatively skewed" or "skewed to the left cheap careprost 3 ml. The symmetrical clustering of values around a central location that is typical of many frequency distributions is called the normal distribution (Figs 12 buy 3ml careprost overnight delivery. The bell-shaped curve that results when a normal distribution is graphed effective careprost 3ml, as shown below buy careprost 3 ml with visa, is called the normal curve. This common bellshaped distribution is the basis of many of the tests of inference that we use to draw conclusions or make generalizations from data. Measures of central tendency Average is a general term which describes the center of a series. There are three common types of averages or measures of central position or central tendency. Analysis of Quantitative Data 147 characteristics of the Measures of central tendency – a. When the distribution has openended classes, its computation would be based on assumption and therefore, may not be valid. Mean/arithmetic Mean (aM) – The sample mean (x) is the sum of all the observed values of a variable divided by the number of observations. The value of i beneath Σ gives the subscript of the first xi to be included in the summation process. The value above Σ gives the subscript of the last xi to be included in the summation. The value of i increases in steps of 1 from the beginning value to the ending value. Thus, all the observations with subscripts ranging from the beginning value to the ending value are included in the sum. Mean for Grouped Data When a particular value (x) occurs more than once, the mean is then obtained by multiplying each value of (x) by frequency (f) of its occurrence and adding together. Mean for Grouped Data with Class-interval When the data is given in the form of class interval, then the first step is to find out the midpoint of each classinterval which will represent all the values falling within a particular classinterval. If we assume that the variable y represents the midpoint of the classinterval weighted by the frequencies. Where xi represents midpoints of the classinterval which is calculated n as x = (Upper limit + Lower limit)/2 and ∑ fi = N i i = 1 examples 1. Calculate the mean for the following frequency distribution: Analysis of Quantitative Data 149 class interval 0-8 8-16 16-24 24-32 32-40 40-48 Frequency 8 7 16 24 15 7 Calculation has been done as per the formula given under heading mean. Median for Ungrouped Data The observation (n) values are arranged in the ascending or descending order of magnitude, then calculate median. Median for Discrete Data The following steps are followed to calculate median for such type of data: • First arrange the data in an ascending order of magnitude. Median for Continuous Data The following steps are to be followed: • Compute the cumulative frequencies. Find out the median weight of 590 infants born in a hospital in one year from the following table: 2. Analysis of Quantitative Data 151 Example: 2 Observations Frequencies Cumulative (Xi) (F )i frequencies (cf) 1 8 8 2 10 18 3 11 29 4 16 45 5 20 65 6 25 90 7 15 105 8 9 114 9 6 120 total 120 (n + 1)/2th value of term = 60. Calculate median: ages: 18 18 22 21 20 18 19 20 18 22 arrange in ascending order 18 18 18 18 19 20 20 21 22 22 Here ‘n’ ( number of observations) =10 (even number) The average of (n/2) i. Calculate median for given data: 5 7 8 9 10 13 15 Arrange values in ascending order (already arranged in ascending order) Here ‘n’ ( number of observations) =7 (odd number) The (n + 1)/2th term (i. Mode Mode is defined as the most frequently occurring value in a data series which occurs. In discrete frequency distribution, mode is the variate which has the maximum frequency. Simple series: In the case of simple series the value which is repeated maximum number of times is the mode of the series. Discrete frequency distribution series: In the case of discrete frequency distribution, mode is the value of the variable corresponding to the maximum frequency. Calculate mode for the following frequency distribution of 2000 child birth records. Find out the mode of the following frequency distribution: series a 8 5 15 23 8 15 28 20 series b 8 10 13 15 17 19 21 20 Mode for series A = 15, but no mode for series B (as no frequency is repeated). Measures of Dispersion In the measures of central tendency, average represents the central position of data but it does not tell us about how the measurements are arranged from the center. Analysis of Quantitative Data 153 The scattering of the observations in the data is studied through measure of dispersion. The range is defined as the difference between the largest and the smallest measurement. In the statistical world, the range is reported as a single number, the difference between maximum and minimum. Among the epidemiologist community, the range is often reported as “from (the minimum) to (the maximum),” i. Disadvantages • Range considers only the largest and smallest observation in the data. Pulse rates of 11 individuals are given below 58 66 70 74 80 86 90 100 79 96 88 R = Highest Value – Lowest Value = 100–58 = 42 2. Hemoglobin level values (in mg %) of 11 patients are as under- 4 10 15 12 11 9 13 14 4 7 8 R = Highest Value – Lowest Value = 15–4 = 11 3. The first quartile (Q ), or 25th percentile, is located such that 25 percent 1 of the data lie below Q1 and 75 percent of the data lie above Q1. The second quartile (Q ), or 50th percentile or median, is located such that half 2 (50 percent) of the data lie below Q and the other half (50 percent) of 2 the data lie above Q2. The third quartile (Q ), or 75th percentile, is located such 3 that 75 percent of the data lie below Q3 and 25 percent of the data lie above Q3. The interquartile range is the difference of the 75th and 25th percentiles (the third and first quartiles). This range includes about onehalf of the observations in the set, leaving onequarter of the observations on each side. Find out the position of the 1st and 3rd quartiles with the following formula: • Position of 1st quartile (Q ) = (1 n +1)/4 • Position of 3rd quartile (Q ) = 3(3 n + 1)/4 = 3 X Q1 3. Observations are arranged in the increasing order like: 4, 5, 7, 8, 9, 11, 13, 15 2. Value of Q :1 The position of Q1 was 2%; therefore, the value of Q1 is equal to the value of the 2nd observation plus one-fourth the difference between the values of the 3rd and 2nd observations. Analysis of Quantitative Data 155 Value of 2nd observation = 5; Value and 3rd observation = 7, so 1 Q1 = 5 + (7–5) = 5 + 2/4 = 5. The incubation period (in days) for 10 patients of infectious hepatitis are given below: 26 22 36 15 27 19 24 18 23 25 156 Research Methodology for Health Professionals – Sr. Calculate the mean deviation for following data with class interval: age group (yrs) 20-30 30-40 40-50 50-60 60-70 70-80 80-90 no. Analysis of Quantitative Data 157 The variance and standard deviation are measures of the deviation or dispersion of observations around the mean of a distribution.
L. Benito. Southern Polytechnic State Univerisity.