By C. Makas. North Georgia College and State University, the Military College of Georgia.

Nor- mally buy 75mg venlor otc, most of these scattered photons fall outside the photopeak window and are rejected generic venlor 75 mg free shipping. However order venlor 75mg amex, a fraction whose photon energy falls within the photopeak window will be counted, but their (X, Y) positions remain uncer- tain causing degradation of the image resolution. There are a few methods of scatter correction, of which the most common method is the use of two windows: a scatter window and a photopeak window. The scatter window is set at a lower energy than the photopeak window, and it is assumed that scatter in the photopeak window is the same as that in the scatter window. The scatter counts in the scatter window are subtracted from the photopeak counts for each projection to obtain the scatter-corrected projections, which are then used for reconstruction. The scatter spectrum is variable in energy; therefore, to have more accu- rate scatter corrections, multiple scatter windows can be used. Scatter cor- rections are made prior to attenuation correction, because the former are amplified during the latter operation. Typically, it consists of intrinsic resolution, collimator reso- lution, and scatter resolution. Spatial resolution deterio- rates but sensitivity increases with increasing slice thickness. As a trade-off between spatial resolution and sensitivity, an optimum slice thickness should be chosen. Sensitivity The sensitivity of an imaging system is always desired to be higher for better image contrast. For con- ventional two-dimensional planar images of good contrast, about 500,000 counts are required. Total counts may be increased by either counting for a longer period or by administering more activity. However, long counting is inconvenient for the patient and administering a larger amount of activ- ity increases the radiation dose to the patient. Other Parameters Other important parameters to evaluate include effects of high-count rates, uniformity, and contrast of images. Ideally this can be achieved by acquiring at least 30 million counts for 64 × 64 images or 120 million counts for 128 × 128 images. For Siemens e-Cam cameras, acquisition of 5 million counts in a 1024 × 1024 matrix is recommended. In determining spatial resolution by the intrinsic method, the two detectors must be kept apart at maximum radius, and a 99mTc point source is placed in a source holder on the rear bed mechanism provided by the manufacturer. The bar phantom is placed on the detector, and the bed is raised to a maximum height. Nowadays, many manufacturers provide a phantom using 5-point sources for low-energy high-resolution collimators or 3-point sources for medium- and high-energy collimators. In the case of 90° configurations, the default radius is applied as given by the manufacturer. This method is also used to check the head alignment and noncircular orbit configuration in multihead camera systems with the computer software. The next daily test is the quality control test that is performed by using a quality phantom provided by the manufacturer. With a multihead camera, does the sensitivity of an imaging device increase or decrease? Which of the following acquisition matrices would give better spatial resolution: a 64 × 64 matrix or a 128 × 128 matrix? In the filtered backprojection method, the Fourier method is preferred to the convolution method. A filter with a low cut-off frequency should be used for noisy data and low count density studies in order not to curtail image detail. Single-photon emission computed tomography in the year 2001: Instrumentation and quality control. Positrons are annihilated in body tissue and produce two 511-keV annihi- lation photons that are emitted in opposite directions (180°). Two photons are detected in an electronic time interval, called “coincidence time window,” by two detectors connected in coincidence. Detectors are arranged in the array of several rings to have the organ of interest in the field of view. Data collected over 360° simultaneously around the body axis of the patient are used to recon- struct the image of the activity distribution in the slice of interest. Because the two opposite photons are detected in a straight line, no collimator is needed to limit the field of view, and the technique is called the electronic collimation. Of these, 82Rb-RbCl is 18 commonly used for myocardial perfusion imaging and F-fluorodeoxyglu- cose for metabolic imaging of the heart, brain, and various types of can- cers. The number of rings in current scanners (18–32), and the number of detectors per ring vary with the manufacturer. The number of rings and, hence, the width of the array of rings define the axial field of view. Typically, each block is about 3-cm deep and grooved into 6 × 8, 7 × 8, or 8 × 8 elements by partial cuts through the crystal with a saw.

Phlebotomy is a treatment for iron overload in such conditions as hereditary hemochromatosis purchase venlor 75mg with amex. Succimer is an orally available substance related to dimercaprol venlor 75 mg visa, used for lead toxicity cheap 75mg venlor visa. Mercury vapor is toxic and its ingestion is treated with di- mercaprol or penicillamine. The most common neurologic manifestation of lead poisoning is peripheral neuropathy, a common sign of which is wristdrop. Lead poisoning also affects the hematopoietic system as a result of inhibition of d-aminolevulinic acid dehydratase (and ferrochelatase). In contrast to the organophosphate insecticides, inorganic forms of arsenic, lead, and cadmium are poorly absorbed through the skin. A 17-year-old male patient was placed on (D) Loading dose ¼ (amount of drug adminis- carbamazepine therapy by his neurologist to tered)/(initial plasma concentration) control newly developed seizures of unknown (E) Loading dose ¼ (desired plasma concentra- etiology. The patient was also recently given a tion of the drug) 3 (volume of distribution) macrolide antibiotic by his family physician for a presumed ‘‘walking pneumonia. A 21-year-old man sustains multiple blunt traumas after being beaten with a baseball bat 5. Aside from his fractures, a serum cre- a-adrenergic receptor agonist that is available atine kinase measurement is dramatically ele- over the counter? They immediately begin to (C) Isoproterenol administer bicarbonate to alkalinize the urine. Pilocarpine is what type of pharmacologic (B) Promoting renal tubular secretion agent? Which of the following correctly describes (D) b-Adrenergic antagonist the formula for a loading dose? Which of the following is a short-acting tion of drug) 3 (clearance) acetylcholinesterase inhibitor? Ultimately, it is decide to use an ultra- (A) Inhibits calcium release from the sarcoplas- short acting b-blocker and closely monitor both mic reticulum his blood pressure and respiratory status. A 63-year-old man with a history of multiple myocardial infarctions is admitted for shortness 13. A diagnosis of congestive heart failure on a diuretic that works by altering the diffusion is made on clinical grounds, and a cardiologist of water relative to sodium (an osmotic orders a positive inotropic agent for his heart diuretic), which is helpful in reducing cerebral failure. Which agent did the physician likely perfusion to the kidneys, so an agent that prescribe? Clonidine works by (A) Mannitol (A) Activating b1-adrenergic receptors (B) Indomethacin (B) Activating a1-adrenergic receptors (C) Furosemide (C) Activating b2-adrenergic receptors (D) Vasopressin (D) Activating a2-adrenergic receptors (E) Probenecid (E) Blocking b-adrenergic receptors 15. Her thyroid- (B) Increases permeability of the collecting stimulating hormone levels are normal, but she duct has increased levels of urinary catecholamines. The surgeon (E) Reduces production of prostaglandins should start therapy with which of the following agents prior to removing the lesion? A 45-year-old man with a 60-pack/year (A) Dopamine history of smoking presents to his primary (B) Phentolamine care provider with loss of appetite, nausea, (C) Pancuronium vomiting, and muscle weakness. Laboratory ble for both asthma and angina now has a kid- results reveal low levels of sodium, which in this ney stone stuck in his right ureter. Which 326 Pharmacology medication might be helpful for this patient’s (C) Chlordiazepoxide symptoms? A 57-year-old man with a strong family (E) Allopurinol history of Parkinson disease sees a neurologist for an evaluation. Which of the following is a common adverse neurologist notes a slight pill-rolling tremor effect of quinidine? He begins treat- (A) Cinchonism ment with levodopa, along with the addition of (B) Lupuslike syndrome carbidopa. What is the mechanism of action of b-block- (C) Inhibits catechol-O-methyltransferase ers in heart disease? The patient in the previous question returns to see his neurologist 3 years later. Which of the following would be useful in the patient’s symptoms have progressed, and the management of arrhythmia due to Wolf- he now has marked bradykinesia and a pro- Parkinson-White syndrome? Which of the following would be a good (A) Memantine option to help a patient fall asleep with minimal (B) Donepezil ‘‘hangover’’? Risperidone works primarily through inhi- psychiatrist with expertise in addiction medi- bition of receptors for cine. He explains that he has recently received (A) Dopamine his third drunk driving citation and fears losing (B) Serotonin his license to practice unless he stops drinking (C) Histamine altogether. He tells the physician that he doesn’t (E) Norepinephrine have time to attend Alcoholics Anonymous and ‘‘wants a pill.

Such an explanation is not ‘sufficient’ (not ¬kan»v order 75 mg venlor with mastercard, to use a word which Diocles mentions later on in the fragment in section 9) discount venlor 75 mg on-line, because it does not account for situations in which quality A is present but not power B 75 mg venlor otc. Nor does Diocles deny that qualities may play a part in the production of a certain effect; but he insists that they do not necessarily produce the effect in question, and that, if they incidentally do so, they need not be the only factors involved in this production. He thereby shows that claim one, apart from being sometimes counterfactual, is also misleadingly formulated – or to put it in Aristotelian terms: it is not qua being sweet that a foodstuff is laxative, and the statement ‘sweet foodstuffs are laxative’ is not true universally. Instead, in section 7 Diocles alleges that ‘what normally results from each of them’ (i. The very fact that Diocles gives an explanation of this kind already indicates that any attempt to associate him with Empiricism or Scepticism is not very likely to be correct. Most likely, I believe, is that the nature of the substance is meant, the sum or total configuration of elements, constituents or qualities the foodstuff consists of and the way they are structured or interrelated – for instance, the proportion between qualities such as warm and cold, dry and wet by which it is characterised. This interpretation is in accordance with Galen’s use of the concept of ‘the whole nature’ (Álh ¡ fÅsiv) or ‘the whole essence’ (Álh ¡ oÉs©a) to denote the cause of the power a foodstuff or drug has, for instance in On the Mixtures and Powers of Simple Drugs (De simplicium medicamentorum temperamentis ac facultatibus, De simpl. Smith’s translation is ambiguous on this point: ‘Rather, one must consider that the whole nature (physis) is responsible (aitios) [for what usually occurs for each]. A second possible interpretation is that ‘the whole nature’ refers to the sum of natural factors that play a part in the production by a certain substance of a certain dietetic effect with a certain patient. Indeed, a number of such factors are mentioned by Galen in the pages following on the Diocles fragment: not only the ‘peculiar essence’ (o«ke©a oÉs©a) of the substance itself, but also climate, geographical area, season, a patient’s natural constitution, his way of life (t‡ –pithdeÅmata), his age, particular characteristics of the stomach and the intestines determine the effect a foodstuff produces in a particular case. A third interpretation of ‘the whole nature’ has been proposed by Jaeger, who argued that the nature of the consuming organism is meant, that is, the constitution of its body, its age, and so on. It therefore seems best to interpret the words ‘the whole nature’ as referring to the nature of the foodstuff. In section 8 Diocles criticises a third claim, which is, like the first, pre- sented as a view which is actually being held by a certain group (‘those who believe... The claim seems to be that in every par- ticular case, one should state the cause why a thing (again we may think of a foodstuff) has a certain dietetic power. At first sight, this claim looks rather different from the ones discussed earlier, for what is at issue is not the identity or the kind of causes sought for but the search for causes itself. Moreover, there is a shift of attention from the universal (‘all’, p†nta in section 5) to the particular (‘each’, –fì —k†stou in section 8). His first argument seems rather obvious: for practical purposes, causal explanation is not often ‘necessary’. For instance, when we know that a certain foodstuff is profitable for people 16 Galen, De alim. His second objection is that a causal explanation of a substance’s having a certain power is in many cases not possible. As for the words ‘many of the things that are’, poll‡ tän Àntwn, it seems that we have to think not only of things or separate entities (e. It is not clear from the text whether by ‘starting-points’ Diocles means fundamental physical states of affairs or logical postulates that should be accepted as valid without further demonstration, comparable to the logical postulates discussed by Aristotle in Metaphysics ,19 but perhaps this is not relevant to the point he wants to make: ‘honey is laxative’ (to mention just an imaginary example) is similar to a postulate like ‘a statement p and its negation not-p cannot both be true at the same time under the same conditions’ in that it does not admit of demonstration. Whereas a real principle like a logical postulate is undemonstrable without qualification (‰pläv, one is tempted to say), foodstuffs and their effects are so only ‘in some way’ (tr»pon tin†). These are usually translated in an Aristotelian-like way by ‘naturally’, ‘by nature’, or ‘normally’, suggesting as Diocles’ intention that it is in the 18 Cf. Diocles of Carystus on the method of dietetics 83 nature of things that many things look like, or are taken as, principles. Yet if we connect the use of the word phusis here with that in section 7 above, a more comprehensible view emerges: phusis again refers to the nature of the substance in question, for example the foodstuff, and kat‡ fÅsin means ‘according to their nature’, ‘in virtue of their nature’. In section 7 the ‘whole nature’ was said to be the cause of the effect the foodstuff normally produces; thus it is relatively easy to understand the statement that in virtue of their nature these foodstuffs and their producing such-and-such an effect are like principles. For the purpose of clarity, let me paraphrase what I think Diocles’ line of thought in this whole fragment amounts to. A foodstuff has its effect due not to one of its particular qualities but to its nature as a whole; as soon as we descend to a level that is lower (e. To be sure, we might be able to explain why honey is sweet (which is, after 21 Jaeger: ‘von Natur’; Torraca: ‘secondo natura’. Kullmann takes kat‡ fÅsin as belonging to ˆrca±v: ‘Viele Gegebenheiten gleichen in gewisser Weise bestimmten naturgemaßen Prinzipien, so daß sie¨ keine Darlegung uber die Ursache zulassen’ (¨ 1974, 351) and he comments on p. Smith’stranslation(‘manythingsareinsomefashionlikefirstprinciplesinnature’) is not explicit on this point, like Frede’s paraphrase: ‘He also maintained that we should treat many facts of nature as primitive, rather than try to explain them in terms of some questionable theory which would serve no further purpose’ (‘Introduction’, 1985, xxii). Bertier’s paraphrase goes too far beyond what is in the text: ‘Apport insignifiant des theories explicatives, dans la mesure ou les realites´ ` ´ ´ contiennent en elles-memes le reflet de leurs principes, et oulˆ ` atheorie n’est qu’une repetition de´ ´ ´ la description du fait’ (1972, 32). Gottschalk (private correspondence) understands the whole sentence as follows: ‘(a) archai, because they are archai, cannot be explained or demonstrated, and (b) any train of reasoning, even if it does not start from the most universal and ultimate archai, must start from something accepted as true for the purpose of that argument, a quasi-arche not subjected to further analysis or demonstration’, and he takes the words kat‡ fÅsin as expressing that ‘Our using such propositions [e. Peck in his 1928 Cambridge PhD thesis ‘Pseudo-Hippocrates Philosophus; or the development of philosophical and other theories as illustrated by the Hippocratic writings, with special reference to De victu and De prisca medicina’, pp.