Calcified plaques

The sequestering agent tetrasodium pyrophosphate (TSPP) removes calcium and magnesium from the saliva, so they can t deposit on teeth as insoluble deposits called tartar (calcified plaque). In this respect it acts as a water-softening agent. However, it won t remove tartar that already exists. 

Diseases of elastic tissue are few compared with those that affect collagen, and in these destruction of preformed elastic fibers appears to occur only in localized areas, particularly in the walls of blood vessels and in the skin. In arteriosclerosis loss of elasticity and breakdown in the structure of the elastic elements in the media of arteries is accompanied by calcification of the media and the development of calcified plaques in the intima. Since calcification of the media may be seen to occur without the development of atheromata, it is thought that this change may be associated in the first place with age. Other age-related changes looked for have been changes in the gross content of elastin in the media and changes in the amino acid... 

Toothpastes are designed with two purposes in mind. First, it must be a mild abrasive for removing calcified plaque from the surface of the... 

Accuracy of Reconstructions. Dense, circumferential calcifications can cause beam hardening and degrade the accuracy of vascular reconstructions. Although this limitation is addressed by dual- and spectral-source CT imaging, optimal methods to accurately measure the degree of vascular stenosis in patients with heavily-calcified plaque are under investigation. 

Plaque that is not removed from the teeth becomes calcified from minerals in the saliva. The calcified plaque is known as tartar. It is possible to control tartar buildup by using toothpastes containing sodium pyrophosphate (Na P20y), which interferes with the mineral crystallization that causes tartar buildup. Beneath the gum line, tartar is a special problem because its presence makes it easier for plaque to grow, which irritates gum tissue and allows the gum to become diseased. Only a dentist or oral hygienist can remove tartar from beneath the gum line. By keeping teeth free from plaque and from prolonged contact with the acids produced by plaque bacteria, we can preserve the hard, stonelike enamel of the tooth. 

In patients with an acute coronary syndrome we have observed non-calcified plaques with low CT density values (20-40 HU) (Becker et al. 2000). 

These soft plaques in the coronary arteries may either correspond to unstable lipid-rich soft plaques or an intra-coronary thrombus formation. In asymptomatic patients and patients with chronic and stable coronary artery disease, frequently non-calcified and calcified plaques were found. The CT density of these plaques maybe in the range of 90 HU and may correspond to stable fibrous rich or fibro-calcified plaques, respectively (Becker et al. 2003). 

Even in contrast-enhanced studies, coronary calcifications can easily be detected and quantified because the density of calcium (> 350 HU) is beyond the density of contrast media in the coronary artery lumen (250-300 HU) (Hong et al. 2002). However, because of partial volume effects, it is much more difficult to quantify non-calcified rather than calcified plaques. The optimal quantification algorithm for the different presentation of coronary atherosclerosis as seen in MDCT is still under development (Fig. 15.4). 

Fig. 8. 6a,b. Calcified dorsal plaques. Longitudinal scans on the ventral aspect of the pen is. a Isoechoic plaque showing small calcifications (arrowheads), b Extensively calcified plaque (open arrow) presenting with back attenuation... 

X-rays in mammography technique and CT are able to detect calcifications of Peyronie plaques and to determine the degree of plaque calcification (Andresen et al. 1998). Non-calcified plaques, however, cannot be shown accurately. The information gained by these methods does not support the use of ionizing radiation for this purpose (Fornara and Gerbershagen 2004). 

One of the limitations of CT is that tissues of different chemical composition but the same X-ray attenuation have the same Flounsfield values. This makes the differentiation and classification of tissue types challenging. Classical examples are the differentiation between calcified plaques and iodinated blood or hyper-dense and contrast-enhanced lesions. 

Fig. 10.5. a Dual-Energy (DE) bone-removal of neck-CTA, axial MPR. Note that bone and calcified plaques (arrowheads) have been completely removed. Stenotic vessel lumen marked by contrast agent (arrows). b DE bone-removal of CTA of the head, axial MPR. All bony structures have been removed, contrast agent at the ICA (arrows) and the cavernous sine (arrowhead), c DE bone-removal, sagittal MPR. Contrast agent at the ICA (arrows), removed calcified plaque at the carotid bulb (arrowhead), d VRT of DE bone-removal head and neck CTA. Removed calcified plaque at the carotid bulb (arrowhead)... 

Fig. 16.3a-d. Hypothetical density of lumen versus plaque on representative cross-sections, a The coronary lumen (filled with an iodine contrast agent at 400 HU) is surrounded by soft plaque and epicardial fat. The problem zone in this situation is the delineation of soft plaque versus epicardial fat b Part of the soft plaque structures are densely calcified. The calcified plaque with a density of 700 HU is oversized due to partial volrnne averaging, but delineation against the lumen is not compromised by contrast issues, c For a hypothetical plaque structure at an initial stage of calcification (Hounsfield units... 

Spectral CT could therefore have a major impact on the clinical value of CT coronary angiography. Without beam hardening artifacts, in-stent lumens become accessible and with partial volume averaging, reduced both vessel lumens adjacent to stent struts and densely calcified plaques are more accurately dehn-eated (Feuerlein et ah 2008). Overall, two new application scenarios could be feasible one is the foUow-up of patients after percutaneous coronary interventions with stent implantation the other is the evaluation of patients with known CAD or calcified vessels. Spectral detector technology may promote CT to become the primary tool for CAD imaging (Roessl and Proksa 2007 Feuerlein et al. 2008). 

In a separate study by Witteman et al. (5), the presence of aortic calcified plaques on routine chest X-ray correlated with a twofold increased risk of cardiovascular death in men and women younger than age 65. A similar relative risk was noted for the development of coronary artery disease, stroke, and intermittent claudication among middle-age women. Lastly, die risk of sudden coronary death in men with calcified... 

Witteman JC, Kannel WB, Wolf PA, et al. Aortic calcified plaques and cardiovascular disease (The Framingham Study). Am J Cardio 1990 66 1060-1064. 

Examples of Raman spectra from three different types of human coronary artery are shown in Fig. 17. The top spectrum was obtained from a sample of nonatherosclerotic (normal) coronary artery, the middle from a noncalcified atheromatous plaque, and the bottom from a calcified plaque. The spectra from these different artery types are distinct and provide clear features for the determination of the chemical composition and for a histological classification of the arterial wall. For example, the normal coronary artery spectrum is dominated by protein features such as the amide I and III modes at 1650 and 1250 cm respectively, and the CH2 bending modes at —1450 cm In noncalcified atheromatous plaques, spectral features of cholesterol and cholesterol esters constitute the major part of the spectrum. The symmetric stretch at 960 cm of the calcium hydroxyapatite phosphate group dominates the spectrum of calcified plaques. 

Solomon A, Sluis-Cremer GK, Thomas RG, Wright VMF (1984) Calcified plaques on mediastinal pleural reflections asso-... 

Macroscopically, pleural plaques are discrete, raised, and irregularly shaped areas (Roberts 1971). They vary in size from a few millimeters to 10 cm. The thinner plaques are only slightly raised above the pleural surface, vdiile the thicker plaques are either smooth or show a fine or coarse nodularity. Most of the plaques have a leathery consistency, but as pleural plaques tend to calcify with time, more heavily calcified plaques are brittle and can be fractured (Roberts 1971). 

No study has investigated the diagnostic performance of CT in detecting pleural plaques by comparison with autopsy as the method of reference, but more plaques are detected using CT than radiography and, except for obviously calcified plaques, CT eliminates false-positive diagnoses of asbestos-related pleural disease caused by extrapleural fat (Friedman et al. 1988). CT is, thus, now widely recommended to detect pleural plaques in asbestos-exposed workers and plays an important role in medico-legal and compensation issues. 

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