The typical HIP case was associated with ultrasound attenuation, positive remodeling, remarkably low computed tomography density, and a high incidence of slow-flow phenomena. Noncontrast T1WI in cardiac magnetic resonance imaging may be useful for the assessment of coronary plaque characterization in patients with coronary artery disease.

Both the increase of the v(e) and the elevation of permeability (K(trans) ) were indicative of a good tumor response to CRT. The pharmacokinetic analysis had potential for monitoring the histopathological response to CRT.

Acetylcholinesterase inhibitors (AChIs)

Many researchers have established the utility of the dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in the differential diagnosis in the head and neck region, especially in the salivary gland tumors. The subjective assessment of the pattern of the time-intensity curve (TIC) or the simple quantification of the TIC, such as the time to peak enhancement (T peak) and the wash-out ratio (WR), is commonly used. Although the semiquantitative evaluations described above have been widely applied, they do not provide information on the underlying pharmacokinetic analysis in tissue. The quantification of DCE-MRI is preferable; therefore, many compartment model analyses have been proposed. The Toft and Kermode (TK) model is one of the most popular compartment models, which provide information about the influx forward volume transfer constant from plasma into the extravascular-extracellular space (EES) and the fractional volume of EES per unit volume of tissue is used in many clinical studies. This paper will introduce the method of pharmacokinetic analysis and also describe the clinical application of this technique in the head and neck region.

A 73-year-old diabetic man underwent multislice computed tomography (MSCT) and noncontrast T1-weighted (T1W) magnetic resonance imaging (MRI) for the evaluation of atypical chest discomfort after an exercise ECG was nondiagnostic. The MSCT demonstrated a low-density positive remodeling plaque and spotty calcification without significant stenosis in the proximal segment of the right coronary artery ( Figure 1A and 1B). Noncontrast T1W MRI, using a 1.5-T MR system (Intera, Philips Medical Systems, Best, the Netherlands), revealed a hyperintense plaque (HIP) in the right coronary artery in an area corresponding to the plaque visualized by MSCT ( Figure 1C and 1D). With clear evidence of atherosclerotic disease, the patient was given glimepiride and voglibose with recommendations for strict diet therapy for treatment of diabetes mellitus; he continued to take aspirin. One year after these examinations, the patient presented with sudden-onset crushing chest pain at our emergency room. Despite the modifications to his medications, his coronary risk factors had not improved (hemoglobin A 1c , 7.1-6.4%, low-density lipoprotein cholesterol, 124 -110 mg/dL; high-density lipoprotein cholesterol, 34 -32 mg/dL). On admission, an ECG showed ST-segment elevation in leads II, III, and aV F . Emergent coronary angiography revealed an obstructive lesion in the proximal segment of the right coronary artery in a region corresponding to the HIP previously identified by MRI (Figure 2A). Intravascular ultrasound confirmed extensive attenuation ( Figure 2B) at that segment, and a bare metal stent was successfully implanted with a distal protection device. After stent implantation, a large amount of debris was collected.Recently, Kawasaki et al 1 reported that the presence of HIP on noncontrast T1W MRI is associated with positive coronary remodeling, low CT density, and ultrasound attenuation by MSCT or intravascular ultrasound. However, it is unknown whether HIP has a greater potential for plaque rupture and subsequent acute coronary syndrome. To our knowledge, Figure 1. Multislice computed tomography (A, curved multiplanar reconstruction; B, horizontal) demonstrates low-density plaque (Ϫ36 Hounsfield units, remodeling index 1.6, arrowheads) with spotty calcification (arrow) in the proximal segment of the right coronary artery. On the corresponding noncontrast T1-weighted magnetic resonance imaging (C, oblique image; D, horizontal), this low-density plaque was visualized as a hyperintense lesion (arrowheads). Figure 2.Right coronary angiography revealed an occlusion of the proximal segment of the right coronary artery (A). On intravascular ultrasound examination (B), a near-circumferential attenuation (arrowheads) was observed at the culprit lesion, corresponding with the plaque observed both by multislice computed tomography and by noncontrast T1-weighted magnetic resonance imaging.