Impact of miscentering on patient dose and image noise in x-ray CT imaging: phantom and clinical studies.

The operation of the bowtie filter in x-ray CT is correct if the object being scanned is properly centered in the scanner's field-of-view. Otherwise, the dose delivered to the patient and image noise will deviate from optimal setting. We investigate the effect of miscentering on image noise and surface dose on three commercial CT scanners. Six cylindrical phantoms with different size and material were scanned on each scanner. The phantoms were positioned at 0, 2, 4 and 6 cm below the isocenter of the scanner's field-of-view. Regression models of surface dose and noise were produced as a function of miscentering magnitude and phantom's size. 480 patients were assessed using the calculated regression models to estimate the influence of patient miscentering on image noise and patient surface dose in seven imaging centers. For the 64-slice CT scanner, the maximum increase of surface dose using the CTDI-32 phantom was 13.5%, 33.3% and 51.1% for miscenterings of 2, 4 and 6 cm, respectively. The analysis of patients' scout scans showed miscentering of 2.2 cm in average below the isocenter. An average increase of 23% and 7% was observed for patient dose and image noise, respectively. The maximum variation in patient miscentering derived from the comparison of imaging centers using the same scanner was 1.6 cm. Patient miscentering may substantially increase surface dose and image noise. Therefore, technologists are strongly encouraged to pay greater attention to patient centering.

Idiopathic hypertrophic subaortic stenosis and aortic regurgitation in an 84-year-old man.

During the ninth decade of life, idiopathic hypertrophic subaortic stenosis (IHSS), particularly when associated with other cardiac disorders, presents a confusing clinical problem. Unless the physician has a high index of suspicion, the diagnosis is easily overlooked, and consequently inappropriate management of the patient may lead to serious complications. One such case in an 84-year-old man is described. Administration of certain drugs may only intensify symptoms. Echocardiography is invaluable for diagnosis. Pertinent clinical features of IHSS in the eighth and ninth age decades are outlined.

ECG changes associated with spontaneous left-sided pneumothorax.

A patient with chronic obstructive pulmonary disease had a 100% pneumothorax on the left side associated with marked ECG changes. The changes occurring in this situation can be confusing. Because of the high prevalence of coronary heart disease in patients presenting with left-sided chest pain, an ECG usually is obtained to rule out acute myocardial infarction, in many instances even before history taking, physical examination, or chest x-ray study is done. Therefore, familiarity with the ECG manifestations of left-sided penumothorax is necessary to avoid delay in establishing the diagnosis and in beginning therapy.

Left atrial thrombus despite anticoagulant therapy in a patient with a mitral valve prosthesis.

Massive left atrial thrombus (MLAT) developed in a patient with porcine heterograft mitral valve, left atrial dilatation, and atrial fibrillation, despite anticoagulant therapy with warfarin sodium (Coumadin). The thrombus obstructed the mitral valve orifice, leading to acute myocardial infarction, pulmonary edema, and death due to cardiogenic shock.

Cardiac arrhythmia and hypopotassemia in association with lithium carbonate overdose.

Cardiac arrhythmia and electrolyte disturbances can occur as a complication of toxic serum levels of lithium salts. In this report, the development of sinus bradycardia and idioventricular rhythm with severe hypokalemia following an overdose ingestion of lithium carbonate was presented. Possible mechanisms and precautionary measures were discussed.