Image quality and dose in computed tomography

Abstract

Radiation exposure to the patient during CT is relatively high, and it is therefore important to optimize the dose so that it is as low as possible but still consistent with required diagnostic image quality. There is no established method for measuring diagnostic image quality; therefore, a set of image quality criteria which must be fulfilled for optimal image quality was defined for the retroperitoneal space and the mediastinum. The use of these criteria for assessment of image quality was tested based on 113 retroperitoneal and 68 mediastinal examinations performed in seven different CT units. All the criteria, except one, were found to be usable for measuring diagnostic image quality. The fulfillment of criteria was related to the radiation dose given in the different departments. By examination of the retroperitoneal space the effective dose varied between 5.1 and 20.0 mSv (milli Sievert), and there was a slight correlation between dose and high percent of "yes" score for the image quality criteria. For examination of the mediastinum the dose range was 4.4-26.5 mSv, and there was no significant increment of image quality at high doses. The great variation of dose at different CT units was due partly to differences regarding the examination procedure, especially the number of slices and the mAs (milli ampere second), but inherent dose variation between different scanners also played a part.

Immediate and Post-Retention Effects of Rapid Maxillary Expansion Investigated by Computed Tomography in Growing Patients

“…As X-ray energy (kilovoltage) decreases, the contrast between structures crossed by the X-ray beam increases. 32,33 With regard to previous reports that used CT images of patients who underwent RME, [18][19][20]34 the present study investigated a notably larger group of patients (17 patients), and observations were recorded both after active expansion and after an adequate period for retention (6 months), thus allowing for reossification and reorganization of the midpalatal sutural tissue. [21][22][23][24] Moreover, all treated subjects received RME therapy before or during the pubertal growth spurt (stages in cervical vertebral maturation from CS1 to CS4).…”

Multidetector CT and Dentascan software: dosimetric evaluation and technique improvement

“…As X-ray energy (kilovoltage) decreases the contrast between the structures crossed by the X-ray beam increases [9,10]. This concept proved to be useful in our experience, as it enabled a marked reduction in the dose administered without affecting image quality.…”

“…This effect is largely exploited in diagnostic imaging performed on babies or children, where a low radiation dose is required [9,10].…”

“…Questo effetto viene agevolmente sfruttato negli esami radiodiagnostici eseguiti su neonati o bambini dove è richiesto un abbassamento della dose di radiazioni fornita [9,10]. Parallelamente, al diminuire dell'energia dei raggi X (voltaggio), aumenta il contrasto tra le diverse strutture attraversate dal fascio di radiazioni [9,10].…”

Improving image accuracy of region‐of‐interest in cone‐beam CT using prior image

“…Dose reduction has been a major concern of radiation medical applications. Reducing patient dose by decreasing the tube current has been suggested by several investigators 1 , 2 , 3 . This approach may increase image noise, which often deteriorates the overall image quality and decreases the image accuracy of the ROI considerably.…”