Patient Weight and Cross-Sectional Dimensions versus Subjective Image Quality at Standard Abdominal CT sions from CT images, these measurements can be easily obtained prior to CT scan with a measuring tape or caliper. Alternatively, these dimensions may be measured on the scout images or a cross-sectional image obtained at a pre- determined level. In addition, a lesser degree of correlation between weight and image quality was found in comparison with transverse diameter, circumference, cross-sectional area and root-mean-square dimension of abdomen. This obser- vation supports the findings reported by Han et al. that ab- dominal fat distribution was more accurately related to the waist circumference than body mass index (18). Furthermore, lesser degree of negative statistical correla- tion between image quality and average anterior abdomi- nal wall fat thickness observed in our study may be ex- plained on the basis of CT evaluation of abdominal fat de- pots reported by Seidell et al. (19). These investigators had documented that intra-abdominal fat area best correlated with the waist circumference while it showed weaker asso- ciations with abdominal skin-fold thickness. In concor- dance with this report, our findings suggest that anterior abdominal wall fat thickness may not be truly representa- tive of total abdominal fat and thus cannot be used as accu- rately to predict CT image quality at given scanning para- meters. Overall, while our data do establish significant negative correlation between abdominal dimensions and image quality, there are some internal variations within our data. There were two patients in our study that had “thin” ab- dominal dimensions (abdominal circumference less than 28-cm) but poor subjective image quality score. Conversely, two patients with abdominal circumference more than 28-cm had better image quality score. These contradictory observations may be explained by the previ- ously described fact that fat enhances tissue contrast and sharpness. Some images with more fat, despite increased thickness, were in fact found to have higher image quality scores despite the beam hardening artifacts and noise, pos- sibly due to greater tissue contrast and sharpness apprecia- tion. For the same reason, images of some patients with less fat were found qualitatively less acceptable because of decreased tissue contrast and sharpness. This explains why we found less than perfect correlation between subjective image quality and other dimensions of the patients. This finding stresses the need for greater emphasis on objective measurement of image quality for radiation dose optimiza- tion as increase in radiation to patients would not necessar- ily lead to enhanced diagnostic efficacy of the study. There are several limitations of our study. Considering the implications of the study, our sample size was relative- ly small especially for patients with greater abdominal di- Korean J Radiol 4(4), December 2003 mensions. Therefore, results of our study may not reflect overall patient population. The statistical results may have been affected by inhomogeneous patient distribution be- tween different sets of abdominal measurements. In addi- tion, we acquired the images in equilibrium phase of con- trast enhancement and the results may not be valid for the dynamic phase imaging. Objective parameters of image quality and relation of these parameters with cross-section- al dimensions of patients were not evaluated in our study. In addition, our data show that there is less than perfect statistical correlation between image quality and anthropo- metric parameters and in some patients “spurious” results of image quality were obtained for these anthropometric parameters. This suggests that in some patients modulation of scanning parameters based on these parameters may not give optimum and desired image quality. In conclusion, our study shows that there is good correla- tion between cross-sectional dimensions and subjective im- age quality. Further investigations should determine whether these dimensions can be used to optimize scan- ning protocols in individual patients based on body habitus and reduce radiation dose to patient population without significant compromise in image quality. Of the cross-sec- tional dimensions evaluated, maximum transverse diame- ter of abdomen is the most accurate predictor of image quality. These studies should, therefore, address feasible means of measuring maximum transverse abdominal diam- eter that will be acceptable in a typical busy daily CT schedule. References 1. Brenner DJ, Elliston CD, Hall EJ, Berdon W. Estimated risks of radiation-induced fatal cancer from pediatric CT. 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