A study on radiation dose and image quality of chest spectral imaging and conventional CT in anthropomorphic phantom / 中华放射医学与防护杂志

Objective To obtain the parameters of optimal spectral scanning mode in chest spectral CT imaging,radiation doses,image quality,CNR and subjective scores are compared in spectral and conventional scan modes with anthropomorphic chest phantom.Methods An anthropomorphic chest phantom underwent both conventional scan and spectral scan using three different protocols:GSI assist mode (protocol A);GSI mode with mean tube current (protocol B);GSI mode with maximum tube current (protocol C).All above scans were performed with the noise index (NI) as 9 and 11 respectively.The radiation dose was recorded,and the SD values of adipose tissue and muscle tissue of 5 different sections were measured in regions of interest (ROls) to evaluate the image quality.All scans were subjectively scored in 5 score system by two senior radiologists on lung markings and branches with the lung window technique.Results The effective dose (E) values of conventional CT scan and protocols A,B and C were 8.0,8.5,6.2,10.4 and 5.3,5.1,4.3,6.2 mSv.When NI =9,the difference of SD values had statistically significance between conventional scan and protocols A,C (F =4.496,P ＜ 0.05).When NI =11,there was statistically significant difference of SD value between conventional scan and protocols A,B,C (F =8.425,P ＜ 0.05).In conventional chest scan,the difference of SD values was statistically significant between NI =9 and 11 (t =-2.570,P ＜ 0.05),while other protocols had no statistically significant difference (P ＞ 0.05).The difference of CNR and subjective score had no statistically significance in either the same NI different scanning modes or the same scanning mode with different NIs.Conclusions Appropriate spectral scanning mode had no significant difference with conventional CT scanning in radiation dose,yet higher image quality can be obtained.Furthermore,appropriate NI can reduce the radiation dose obviously while the similar image quality was achieved.Considering the two factors,GSI assist mode can achieve balance between radiation dose and image quality.

Comparison of the Usefulness of MDCT (Multidetective Computed Tomogram) in Facial Bone Fractures

PURPOSE: In maxillofacial surgery, proper preoperative diagnosis is very important in achieving good postoperative results. Although conventional CT scans are useful for visual representations of fractures, they cannot provide direct guidance for reconstructing facial bone fractures. However, the recent technology of multislice scanning has brought many clinical benefits to CT images. Direct correlations can be made between preoperative imaging data and operative planning. The aim of the current study is to evaluate the differences between conventional CT and multidetective three-dimensional CT(3D MDCT) measurements in craniofacial deformities. METHODS: From January 2005 to November 2005, MDCT scans of 41 patients were evaluated by comparing them with conventional CT scans. The 3D MDCT images were assessed and reviewed by using a simple scoring system. RESULTS: The 3D MDCT scans offered easy interpretation, facilitated surgical planning, and clarified postoperative results in malar complex fractures, mandibular fractures, and extensive maxillofacial fractures and cranioplasty. However, 3D MDCT images were not superior to conventional CT scans in the diagnosis of blowout fractures. CONCLUSION: In spite of its limitations, the 3D MDCT provided additional and more comprehensive information than the conventional CT for preoperative assessment of craniofacial deformities. Therefore, the 3D MDCT can be a useful tool for diagnosis and systematic treatment planning in craniofacial skeletal deformities.

Accuracy of conventional CT in predicting resectability of cholangiocarcinoma: A retrospective review.

Objective : Cholangiocarcioma is the common malignant bile duct tumor Thailand, particularly in the Northeastern part of the country. Since tumor resection is the curative treatment for Cholangiocarcioma, preoperative imaging plays and important role in evaluating the extension and resectability status of this tumor. This present work was designed to assess the capability of cinventional CT scan in predicting the resectability of Cholangiocarcioma. Materials and methods : Conventional CT of twenty three patients who had pathologically proven Cholangiocarcioma, were retrospectively reviewed between January 2002 and Decem ber 2002. The CT images were interpreted by 2 gastrointestinal radiologists with consensus. Results : The accuracy was 87%, positive predictive value 57% and negative predictive value 100%. Conclusion : CT scan remains and important tool that can provide valuable information regarding the criteria for resectability.