Low dose computed tomography scan in paranasal sinusitis, is it sufficient?

Background: Computed tomography (CT) has become a useful diagnostic modality in evaluation of the paranasal sinuses & an integral part of surgical planning. Because of the high inherent contrast in the paranasal sinuses and nasal cavity, a low-dose technique can be used. Aim of study: to compare anatomical diagnostic image value assessment of low dose and standard dose protocol of computed tomography scanning of paranasal sinuses based on subjective assessment. Patients and methods: A prospective study was done in Baghdad teaching hospital and X-Ray institute over a period of 11 months. A group of 100 patients referred from ear, nose and throat outpatient clinic with clinically suspected sinusitis were examined by low dose (milliampere second (mAs= 30) and standard dose (mAs=100) protocol sinus CT scan, each patient was examined in the same day, after obtaining their oral consent. The patient was examined in supine position using 64 slice multidetector computed tomography (MDCT). Scans were reviewed by three experienced radiologists independently to evaluate image quality and important anatomical structures, using both soft tissue and bone window algorithms. These criteria were scored and the scores were added together to achieve an overall quality rating. Results: According to image quality scoring & relevant anatomic landmarks scoring, all the findings and all the structures in both groups were well defined. On evaluating the mucosa of the paranasal sinuses, normal and pathologic mucosal structures were scored as very well defined in all of the patients. The interobserver agreement was excellent. Conclusion: Further reduction of tube current (mAs) in CT scanning of paranasal sinuses in uncomplicated sinusitis is thought to be possible without reduction in diagnostic quality of the images. The radiation dose has been reduced by 70% by using lose dose protocol.