The aim of this article is to assess Tamil Nadu pediatric computed tomography (CT) diagnostic reference levels (DRLs) by collecting radiation dose data for the most commonly performed CT examinations. This work was performed for thirty CT scanners installed in various parts of the Tamil Nadu region. The patient cohort was divided into two age groups: <1 year, and 1-5 years. CT dose indices were measured using a 10 cm3 pencil ion chamber with pediatric head and body polymethyl methacrylate phantoms. Dose data such as volumetric CT dose index (CTDIv) and dose length product (DLP) on a minimum of twenty average-sized pediatric patients in each category were recorded to calculate a mean site CTDIv and DLP value. The rounded 75th percentile was used to calculate a pediatric DRL for each hospital, and then region by compiling all results. Data were collected for 3600 pediatric patients. Pediatric CT DRL for two age groups: <1 year (CTDIv and DLP of head [20 mGy, 352 mGy.cm], chest [7 mGy, 120 mGy.cm] and abdomen [12 mGy, 252 mGy.cm]), and 1-5 years (CTDIv and DLP of head [38 mGy, 505 mGy.cm], chest [8 mGy, 132 mGy.cm] and abdomen [14 mGy, 270 mGy.cm]) for select procedures have been calculated. Proposed pediatric DRLs of CTDIv and DLP for head procedure were lower, and for chest and abdomen procedures were higher than European pediatric DRLs for both age groups.

Background: To suggest South India CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations. Materials and Methods: A pilot study investigated the most frequent CT examinations. 110 CT sites were asked to complete a survey booklet to allow the recording of CT parameters for each of 3 CT examinations during a 1 year time period. Dose data such Volumetric Computed Tomography Dose Index (CTDIv) and Dose length product (DLP) on a minimum of 50 average-sized patients in each category were recorded to calculate a mean site CTDIvol and DLP value. The rounded 75th percentile was used to calculate a DRL for each site and the region by compiling all results. Results are compared with international DRL data. Results: Data were collected for 16,500 patients. All equipment had multislice capability (2-256 slices). DRLs are proposed using CTDIvol (mGy) and DLP (mGy.cm) for CT head (47 and 1041 respectively), CT chest (10 and 445 respectively), and CT abdomen (12 and 550 respectively). These values are lower than current DRLs and comparable to other international studies. Wide variations in mean doses are noted across the region. Conclusion: Baseline figures for South India CT DRLs are provided on the most frequently performed CT examinations. It was noted that there was a wide variation in mean doses among the CT scanners used during diagnosis. The differences in CT doses between CT scanner departments as well as identical scanners suggest a large potential for optimization of examinations.

In the present work, a pediatric head and body phantom was fabricated using polymethyl methacrylate (PMMA) at a low cost when compared to commercially available phantoms for the purpose of computed tomography (CT) dosimetry. The dimensions of head and body phantoms were 10 cm diameter, 15 cm length and 16 cm diameter, 15 cm length, respectively. The dose from a 128-slice CT machine received by the head and body phantom at the center and periphery were measured using a 100 mm pencil ion chamber and 150 mm CT dose profiler (CTDP). Using these values, the weighted computed tomography dose index (CTDIw) and in turn the volumetric CTDI (CTDIv) were calculated for various combinations of tube voltage and current-time product. A similar study was carried out using standard calibrated phantom and the results have been compared with the fabricated ones to ascertain that the performance of the latter is equivalent to that of the former. Finally, CTDIv measured using fabricated and standard phantoms were compared with respective values displayed on the console. The difference between the values was well within the limits specified by Atomic Energy Regulatory Board (AERB), India. These results indicate that the cost-effective pediatric phantom can be employed for CT dosimetry.

Sir, The authors in their earlier article[1] had estimated tentatively the diagnostic reference levels (DRL) as the third quartile values of weighted computed tomography dose index (CTDIw), volumetric CTDI (CTDIv), and dose length product (DLP); after a detailed survey of the distribution of dose received by patients during diagnosis using CT scanners located in Puducherry region of South India. The procedure and details of dosimetry using standard head and body phantoms and pencil ionization chamber were fully discussed in that article. The present work is a logical extension of the earlier study, conducted for the Kerala region and was undertaken as part of the establishment and consolidation of DRL values for the southern zone of India, comprising the states of Tamil Nadu,[2] Puducherry, Kerala, Karnataka, and Andhra Pradesh. The importance of establishment of regional DRL values can be gauged from the fact that in advanced countries like US, the mean dose and dose range received by patients in CT examinations has diminished considerably in subsequent years.[3]

Computed Tomography scanner plays a prominent role in diagnosing diseases, injuries and other abnormalities in pediatric patients. For an individual child, the risks of CT are small and the benefit always outweighs the risks when used appropriately. CT system manufacturers have recently implemented a dose display Weighted CT Dose Index on their system's operating consoles in accordance with IEC Standard 60601-2-44. This dose display feature provides a reference dose to CTDI head and body phantoms for any selected head or body scan protocol. However, the displayed CTDIw reference dose always underestimates the actual dose delivered to infants and young children up to about the age of one year. In order to quantify this underestimation. In the current study we developed indigenous pediatric CTDI head, body phantom to suit our average Indian infant size at comparably a low cost. The dimension of the head and body phantom were 10 cm and 16 cm respectively. This simulates the X-ray attenuation of an infant head or body. CT Dose measurements on this phantom were carried out using a calibrated 150mm CT dose profiler with dose profile analyzer software, from RTI Electronics, Sweden. The profiler was calibrated to read the dose in phantom directly. Dose received in the head, body phantom at the centre and periphery was measured by five point method. Using these values weighed computed tomography dose index 29.78 mGy, 15.32 mGy, and 15.32 mGy, for head, chest, and abdomen respectively were calculated. The results of the study have been compared with the estimated console value and are well within the acceptable level approved by Atomic Energy Regulatory Board, India.

Computed tomography (CT) scanner under operating conditions has become a major source of human exposure to diagnostic X-rays. In this context, weighed CT dose index (CTDIw), volumetric CT dose index (CTDIv), and dose length product (DLP) are important parameter to assess procedures in CT imaging as surrogate dose quantities for patient dose optimization. The current work aims to estimate the existing dose level of CT scanner for head, chest, and abdomen procedures in Pudhuchery in south India and establish dose reference level (DRL) for the region. The study was carried out for six CT scanners in six different radiology departments using 100 mm long pencil ionization chamber and polymethylmethacrylate (PMMA) phantom. From each CT scanner, data pertaining to patient and machine details were collected for 50 head, 50 chest, and 50 abdomen procedures performed over a period of 1 year. The experimental work was carried out using the machine operating parameters used during the procedures. Initially, dose received in the phantom at the center and periphery was measured by five point method. Using these values CTDIw, CTDIv, and DLP were calculated. The DRL is established based on the third quartile value of CTDIv and DLP which is 32 mGy and 925 mGy.cm for head, 12 mGy and 456 mGy.cm for chest, and 16 mGy and 482 mGy.cm for abdomen procedures. These values are well below European Commission Dose Reference Level (EC DRL) and comparable with the third quartile value reported for Tamil Nadu region in India. The present study is the first of its kind to determine the DRL for scanners operating in the Pudhuchery region. Similar studies in other regions of India are necessary in order to establish a National Dose Reference Level.