Mean Dose Length Product Values Research Articles

Dual-Layer Detector Head CT to Maintain Image Quality While Reducing the Radiation Dose in Pediatric Patients.

Radiation exposure in the CT diagnostic imaging process is a conspicuous concern in pediatric patients. This study aimed to evaluate whether 60-keV virtual monoenergetic images of the pediatric cranium in dual-layer CT can reduce the radiation dose while maintaining image quality compared with conventional images. One hundred six unenhanced pediatric head scans acquired by dual-layer CT were retrospectively assessed. The patients were assigned to 2 groups of 53 and scanned with 250 and 180 mAs, respectively. Dose-length product values were retrieved, and noise, SNR, and contrast-to-noise ratio were calculated for each case. Two radiologists blinded to the reconstruction technique used evaluated image quality on a 5-point Likert scale. Statistical assessment was performed with ANOVA and the Wilcoxon test, adjusted for multiple comparisons. Mean dose-length product values were 717.47 (SD, 41.52) mGy×cm and 520.74 (SD, 42) mGy×cm for the 250- and 180-mAs groups, respectively. Irrespective of the radiation dose, noise was significantly lower, SNR and contrast-to-noise ratio were significantly higher, and subjective analysis revealed significant superiority of 60-keV virtual monoenergetic images compared with conventional images (all P < .001). SNR, contrast-to-noise ratio, and subjective evaluation in 60-keV virtual monoenergetic images were not significantly different between the 2 scan groups (P > .05). Radiation dose parameters were significantly lower in the 180-mAs group compared with the 250-mAs group (P < .001). Dual-layer CT 60-keV virtual monoenergetic images allowed a radiation dose reduction of 28% without image-quality loss in pediatric cranial CT.

A Comparison of the Mean CTDIvol and DLP Values for Adult Abdominal CT Examination for MTRH, Eldoret Hospital, St. Luke’s Hospital and Mediheal Hospital: A Retrospective Study

Background: Advances in Computed Tomography (CT) have facilitated widespread use of medical imaging while increasing patient lifetime exposure to ionizing radiation. In Kenya we use the international DRLs as our point of reference and so far, no regional protocols for abdominal CT scan have been adopted. This study endeavors to form a basis for dose reference levels protocols for abdominal CT scan in Uasin Gishu County. Objective: To compare the mean CTDIvol and DLP values for adult abdominal CT examination for MTRH, Eldoret Hospital, St. Luke’s Hospital and Mediheal Hospital. Methods: This was a retrospective review of CT scans of 700 adult patients conducted in Uasin Gishu healthcare system at MTRH, Eldoret Hospital, Mediheal Hospital and St. Luke’s Hospital in a period of 1 year in the year 2021 using systematic and consecutive sampling. The Volumetric CT-dose index (CTDIvol) and dose length product (DLP) length from CT abdominal scans for the adults were collected from the various CT scans dose tracking software’s. Results: The mean age of patients who underwent CT abdominal scans was 52 years with majority being females at 53 %. The mean CTDIvol was 81. (SD=22.2) and the mean DLP values was 1699.1 (SD=1053.1). Comparison by scan model demonstrated the median for the Total DLP and for the CTDIvol significantly differed by the model with the median for the Neusoft model being highest at 2538 mGy.cm and 10.3mGy respectively while those for the Siemens were the lowest for the two markers at 1318.5 mGy.cm for the DLP and 5.39mGy respectively. These findings were statistically significant with a p value of &lt; 0.001. Comparison by the type of facility showed that the median DLP and CTDIvol values were significantly higher in the public facilities at 1668.8mGy.cm and 6.3mGy respectively when compared to private facilities at 1282.4mGy.cm and 5.9mGy with a p value of &lt;0.001. The Local Dose reference level (LDRL) was set as the median value for CTDIVOL and DLP at 6.1mGy and 1465 mGy.cm respectively. Conclusions: The LDRLs for the patients undergoing abdominal CT examination in Uasin Gishu healthcare system were markedly lower than the regional and the international values for the same abdominal CT examination.

Statistical study for Radiation Dose Reference levels of Adult Computer Tomography Abdominal studies in Eldoret Kenya

Objective: To establish dose reference levels for the adult abdominal CT scan modality at MTRH, Eldoret Hospital, St. Luke’s Hospital and Medi heal Hospital in reference to the international DRLs. Methods: A retrospective study, reviewed CT scans of 700 adult patients conducted in the 4 health institutions from Uasin Gishu healthcare system in a period of 1 year in the year 2021 using systematic and consecutive sampling. The Volumetric CT-dose index (CTDIvol) and dose length product (DLP) length from the various adult CT abdominal scans were obtained. Results: The mean CTDIvol was 8.1 (22.2) and the mean DLP values was 1699.1 (1053.1). Comparison by scan model it was observed that the median for the Total DLP and for the CTDIvol significantly differed by the model with the median for the Neusoft model being highest at 2538 mGy.cm and 10.3mGy respectively while those for the Siemens were the lowest for the two markers at 1318.5 mGy.cm for the DLP and 5.39mGy respectively. These findings were statistically significant with a p value of &lt; 0.001. Comparison by the type of facility it was observed that the median DLP and CTDIvol values were significantly higher in the public facilities at 1668.8mGy.cm and 6.3mGy respectively when compared to private facilities at 1282.4mGy.cm and 5.9mGy with a p value of &lt;0.001.The Local Dose reference level (LDRL) was set as the median value for CTDIVOL and DLP at 6.1mGy respectively. Conclusions: The LDRLs for the adult patients undergoing abdominal CT examination in Uasin Gishu healthcare system were markedly lower than the regional and the international values for the same abdominal CT examination.

CT dose management for neurologic events in patients with cardiac devices: Radiation exposure variation in patients with cardiac devices.

To compare the inter-center cranial computed tomography (CT) acquisition rates, CT findings, CT related radiation dose, and variability of CT acquisition parameters for neurologic events among patients with implantable cardioverter-defibrillator (ICD) or left ventricular assist device (LVAD). A total of 224 patients [ICD group (n = 155) and LVAD group (n = 69)] who had at least one cranial CT scan were enrolled from three medical centers. The variability and effect of the number, indication, and findings of cranial CT scans as well as CT acquisition parameters including tube potential, tube current, tube rotation time (TI), slice collimation (cSL), and spiral or sequential scanning techniques on CT dose index volume (CTDIvol), total dose length product (DLP) were analyzed. The mean DLP value of Center A and mean CTDIvol values of Center A and C were significantly lower than Center B (p < 0.001). The mean CTDIvol and DLP values in the ICD group were substantially lower than the LVAD group (p<0.001). The most potent parameters causing the changes in CTDIvol and DLP were kV, mAs values, and CT scanning technique as sequential or spiral according to multivariate linear regression analysis. Cranial CT acquisition parameters and radiation doses vary significantly between centers, which necessitates optimization of cranial CT protocols to overcome the cumulative radiation dose burden in patients with neurologic events.

Retrospective review of CT brain image quality, diagnostic adequacy and radiation dose in a paediatric population imaged at a non-paediatric tertiary hospital.

Minimising radiation exposure in paediatric imaging examinations whilst maintaining acceptable diagnostic quality continues to present a challenge. The aims of this study were to assess institutional compliance of paediatric CT brain (CTB) examinations performed in an adult hospital with ARPANSA radiation dose recommendations and to compare qualitative CTB diagnostic acceptability with objective imaging parameters and radiation dose. A retrospective review of 115 consecutive paediatric CTB examinations was undertaken at an adult tertiary referral centre in Australia over a 2-year period. Dose length product (DLP) was compared with the ARPANSA standards. CTB image quality was subjectively classified by two neuroradiologists independently, with discordant results resolved by consensus. Objective assessment of image quality included measurements of signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of grey and white matter. All patient scans complied with ARPANSA DLP recommendations; however, 10 out of 115 scans were classified as being of diagnostically suboptimal image quality. These scans had significantly lower mean DLP values compared with diagnostically adequate examinations (105.1 vs 379.2 mGy.cm; P<0.0001). CTB scans of adequate diagnostic quality, when compared to suboptimal scans, had significantly higher CNR (1.8 vs 1.1; P<0.0001) and SNR in grey (7.1 vs 4.6; P<0.0001) and white matter (5.6 vs 3.8; P<0.0001). All CTB examinations in this series complied with the ARPANSA DLP recommendations; however, 9% were of suboptimal diagnostic image quality. While it is important to minimize unnecessary radiation exposure, our results suggest that excessively low DLP values can lead to suboptimal diagnostic image quality.

An audit of patient radiation in low-dose CT pulmonary angiography

ObjectivesAssesment of radiation dose implementing low-dose CTPA protocols. MethodRetrospective analysis of radiation dose in two groups of adult patients, who underwent CECT chest and who were scanned by low-dose CTPA protocol from April 2014 to June 2015. Dose reduction techniques in CTPA included low kVp and iterative reconstruction.The values for CT dose index/volume and the dose-length product (DLP) were available from patients’ information sheet. Effective dose (ED) was calculated by multiplying DLP by body-specific conversion factor, k factor, 0.014.Statistical analysis using SPSS 16 was done for mean DLP, ED as well as paired T-test for comparison of groups. ResultsDLP for CECT chest protocol was 218mGycm. Mean DLP value when applying low-dose CTPA technique was 166.2mGycm. The ED from CECT chest protocol was 1.6–6.3mSv, while using low-dose CTPA protocol it ranged from 1.2 to 4.3mSv.Statistically significant reduction of 23% of mean effective dose was achieved in Group 2. P value is less than 0.01. ConclusionsLow-dose CTPA protocol results in ED values that are significantly lower than CECT chest protocol and within accepted range for international radiation dose of CTPA.

Experiences of using a commercial dose management system (GE DoseWatch) for CT examinations.

To assess the use of a commercial dose management system (GE DoseWatch; GEMS, Milwaukee, WI) for CT dose management for six common CT examinations. Data were acquired over several months using GE DoseWatch for six common CT examinations on three CT scanners. The dose length product (DLP) was taken as the dose indicator. The data were analysed using four different filtering methods: study description, the National Interim Clinical Imaging Procedure code, protocol name and a more detailed filtering method (the reference data set). The filtering methods were compared using an analysis of variance and multiple comparison technique. The different scanners were compared using the reference data set. It was found that integrating DoseWatch with the radiology information system provided improved results compared with using the study description. Filtering by study description was found to be a poor indicator of the mean dose for all three scanners and consistently overestimated (p < 0.05) the head and thorax-abdo-pelvis mean DLP values, despite the large sample sizes. Filtering by the National Interim Clinical Imaging Procedure code or protocol name produced mean DLPs which were not statistically different from the reference data. The scanner intercomparison showed some significant differences between the scanners, usually due to different tube current modulation settings. The use of a commercial dose monitoring system provided fast and efficient filtering of substantial amounts of data. The filtering method affected the mean DLP value despite large sample sizes. Dose management systems are relatively new in the UK, and this article shares knowledge on the use of one system.

Establishment of diagnostic reference levels in computed tomography for paediatric patients in Sudan: a pilot study.

Paediatric patients are recognised to be at higher risk of developing radiation-induced cancer than adults. The purpose of this pilot study was to evaluate the radiation doses to paediatric patients during computed tomography (CT) procedures in order to propose local diagnostic reference levels (DRLs). A total of 296 patients (aged 6-10 y) were investigated in 8 hospitals equipped with 64-, 16- and dual-slice CT machines. The mean dose length product values were 772, 446 and 178 mGy cm for head, abdomen and chest, respectively. Imaging protocols were not adapted to the patient's weight in certain CT machines. The results confirmed that paediatric patients are exposed to an unnecessary radiation dose. The established DRLs were higher than those available in other countries. This study showed the need for harmonisation of the practice in CT departments and radiation dose optimisation.

An education and training programme for radiological institutes: impact on the reduction of the CT radiation dose

To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy. Ten radiological institutes were counselled. The optimisation programme included a small group workshop and a lecture on radiation dose reduction strategies. The radiation dose used for five CT protocols (paranasal sinuses, brain, chest, pulmonary angiography and abdomen) was assessed using the dose-length product (DLP) before and after the optimisation programme. The mean DLP values were compared with national diagnostic reference levels (DRLs). The average reduction of the DLP after optimisation was 37% for the sinuses (180 vs. 113 mGycm, P < 0.001), 9% for the brain (982 vs. 896 mGycm, P < 0.05), 24% for the chest (425 vs. 322 mGycm, P < 0.05) and 42% for the pulmonary arteries (352 vs. 203 mGycm, P < 0.001). No significant change in DLP was found for abdominal CT. The post-optimisation DLP values of the sinuses, brain, chest, pulmonary arteries and abdomen were 68%, 10%, 20%, 55% and 15% below the DRL, respectively. The education and training programme for radiological institutes is effective in achieving a substantial reduction in CT radiation dose.

Towards dose reduction in CT: patient radiation dose assessment for CT examinations at university health center in Canada and comparison with national diagnostic reference levels

Dose indicators such as the computed tomography dose index (CTDI) and dose-length product (DLP) were gathered for all routine abdomen-pelvis, chest and head examinations performed on all computed tomography (CT) scanners at a University Health Center (UHC) in Canada. These indicators were analysed and compared with the range of diagnostic reference levels (DRLs) suggested by Health Canada and with DRLs in other countries. Mean DLP values varied from one scanner to another, but mean values at the UHC (750 mGy cm(-1) for abdomen-pelvis CT, 349 mGy cm(-1) for chest CT and 1181 mGy cm(-1) for head CT) were all below the upper limit of the range of DRLs suggested by Health Canada. Local DRLs at the UHC were set to 810 mGy cm(-1) for abdomen-pelvis CT, 345 mGy cm(-1) for chest CT and 1205 mGy cm(-1) for head CT. Results, however, show the need for protocols revisions, since some scanners exhibit mean DLP values slightly below or above the upper limit of the range of DRLs suggested by Health Canada.

Quality criteria implementation for brain and lumbar spine CT examinations.

A study was undertaken to implement the quality criteria proposed by the European Commission for brain general and lumbar spine (disc herniation) CT examinations. The proposed criteria were evaluated for samples including 93 brain and 86 lumbar spine CT examinations, with special emphasis on the diagnostic and radiation dose requirements. The extent to which the image criteria had been achieved was evaluated after two independent observers had each read the images twice. Dose measurements were conducted in parallel to estimate the proposed dose quantities needed to obtain the images. For brain examinations, we found that a group of image criteria were largely met, and met uniformly in all sites. One criterion (1.2.5) was frequently fulfilled but had intermediate values for two sites; the remaining criteria were fulfilled to different extents, although for criteria 1.2.1 and 1.2.2, scores were lower than 50% and 70%, respectively. The mean percentage image quality score had values between 57% and 78%, with variation coefficients in the range 30-68%. Mean values of the dose quantities were in the ranges 44-74 mGy for weighted CT dose index (CTDIw), 497-1018 mGy cm for dose-length product (DLP) and 1.1-2.2 mSv for effective dose (E). CTDIw and DLP were not correlated because of significant variations in the scanned length, whereas DLP and E were strongly correlated. A weak relationship between image quality score and DLP was found for the sample as a whole. For lumbar spine examinations, none of the critical reproduction image criteria was systematically achieved. One group of criteria (1.2.7, 1.2.8 and 1.2.9) was fulfilled to a large extent in many departments, but fulfilment of the remainder varied widely. The mean score fluctuated in the range 39-88%, with three groups of differences: low (39-51%), intermediate (67-71%) and high (85-88%). Mean values of the CTDIw varied between sites in the range 27-48 mGy. Mean DLP values varied between 188 mGy cm and 333 mGy cm, and the mean effective dose ranged between 3 mSv and 5 mSv. There were significant differences in effective dose between men and women. By sites, there was no relationship between DLP and mean score, with the highest image score associated with intermediate dose values. The percentage disagreement among the observers about a given criterion ranged between 2% and 22% for brain, and between 3% and 46% for lumbar spine.