A patient-centric approach to quality control and dosimetry in CT including CBCT

One measurement and an algebraic formula are used to calculate the incident air kerma (K_a,i) at the skin after any CT examination, including cone-beam CT (CBCT) and multi-slice CT (MSCT).Empty scans were performed with X-ray CBCT systems (dental, C-arm and linac guidance scanners) as well as two MSCT scanners. The accumulated K_a,i at the flat panel (in CBCT) or the maximum incident air kerma at the isocentre (in MSCT) were measured using a solid-state probe. The average K_a,i(skin), at the skin of a hypothetical patient, was calculated using the proposed formula. Additional measurements of dose at the isocentre (D_FOV) and kerma-area product (KAP), as well as K_a,i(skin) from thermoluminiscence dosimeters (TLDs) and size-specific dose estimates are presented for comparison.The K_a,i(skin) for the standard head size in the dental scanner, the C-arm (high dose head protocol) and the linac (head protocol) were respectively 3.33 ± 0.19 mGy, 15.15 ± 0.76 mGy and 3.23 ± 0.16 mGy. For the first MSCT, the calculated K_a,i(skin) was 13.1 ± 0.7 mGy and the TLDs provided a K_a,i(skin) between 10.3 ± 1.1 mGy and 13.8 ± 1.4 mGy.Estimation of patient air kerma in tomography with an uncertainty below 7% is thus feasible using an empty scan and conventional measurement tools. The provided equations and website can be applied to a standard size for the sake of quality control or to several sizes for the definition of diagnostic reference levels (DRLs). The obtained incident air kerma can be directly compared to the K_a,i from other X-ray modalities as recommended by ICRU and IAEA.     

Local diagnostic reference levels for intraoral dental radiography in the public hospitals of Cyprus

PurposeThe purpose of this study was to determine local DRLs for children and adults undergoing intraoral dental examinations at the intraoral radiology units of the public hospitals in Cyprus.MethodsMeasurements were made on all the twenty intraoral X-ray units of the public hospitals in Cyprus with the intention to establish the local DRLs for all the possible intraoral X-ray examinations for children and adults. All units are film based. The measurements were made by a Dose Area Product (DAP) meter (GAMMEX RMI 841-RD) placed at the surface of the dental unit’s X-ray shaping cone (FSD 20 cm). A diagnostic radiology dosimeter (Dosimax Plus A) was also placed at an FSD of 100 cm to compare the dose reading between the two dosimeters.ResultsDRLs were established at the 3rd quartile for 7 exposure settings corresponding to 12 types of teeth (Adult and children mandibular and maxillary incisor, premolar and molar) with values of 197, 163, 128, 102, 81, 65 and 49 mGycm⁻² and 7.23, 5.94, 4.75, 3.68, 3.10, 2.41 and 1.88 mGy for benchmark nominal exposure times of 1000, 800, 640, 500, 400, 320 and 250 ms respectively, at a nominal exposure voltage of 70 kVp.ConclusionsThe local DRLs of the present study compare well with other similar published DRLs.     

Establishing national diagnostic reference levels (DRLs) for computed tomography in Egypt

ObjectivesTo establish national diagnostic reference levels (DRLs) in Egypt for computed tomography (CT) examinations of adults and identify the potential for optimization.MethodsData from 3762 individual patient’s undergoing CT scans of head, chest (high resolution), abdomen, abdomen-pelvis, chest-abdomen-pelvis and CT angiography (aorta and both lower limbs) examinations in 50 CT facilities were collected. This represents 20% of facilities in the country and all of the 27 Governorates. Results were compared with DRLs of UK, USA, Canada, Japan, Australia and France.ResultsThe Egyptian DRLs for CTDI_vol in mGy are for head: 30, chest (high resolution): 22, abdomen (liver metastasis): 31, abdomen-pelvis: 31, chest-abdomen–pelvis: 33 and CT angiography (aorta and lower limbs): 37. The corresponding DRLs for DLP in mGy.cm are 1360, 420, 1425, 1325, 1320 and 1320. For head CT, the Egyptian DRL for CTDI_vol is 2–3 times lower than the DRLs from other countries. However, the DRL in terms of DLP is in the same range or higher as compared to others. The Egyptian DRL for chest CT (high resolution) is similar to others for DLP but higher for CTDI_vol. For abdomen and abdomen-pelvis DRLs for CTDI_vol are higher than others. For DLP, the DRLs for abdomen are higher than DRL in UK and lower than those in Japan, while for abdomen-pelvis they are higher than other countries.ConclusionDespite lower DRLs for CTDI_vol, an important consistent problem appears to be higher scan range as DRLs for DLP are higher.     

Web-based platform for patient dose surveys in diagnostic and interventional radiology in Bulgaria: Functionality testing and optimisation

In the period 2013–2016 the National Centre of Radiobiology and Radiation Protection (NCRRP) at the Ministry of Health of Bulgaria has developed a web based platform for performing national patient dose surveys and establishing Diagnostic Reference Levels (DRLs). It is accessible via internet browser, allowing the users to submit data remotely. Electronic questionnaires, specific for radiography, fluoroscopy, image guided interventional procedures, mammography and CT, were provided. Short and clear manuals were added to guide users and minimise human errors. The web-based data collection platform is functional and is currently being used for performing the third national dose survey in Bulgaria, launched in 2016. Data analysis is facilitated due to the standardisation of collected data and their storing. Using the platform, the participating facilities can establish their typical dose levels based on the median value, and compare them to DRLs. A disadvantage of the platform is the need to enter data manually, but it is opened for future upgrades for automatic data harvesting and analysis. Various practical approaches were used to overcome the lack of qualified human resources and insufficient understanding of the DRL and dose tracking concept and to motivate facilities to submit data.