Dual-energy computed tomography quality control: Initial experiences with a semi-automatic analysis tool.

PURPOSE: A quality control (QC) system for dual-energy CT (DECT) was developed. The scope of the QC system was to monitor both the constancy of the CT images and the software used in calculating the DECT derived maps. Longitudinal analysis was based on a standard imaging protocol, a commercial multi-energy phantom, and a semi-automatic analysis tool. METHODS: The phantom consisted of an elliptical body section with round slots for interchangeable inserts. It was scanned with 90kVp/Sn150kVp, automatic tube current modulation, and 9.6 mGy CTDIvol. From the two conventional CT images, scanner manufacturer's software was used to provide virtual monoenergetic images at two different energies, effective atomic number (Zeff) maps, and iodine concentration maps. The images were analyzed using an open-source tool allowing user-selected statistics of interest. The means and standard deviations of the phantom background and the iodine, calcium, and water inserts were recorded. The QC tool is available at github.com/tomakela/dectqatool. RESULTS: The obtained results were generally highly consistent over time, except for the smaller diameter iodine inserts. A small change inZeff was observed after a DECT software update. The developed QC tool aided the analysis robustness: the segmentations were modifiable when needed, and small rotations or air bubbles in the water insert were easily corrected. CONCLUSION: The developed QC system provided easy-to-use workflow for constancy measurements. A small deviation due to change in the post-processing was detected. The proposed imaging protocol and analysis steps, and the reported measurement variations can aid in determining action levels for DECT QC.

Effect of varying displays and room illuminance on caries diagnostic accuracy in digital dental radiographs.

In clinical practice, digital radiographs taken for caries diagnostics are viewed on varying types of displays and usually in relatively high ambient lighting (room illuminance) conditions. Our purpose was to assess the effect of room illuminance and varying display types on caries diagnostic accuracy in digital dental radiographs. Previous studies have shown that the diagnostic accuracy of caries detection is significantly better in reduced lighting conditions. Our hypothesis was that higher display luminance could compensate for this in higher ambient lighting conditions. Extracted human teeth with approximal surfaces clinically ranging from sound to demineralized were radiographed and evaluated by 3 observers who detected carious lesions on 3 different types of displays in 3 different room illuminance settings ranging from low illumination, i.e. what is recommended for diagnostic viewing, to higher illumination levels corresponding to those found in an average dental office. Sectioning and microscopy of the teeth validated the presence or absence of a carious lesion. Sensitivity, specificity and accuracy were calculated for each modality and observer. Differences were estimated by analyzing the binary data assuming the added effects of observer and modality in a generalized linear model. The observers obtained higher sensitivities in lower illuminance settings than in higher illuminance settings. However, this was related to a reduction in specificity, which meant that there was no significant difference in overall accuracy. Contrary to our hypothesis, there were no significant differences between the accuracy of different display types. Therefore, different displays and room illuminance levels did not affect the overall accuracy of radiographic caries detection.

NMR-based metabolomics approach on optimization of malolactic fermentation of sea buckthorn juice with Lactiplantibacillus plantarum.

This work investigated the impact of malolactic fermentation on the metabolomic profile of sea buckthorn juice to optimize the fermentation process for flavor modification. Six strains of L. plantarum were used with varied pH of the juice, cell acclimation, and fermentation time. 1H-NOESY spectra were acquired from fresh and fermented juices with a total of 46 metabolites identified. Less sugars and quinic acid were metabolized at pH 2.7 while oxidation of ascorbic acid was reduced at pH 3.5. l-Malic acid, essential amino acids, and nucleosides were consumed early during fermentation while sugars in general were consumed later in the fermentation. If deacidification is the main target of fermentation, strains that produce less acids and ferment less sugars, shorter fermentation time, and lower starter pH should be used. Higher starter pH and longer fermentation time promote formation of antimicrobial compounds and potentially increase antioxidant stability.

PATIENT-SPECIFIC DOSE ESTIMATES IN DYNAMIC COMPUTED TOMOGRAPHY MYOCARDIAL PERFUSION EXAMINATION.

The study aimed to implement realistic source models of a computed tomography (CT) scanner and Monte Carlo simulations to actual patient data and to calculate patient-specific organ and effective dose estimates for patients undergoing dynamic CT myocardial perfusion examinations. Source models including bowtie filter, tube output and x-ray spectra were determined for a dual-source Siemens Somatom Definition Flash scanner. Twenty CT angiography patient datasets were merged with a scaled International Commission on Radiological Protection (ICRP) 110 voxel phantom. Dose simulations were conducted with ImpactMC software. Effective dose estimates varied from 5.0 to 14.6 mSv for the 80 kV spectrum and from 8.9 to 24.7 mSv for the 100 kV spectrum. Significant differences in organ doses and effective doses between patients emphasise the need to use actual patient data merged with matched anthropomorphic anatomy in the dose simulations to achieve a reasonable level of accuracy in the dose estimation procedure.

Expanding the medical physicist curricular and professional programme to include Artificial Intelligence.

PURPOSE: To provide a guideline curriculum related to Artificial Intelligence (AI), for the education and training of European Medical Physicists (MPs). MATERIALS AND METHODS: The proposed curriculum consists of two levels: Basic (introducing MPs to the pillars of knowledge, development and applications of AI, in the context of medical imaging and radiation therapy) and Advanced. Both are common to the subspecialties (diagnostic and interventional radiology, nuclear medicine, and radiation oncology). The learning outcomes of the training are presented as knowledge, skills and competences (KSC approach). RESULTS: For the Basic section, KSCs were stratified in four subsections: (1) Medical imaging analysis and AI Basics; (2) Implementation of AI applications in clinical practice; (3) Big data and enterprise imaging, and (4) Quality, Regulatory and Ethical Issues of AI processes. For the Advanced section instead, a common block was proposed to be further elaborated by each subspecialty core curriculum. The learning outcomes were also translated into a syllabus of a more traditional format, including practical applications. CONCLUSIONS: This AI curriculum is the first attempt to create a guideline expanding the current educational framework for Medical Physicists in Europe. It should be considered as a document to top the sub-specialties' curriculums and adapted by national training and regulatory bodies. The proposed educational program can be implemented via the European School of Medical Physics Expert (ESMPE) course modules and - to some extent - also by the national competent EFOMP organizations, to reach widely the medical physicist community in Europe.

Organ doses and effective doses in pediatric radiography: patient-dose survey in Finland.

BACKGROUND: Use of the effective dose in diagnostic radiology permits the radiation exposure of diverse diagnostic procedures to be quantified. Fundamental knowledge of patient doses enhances the implementation of the "as low as reasonably achievable" (ALARA) principle. PURPOSE: To provide comparative information on pediatric examination protocols and patient doses in skull, sinus, chest, abdominal, and pelvic radiography examinations. MATERIAL AND METHODS: 24 Finnish hospitals were asked to register pediatric examination data, including patient information and examination parameters and specifications. The total number of examinations in the study was 1916 (1426 chest, 228 sinus, 96 abdominal, 94 skull, and 72 pelvic examinations). Entrance surface dose (ESD) and dose-area products (DAP) were calculated retrospectively or DAP meters were used. Organ doses and effective doses were determined using a Monte Carlo program (PCXMC). RESULTS: There was considerable variation in examination protocols between different hospitals, indicating large variations in patient doses. Mean effective doses of different age groups ranged from 5 microSv to 14 microSv in skull and sinus examinations, from 25 microSv to 483 microSv in abdominal examinations, and from 6 microSv to 48 microSv in chest examinations. CONCLUSION: In chest and sinus examinations, the amount of data was extensive, allowing national pediatric diagnostic reference levels to be defined. Parameter selection in pediatric examination protocols should be harmonized in order to reduce patient doses and improve optimization.

Cone-beam computed tomography: a new method for imaging of the temporal bone.

BACKGROUND: Clinical cone-beam computed tomography (CBCT), used in diagnostics of dental and maxillofacial radiology for almost 10 years, allows three-dimensional (3D) imaging of a focused area, with reasonable radiation dose. PURPOSE: To clarify the applicability of CBCT in imaging of the temporal bone. MATERIAL AND METHODS: We imaged cadaver temporal bones, one non-operated and five postmortem operated, with CBCT to evaluate the accuracy of this method in showing clinically important landmarks and the positions of middle-ear implants. In addition, to clarify the imaging protocols for the best possible result, we conducted a contrast-to-noise ratio (CNR) analysis by imaging a specially built phantom insert with different protocols. RESULTS: For all the temporal bones, image quality was good and of diagnostic value, and the surgical landmarks as well as positions and details of the implants could be accurately observed. Based on measurements conducted with the phantom, the best possible clarity of the images with the machine used (3D Accuitomo; Morita Co., Kyoto, Japan) was achieved with a tube voltage of 80 kVp and a current of 4 mA. CONCLUSION: Cone-beam CT is a promising new method for otologic imaging, based on its accuracy and relatively low radiation exposure per investigation.

CT beam dosimetric characterization procedure for personalized dosimetry.

Personalized dosimetry in computed tomography (CT) can be realized by a full Monte Carlo (MC) simulation of the scan procedure. Essential input data needed for the simulation are appropriate CT x-ray source models and a model of the patient's body which is based on the CT image. The purpose of this work is to develop comprehensive procedures for the determination of CT x-ray source models and their verification by comparison of calculated and measured dose distributions in physical phantoms. Mobile equipment together with customized software was developed and used for non-invasive determination of equivalent source models of CT scanners under clinical conditions. Standard and physical anthropomorphic CT dose phantoms equipped with real-time CT dose probes at five representative positions were scanned. The accumulated dose was measured during the scan at the five positions. ImpactMC, an MC-based CT dose software program, was used to simulate the scan. The necessary inputs were obtained from the scan parameters, from the equivalent source models and from the material-segmented CT images of the phantoms. 3D dose distributions in the phantoms were simulated and the dose values calculated at the five positions inside the phantom were compared to measured dose values. Initial results were obtained by means of a General Electric Optima CT 660 and a Toshiba (Canon) Aquilion ONE. In general, the measured and calculated dose values were within relative uncertainties that had been estimated to be less than 10%. The procedures developed were found to be viable and rapid. The procedures are applicable to any scanner type under clinical conditions without making use of the service mode with stationary x-ray tube position. Results show that the procedures are well suited for determining and verifying the equivalent source models needed for personalized CT dosimetry based on post-scan MC calculations.

Boron detection from blood samples by ICP-AES and ICP-MS during boron neutron capture therapy.

OBJECTIVE: The concept of boron neutron capture therapy (BNCT) involves infusion of a (10)B containing tracer into the patient's bloodstream followed by local neutron irradiation(s). Accurate estimation of the blood boron level for the treatment field before irradiation is required. Boron concentration can be quantified by inductively coupled plasma atomic emission spectrometry (ICP-AES), mass spectrometry (ICP-MS), spectrofluorometric and direct current atomic emission spectrometry (DCP-AES) or by prompt gamma photon detection methods. MATERIAL AND METHODS: The blood boron concentrations were analysed and compared using ICP-AES and ICP-MS to ensure congruency of the results if the analysis had to be changed during the treatment, e.g. for technical reasons. The effect of wet-ashing on the results was studied in addition. RESULTS: The mean of all samples analysed with ICP-MS was 5.8 % lower than with ICP-AES coupled to wet-ashing (R (2) = 0.88). Without wet-ashing, the mean of all samples analysed with ICP-MS was 9.1 % higher than with ICP-AES (R (2) = 0.99). CONCLUSIONS: Boron concentration analysed from whole blood samples with ICP-AES correlated well with the values of ICP-MS with wet-ashing of the sample matrix, which is generally considered the reference method. When using these methods in parallel at certain intervals during the treatments, reliability of the blood boron concentration values remains satisfactory, taking into account the required accuracy of dose determination in the irradiation of cancer patients.

Automatic image quality quantification and mapping with an edge-preserving mask-filtering algorithm.

BACKGROUND: Imaging modalities in digital radiology produce large amounts of data for which image quality should be determined in order to validate the diagnostic operation. PURPOSE: To develop an automatic method for image quality assessment. MATERIAL AND METHODS: A filtering algorithm using a moving square mask was applied to create a map of filtered local intensity and noise values. Image quality scores were calculated from the filtered image data. The procedure was applied to technical and anthropomorphic (radiosurgery verification phantom [RSVP] head) phantom images obtained with varying radiation dose, field of view (FOV), and image content. The method was also applied to a clinical computed tomography (CT) brain image. RESULTS: The image quality score (IQs) of the phantom images increased from 0.51 to 0.82 as the radiation dose (CTDIvol) increased from 9.2 to 74.3 mGy. Correlation of the IQs with the pixel noise was R(2)=0.99. The deviation (1 SD) of IQs was 2.8% when the reconstruction FOV was set between 21 and 25 cm. The correlation of IQs with the pixel noise was R(2)=0.98 with variable image contents and dose. Automatic tube current modulation applied to the RSVP phantom scan reduced the variation in the calculated image quality score by about 60% compared to the use of a fixed tube current. CONCLUSION: The image quality score provides an efficient tool for automatic quantification of image quality. The presented method also produces a 2D image quality map, which can be used for further image analysis.

Fetal radiation dose in three common CT examinations during pregnancy - Monte Carlo study.

PURPOSE: To determine fetal doses in different stages of pregnancy in three common computed tomography (CT) examinations: pulmonary CT angiography, abdomino-pelvic and trauma scan with Monte Carlo (MC) simulations. METHODS: An adult female anthropomorphic phantom was scanned with a 64-slice CT using pulmonary angiography, abdomino-pelvic and trauma CT scan protocols. Three different sized gelatin boluses placed on the phantom's abdomen simulated different stages of pregnancy. Intrauterine dose was used as a surrogate to a dose absorbed to the fetus. MC simulations were performed to estimate uterine doses. The simulation dose levels were calibrated with volumetric CT dose index (CTDIvol) measurements and MC simulations in a cylindrical CTDI body phantom and compared with ten point doses measured with metal-oxide-semiconductor field-effect-transistor dosimeters. Intrauterine volumes and uterine walls were segmented and the respective dose volume histograms were calculated. RESULTS: The mean intrauterine doses in different stages of pregnancy varied from 0.04 to 1.04mGy, from 4.8 to 5.8mGy, and from 9.8 to 12.6mGy in the CT scans for pulmonary angiography, abdomino-pelvic and trauma CT scans, respectively. MC simulations showed good correlation with the MOSFET measurement at the measured locations. CONCLUSIONS: The three studied examinations provided highly varying fetal doses increasing from sub-mGy level in pulmonary CT angiography to notably higher levels in abdomino-pelvic and trauma scans where the fetus is in the primary exposure range. Volumetric dose distribution offered by MC simulations in an appropriate anthropomorphic phantom provides a comprehensive dose assessment when applied in adjunct to point-dose measurements.

Radiation exposure in body computed tomography examinations of trauma patients.

Multi-slice CT provides an efficient imaging modality for trauma imaging. The purpose of this study was to provide absorbed and effective dose data from CT taking into account the patient size and compare such doses with the standard CT dose quantities based on standard geometry. The CT examination data from abdominal and thoracic scan series were collected from 36 trauma patients. The CTDI(vol), DLP(w) and effective dose were determined, and the influence of patient size was applied as a correction factor to calculated doses. The patient size was estimated from the patient weight as the effective radius based on the analysis from the axial images of abdominal and thoracic regions. The calculated mean CTDI(vol), DLP(w) and effective dose were 15.2 mGy, 431 mGy cm and 6.5 mSv for the thorax scan, and 18.5 mGy, 893 mGy cm and 14.8 mSv for the abdomen scan, respectively. The doses in the thorax and abdomen scans taking the patient size into account were 34% and 9% larger than the standard dose quantities, respectively. The use of patient size in dose estimation is recommended in order to provide realistic data for evaluation of the radiation exposure in CT, especially for paediatric patients and smaller adults.

1H MRS studies in the Finnish boron neutron capture therapy project: detection of 10B-carrier, L-p-boronophenylalanine-fructose.

This article summarizes the current status of 1H MRS in detecting and quantifying a boron neutron capture therapy (BNCT) boron carrier, L-p-boronophenylalanine-fructose (BPA-F) in vivo in the Finnish BNCT project. The applicability of 1H MRS to detect BPA-F is evaluated and discussed in a typical situation with a blood containing resection cavity within the gross tumour volume (GTV). 1H MRS is not an ideal method to study BPA concentration in GTV with blood in recent resection cavity. For an optimal identification of BPA signals in the in vivo 1H MR spectrum, both pre- and post-infusion 1H MRS should be performed. The post-infusion spectroscopy studies should be scheduled either prior to or, less optimally, immediately after the BNCT. The pre-BNCT MRS is necessary in order to utilise the MRS results in the actual dose planning.

Conformance of mean glandular dose from phantom and patient data in mammography.

In mammography dosimetry, phantoms are often used to represent breast tissue. The conformance of phantom- and patient-based mean glandular dose (MGD) estimates was evaluated mainly from the aspect of diagnostic reference levels. Patient and phantom exposure data were collected for eight diagnostic and three screening mammography devices. More extensive assessments were performed for two devices. The average breast thickness was close to the nationally used reference of 50 mm in diagnostic (50 mm, SD = 13 mm, n = 5342) and screening (47 mm, SD = 13 mm, n = 395) examinations. The average MGD for all breasts differed by 2% from the MGD determined for breasts in the limited compressed thickness range of 40-60 mm. The difference between phantom- and patient-based MGD estimations was up to 30%. Therefore, phantom measurements cannot replace patient dose data in MGD determination.

Indication-based national diagnostic reference levels for paediatric CT: a new approach with proposed values.

Indication-based national diagnostic reference levels (DRLs) for a few most common paediatric computed tomography (CT) examinations are proposed. Patient dose data (CTDI vol and dose length product) were collected for over 1000 patients in 4 university hospitals with best experiences in paediatric CT. Four indications for chest CT and two for abdomen (abdomen + pelvis), chest + abdomen and head CT were considered. The DRLs for the body examinations are proposed as exponential DRL-curves, where CTDI vol and dose length product are presented as a function of patient weight. The same DRL curve applies to all the indications studied. The basic 75 % level curve is supplemented by 50 % level curve to enable considerations on varying levels of technology. For head CT, DRLs are proposed for a few age groups (1, 1-5, 5-10 and 10-15 y), separately for routine CT and CT for ventricular size. The proposed DRLs are generally lower than the few published DRLs in other countries.

Models for estimation of the (10)B concentration after BPA-fructose complex infusion in patients during epithermal neutron irradiation in BNCT.

PURPOSE: To create simple and reliable models for clinical practice for estimating the blood (10)B time-concentration curve after p-boronophenylalanine fructose complex (BPA-F) infusion in patients during neutron irradiation in boron neutron capture therapy (BNCT). METHODS AND MATERIALS: BPA-F (290 mg BPA/kg body weight) was infused i.v. during two hours to 10 glioblastoma multiforme patients. Blood samples were collected during and after the infusion. Compartmental models and bi-exponential function fit were constructed based on the (10)B blood time-concentration curve. The constructed models were tested with data from six additional patients who received various amounts of infused BPA-F and data from one patient who received a one-hour infusion of 170 mg BPA/kg body weight. RESULTS: The resulting open two-compartment model and bi-exponential function estimate the clearance of (10)B after 290 mg BPA/kg body weight infusion from the blood with satisfactory accuracy during the first irradiation field (1 ppm, i.e., 7%). The accuracy of the two models in predicting the clearance of (10)B during the second irradiation field are for two-compartment model 1.0 ppm (8%) and 0.2 ppm (2%) for bi-exponential function. The models predict the average blood (10)B concentration with an increasing accuracy as more data points are available during the treatment. CONCLUSION: By combining the two models, a robust and practical modeling tool is created for the estimation of the (10)B concentration in blood after BPA-F infusion.

Enhanced blood boron concentration estimation for BPA-F mediated BNCT.

The blood boron concentration regulates directly the BNCT irradiation time in which the prescribed dose to the patient is delivered. Therefore a proper estimation of the blood boron concentration for the treatment field based on the measured blood samples before irradiation is required. The bi-exponential model fit using Levenberg-Marquardt method was implemented for this purpose to provide the blood boron concentration estimates directly to the treatment data flow during the BNCT procedure. The harmonic mean bi-exponential decay half-lives of the studied patient data (n=28) were 15+/-8 and 320+/-70 min for the faster and slower half-life. The model uncertainty (n=28) was reasonably low, 0.7+/-0.1 microg/g (about 5%). The implemented algorithm provides a robust method for temporal blood boron concentration estimation for BPA-F mediated BNCT. Utilization of the infusion data improves the reliability of the estimate. The overall data flow during the treatment fulfills the practical requirements concerning the BNCT procedure.

Design and construction of shoulder recesses into the beam aperture shields for improved patient positioning at the FiR 1 BNCT facility.

Improvements have been made at the FiR 1 BNCT facility to ease the positioning of the patient with a tumor in the head and neck region into a lateral neutron beam. Shoulder recesses were constructed horizontally on both sides of the beam aperture. When shoulder recesses are not needed, they are filled with neutron attenuating filling blocks. MCNP simulations using an anthropomorphic human model BOMAB phantom showed that the main contribution to the increase in the effective dose to the patient's body due to the shoulder recesses was from the neutron dose of the arm. In a position when one arm is inside the shoulder recess, the maximal effective dose of the patient was estimated to be 0.7Sv/h. Dose measurements using the twin ionization chamber technique showed that the neutron dose increased on the sides as predicted by the MCNP model but there was no noticeable change in the gamma doses. When making the recesses into the lithium containing neutron shield material tritium contamination was confined using an underpressurized glove box and machine tools with local exhaust. The shoulder recesses give space for more flexible patient positioning and can be considered as a significant improvement of the Finnish BNCT facility.

Assessment of the effective dose in supine, prone, and oblique positions in the maxillofacial region using a novel combined extremity and maxillofacial cone beam computed tomography scanner.

OBJECTIVE: The objectives of this study were to assess the organ and effective doses (International Commission on Radiological Protection [ICRP] 103 standard) resulting from supine, prone, and oblique phantom positions in the maxillofacial region using a novel cone beam computed tomography (CBCT) device and to compare the results with conventional dental CBCT and multislice computed tomography (MSCT) devices. STUDY DESIGN: Measurements were performed using an anthropomorphic RANDO head phantom (Radiation Analogue Dosimetry System) with 20 MOSFET (metal-oxide-semiconductor field-effect transistor) dosimeters placed in the most radiosensitive maxillofacial organs. Effective doses were measured in 3 phantom positions using a combined extremity and maxillofacial CBCT device: the Planmed Verity CBCT scanner. Reference values were measured in the upright position with 2 CBCT devices and in the prone position with one MSCT scanner. RESULTS: The Planmed Verity CBCT scanner effective doses were 247 µSv in supine, 192 µSv in prone, and 134 µSv in oblique position. The effective dose with ProMax 3D MAX CBCT was 168 µSv; with i-CAT Next Generation, 170 µSv; and with Philips Brilliance 64 MSCT, 781 µSv. CONCLUSIONS: Head positioning has an important effect on the organ and effective doses. The Planmed Verity CBCT scanner effective dose results were comparable with those attained on 2 conventional CBCT devices and were considerably lower than the MSCT scanner results.