Head CT: Image quality improvement with ASIR-V using a reduced radiation dose protocol for children

Objective

To investigate the quality of images reconstructed with adaptive statistical iterative reconstruction V (ASIR-V), using pediatric head CT protocols.

Methods

A phantom was scanned at decreasing 20% mA intervals using our standard pediatric head CT protocols. Each study was then reconstructed at 10% ASIR-V intervals. After the phantom study, we reduced mA by 10% in the protocol for <3-year-old patients and applied 30% ASIR-V and by 30% in the protocol for 3- to 15-year-old patients and applied 40% ASIR-V.

Results

Increasing the percentage of ASIR-V resulted in lower noise and higher contrast-to-noise ratio (CNR) and preserved spatial resolution in the phantom study. Compared to a conventional-protocol, reduced-dose protocol with ASIR-V achieved 12.8% to 34.0% of dose reduction and showed images of lower noise (9.22 vs. 10.73, P?=?0.043) and higher CNR in different levels (centrum semiovale, 2.14 vs. 1.52, P?=?0.003; basal ganglia, 1.46 vs. 1.07, P?=?0.001; and cerebellum, 2.18 vs. 1.33, P?<?0.001). Qualitative analysis showed higher gray-white matter differentiation and sharpness and preserved overall diagnostic quality in the images with ASIR-V.

Conclusions

Use of ASIR-V allowed a 12.8% to 34.0% dose reduction in each age group with potential to improve image quality.

Key points

? It is possible to reduce radiation dose and improve image quality with ASIR-V. ? We improved noise and CNR and decreased radiation dose. ? Sharpness improved with ASIR-V. ? Total radiation dose was decreased by 12.8% to 34.0%.

     

Dose and image-quality evaluation in synchrotron radiation mammography

Monochromatic X-ray beam produced by synchrotron radiation may be considered an ideal probe in some fields of diagnostic radiology. In this paper the potential of monochromatic synchrotron radiation X-ray beam in mammography is analyzed. The image quality of four different phantom radiographs, obtained using two different energies equal to 17 and 18 keV, respectively, and a mammographic film/screen system, is assessed. The doses have been determined for both energies by using thermoluminescent dosimeters and a 5-cm thick phantom having a composition of 50% water and 50% fat. The results have been compared with those obtained in the same manner using a mammographic unit equipped with a molybdenum anode, molybdenum filter tube and antiscanner grid. The radiographs obtained with synchrotron radiation show higher contrast and less blur than those obtained with a conventional mammographic system. The average breast doses, 1.55 and 0.80 mGy at 17 and 18 keV, respectively, are comparable with the dose (1.51 mGy) of the conventional technique. Correspondence to: M. Gambaccini     

Interpretation of skull radiographs for facial fractures by medical staff working in UK emergency departments: a pilot study

OBJECTIVES: This was a pilot study to determine the ability of hospital doctors (1) to assess the technical quality of occipitomental (OM) radiographs and (2) to identify facial fractures. METHOD: Twenty-two doctors from four UK Accident and Emergency (A&E) departments participated in a two part study: Part A was a postal questionnaire containing questions on demographic data, educational background, selection criteria, assessing radiographs and radiation protection; and Part B was a clinical viewing session to interpret 20 randomized OM radiographs divided into four groups; technically good and poor without fractures, and technically good and poor with fractures. RESULTS: Study participants ranged from junior house officers to senior consultants. There was considerable variation in educational background and radiographic interpretation instruction at undergraduate and postgraduate level. OM radiographs constituted 10% of all skull radiographs examined per week, yet only 40% of the doctors felt confident when assessing technical quality. The majority of participants had only a limited knowledge of radiation protection legislation. During the viewing session, only 50% of the participants correctly identified those radiographs with fractures and those with technique errors. There was no significant difference between house officers and other grades of staff. A higher level of seniority did not equate with greater interpretative ability. Subjective confidence in assessing film quality did not correlate with the actual film viewing. CONCLUSION: Only half of the A&E doctors taking part in the study were able to correctly assess film quality and identify facial fractures on OM radiographs. If the pilot sample is representative, then the findings are of considerable concern.     

Numerical deconvolution to enhance sharpness and contrast of portal images for radiotherapy patient positioning verification

Purpose

The quality of megavoltage clinical portal images is impaired by physical and geometrical effects. This image blurring can be corrected by a fast numerical two-dimensional (2D) deconvolution algorithm implemented in the electronic portal image device. We present some clinical examples of deconvolved portal images and evaluate the clinical advantages achieved by the improved sharpness and contrast.

Materials and methods

The principle of numerical 2D image deconvolution and the enhancement of sharpness and contrast thereby achieved are shortly explained. The key concept is the convolution kernel?K(x,y), the mathematical equivalent of the smearing or blurring of a picture, and the computer-based elimination of this influence.

Results

Enhancements of sharpness and contrast were observed in all clinical portal images investigated. The images of fine bone structures were restored. The identification of organ boundaries and anatomical landmarks was improved, thereby permitting a more accurate comparison with the x-ray simulator radiographs. The visibility of prostate gold markers is also shown to be enhanced by deconvolution.

Conclusion

The blurring effects of clinical portal images were eliminated by a numerical deconvolution algorithm that leads to better image sharpness and contrast. The fast algorithm permits the image blurring correction to be performed in real time, so that patient positioning verification with increased accuracy can be achieved in clinical practice.     

The impact of COVID-19 upon student radiographers and clinical training

IntroductionTo investigate student clinical placement concerns and opinions, during the initial COVID-19 pandemic outbreak and to inform educational institution support planning.MethodsBetween mid-June to mid-July 2020, educational institutions from 12 countries were invited to participate in an online survey designed to gain student radiographer opinion from a wide geographical spread and countries with varying levels of COVID-19 cases.Results1277 respondents participated, of these 592 had completed clinical placements during January to June 2020. Accommodation and cohabiting risks were identified as challenging, as was isolation from family, travel to clinical placements, and to a lesser extent childcare. Students stated they had been affected by the feeling of isolation and concerns about the virus whilst on placement. Overall 35.4% of all respondents were ‘Not at all worried’ about being a radiographer, however, 64.6% expressed varying levels of concern and individual domestic or health situations significantly impacted responses (p ≤ 0.05). Year 4 students and recent graduates were significantly more likely to be ‘Not worried at all’ compared to Year 2 and 3 students (p ≤ 0.05). The need for improved communication regarding clinical placements scheduling was identified as almost 50% of students on clinical placements between January to June 2020 identified the completion of assessments as challenging. Furthermore, only 66% of respondents with COVID-19 imaging experience stated being confident with personal protective equipment (PPE) use.ConclusionStudent radiographers identified key challenges which require consideration to ensure appropriate measures are in place to support their ongoing needs. Importantly PPE training is required before placement regardless of prior COVID-19 imaging experience.Implications for practiceAs the next academic year commences, the study findings identify important matters to be considered by education institutions with responsibility for Radiography training and as students commence clinical placements during the on-going global COVID-19 pandemic.     

Three-dimensional hindfoot alignment measurements based on biplanar radiographs: comparison with standard radiographic measurements

Objective

To establish a hindfoot alignment measurement technique based on low-dose biplanar radiographs and compare with hindfoot alignment measurements on long axial view radiographs, which is the current reference standard.

Materials and methods

Long axial view radiographs and low-dose biplanar radiographs of a phantom consisting of a human foot skeleton embedded in acrylic glass (phantom A) and a plastic model of a human foot in three different hindfoot positions (phantoms B1–B3) were imaged in different foot positions (20° internal to 20° external rotation). Two independent readers measured hindfoot alignment on long axial view radiographs and performed 3D hindfoot alignment measurements based on biplanar radiographs on two different occasions. Time for three-dimensional (3D) measurements was determined. Intraclass correlation coefficients (ICC) were calculated.

Results

Hindfoot alignment measurements on long axial view radiographs were characterized by a large positional variation, with a range of 14°/13° valgus to 22°/27° varus (reader 1/2 for phantom A), whereas the range of 3D hindfoot alignment measurements was 7.3°/6.0° to 9.0°/10.5° varus (reader 1/2 for phantom A), with a mean and standard deviation of 8.1°?±?0.6/8.7°?±?1.4 respectively. Interobserver agreement was high (ICC?=?0.926 for phantom A, and ICC?=?0.886 for phantoms B1–B3), and agreement between different readouts was high (ICC?=?0.895–0.995 for reader 1, and ICC?=?0.987–0.994 for reader 2) for 3D measurements. Mean duration of 3D measurements was 84?±?15/113?±?15 s for reader 1/2.

Conclusion

Three-dimensional hindfoot alignment measurements based on biplanar radiographs were independent of foot positioning during image acquisition and reader independent. In this phantom study, the 3D measurements were substantially more precise than the standard radiographic measurements.     

Novel Lead-Free Drape Applied to the X-Ray Detector Protects against Scatter Radiation in the Angiography Suite

PurposeTo evaluate a sterile, disposable lead-free drape for reducing scatter radiation exposure during fluoroscopy-guided procedures.Materials and MethodsComputer-aided design software was used to model a procedure room with a thoracic anthropomorphic phantom on the angiography table. Using this model, measurements of scatter radiation were made from the phantom before and after the application of the drape using a collimated and full field of view in low-output conditions (70 kVp, 48 mA) and high-output conditions (125 kVp, 156 mA). Transmission of x-rays through the drape and entrance exposure rates were also measured. Statistical significance was measured using a Student t test.ResultsScatter radiation was attenuated throughout the procedure room when the drape was applied. The highest level of scatter radiation was detected in the expected position of the operator, adjacent to the phantom. Radioprotection by the drape was the greatest in this position: 71.5% attenuation at waist level and 89% at neck level (P < .0001). The use of the drape did not result in an increase of backscatter radiation to the phantom.ConclusionsThe use of this drape significantly reduces scatter radiation in the procedure room; this effect is maximal in close proximity to the phantom.     

IMRT Quality Assurance Using a Second Treatment Planning System

We used a second treatment planning system (TPS) for independent verification of the dose calculated by our primary TPS in the context of patient-specific quality assurance (QA) for intensity-modulated radiation therapy (IMRT). QA plans for 24 patients treated with inverse planned dynamic IMRT were generated using the Nomos Corvus TPS. The plans were calculated on a computed tomography scan of our QA phantom that consists of three Solid Water slabs sandwiching radiochromic films, and an ion chamber that is inserted into the center slab of the phantom. For the independent verification, the dose was recalculated using the Varian Eclipse TPS using the multileaf collimator files and beam geometry from the original plan. The data was then compared in terms of absolute dose to the ion chamber volume as well as relative dose on isodoses calculated at the film plane. The calculation results were also compared with measurements performed for each case. When comparing ion chamber doses, the mean ratio was 0.999 (SD 0.010) for Eclipse vs. Corvus, 0.988 (SD 0.020) for the ionization chamber measurements vs. Corvus, and 0.989 (SD 0.017) for the ionization chamber measurements vs. Eclipse. For 2D doses with gamma histogram, the mean value of the percentage of pixels passing the criteria of 3%, 3 mm was 94.4 (SD 5.3) for Eclipse vs. Corvus, 85.1 (SD 10.6) for Corvus vs. film, and 93.7 (SD 4.1) for Eclipse vs. film; and for the criteria of 5%, 3 mm, 98.7 (SD 1.5) for Eclipse vs. Corvus, 93.0 (SD 7.8) for Corvus vs. film, and 98.0 (SD 1.9) for Eclipse vs. film. We feel that the use of the Eclipse TPS as an independent, accurate, robust, and time-efficient method for patient-specific IMRT QA is feasible in clinic.     

Transient ischemic dilation for coronary artery disease in quantitative analysis of same-day sestamibi myocardial perfusion SPECT

Background

Transient ischemic dilation (TID) of the left ventricle in myocardial perfusion SPECT (MPS) has been shown to be a clinically useful marker of severe coronary artery disease (CAD). However, TID has not been evaluated for 99mTc-sestamibi rest/stress protocols (Mibi-Mibi). We aimed to develop normal limits and evaluate diagnostic power of TID ratio for Mibi-Mibi scans.

Methods

TID ratios were automatically derived from static rest/stress MPS (TID) and gated rest/stress MPS from the end-diastolic phase (TID_ed) in 547 patients who underwent Mibi-Mibi scans [215 patients with correlating coronary angiography and 332 patients with low likelihood (LLk) of CAD]. Scans were classified as severe (??70% stenosis in proximal left anterior descending (pLAD) artery or left main (LM), or ??90% in ??2 vessels), mild to moderate (??90% stenosis in 1 vessel or ??70%-90% in ??1 vessel except pLAD or LM), and normal (<70% stenosis or LLk group). Another classification based on the angiographic Duke prognostic CAD index (DI) was also applied: DI????50, 30????DI?<?50 and DI?<?30 or LLk group.

Results

The upper normal limits were 1.19 for TID and 1.23 for TID_ed as established in 259 LLk patients. Both ratios increased with disease severity (P?<?.0001). Incidence of abnormal TID increased from 2% in normal patients to >36% in patients with severe CAD. Similarly, when DI was used to classify disease severity, the average ratios showed significant increasing trend with DI increase (P?<?.003); incidence of abnormal TID also increased with increasing DI. The incidence of abnormal TID in the group with high perfusion scores significantly increased compared to the group with low perfusion scores (stress total perfusion deficit, TPD?<?3%) (P?<?.0001). The sensitivity for detecting severe CAD improved for TID when added to mild to moderate perfusion abnormality (3%????TPD?<?10%): 71% vs 64%, P?<?.05; and trended to improve for TID_ed/TID_es: 69% vs 64%, P?=?.08, while the accuracy remained consistent if abnormal TID was considered as a marker in addition to stress TPD. Similar results were obtained when DI was used for the definition of severe CAD (sensitivity: 76% vs 66%, P?<?.05 when TID was combined with stress TPD).

Conclusion

TID ratios obtained from gated or ungated Mibi-Mibi MPS and are useful markers of severe CAD.     

Deep Learning Algorithm for Simultaneous Noise Reduction and Edge Sharpening in Low-Dose CT Images: A Pilot Study Using Lumbar Spine CT

ObjectiveThe purpose of this study was to assess whether a deep learning (DL) algorithm could enable simultaneous noise reduction and edge sharpening in low-dose lumbar spine CT.Materials and MethodsThis retrospective study included 52 patients (26 male and 26 female; median age, 60.5 years) who had undergone CT-guided lumbar bone biopsy between October 2015 and April 2020. Initial 100-mAs survey images and 50-mAs intraprocedural images were reconstructed by filtered back projection. Denoising was performed using a vendor-agnostic DL model (ClariCT.AI™, ClariPI) for the 50-mAS images, and the 50-mAs, denoised 50-mAs, and 100-mAs CT images were compared. Noise, signal-to-noise ratio (SNR), and edge rise distance (ERD) for image sharpness were measured. The data were summarized as the mean ± standard deviation for these parameters. Two musculoskeletal radiologists assessed the visibility of the normal anatomical structures.ResultsNoise was lower in the denoised 50-mAs images (36.38 ± 7.03 Hounsfield unit [HU]) than the 50-mAs (93.33 ± 25.36 HU) and 100-mAs (63.33 ± 16.09 HU) images (p < 0.001). The SNRs for the images in descending order were as follows: denoised 50-mAs (1.46 ± 0.54), 100-mAs (0.99 ± 0.34), and 50-mAs (0.58 ± 0.18) images (p < 0.001). The denoised 50-mAs images had better edge sharpness than the 100-mAs images at the vertebral body (ERD; 0.94 ± 0.2 mm vs. 1.05 ± 0.24 mm, p = 0.036) and the psoas (ERD; 0.42 ± 0.09 mm vs. 0.50 ± 0.12 mm, p = 0.002). The denoised 50-mAs images significantly improved the visualization of the normal anatomical structures (p < 0.001).ConclusionDL-based reconstruction may enable simultaneous noise reduction and improvement in image quality with the preservation of edge sharpness on low-dose lumbar spine CT. Investigations on further radiation dose reduction and the clinical applicability of this technique are warranted.     

The radiology workforce's response to the COVID-19 pandemic in the Middle East,North Africa and India

IntroductionThis study aimed to investigate the response of the radiology workforce to the impact of the coronavirus disease 2019 (COVID-19) pandemic on professional practice in India and eight other Middle Eastern and North African countries. It further investigated the levels of fear and anxiety among this workforce during the pandemic.MethodsA quantitative cross-sectional study was conducted using an online survey from 22 May-2 June 2020 among radiology workers employed during the COVID-19 pandemic. The survey collected information related to the following themes: (1) demographic characteristics, (2) the impact of COVID-19 on radiology practice, and (3) fear and (4) anxiety emanating from the global pandemic.ResultsWe received 903 responses. Fifty-eight percent had completed training on infection control required for handling COVID-19 patients. A large proportion (79.5%) of the respondents strongly agreed or agreed that personal protective equipment (PPE) was adequately available at work during the pandemic. The respondents reported experiences of work-related stress (42.9%), high COVID-19 fear score (83.3%) and anxiety (10%) during the study period.ConclusionThere was a perceived workload increase in general x-ray and Computed Tomography imaging procedures because they were the key modalities for the initial and follow-up investigations of COVID-19. However, there was adequate availability of PPE during the study period. Most radiology workers were afraid of being infected with the virus. Fear was predominant among workers younger than 30 years of age and also in temporary staff. Anxiety occurred completely independent of gender, age, experience, country, place of work, and work status.Implications for practiceIt is important to provide training and regular mental health support and evaluations for healthcare professionals, including radiology workers, during similar future pandemics.     

Experimental Analysis of Radiation Protection Offered by a Novel Exoskeleton-Based Radiation Protection System versus Conventional Lead Aprons

PurposeTo evaluate the radiation protection offered by an exoskeleton-based radiation protection system (Stemrad MD) and to compare it with that offered by conventional lead aprons.MethodsThe experimental setup involved 2 anthropomorphic phantoms, an operator, a patient, and a C-arm as the x-ray radiation source. Thermoluminescent detectors were used to measure radiation doses to different radiosensitive body parts on the operator phantom both with the exoskeleton and a conventional lead apron at the left radial and right femoral positions. Detected radiation doses for the exoskeleton and lead apron for different body parts and positions were compared.ResultsAt the left radial position, the mean radiation dose (mGy) reduction by the exoskeleton compared with that by the lead apron was >90% for the left eye lens (0.22 ± 0.13 vs 5.18 ± 0.08; P < .0001), right eye lens (0.23 ± 0.13 vs 4.98 ± 0.10; P < .0001), left head (0.11 ± 0.16 vs 3.53 ± 0.07; P < .0001), right head (0.27 ± 0.09 vs 3.12 ± 0.10; P < .0001), and left brain (0.04 ± 0.08 vs 0.46 ± 0.07; P < .0001). At the right femoral position, radiation reduction was >90% for the left eye lens (0.14 ± 0.10 vs 4.16 ± 0.09; P < .0001), right eye lens (0.06 ± 0.08 vs 1.90 ± 0.11; P < .0001), left head (0.10 ± 0.08 vs 4.39 ± 0.08; P < .0001), left brain (0.03 ± 0.07 vs 1.44 ± 0.08; P < .0001), right brain (0.00 ± 0.14 vs 0.11 ± 0.13; P = .06), and thyroid (0.04 ± 0.07 vs 0.27 ± 0.09; P < .0001). Protection of the torso was equivalent to that offered by conventional lead aprons.ConclusionsThe exoskeleton-based system provided superior radiation protection to the physician compared with that provided by conventional lead aprons. The effects are particularly impactful for the brain, eye lens, and head areas.     

Novel information theory based method for superimposition of lateral head radiographs and cone beam computed tomography images

Objectives

The aim was to introduce a novel alignment criterion, focus mutual information (FMI), for the superimposition of lateral cephalometric radiographs and three dimensional (3D) cone beam computed images as well as the assessment of the alignment characteristics of the new method and comparison of the novel methodology with the region of interest (ROI) approach.

Methods

Implementation of a FMI criterion-based methodology that only requires the approximate indication of stable structures in one single image. The robustness of the method was first addressed in a phantom experiment comparing the new technique with a ROI approach. Two consecutive cephalometric radiographs were then obtained, one before and one after functional twin block application. These images were then superimposed using alignment by FMI where the following were focused on, in several ways: (1) cranial base and acoustic meatus, (2) palatal plane and (3) mandibular symphysis. The superimposed images were subtracted and coloured. The applicability to cone beam CT (CBCT) is illustrated by the alignment of CBCT images acquired before and after craniofacial surgery.

Results

The phantom experiment clearly shows superior alignment when compared to the ROI approach (Wilcoxon n = 17, Z = −3.290, and P = 0.001), and robustness with respect to the choice of parameters (one-sample t-test n = 50, t = −12.355, and P = 0.000). The treatment effects are revealed clearly in the subtraction image of well-aligned cephalometric radiographs. The colouring scheme of the subtraction image emphasises the areas of change and visualizes the remodelling of the soft tissue.

Conclusions

FMI allows for cephalometry without tracing, it avoids the error inherent to the use of landmarks and the interaction of the practitioner is kept to a minimum. The robustness to focal distribution variations limits the influence of possible examiner inaccuracy.     

Comparison of radiation dose, workflow, patient comfort and financial break-even of standard digital radiography and a novel biplanar low-dose X-ray system for upright full-length lower limb and whole spine radiography

Objective

To compare the radiation dose, workflow, patient comfort, and financial break-even of a standard digital radiography and a biplanar low-dose X-ray system.

Materials and methods

A standard digital radiography system (Ysio, Siemens Healthcare, Erlangen, Germany) was compared with a biplanar X-ray unit (EOS, EOS imaging, Paris, France) consisting of two X-ray tubes and slot-scanning detectors, arranged at an angle of 90° allowing simultaneous vertical biplanar linear scanning in the upright patient position. We compared data of standing full-length lower limb radiographs and whole spine radiographs of both X-ray systems.

Results

Dose–area product was significantly lower for radiographs of the biplanar X-ray system than for the standard digital radiography system (e.g. whole spine radiographs; standard digital radiography system: 392.2?±?231.7 cGy*cm² versus biplanar X-ray system: 158.4?±?103.8 cGy*cm²). The mean examination time was significantly shorter for biplanar radiographs compared with standard digital radiographs (e.g. whole spine radiographs: 449 s vs 248 s). Patients’ comfort regarding noise was significantly higher for the standard digital radiography system. The financial break-even point was 2,602 radiographs/year for the standard digital radiography system compared with 4,077 radiographs/year for the biplanar X-ray unit.

Conclusion

The biplanar X-ray unit reduces radiation exposure and increases subjective noise exposure to patients. The biplanar X-ray unit demands a higher number of examinations per year for the financial break-even point, despite the lower labour cost per examination due to the shorter examination time.     

Options for radiation dose optimisation in pelvic digital radiography: A phantom study

PurposeTo investigate the effects of phantom orientation and AEC chamber selection on radiation dose and image quality (IQ) for digital radiography (DR) examinations of the pelvis.MethodsA phantom study was conducted using a DR detector, utilising all AEC chamber combinations. Current recommended orientation (Cr-AEC) was with the outer AEC chambers cranially orientated. mAs (given), source-to-skin distance and kV_p data facilitated entrance surface dose and effective dose calculations. Six anatomical areas were blindly graded by two observers (3-point scale) for IQ. Statistical differences in radiation dose were determined using the paired Student’s t-test. IQ data was analysed for inter-observer variability (ICC) and statistical differences (Wilcoxon test).ResultsSwitching phantom orientation (caudally orientated outer AEC chambers: Ca-AEC) reduced mean radiation dose by 36.8%, (p < 0.001). A minor reduction in median IQ (15.5 vs. 15) was seen (p < 0.001). One Ca-AEC orientated image (1.6%) had all anatomical areas graded ‘inadequate’ by at least one observer; all other images were considered ‘adequate’ for all areas. In the Ca-AEC orientation, at least a 44% dose reduction was achievable (p < 0.001) when only the outer AEC chambers were used. In the Cr-AEC orientation, at least 11% dose reduction was achieved (p < 0.001); here the central chamber was used alone, or in combination. IQ scores fell, but remained ‘adequate’.ConclusionSwitching pelvic orientation relative to AEC chamber position can optimise radiation dose during pelvic radiography. AEC chamber position should be clearly marked on equipment to facilitate this. AEC selection should be an active process.     

Verbesserte Lagerungsreproduzierbarkeit eines nichtinvasiven Hochpräzisionsmaskensystems in der stereotaktischen Radiotherapie durch eine integrierte Kieferfixierung

BACKGROUND: For high precision radiotherapy of the neurocranium a precise, reproducible positioning technique is the basic prerequisite. The aim of this study was to assess the influence of a modification of the commercially available stereotactical BrainLab-head mask system on accuracy in patient positioning during fractionated radiotherapy. MATERIAL AND METHODS: 29 patients were treated with stereotactic radiotherapy of the head. Immobilization was provided by a two layer thermoplastic mask system (BrainLab). 18 of these patients received an additional custom made fixation either of the upper jaw (OKF) or of the mandibula (UKF). The positioning accuracy was assessed by measurements of the shifting of anatomical landmarks in relation to the rigid mask system on biplanar simulator films using a digital imaging system. Before each measurement a fine adjustment of the simulator to an optical ring system was performed. The reference radiographs were done just before CT-planning. During a 2-7 weeks lasting course of radiotherapy displacement measurements in relation to the reference images for all three dimensions (z, y and x) were done once a week. In 29 patients 844 measurements were analyzed. RESULTS: An additional jaw fixation improves the reproducibility of patient positioning significantly in all three spatial dimensions. The standard deviation in lateral direction (x) was 0.6 mm with jaw fixation vs. 0.7 mm without jaw fixation (p < 0.001); in longitudinal direction (z) (measured in 0 degree radiographs) 0.5 mm vs. 1.3 mm (p < 0.001); in longitudinal direction (measured in 90 degrees radiographs) 0.5 mm vs. 1.5 mm (p < 0.001); in vertical direction (y) 0.6 mm vs. 0.9 mm (p = 0.001). No significant differences in standard deviations were found comparing OKF (n = 14) with UKF (n = 4). CONCLUSION: A significant improvement in reposition accuracy using an additional, individually formed jaw fixation can be acquired. The variability of positioning can be reduced especially in the z-direction. A further reduction of the safety margin around the target volume--especially in benign tumors--is possible by improved fixation technique.     

Variation in pelvic radiography practice: Why can we not standardise image acquisition techniques?

IntroductionPelvic radiographs remain an essential investigation in orthopaedic practice. Although it is recognised that acquisition techniques can affect image appearances and measurement accuracy, it remains unclear what variation in practice exists and what impact this could have on decision making.MethodThis was a cross sectional survey of UK radiology departments utilising an electronic tool. An introductory letter and link was distributed. Responses were received from 69 unique hospital sites within the specified timeframe, a response rate of 37.9%.ResultsThere was no consistent technique for the positioning of patients for pelvic radiographs. The distance varied between 90 and 115 cm and 10 different centering points were described. In relation to leg position, the feet are usually internally rotated (65 of 69 [94.2%]). Only 1 teaching hospital (1 of 69 [1.4%]) uses a weight-bearing position as standard.Orthopaedic calibration devices were not in routine use, with only 21 using on pelvic x-rays (30.4%). Further, the type of device and application criteria were inconsistent.ConclusionsTo our knowledge this is the first study to directly compare radiographic positioning across hospital sites. Our data demonstrated marked variation in technique for pelvis radiographs with associated implications for clinical decision making. Research is required to determine the standard technique and quality outcome measures to provide confidence in diagnostic interpretation particularly for serial radiographs.     

Dose reduction with adaptive statistical iterative reconstruction for paediatric CT: phantom study and clinical experience on chest and abdomen CT

Objectives

To assess the benefit and limits of iterative reconstruction of paediatric chest and abdominal computed tomography (CT).

Methods

The study compared adaptive statistical iterative reconstruction (ASIR) with filtered back projection (FBP) on 64-channel MDCT. A phantom study was first performed using variable tube potential, tube current and ASIR settings. The assessed image quality indices were the signal-to-noise ratio (SNR), the noise power spectrum, low contrast detectability (LCD) and spatial resolution. A clinical retrospective study of 26 children (M:F?=?14/12, mean age: 4 years, range: 1–9 years) was secondarily performed allowing comparison of 18 chest and 14 abdominal CT pairs, one with a routine CT dose and FBP reconstruction, and the other with 30 % lower dose and 40 % ASIR reconstruction. Two radiologists independently compared the images for overall image quality, noise, sharpness and artefacts, and measured image noise.

Results

The phantom study demonstrated a significant increase in SNR without impairment of the LCD or spatial resolution, except for tube current values below 30–50 mA. On clinical images, no significant difference was observed between FBP and reduced dose ASIR images.

Conclusion

Iterative reconstruction allows at least 30 % dose reduction in paediatric chest and abdominal CT, without impairment of image quality.

Key points

? Iterative reconstruction helps lower radiation exposure levels in children undergoing CT. ? Adaptive statistical iterative reconstruction (ASIR) significantly increases SNR without impairing spatial resolution. ? For abdomen and chest CT, ASIR allows at least a 30 % dose reduction.     

Lead Apron Inspection Using Infrared Light: A Model Validation Study

PurposeTo evaluate defect detection in radiation protective apparel, typically called lead aprons, using infrared (IR) thermal imaging. The use of IR lighting eliminates the need for access to x-ray–emitting equipment and radiation dose to the inspector.Materials and MethodsThe performance of radiation workers was prospectively assessed using both a tactile inspection and the IR inspection with a lead apron phantom over a 2-month period. The phantom was a modified lead apron with a series of nine holes of increasing diameter ranging from 2 to 35 mm in accordance with typical rejection criteria. Using the tactile method, a radiation worker would feel for the defects in the lead apron. For the IR inspection, a 250-W IR light source was used to illuminate the lead apron phantom; an IR camera detected the transmitted radiation. The radiation workers evaluated two stills from the IR camera.ResultsFrom the 31 participants inspecting the lead apron phantom with the tactile method, only 2 participants (6%) correctly discovered all 9 holes and 1 participant reported a defect that was not there; 10 of the 20 participants (50%) correctly identified all 9 holes using the IR method. Using a weighted average, 5.4 defects were detected with the tactile method and 7.5 defects were detected with the IR method.ConclusionIR light can penetrate an apron’s protective outer fabric and illuminate defects below the current standard rejection size criteria. The IR method improves defect detectability as compared with the tactile method.