Computed tomography with adjusted dose for body mass index may be superior to whole-body radiography especially in elderly patients with multiple myeloma.

BACKGROUND: Whole-body skeletal radiography has traditionally been used in the management of multiple myeloma for defining treatment strategies. For several reasons, radiography has been replaced by computed tomography (CT) covering the same regions. PURPOSE: To evaluate the body mass index (BMI) adjusted effective radiation dose from two different methods of whole-body radiologic imaging for multiple myeloma assessment. MATERIAL AND METHODS: The current investigation analyses the dose to patients resulting from the two methods, conventional radiography supplemented with tomosynthesis (203 examinations) and CT (264 examinations). All patients subject to myeloma staging for 4.5 years were included in the study. Exposure parameters were collected from the PACS and conversion factors were calculated using the software packages PCXMC and VirtualDose enabling the calculation of the effective dose to each patient based on BMI. The Mann-Whitney U test was used for comparisons between groups. RESULTS: Patients were subject to a median effective dose of 2.5 mSv for conventional radiography and 5.1 mSv for CT, a statistically significant difference. CONCLUSION: The effective dose for whole-body CT in assessing multiple myeloma is twice as high as for whole-body skeletal survey with modern digital radiography, but at a low level and considerably less than the levels quoted in the earlier studies of ∼30 mSv when the technique was first explored.

Investigating Differences in Behavior and Brain in Human-Human and Human-Autonomous Vehicle Interactions in Time-Critical Situations.

Some studies provide evidence that humans could actively exploit the alleged technological advantages of autonomous vehicles (AVs). This implies that humans may tend to interact differently with AVs as compared to human driven vehicles (HVs) with the knowledge that AVs are programmed to be risk-averse. Hence, it is important to investigate how humans interact with AVs in complex traffic situations. Here, we investigated whether participants would value interactions with AVs differently compared to HVs, and if these differences can be characterized on the behavioral and brain-level. We presented participants with a cover story while recording whole-head brain activity using fNIRS that they were driving under time pressure through urban traffic in the presence of other HVs and AVs. Moreover, the AVs were programmed defensively to avoid collisions and had faster braking reaction times than HVs. Participants would receive a monetary reward if they managed to finish the driving block within a given time-limit without risky driving maneuvers. During the drive, participants were repeatedly confronted with left-lane turning situations at unsignalized intersections. They had to stop and find a gap to turn in front of an oncoming stream of vehicles consisting of HVs and AVs. While the behavioral results did not show any significant difference between the safety margin used during the turning maneuvers with respect to AVs or HVs, participants tended to be more certain in their decision-making process while turning in front of AVs as reflected by the smaller variance in the gap size acceptance as compared to HVs. Importantly, using a multivariate logistic regression approach, we were able to predict whether the participants decided to turn in front of HVs or AVs from whole-head fNIRS in the decision-making phase for every participant (mean accuracy = 67.2%, SD = 5%). Channel-wise univariate fNIRS analysis revealed increased brain activation differences for turning in front of AVs compared to HVs in brain areas that represent the valuation of actions taken during decision-making. The insights provided here may be useful for the development of control systems to assess interactions in future mixed traffic environments involving AVs and HVs.

A Nordic-Baltic perspective on indications for proton therapy with strategies for identification of proper patients.

The beneficial effects of protons are primarily based on reduction of low to intermediate radiation dose bath to normal tissue surrounding the radiotherapy target volume. Despite promise for reduced long-term toxicity, the percentage of cancer patients treated with proton therapy remains low. This is probably caused by technical improvements in planning and delivery of photon therapy, and by high cost, low availability and lack of high-level evidence on proton therapy. A number of proton treatment facilities are under construction or have recently opened; there are now two operational Scandinavian proton centres and two more are under construction, thereby eliminating the availability hurdle. Even with the advantageous physical properties of protons, there is still substantial ambiguity and no established criteria related to which patients should receive proton therapy. This topic was discussed in a session at the Nordic Collaborative Workshop on Particle Therapy, held in Uppsala 14-15 November 2019. This paper resumes the Nordic-Baltic perspective on proton therapy indications and discusses strategies to identify patients for proton therapy. As for indications, neoplastic entities, target volume localisation, size, internal motion, age, second cancer predisposition, dose escalation and treatment plan comparison based on the as low as reasonably achievable (ALARA) principle or normal tissue complication probability (NTCP) models were discussed. Importantly, the patient selection process should be integrated into the radiotherapy community and emphasis on collaboration across medical specialties, involvement of key decision makers and knowledge dissemination in general are important factors. An active Nordic-Baltic proton therapy organisation would also serve this purpose.

Effective dose in low-dose CT compared with radiography for templating of total hip arthroplasty.

Background Recently, total hip arthroplasty (THA) has come to focus on restoration of individual anatomy including femoral neck anteversion and global offset (femoral and acetabular offset). Three-dimensional (3D) computed tomography (CT) data could provide a better basis for preoperative templating. The use of CT has been hampered by high radiation dose. Purpose To evaluate the effective dose used in pelvis and hip CT for THA templating. Material and Methods CT data from two clinical trials of THA were evaluated for CT scan length and volume CT dose index (CTDIvol). The effective doses from hip-knee-ankle CT and pelvis and hip radiography were compared. Conversion factors for effective dose for radiography were calculated using the PCXMC software. Results A reduced dose CT protocol for pelvis imaging gave a substantial dose reduction compared with standard CT, while maintaining sufficient image quality. Between the two clinical trials there was a significant reduction in effective CT dose corresponding to changes in the CT protocol ( P < 0.01). The CT dose for the latter group was similar to, but nevertheless significantly higher than for, radiography ( P < 0.01). However, in the latter group the theoretical minimum dose for CT, using the minimum scan length required by the templating software, was equal to the dose from radiography. Conclusion Although the CT dose remained higher than for radiography, potential reductions in scan length could reduce the dose further so that CT would have a comparable level of risk to radiography with the added benefit of 3D templating.

Tomosynthesis of the thoracic spine: added value in diagnosing vertebral fractures in the elderly.

OBJECTIVES: Thoracic spine radiography becomes more difficult with age. Tomosynthesis is a low-dose tomographic extension of radiography which may facilitate thoracic spine evaluation. This study assessed the added value of tomosynthesis in imaging of the thoracic spine in the elderly. METHODS: Four observers compared the image quality of 50 consecutive thoracic spine radiography and tomosynthesis data sets from 48 patients (median age 67 years, range 55-92 years) on a number of image quality criteria. Observer variation was determined by free-marginal multirater kappa. The conversion factor and effective dose were determined from the dose-area product values. RESULTS: For all observers significantly more vertebrae were seen with tomosynthesis than with radiography (mean 12.4/9.3, P < 0.001) as well as significantly more fractures (mean 0.9/0.7, P = 0.017). The image quality score for tomosynthesis was significantly higher than for radiography, for all evaluated structures. Tomosynthesis took longer to evaluate than radiography. Despite this, all observers scored a clear preference for tomosynthesis. Observer agreement was substantial (mean κ = 0.73, range 0.51-0.94). The calibration or conversion factor was 0.11 mSv/(Gy cm2) for the combined examination. The resulting effective dose was 0.87 mSv. CONCLUSION: Tomosynthesis can increase the detection rate of thoracic vertebral fractures in the elderly, at low added radiation dose. KEY POINTS: • Tomosynthesis helps evaluate the thoracic spine in the elderly. • Observer agreement for thoracic spine tomosynthesis was substantial (mean κ = 0.73). • Significantly more vertebrae and significantly more fractures were seen with tomosynthesis. • Tomosynthesis took longer to evaluate than radiography. • There was a clear preference among all observers for tomosynthesis over radiography.

Designing driver assistance systems with crossmodal signals: multisensory integration rules for saccadic reaction times apply.

Modern driver assistance systems make increasing use of auditory and tactile signals in order to reduce the driver's visual information load. This entails potential crossmodal interaction effects that need to be taken into account in designing an optimal system. Here we show that saccadic reaction times to visual targets (cockpit or outside mirror), presented in a driving simulator environment and accompanied by auditory or tactile accessories, follow some well-known spatiotemporal rules of multisensory integration, usually found under confined laboratory conditions. Auditory nontargets speed up reaction time by about 80 ms. The effect tends to be maximal when the nontarget is presented 50 ms before the target and when target and nontarget are spatially coincident. The effect of a tactile nontarget (vibrating steering wheel) was less pronounced and not spatially specific. It is shown that the average reaction times are well-described by the stochastic "time window of integration" model for multisensory integration developed by the authors. This two-stage model postulates that crossmodal interaction occurs only if the peripheral processes from the different sensory modalities terminate within a fixed temporal interval, and that the amount of crossmodal interaction manifests itself in an increase or decrease of second stage processing time. A qualitative test is consistent with the model prediction that the probability of interaction, but not the amount of crossmodal interaction, depends on target-nontarget onset asynchrony. A quantitative model fit yields estimates of individual participants' parameters, including the size of the time window. Some consequences for the design of driver assistance systems are discussed.

Effective dose from chest tomosynthesis in children.

Tomosynthesis (digital tomography) is a recently introduced low-dose alternative to CT in the evaluation of the lungs in patients with cystic fibrosis and pulmonary nodules. Previous studies have reported an adult effective dose of 0.12-0.13 mSv for chest tomosynthesis. The aim of this study was to determine the paediatric effective dose from the dose-area-product. During a 3-y period, 38 children with cystic fibrosis and 36 paediatric oncology patients were examined with chest tomosynthesis, totally 169 posteroanterior and 17 anteroposterior examinations (40 boys and 34 girls, mean age 13.7 y, range 7-20 y). Using recently reported paediatric chest tomosynthesis conversion factors (0.23-1.09 mSv Gy cm(-2)) corrected for sex, age and energy, the mean posteroanterior effective dose calculated was 0.17 mSv; using the proposed simplified conversion factors of 0.6 (8-10 y), 0.4 (11-14 y) and 0.3 mSv Gy cm(-2) (15-19 y), the mean posteroanterior effective dose calculated was 0.15 mSv. As the difference in the calculated effective dose was minor, it is recommendable to use the simplified conversion factors. Using the conversion factor for adult chest tomosynthesis (0.26 mSv Gy cm(-2)), the mean effective dose was 0.11 mSv. Anteroposterior exposures had considerably higher effective dose. By using conversion factors adapted for children, the calculated risks from radiologic procedures will be more accurate.

Conversion factors for estimation of effective dose in paediatric chest tomosynthesis.

For chest tomosynthesis in adults, a conversion factor of 0.26 mSv/Gy cm² has been reported for calculating the effective dose from the registered dose-area-product. The aim of this study was to determine conversion factors for chest tomosynthesis in children. Using the Monte Carlo-based computer software PCXMC 2.0, simulations were performed on modified phantoms for males and females aged 8-19 y, in the posteroanterior and anteroposterior projection, with energies 80-140 kV and copper filtration 0.1-0.3 mm. Resulting conversion factors ranged between 0.23 and 1.09 mSv/Gy cm², decreased with patient age, were significantly higher in the anteroposterior projection and increased with increased energy or copper filtration. To avoid an underestimation of effective dose in children, it is recommended to use age-dependent conversion factors. As a simplified approach, three conversion factors might be used for posteroanterior chest tomosynthesis and radiography in children, namely 0.6 (8-10 y), 0.4 (11-14 y) and 0.3 mSv/Gy cm² (15-19 y).

Combined laparoscopic-endoscopic resections of colorectal polyps: 10-year experience and follow-up.

BACKGROUND: Large, colorectal polyps or those that are difficult to access may be unamenable to conventional snare polypectomy and may require surgical resection. This study was designed to evaluate the resection of such lesions by the use of combined laparoscopic-endoscopic resections (CLER). METHODS: Patients who had received CLER for colorectal polyps between January 1997 and December 2006 were identified from a prospectively maintained database. Patients with biopsies consistent with invasive cancer were excluded from the combined approach. Baseline characteristics, surgical, pathological, postoperative, and follow-up data of patients and lesions were reviewed. RESULTS: A total of 146 consecutive patients underwent CLER for 154 lesions, and 120 (82%) patients underwent local excision (i.e., laparoscopy-assisted endoscopic resection, endoscopy-assisted wedge resection, and endoscopy-assisted transluminal resection). Twenty-six (18%) patients received endoscopy-assisted segmental colon resection. Conversion rate was 5% and intraoperative complications occurred in two patients (1%). Major postoperative complications occurred in five patients (3%), necessitating surgical reintervention in four of them. Follow-up colonoscopy revealed metachronous adenomas in 33 patients, of which 8 patients showed macroscopic or microscopic characteristics of advanced lesions. One patient, who had been converted to open resection because of incomplete laparoscopic resection of an adenoma, developed relapse of the initial adenoma and was successfully treated with repeat CLER accounting for a local recurrence rate of 0.9%. CONCLUSIONS: Combined laparoscopic-endoscopic resection is an efficient, safe, and minimally invasive alternative to open resection for selected patients with difficult polyps, but it should be restricted to benign disease.

Beam modeling and verification of a photon beam multisource model.

Dose calculations for treatment planning of photon beam radiotherapy require a model of the beam to drive the dose calculation models. The beam shaping process involves scattering and filtering that yield radiation components which vary with collimator settings. The necessity to model these components has motivated the development of multisource beam models. We describe and evaluate clinical photon beam modeling based on multisource models, including lateral beam quality variations. The evaluation is based on user data for a pencil kernel algorithm and a point kernel algorithm (collapsed cone) used in the clinical treatment planning systems Helax-TMS and Nucletron-Oncentra. The pencil kernel implementations treat the beam spectrum as lateral invariant while the collapsed cone involves off axis softening of the spectrum. Both algorithms include modeling of head scatter components. The parameters of the beam model are derived from measured beam data in a semiautomatic process called RDH (radiation data handling) that, in sequential steps, minimizes the deviations in calculated dose versus the measured data. The RDH procedure is reviewed and the results of processing data from a large number of treatment units are analyzed for the two dose calculation algorithms. The results for both algorithms are similar, with slightly better results for the collapsed cone implementations. For open beams, 87% of the machines have maximum errors less than 2.5%. For wedged beams the errors were found to increase with increasing wedge angle. Internal, motorized wedges did yield slightly larger errors than external wedges. These results reflect the increased complexity, both experimentally and computationally, when wedges are used compared to open beams.

Verification of dose calculations with a clinical treatment planning system based on a point kernel dose engine.

Dose calculations with a collapsed cone algorithm implemented in a clinical treatment planning system have been studied. The algorithm has been evaluated in homogeneous as well as in heterogeneous media, and the results have been compared to measurements and Monte Carlo simulations. Commonly encountered clinical beam configurations as well as more complex geometries have been pursued to test the limitations of the model. The results show that the accuracy level reached allows for clinical use. Some situations, e.g., large wedge beams and dose calculations in the build up region, not specific to the collapsed cone model, show deviations (outside +/- 3%) compared to measurements.

Dosimetric verification of modulated photon fields by means of compensators for a kernel model.

The approach in treatment planning of applying beam quality correction factors to model compensator-induced depth-hardening effects is investigated and the present work comprises a dosimetric verification of the model for a common compensator material. Lead sheet modulators for four different phantom shapes were designed using a treatment planning system based on the model. The modulators were designed to yield homogeneous dose in a plane. The calculated modulation created by the lead sheets was re-imported into the treatment planning system and applied to a water phantom geometry for verification purposes. Comparing measurements, a total of 31 different geometries were measured, with calculations in this geometry showing good agreement for depth doses, dose profiles and output data with a maximum deviation of 4% except locally in the penumbra region and close to the edges of the cut lead sheets.