The first probe of a FLASH proton beam by PET

The recently observed FLASH effect related to high doses delivered with high rates has the potential to revolutionize radiation cancer therapy if promising results are confirmed and an underlying mechanism understood. Comprehensive measurements are essential to elucidate the phenomenon. We report the first-ever demonstration of measurements of successive in-spill and post-spill emissions of gammas arising from irradiations by a FLASH proton beam. A small positron emission tomography (PET) system was exposed in an ocular beam of the Proton Therapy Center at MD Anderson Cancer Center to view phantoms irradiated by 3.5 × 1010protons with a kinetic energy of 75.8 MeV delivered in 101.5 ms-long spills yielding a dose rate of 164 Gy s-1. Most in-spill events were due to prompt gammas. Reconstructed post-spill tomographic events, recorded for up to 20 min, yielded quantitative imaging and dosimetric information. These findings open a new and novel modality for imaging and monitoring of FLASH proton therapy exploiting in-spill prompt gamma imaging followed by post-spill PET imaging.

The accuracy of helium ion CT based particle therapy range prediction: an experimental study comparing different particle and x-ray CT modalities

This work provides a quantitative assessment of helium ion CT (HeCT) for particle therapy treatment planning. For the first time, HeCT based range prediction accuracy in a heterogeneous tissue phantom is presented and compared to single-energy x-ray CT (SECT), dual-energy x-ray CT (DECT) and proton CT (pCT). HeCT and pCT scans were acquired using the US pCT collaboration prototype particle CT scanner at the Heidelberg Ion-Beam Therapy Center. SECT and DECT scans were done with a Siemens Somatom Definition Flash and converted to RSP. A Catphan CTP404 module was used to study the RSP accuracy of HeCT. A custom phantom of 20 cm diameter containing several tissue equivalent plastic cubes was used to assess the spatial resolution of HeCT and compare it to DECT. A clinically realistic heterogeneous tissue phantom was constructed using cranial slices from a pig head placed inside a cylindrical phantom (ø150 mm). A proton beam (84.67 mm range) depth-dose measurement was acquired using a stack of GafchromicTM EBT-XD films in a central dosimetry insert in the phantom. CT scans of the phantom were acquired with each modality, and proton depth-dose estimates were simulated based on the reconstructions. The RSP accuracy of HeCT for the plastic phantom was found to be 0.3 ± 0.1%. The spatial resolution for HeCT of the cube phantom was 5.9 ± 0.4 lp cm-1for central, and 7.6 ± 0.8 lp cm-1for peripheral cubes, comparable to DECT spatial resolution (7.7 ± 0.3 lp cm-1and 7.4 ± 0.2 lp cm-1, respectively). For the pig head, HeCT, SECT, DECT and pCT predicted range accuracy was 0.25%, -1.40%, -0.45% and 0.39%, respectively. In this study, HeCT acquired with a prototype system showed potential for particle therapy treatment planning, offering RSP accuracy, spatial resolution, and range prediction accuracy comparable to that achieved with a commercial DECT scanner. Still, technical improvements of HeCT are needed to enable clinical implementation.

Improvements in beam's eye view fiducial tracking using a novel multilayer imager

Purpose.Electronic portal image devices (EPIDs) have been investigated previously for beams-eye view (BEV) applications such as tumor tracking but are limited by low contrast-to-noise ratio and detective quantum efficiency. A novel multilayer imager (MLI), consisting of four stacked flat-panels was used to measure improvements in fiducial tracking during liver stereotactic body radiation therapy (SBRT) procedures compared to a single layer EPID.Methods.The prototype MLI was installed on a clinical TrueBeam linac in place of the conventional DMI single-layer EPID. The panel was extended during volumetric modulated arc therapy SBRT treatments in order to passively acquire data during therapy. Images were acquired for six patients receiving SBRT to liver metastases over two fractions each, one with the MLI using all 4 layers and one with the MLI using the top layer only, representing a standard EPID. The acquired frames were processed by a previously published tracking algorithm modified to identify implanted radiopaque fiducials. Truth data was determined using respiratory traces combined with partial manual tracking. Results for 4- and 1-layer mode were compared against truth data for tracking accuracy and efficiency. Tracking and noise improvements as a function of gantry angle were determined.Results. Tracking efficiency with 4-layers improved to 82.8% versus 58.4% for the 1-layer mode, a relative improvement of 41.7%. Fiducial tracking with 1-layer returned a root mean square error (RMSE) of 2.1 mm compared to 4-layer RMSE of 1.5 mm, a statistically significant (p < 0.001) improvement of 0.6 mm. The reduction in noise correlated with an increase in successfully tracked frames (r = 0.913) and with increased tracking accuracy (0.927).Conclusion. Increases in MV photon detection efficiency by utilization of a MLI results in improved fiducial tracking for liver SBRT treatments. Future clinical applications utilizing BEV imaging may be enhanced by including similar noise reduction strategies.

Clinical translation of a new flat-panel detector for beam's-eye-view imaging

Electronic portal imaging devices (EPIDs) lend themselves to beams-eye view clinical applications, such as tumor tracking, but are limited by low contrast and detective quantum efficiency (DQE). We characterize a novel EPID prototype consisting of multiple layers and investigate its suitability for use under clinical conditions. A prototype multi-layer imager (MLI) was constructed utilizing four conventional EPID layers, each consisting of a copper plate, a Gd2O2S:Tb phosphor scintillator, and an amorphous silicon flat panel array detector. We measured the detector's response to a 6 MV photon beam with regards to modulation transfer function, noise power spectrum, DQE, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and the linearity of the detector's response to dose. Additionally, we compared MLI performance to the single top layer of the MLI and the standard Varian AS-1200 detector. Pre-clinical imaging was done on an anthropomorphic phantom, and the detector's CNR, SNR and spatial resolution were assessed in a clinical environment. Images obtained from spine and liver patient treatment deliveries were analyzed to verify CNR and SNR improvements. The MLI has a DQE(0) of 9.7%, about 5.7 times the reference AS-1200 detector. Improved noise performance largely drives the increase. CNR and SNR of clinical images improved three-fold compared to reference. A novel MLI was characterized and prepared for clinical translation. The MLI substantially improved DQE and CNR performance while maintaining the same resolution. Pre-clinical tests on an anthropomorphic phantom demonstrated improved performance as predicted theoretically. Preliminary patient data were analyzed, confirming improved CNR and SNR. Clinical applications are anticipated to include more accurate soft tissue tracking.

Combined influence of CT random noise and HU-RSP calibration curve nonlinearities on proton range systematic errors

Proton range random and systematic uncertainties are the major factors undermining the advantages of proton therapy, namely, a sharp dose falloff and a better dose conformality for lower doses in normal tissues. The influence of CT artifacts such as beam hardening or scatter can easily be understood and estimated due to their large-scale effects on the CT image, like cupping and streaks. In comparison, the effects of weakly-correlated stochastic noise are more insidious and less attention is drawn on them partly due to the common belief that they only contribute to proton range uncertainties and not to systematic errors thanks to some averaging effects. A new source of systematic errors on the range and relative stopping powers (RSP) has been highlighted and proved not to be negligible compared to the 3.5% uncertainty reference value used for safety margin design. Hence, we demonstrate that the angular points in the HU-to-RSP calibration curve are an intrinsic source of proton range systematic error for typical levels of zero-mean stochastic CT noise. Systematic errors on RSP of up to 1% have been computed for these levels. We also show that the range uncertainty does not generally vary linearly with the noise standard deviation. We define a noise-dependent effective calibration curve that better describes, for a given material, the RSP value that is actually used. The statistics of the RSP and the range continuous slowing down approximation (CSDA) have been analytically derived for the general case of a calibration curve obtained by the stoichiometric calibration procedure. These models have been validated against actual CSDA simulations for homogeneous and heterogeneous synthetical objects as well as on actual patient CTs for prostate and head-and-neck treatment planning situations.

The association between sleep quality, low back pain and disability: A prospective study in routine practice

BACKGROUND

The objective of this study was to estimate the association between sleep quality (SQ) and improvements in low back pain (LBP) and disability, among patients treated for LBP in routine practice.

METHODS

This prospective cohort study included 461 subacute and chronic LBP patients treated in 11 specialized centres, 14 primary care centres and eight physical therapy practices across 12 Spanish regions. LBP, leg pain, disability, catastrophizing, depression and SQ were assessed through validated questionnaires upon recruitment and 3 months later. Logistic regression models were developed to assess: (1) the association between the baseline score for SQ and improvements in LBP and disability at 3 months, and (2) the association between improvement in SQ and improvements in LBP and disability during the follow-up period.

RESULTS

Seventy-three per cent of patients were subacute. Median scores at baseline were four points for both pain and disability, as assessed with a visual analog scale and the Roland-Morris Questionnaire, respectively. Regression models showed (OR [95% CI]) that baseline SQ was not associated with improvements in LBP (0.99 [0.94; 1.06]) or in disability (0.99 [0.93; 1.05]), although associations existed between 'improvement in SQ' and 'improvement in LBP' (4.34 [2.21; 8.51]), and 'improvement in SQ' and 'improvement in disability' (4.60 [2.29; 9.27]).

CONCLUSIONS

Improvement in SQ is associated with improvements in LBP and in disability at 3-month follow-up, suggesting that they may reflect or be influenced by common factors. However, baseline SQ does not predict improvements in pain or disability.

SIGNIFICANCE

In clinical practice, sleep quality, low back pain and disability are associated. However, sleep quality at baseline does not predict improvement in pain and disability.

An Overview of Lipid Droplets in Cancer and Cancer Stem Cells

For decades, lipid droplets have been considered as the main cellular organelles involved in the fat storage, because of their lipid composition. However, in recent years, some new and totally unexpected roles have been discovered for them: (i) they are active sites for synthesis and storage of inflammatory mediators, and (ii) they are key players in cancer cells and tissues, especially in cancer stem cells. In this review, we summarize the main concepts related to the lipid droplet structure and function and their involvement in inflammatory and cancer processes.

Prospective study on cost-effectiveness of home-based motor assessment in Parkinson's disease

Introduction Treatment adjustments in Parkinson's disease (PD) are in part dependent on motor assessments. The aim of this study was to evaluate the cost-effectiveness of home-based motor monitoring plus standard in-office visits versus in-office visits alone in patients with advanced PD. Methods The procedures consisted of a prospective, one-year follow-up, randomized, case-control study. A total of 40 patients with advanced PD were randomized into two groups: 20 patients underwent home-based motor monitoring by using wireless motion sensor technology, while the other 20 patients had in-office visits. Motor and non-motor symptom severities, quality of life, neuropsychiatric symptoms, and comorbidities were assessed every four months. Direct costs were assessed using a standardized questionnaire. Cost-effectiveness was assessed using the incremental cost-effectiveness ratio (ICER). Results Both groups of PD patients were largely comparable in their clinical and demographic variables at baseline; however, there were more participants using levodopa-carbidopa intestinal gel in the home-based motor monitoring group. There was a trend for lower Unified Parkinson's Disease Rating Scale functional status (UPDRS II) scores in the patients monitored at home compared to the standard clinical follow-up ( p = 0.06). However, UPDRS parts I, III, IV and quality-adjusted life-years scores were similar between both groups. Home-based motor monitoring was cost-effective in terms of improvement of functional status, motor severity, and motor complications (UPDRS II, III; IV subscales), with an ICER/UPDRS ranging from €126.72 to €701.31, respectively. Discussion Home-based motor monitoring is a tool which collects cost-effective clinical information and helps augment health care for patients with advanced PD.

Spanish adaptation of the Quality of Life Index-Spinal Cord Injury version

STUDY DESIGN

A cross-sectional, validation study.

OBJECTIVES

To (a) develop the Spanish version of the Quality of Life Index-Spinal Cord Injury version (SV-QLI/SCI) and (b) assess its psychometric characteristics among permanent wheelchair users and specifically among those with SCI.

SETTING

Associations of wheelchair users in Mallorca (Spain).

METHODS

Two forward and backward translations of the QLI/SCI into Spanish were carried out separately. Seventy-seven subjects were randomly selected among the members of the associations. They completed the SV-QLI/SCI and validated instruments to measure depression and spinal pain upon recruitment and 14 days later. Assessments included comprehensibility, reproducibility, floor and ceiling effects and correlations between quality of life, pain and depression (Spearman's correlation coefficient). Analyses were repeated excluding data from subjects without SCI.

RESULTS

Three items of the SV-QLI/SCI required rephrasing. Reproducibility was 'almost perfect' for the entire questionnaire and its 'Health and functioning' subscale, 'substantial' for the 'Social and economic' and 'Family' subscales and 'moderate' for the 'Psychological/spiritual' subscale. Floor effect was not observed, and only for the 'Family' subscale >3% of the subjects reached the maximum possible score. The correlation between quality of life and depression was the strongest (r=-0.628). Results were virtually identical in the subsample with SCI.

CONCLUSION

These results support the use of the SV-QLI/SCI among Spanish-speaking wheelchair users.

A Parkinson's disease tele-education program for health care providers in Cameroon

BACKGROUND

In Sub-Saharan countries, most patients with Parkinson's disease are underdiagnosed and untreated, with a marked shortage of qualified personnel.

OBJECTIVES

To develop a tele-education Parkison's disease program for health providers in Douala (Cameroon).

METHODS

Feasibility, satisfaction, pre-post course medical knowledge improvement and patients' access were analyzed.

RESULTS

Twenty lectures over the course of a year which connected participants with movement disorder experts using live, synchronous video conferences, and teaching materials were given. Thirty-three health professionals (52.4% women) including 16 doctors, and 17 allied health professionals and 18 speakers participated. Videoconferences were successfully completed in 80%, participation ranged from 20% to 70%, and satisfaction was at least above average in 70% of the participants. Whereas medical knowledge was dramatically improved, post-course patient access was not changed.

CONCLUSION

Tele-education for movement disorders in low-income countries is feasible. However, better access and patient care should be ensured as the final outcome for tele-health education. A sustainability plan is crucial to continue with this important need.