Optimal omegas - barriers and novel methods to narrow omega-3 gaps. A narrative review

Dietary intakes of omega-3 long chain polyunsaturated fatty acids (O3LC-PUFAs) such as eicosapentaenoic and docosahexaenoic acid are central to development and health across the life course. O3LC-PUFAs have been linked to neurological development, maternal and child health and the etiology of certain non-communicable diseases including age-related cognitive decline, cardiovascular disease, and diabetes. However, dietary inadequacies exist in the United Kingdom and on a wider global scale. One predominant dietary source of O3LC-PUFAs is fish and fish oils. However, growing concerns about overfishing, oceanic contaminants such as dioxins and microplastics and the trend towards plant-based diets appear to be acting as cumulative barriers to O3LC-PUFAs from these food sources. Microalgae are an alternative provider of O3LC-PUFA-rich oils. The delivery of these into food systems is gaining interest. The present narrative review aims to discuss the present barriers to obtaining suitable levels of O3LC-PUFAs for health and wellbeing. It then discusses potential ways forward focusing on innovative delivery methods to utilize O3LC-PUFA-rich oils including the use of fortification strategies, bioengineered plants, microencapsulation, and microalgae.

Automated detection, delineation and quantification of whole-body bone metastasis using FDG-PET/CT images

Non-small cell lung cancer (NSCLC) patients with the metastatic spread of disease to the bone have high morbidity and mortality. Stereotactic ablative body radiotherapy increases the progression free survival and overall survival of these patients with oligometastases. FDG-PET/CT, a functional imaging technique combining positron emission tomography (PET) with 18 F-fluorodeoxyglucose (FDG) and computer tomography (CT) provides improved staging and identification of treatment response. It is also associated with reduction in size of the radiotherapy tumour volume delineation compared with CT based contouring in radiotherapy, thus allowing for dose escalation to the target volume with lower doses to the surrounding organs at risk. FDG-PET/CT is increasingly being used for the clinical management of NSCLC patients undergoing radiotherapy and has shown high sensitivity and specificity for the detection of bone metastases in these patients. Here, we present a software tool for detection, delineation and quantification of bone metastases using FDG-PET/CT images. The tool extracts standardised uptake values (SUV) from FDG-PET images for auto-segmentation of bone lesions and calculates volume of each lesion and associated mean and maximum SUV. The tool also allows automatic statistical validation of the auto-segmented bone lesions against the manual contours of a radiation oncologist. A retrospective review of FDG-PET/CT scans of more than 30 candidate NSCLC patients was performed and nine patients with one or more metastatic bone lesions were selected for the present study. The SUV threshold prediction model was designed by splitting the cohort of patients into a subset of 'development' and 'validation' cohorts. The development cohort yielded an optimum SUV threshold of 3.0 for automatic detection of bone metastases using FDG-PET/CT images. The validity of the derived optimum SUV threshold on the validation cohort demonstrated that auto-segmented and manually contoured bone lesions showed strong concordance for volume of bone lesion (r = 0.993) and number of detected lesions (r = 0.996). The tool has various applications in radiotherapy, including but not limited to studies determining optimum SUV threshold for accurate and standardised delineation of bone lesions and in scientific studies utilising large patient populations for instance for investigation of the number of metastatic lesions that can be treated safety with an ablative dose of radiotherapy without exceeding the normal tissue toxicity.

High-resolution entry and exit surface dosimetry in a 1.5 T MR-linac

The magnetic field of a transverse MR-linac alters electron trajectories as the photon beam transits through materials, causing lower doses at flat entry surfaces and increased doses at flat beam-exiting surfaces. This study investigated the response of a MOSFET detector, known as the MOSkin™, for high-resolution surface and near-surface percentage depth dose measurements on an Elekta Unity. Simulations with Geant4 and the Monaco treatment planning system (TPS), and EBT-3 film measurements, were also performed for comparison. Measured MOSkin™ entry surface doses, relative to D_max, were (9.9 ± 0.2)%, (10.1 ± 0.3)%, (11.3 ± 0.6)%, (12.9 ± 1.0)%, and (13.4 ± 1.0)% for 1 × 1 cm², 3 × 3 cm², 5 × 5 cm², 10 × 10 cm², and 22 × 22 cm² fields, respectively. For the investigated fields, the maximum percent differences of Geant4, TPS, and film doses extrapolated and interpolated to a depth suitable for skin dose assessment at the beam entry, relative to MOSkin™ measurements at an equivalent depth were 1.0%, 2.8%, and 14.3%, respectively, and at a WED of 199.67 mm at the beam exit, 3.2%, 3.7% and 5.7%, respectively. The largest measured increase in exit dose, due to the electron return effect, was 15.4% for the 10 × 10 cm² field size using the MOSkin™ and 17.9% for the 22 × 22 cm² field size, using Geant4 calculations. The results presented in the study validate the suitability of the MOSkin™ detector for transverse MR-linac surface dosimetry.

2D monolithic silicon-diode array detectors in megavoltage photon beams: does the fabrication technology matter? A medical physicist's perspective

A family of prototype 2D monolithic silicon-diode array detectors (MP512, Duo, Octa) has been proposed by the Centre for Medical Radiation Physics, University of Wollongong (Australia) for relative dosimetry in small megavoltage photon beams. These detectors, which differ in the topology of their 512 sensitive volumes, were originally fabricated on bulk p-type substrates. More recently, they have also been fabricated on epitaxial p-type substrates. In the literature, their performance has been individually characterized for quality assurance (QA) applications. The present study directly assessed and compared that of a MP512-bulk and that of a MP512-epitaxial in terms of radiation hardness, long-term stability, response linearity with dose, dose per pulse and angular dependence. Their measurements of output factors, off-axis ratios and percentage depth doses in square radiation fields collimated by the jaws and produced by 6 MV and 10 MV flattened photon beams were then benchmarked against those by commercially available detectors. The present investigation was aimed at establishing, from a medical physicist's perspective, how the bulk and epitaxial fabrication technologies would affect the implementation of the MP512s into a QA protocol. Based on results, the MP512-epitaxial would offer superior radiation hardness, long-term stability and achievable uniformity and reproducibility of the response across the 2D active area.

2D monolithic silicon-diode array detectors in megavoltage photon beams: does the fabrication technology matter? A medical physicist's perspective

A family of prototype 2D monolithic silicon-diode array detectors (MP512, Duo, Octa) has been proposed by the Centre for Medical Radiation Physics, University of Wollongong (Australia) for relative dosimetry in small megavoltage photon beams. These detectors, which differ in the topology of their 512 sensitive volumes, were originally fabricated on bulk p-type substrates. More recently, they have also been fabricated on epitaxial p-type substrates. In the literature, their performance has been individually characterized for quality assurance (QA) applications. The present study directly assessed and compared that of a MP512-bulk and that of a MP512-epitaxial in terms of radiation hardness, long-term stability, response linearity with dose, dose per pulse and angular dependence. Their measurements of output factors, off-axis ratios and percentage depth doses in square radiation fields collimated by the jaws and produced by 6 MV and 10 MV flattened photon beams were then benchmarked against those by commercially available detectors. The present investigation was aimed at establishing, from a medical physicist's perspective, how the bulk and epitaxial fabrication technologies would affect the implementation of the MP512s into a QA protocol. Based on results, the MP512-epitaxial would offer superior radiation hardness, long-term stability and achievable uniformity and reproducibility of the response across the 2D active area.

Long-term follow-up after traditional versus modified perineal approach in the management of female epispadias

OBJECTIVE

Isolated female epispadias (IFE) is a rare congenital anomaly. The defect extends to the bladder neck, which is usually incompetent. The traditional surgical approach includes urethral and genital reconstruction in the first year, followed by bladder neck reconstruction (Young-Dees-Leadbetter cervicoplasty (YDL)) at the age of social continence. An alternative single-stage technique includes urethral, bladder neck and clitoris repair by a perineal approach. The aim of the present study was to describe long-term follow-up of patients who underwent the traditional vs alternative approach.

MATERIALS AND METHODS

A retrospective review was performed of all female epispadias cases managed between 2000 and 2013. The YDL procedure (Group 1) vs single-stage perineal approach (Group 2) cases were followed and compared. Collected variables included: patients' demographics, age at diagnosis and surgery, presence of associated anomalies, clinical presentation, presence of vesicoureteral reflux (VUR), and pre-operative and postoperative continence.

RESULTS

A total of 12 cases of female epispadias were managed and followed between 2000 and 2013. No major complications occurred in either group. Urinary continence evaluated in seven children showed that none (0/3) and 4/7 (57%) were continent following the initial procedure in Group 1 and Group 2, respectively. All patients in Group 1 failed to achieve continence and required re-intervention.

CONCLUSIONS

Female epispadias could be successfully repaired using a single-stage modified perineal approach that achieved good continence with volitional voiding, good cosmetic results and compared favorably with the ones repaired with the YDL technique. The additional step of performing bladder neck tailoring to achieve a funneling configuration seemed to be useful in improving continence.

Technical Note: Experimental results from a prototype high-field inline MRI-linac

PURPOSE

The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac.

METHODS

The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enabling shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID).

RESULTS

(1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis.

CONCLUSIONS

A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.

Sensitivity of assays for the detection of HPA-1a antibodies: results of an international workshop demonstrating the impact of cation chelation from integrin αIIbβ3 on three widely used assays

BACKGROUND AND OBJECTIVES

HPA-1a antibodies account for 70-80% of cases of fetal-neonatal alloimmune thrombocytopenia (FNAIT) in Caucasians. However, numerous workshops have demonstrated variability in their detection. We recently showed that exposure of αIIbβ3 to ethylene diamine tetraacetic acid (EDTA) affected binding of many anti-αIIbβ3 monoclonal, and HPA-1a allo-, antibodies; this adversely affected sensitivity of the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay and indirect platelet immunofluorescence test (PIFT). This study presents results from an international workshop studying the impact of cation chelation on HPA-1a antibody detection in routine diagnostic laboratories.

MATERIALS AND METHODS

Serum and EDTA-anticoagulated plasma samples containing anti-HPA-1a were distributed to 39 laboratories. Participants were asked to detect and identify any HPA antibodies present.

RESULTS

2/39 (5.1%) participants were able to detect and identify anti-HPA-1a in the serum, but not in the plasma sample. EDTA plasma reduced MAIPA assay sensitivity by ≥ 20% in 17/24 (70.8%) laboratories and by ≥ 50% in 9/24 (37.5%) when using HPA-1a1a platelets (mean: 27.7%, range 0-85.1%); when using HPA-1a1b platelets 3/4 (75%), participants reported ≥ 50% loss of sensitivity (mean 65.6%, range 0-96.6%). A small but significant increase in optical densities was observed in antigen capture ELISA assays when using plasma (mean difference: 0.081, P < 0.01). Insufficient PIFT data were returned to draw firm conclusions.

CONCLUSION

Use of EDTA plasma significantly affects the sensitivity of the MAIPA assay and can affect detection of even potent, FNAIT-causing examples of anti-HPA-1a. These data highlight the importance of use of αIIbβ3 in an appropriate conformation for the sensitive detection of anti-HPA-1a.

The potential for an enhanced role for MRI in radiation-therapy treatment planning

The exquisite soft-tissue contrast of magnetic resonance imaging (MRI) has meant that the technique is having an increasing role in contouring the gross tumor volume (GTV) and organs at risk (OAR) in radiation therapy treatment planning systems (TPS). MRI-planning scans from diagnostic MRI scanners are currently incorporated into the planning process by being registered to CT data. The soft-tissue data from the MRI provides target outline guidance and the CT provides a solid geometric and electron density map for accurate dose calculation on the TPS computer. There is increasing interest in MRI machine placement in radiotherapy clinics as an adjunct to CT simulators. Most vendors now offer 70 cm bores with flat couch inserts and specialised RF coil designs. We would refer to these devices as MR-simulators. There is also research into the future application of MR-simulators independent of CT and as in-room image-guidance devices. It is within the background of this increased interest in the utility of MRI in radiotherapy treatment planning that this paper is couched. The paper outlines publications that deal with standard MRI sequences used in current clinical practice. It then discusses the potential for using processed functional diffusion maps (fDM) derived from diffusion weighted image sequences in tracking tumor activity and tumor recurrence. Next, this paper reviews publications that describe the use of MRI in patient-management applications that may, in turn, be relevant to radiotherapy treatment planning. The review briefly discusses the concepts behind functional techniques such as dynamic contrast enhanced (DCE), diffusion-weighted (DW) MRI sequences and magnetic resonance spectroscopic imaging (MRSI). Significant applications of MR are discussed in terms of the following treatment sites: brain, head and neck, breast, lung, prostate and cervix. While not yet routine, the use of apparent diffusion coefficient (ADC) map analysis indicates an exciting future application for functional MRI. Although DW-MRI has not yet been routinely used in boost adaptive techniques, it is being assessed in cohort studies for sub-volume boosting in prostate tumors.

An International reference reagent for the detection of anti-human neutrophil antigen-1a

BACKGROUND AND OBJECTIVES

Testing for neutrophil antibodies has become more common as awareness of transfusion-related acute lung injury (TRALI) has increased. However, unlike other areas of blood cell antibody testing, there are no certified reference reagents available with which laboratories can determine the sensitivity of detection of their assays. This report describes the production and evaluation of a freeze-dried preparation of human plasma, code 09/284, containing anti-human neutrophil antigen-1a (anti-HNA-1a) for use as a minimum sensitivity reagent.

MATERIALS AND METHODS

One-millilitre of aliquots of plasma containing anti-HNA-1a were freeze-dried in glass ampoules. To characterize the material, 24 laboratories took part in an international collaborative study. The participants evaluated doubling dilutions of the material using their in-house routine assays and recorded the highest dilution in which the antibody could be detected.

RESULTS

When diluted 1 in 4, most laboratories were able to detect the anti-HNA-1a in the material, and the participants agreed that this was an appropriate level to set as the minimum sensitivity required.

CONCLUSIONS

In October 2011, the WHO Expert Committee on Biological Standardization approved the material 09/284 as an International Reference Reagent for the detection of anti-HNA-1a.

SU-E-T-20: Removal of Electron Contamination in Longitudinal Field MRI-Linac Systems: A Monte Carlo Study

PURPOSE

The prototype inline MRI-linac system has some advantages over perpendicular models including avoiding the electron return effect. One of the disadvantages of the inline approach is the increased skin dose, estimated to be 400-1000% of the dmax dose. The purpose of this work was to design a feasible method to reduce this skin dose to acceptable levels.

METHODS

Magnetic modeling of proposed MRI-linac designs have been simulated with the inclusion of an optimized permanent magnet system to purge/deflect the electron contamination. The region of air above the phantom was also replaced with a helium bag (region of helium gas) and a beam scrapper below the deflector was added to collect deflected off-axis contamination. Monte Carlo simulations were then performed including the accurate 3D magnetic field maps. Surface dosimetry was recorded to verify the changes to the skin doses.

RESULTS

Magnetic modelling showed that an optimized NdFeB permanent magnet system located outside the MRI coils (below the MLC's) can provide a strong enough region to purge/deflect a significant portion of the electron contamination from the x-ray beam. The impact on the MRI uniformity is around 100 ppm and hence is correctable via active/passive shimming of the MRI. The helium region also significantly limits the production of contamination traveling towards the phantom surface. Entry doses near CAX are predicted to be similar to the 0 T case.

CONCLUSIONS

Magnetic and Monte Carlo modeling were performed to estimate the effect that a permanent magnet purging system, beam scrapper, and helium bag would have on lowering the skin doses in an inline MRI-Linac system. MRI non-uniformities introduced by the deflector could be corrected, contamination is mostly purged or blocked, and the helium bag minimizes air-generated contamination. As a result skin doses are comparable to having zero magnetic field.

Independent quality assurance of a helical tomotherapy machine using the dose magnifying glass

PURPOSE

Helical tomotherapy is a complex delivery technique, integrating CT image guidance and intensity modulated radiotherapy in a single system. The integration of the CT detector ring on the gantry not only allows patient position verification but is also often used to perform various QA procedures. This convenience lacks the rigor of a machine-independent QA process.

METHODS

In this article, a Si strip detector, known as the Dose Magnifying Glass (DMG), was used to perform machine-independent QA measurements of the multileaf collimator alignment, leaf open time threshold, and leaf fluence output factor (LFOF).

RESULTS

The DMG measurements showed good agreements with EDR2 film for the MLC alignment test while the CT detector agrees well with DMG measurements for leaf open time threshold and LFOF measurements. The leaf open time threshold was found to be approximately 20 ms. The LFOF measured with the DMG agreed within error with the CT detector measured LFOF.

CONCLUSIONS

The DMG with its 0.2 mm spatial resolution coupled to TERA ASIC allowed real-time high temporal resolution measurements of the tomotherapy leaf movement. In conclusion, DMG was shown to be a suitable tool for machine-independent QA of a tomotherapy unit.