Deep learning MRI-only synthetic-CT generation for pelvis, brain and head and neck cancers.

BACKGROUND AND PURPOSE: MRI-only planning relies on dosimetrically accurate synthetic-CT (sCT) generation to allow dose calculation. Here we validated the dosimetric accuracy of sCTs generated using a deep learning algorithm for pelvic, brain and head and neck (H&N) cancer sites using variable MRI data from multiple scanners. METHODS: sCT generation models were trained using a cycle-GAN algorithm, using paired MRI-CT patient data. Input MRI sequences were: T2 for pelvis, T1 with gadolinium (T1Gd) and T2 FLAIR for brain and T1 for H&N. Patient validation sCTs were generated for each site (49 - pelvis, 25 - brain and 30 - H&N). VMAT plans, following local clinical protocols, were calculated on planning CTs and recalculated on sCTs. HU and dosimetric differences were assessed, including DVH differences and gamma index (2 %/2mm). RESULTS: Mean absolute error (MAE) HU differences were; 48.8 HU (pelvis), 118 HU (T2 FLAIR brain), 126 HU (T1Gd brain) and 124 HU (H&N). Mean primary PTV D95% dose differences for all sites were < 0.2 % (range: -0.9 to 1.0 %). Mean 2 %/2mm and 1 %/1mm gamma pass rates for all sites were > 99.6 % (min: 95.3 %) and > 97.3 % (min: 80.1 %) respectively. For all OARs for all sites, mean dose differences were < 0.4 %. CONCLUSION: Generated sCTs had excellent dosimetric accuracy for all sites and sequences. The cycle-GAN model, available on the research version of a commercial treatment planning system, is a feasible method for sCT generation with high clinical utility due to its ability to use variable input data from multiple scanners and sequences.

The role and potential of using quantitative MRI biomarkers for imaging guidance in brain cancer radiotherapy treatment planning: A systematic review.

Background and purpose: Improving the accuracy of brain tumour radiotherapy (RT) treatment planning is important to optimise patient outcomes. This systematic review investigates primary studies providing clinical evidence for the integration of quantitative magnetic resonance imaging (qMRI) biomarkers and MRI radiomics to optimise brain tumour RT planning. Materials and methods: PubMed, Scopus, Embase and Web of Science databases were searched for all years until June 21, 2022. The search identified original articles demonstrating clinical evidence for the use of qMRI biomarkers and MRI radiomics for the optimization of brain cancer RT planning. Relevant information was extracted and tabulated, including qMRI metrics and techniques, impact on RT plan optimization and changes in target and normal tissue contouring and dose distribution. Results: Nineteen articles met the inclusion criteria. Studies were grouped according to the qMRI biomarkers into: 1) diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI; five studies); 2) diffusion tensor imaging (DTI; seven studies); and 3) MR spectroscopic imaging (MRSI; seven studies). No relevant MRI-based radiomics studies were identified. Integration of DTI maps offers the potential for improved organs at risk (OAR) sparing. MRSI metabolic maps are a promising technique for improving delineation accuracy in terms of heterogeneity and infiltration, with OAR sparing. No firm conclusions could be drawn regarding the integration of DWI metrics and PWI maps. Conclusions: Integration of qMRI metrics into RT planning offers the potential to improve delineation and OAR sparing. Clinical trials and consensus guidelines are required to demonstrate the clinical benefits of such approaches.

Assessment of CBCT-based synthetic CT generation accuracy for adaptive radiotherapy planning.

PURPOSE: Cone-beam CT (CBCT)-based synthetic CT (sCT) dose calculation has the potential to make the adaptive radiotherapy (ART) pathway more efficient while removing subjectivity. This study assessed four sCT generation methods using 15 head-and-neck rescanned ART patients. Each patient's planning CT (pCT), rescan CT (rCT), and CBCT post-rCT was acquired with the CBCT deformably registered to the rCT (dCBCT). METHODS: The four methods investigated were as follows: method 1-deformably registering the pCT to the dCBCT. Method 2-assigning six mass density values to the dCBCT. Method 3-iteratively removing artifacts and correcting the dCBCT Hounsfield units (HU). Method 4-using a cycle general adversarial network machine learning model (trained with 45 paired pCT and CBCT). Treatment plans were created on the rCT and recalculated on each sCT. Planning target volume (PTV) and organ-at-risk (OAR) structures were contoured by clinicians on the rCT (high-dose PTV, low-dose PTV, spinal canal, larynx, brainstem, and parotids) to allow the assessment of dose-volume histogram statistics at clinically relevant points. RESULTS: The HU mean absolute error (MAE) and minimum dose gamma index pass rate (2%/2 mm) were calculated, and the generation time was measured for 15 patients using the rCT as the comparator. For methods 1-4 the MAE, gamma index analysis, and generation time were as follows: 59.7 HU, 100.0%, and 143 s; 164.2 HU, 95.2%, and 232 s; 75.7 HU, 99.9%, and 153 s; and 79.4 HU, 99.8%, and 112 s, respectively. Dose differences for PTVs and OARs were all <0.3 Gy except for method 2 (<0.5 Gy). CONCLUSION: All methods were considered clinically viable. The machine learning method was found to be most suitable for clinical implementation due to its high dosimetric accuracy and short generation time. Further investigation is required for larger anatomical changes between the CBCT and pCT and for other anatomical sites.

Optimal settings and advantages of drones as a tool for canopy arthropod collection.

The growing field of aeroecology is limited by difficulties associated with sampling in the air column. Aerial insects are particularly hard to sample, despite being the main prey in the air column, with some recent studies attempting to use drones as a collection method. We conducted a study to determine the optimal drone settings for collecting insects above the canopy, where drones are seldom used. By attaching a net to the body of a small, commercial drone, we tested yield from different height, speed, and net settings in wetlands, as well as compared insect diversity across different habitat canopies. Height was the most important setting; grazing the canopy yielded significantly more insects than flying one meter above it. Speed, drone type, and net size did not influence the number of insects caught per trial. Wetland canopies had higher abundance, diversity, and species richness in its arthropod populations compared to forest canopies or lakes. Compared to the yield of Lindgren funnels-a traditional sampling method in entomology-drones captured higher diversity and abundance of insects in a fraction of the time. This study confirms that drones are an efficient and accurate way to collect canopy arthropods.

Outcomes following common bile duct exploration versus endoscopic stone extraction before, during and after laparoscopic cholecystectomy for patients with common bile duct stones.

BACKGROUND: Laparoscopic common bile duct exploration (LCBDE) and endoscopic retrograde cholangiopancreatography (ERCP) are two methods of retrieving common bile duct (CBD) stones. The best method for CBD stone removal is debatable. The aim of this study was to compare outcomes following LCBDE and/or ERCP, including laparoscopic cholecystectomy. METHODS: Data were collected retrospectively for patients undergoing LCBDE and/or ERCP at a single centre from 2008 to 2018. Patients were grouped by intention-to-treat (single-stage LCBDE, pre-operative-, intra-operative-, or post-operative ERCP) and eventual plan (surgical or endoscopic). Outcomes included complication rates (minor Clavien-Dindo 1/2, major Clavien-Dindo 3/4, non-biliary complications) and mortality. RESULTS: Of 671 patients, 578 patients received LCBDE and 93 patients received ERCP as primary care. Endoscopic clearance had significantly higher complications and mortality compared to surgical clearance. On an intention-to-treat basis LCBDE had the lowest minor-, major- and non-biliary complications, and mortality (5.2%, 6.1%, 2.9% and 0.5%, respectively), whilst pre-operative ERCP the worst (39.6%, 27.1%, 29.2% and 8.3%, respectively) (p=<0.001). LCBDE and postERCP had similar major complications and mortality. CONCLUSION: Surgical clearance of CBD stones was potentially safer than endoscopic clearance. Pre-operative ERCP had the worst outcomes. LCBDE and postERCP are likely to have similar short-term patient outcomes.

The benefit of MR-only radiotherapy treatment planning for anal and rectal cancers: A planning study.

INTRODUCTION: Limited evidence exists showing the benefit of magnetic resonance (MR)-only radiotherapy treatment planning for anal and rectal cancers. This study aims to assess the impact of MR-only planning on target volumes (TVs) and treatment plan doses to organs at risks (OARs) for anal and rectal cancers versus a computed tomography (CT)-only pathway. MATERIALS AND METHODS: Forty-six patients (29 rectum and 17 anus) undergoing preoperative or radical external beam radiotherapy received CT and T2 MR simulation. TV and OARs were delineated on CT and MR, and volumetric arc therapy treatment plans were optimized independently (53.2 Gy/28 fractions for anus, 45 Gy/25 fractions for rectum). Further treatment plans assessed gross tumor volume (GTV) dose escalation. Differences in TV volumes and OAR doses, in terms of Vx Gy (organ volume (%) receiving x dose (Gy)), were assessed. RESULTS: MR GTV and primary planning TV (PTV) volumes systematically reduced by 13 cc and 98 cc (anus) and 44 cc and 109 cc (rectum) respectively compared to CT volumes. Statistically significant OAR dose reductions versus CT were found for bladder and uterus (rectum) and bladder, penile bulb, and genitalia (anus). With GTV boosting, statistically significant dose reductions were found for sigmoid, small bowel, vagina, and penile bulb (rectum) and vagina (anus). CONCLUSION: Our findings provide evidence that the introduction of MR (whether through MR-only or CT-MR pathways) to radiotherapy treatment planning for anal and rectal cancers has the potential to improve treatments. MR-related OAR dose reductions may translate into less treatment-related toxicity for patients or greater ability to dose escalate.

Confinement loss of anti-resonant capillaries with curved boundaries.

A systematic analysis of the dependence of the confinement loss of an anti-resonant capillary on the curvature of the core surround is presented. The core boundary is described by circular arcs and the construction allows for a wide range of core shapes to be considered. It is found that both negative and positive curvatures substantially reduce the confinement loss relative to that of a circular anti-resonant capillary and that this effect is insensitive to the size of the core relative to the wavelength and to the properties of the glass capillary wall. In contrast, for a solid core surround there is a small increase in the confinement loss with curvature. Results of scalar and vector calculations are shown to be similar. A qualitative explanation of the results is proposed based on azimuthal confinement of the wave fields generated by the curved boundaries.

Patient position verification in magnetic-resonance imaging only radiotherapy of anal and rectal cancers.

BACKGROUND AND PURPOSE: Magnetic resonance (MR)-only treatment pathways require either the MR-simulation or synthetic-computed tomography (sCT) as an alternative reference image for cone beam computed tomography (CBCT) patient position verification. This study assessed whether using T2 MR or sCT as CBCT reference images introduces systematic registration errors as compared to CT for anal and rectal cancers. MATERIALS AND METHODS: A total of 32 patients (18 rectum,14 anus) received pre-treatment CT- and T2 MR- simulation. Routine treatment CBCTs were acquired. sCTs were generated using a validated research model. The local clinical registration protocol, using a grey-scale registration algorithm, was performed for 216 CBCTs using CT, MR and sCT as the reference image. Linear mixed effects modelling identified systematic differences between modalities. RESULTS: Systematic translation and rotation differences to CT for MR were -0.3 to + 0.3 mm and -0.1 to 0.4° for anal cancers and -0.4 to 0.0 mm and 0.0 to 0.1° for rectal cancers, and for sCT were -0.4 to + 0.8 mm, -0.1 to 0.2° for anal cancers and -0.6 to + 0.2 mm, -0.1 to + 0.1° for rectal cancers. CONCLUSIONS: T2 MR or sCT can successfully be used as reference images for anal and rectal cancer CBCT position verification with systematic differences to CT <±1 mm and <±0.5°. Clinical enabling of alternative modalities as reference images by vendors is required to reduce challenges associated with their use.

Fewer bat passes are detected during small, commercial drone flights.

Advances in technological capabilities, operational simplicity and cost efficiency have promoted the rapid integration of unmanned aerial vehicles (UAVs) into ecological research, providing access to study taxa that are otherwise difficult to survey, such as bats. Many bat species are currently at risk, but accurately surveying populations is challenging for species that do not roost in large aggregations. Acoustic recorders attached to UAVs provide an opportunity to survey bats in challenging habitats. However, UAVs may alter bat behaviour, leading to avoidance of the UAV, reduced detection rates and inaccurate surveys. We evaluated the number of bat passes detected with and without the presence of a small, commercial UAV in open habitats. Only 22% of bat passes were recorded in the presence of the UAV (0.23 ± 0.09 passes/min) compared to control periods without the UAV (1.03 ± 0.17 passes/min), but the effect was smaller on the big brown bat/silver-haired bat (Eptesicus fuscus/Lasionycteris noctivagans) acoustic complex. Noise interference from the UAV also reduced on-board bat detection rates. We conclude that acoustic records attached to UAVs may inaccurately survey bat populations due to low and variable detection rates by such recorders.

Additive Manufacturing of Sensors for Military Monitoring Applications.

The US Department of Defense (DoD) realizes the many uses of additive manufacturing (AM) as it has become a common fabrication technique for an extensive range of engineering components in several industrial sectors. 3D Printed (3DP) sensor technology offers high-performance features as a way to track individual warfighters on the battlefield, offering protection from threats such as weaponized toxins, bacteria or virus, with real-time monitoring of physiological events, advanced diagnostics, and connected feedback. Maximum protection of the warfighter gives a distinct advantage over adversaries by providing an enhanced awareness of situational threats on the battle field. There is a need to further explore aspects of AM such as higher printing resolution and efficiency, with faster print times and higher performance, sensitivity and optimized fabrication to ensure that soldiers are more safe and lethal to win our nation's wars and come home safely. A review and comparison of various 3DP techniques for sensor fabrication is presented.

Should Common Bile Duct Exploration for Choledocholithiasis Be a Specialist-Only Procedure?

Background: Common bile duct exploration (CBDE) is performed uncommonly. Issues surrounding its uptake in the laparoscopic era include perceived difficulty and lack of training. We aim to determine the success of CBDE performed by "specialist" and "nonspecialist" common bile duct (CBD) surgeons to determine whether there is a substantial difference in success and safety. Methods: A 10-year retrospective audit was performed of patients undergoing CBD exploration for choledocholithiasis. Northern Health maintains an on-call available "specialist" CBD surgeon roster to aid with CBDE. Results: Five hundred fifty-one patients were identified, of which 489/551 (88.7%) patients had stones successfully cleared. Specialists had a higher success rate (90.8% versus 82.6%, P = .008), associated with a longer surgical time. Method (transcystic or transductal), approach (laparoscopic or open), and indication for operation were similar between groups. There was no significant difference in complications. To be confident of a surgeon having an 80% success rate, 70 procedures over 10 years were required, however, an "in-control" 50% success rate may only require 1 procedure per year. Conclusion: While specialist CBDE surgeons have improved success rates, nonspecialist general surgeons also have a good and comparable success rate with an equivalent complication rate. With realistic annual targets, nonspecialist CBD surgeons should be encouraged to perform CBDE in centers without specialist support.

Factors That Predict the Success of Laparoscopic Common Bile Duct Exploration for Choledocholithiasis: A 10-Year Study.

BACKGROUND: Laparoscopic common bile duct exploration (LCBDE) can be performed to treat choledocholithiasis at the time of laparoscopic cholecystectomy. The aim of this study was to identify factors that predict the success of LCBDE. MATERIALS AND METHODS: A retrospective audit was performed on patients who underwent LCBDE for the management of choledocholithiasis at Northern Health between 2008 and 2018. RESULTS: A total of 513 patients were identified with an overall success rate of 90.8%. Most LCBDE were done through a transcystic approach with the remainder through a choledochotomy. When comparing patients with a successful operation to those that were unsuccessful, univariate analysis demonstrated significant differences in preoperative white cell count and number of duct stones found. Age and elevated nonbilirubin liver function tests were found to be significant factors associated with the failure of LCBDE on multivariate analysis. The likelihood of a failed operation in those with multiple stones was observed to be almost halved compared with patients with single stone although this did not reach significance [odds ratio (OR): 0.53, 95% confidence interval (CI): 0.28-1.01, P=0.055]. Multivariate analysis indicated that unsuccessful procedures (OR: 10.13, 95% CI: 4.34-23.65, P<0.001) and multiple duct stones (OR: 3.79, 95% CI: 1.66-8.67, P=0.002) were associated with an increased risk of severe complications. CONCLUSIONS: A single impacted stone may be more difficult to remove, however complications were more likely to be associated with multiple duct stones. With no other clinically relevant predictive factors, and because of the high success of the procedure and the low morbidity, LCBDE remains an option for all patients with choledocholithiasis.

Toward genetic modification of plant-parasitic nematodes: delivery of macromolecules to adults and expression of exogenous mRNA in second stage juveniles.

Plant-parasitic nematodes are a continuing threat to food security, causing an estimated 100 billion USD in crop losses each year. The most problematic are the obligate sedentary endoparasites (primarily root knot nematodes and cyst nematodes). Progress in understanding their biology is held back by a lack of tools for functional genetics: forward genetics is largely restricted to studies of natural variation in populations and reverse genetics is entirely reliant on RNA interference. There is an expectation that the development of functional genetic tools would accelerate the progress of research on plant-parasitic nematodes, and hence the development of novel control solutions. Here, we develop some of the foundational biology required to deliver a functional genetic tool kit in plant-parasitic nematodes. We characterize the gonads of male Heterodera schachtii and Meloidogyne hapla in the context of spermatogenesis. We test and optimize various methods for the delivery, expression, and/or detection of exogenous nucleic acids in plant-parasitic nematodes. We demonstrate that delivery of macromolecules to cyst and root knot nematode male germlines is difficult, but possible. Similarly, we demonstrate the delivery of oligonucleotides to root knot nematode gametes. Finally, we develop a transient expression system in plant-parasitic nematodes by demonstrating the delivery and expression of exogenous mRNA encoding various reporter genes throughout the body of H. schachtii juveniles using lipofectamine-based transfection. We anticipate these developments to be independently useful, will expedite the development of genetic modification tools for plant-parasitic nematodes, and ultimately catalyze research on a group of nematodes that threaten global food security.

Quality of recovery assessment of day case and multiday stay patients undergoing elective laparoscopic cholecystectomy.

Objectives: Many laparoscopic cholecystectomy operations are performed with at least overnight admission. Current research shows that laparoscopic cholecystectomy is safe and feasible to do as a day case. Patient centred outcomes are less well understood. Material and Methods: Elective laparoscopic cholecystectomy patients at a single metropolitan hospital in Melbourne, Australia were surveyed 24 hours after surgery using the 15-question Quality of Recovery (QoR-15) survey. A comparison was made between day case surgeries and multi-day surgeries. Results: One hundred and eight patients were recruited consisting of 34 day case and 74 multi-day patients. Patient groups did not differ in terms of age, sex or postoperative morbidity. The multi-day group had a higher proportion of comorbid patients (p-value = 0.03). There was no significant dif- ference in overall QoR-15 score between the two groups, although there was an observed trend towards a higher score in the day case group (132.0 vs 127.9, p= 0.147). QoR-15 individual question results showed that day cases rated significantly better for sleep quality and for less feelings of anxiety or worry. The differences narrowed when comparing patient groups as they were booked (intention-to-treat). There were no identified sub-groups that had a significantly higher score if admitted multi-day. Conclusion: Quality of recovery following day case laparoscopic cholecystectomy is just as good, if not better, than multi-day cases. Laparoscopic cholecystectomy as a day case is both safe and economically superior to multi-day management. This gives further weight to current recommendations suggesting that the majority of laparoscopic cholecystectomy operations could be performed as day cases.

Multicentre, deep learning, synthetic-CT generation for ano-rectal MR-only radiotherapy treatment planning.

BACKGROUND AND PURPOSE: Comprehensive dosimetric analysis is required prior to the clinical implementation of pelvic MR-only sites, other than prostate, due to the limited number of site specific synthetic-CT (sCT) dosimetric assessments in the literature. This study aims to provide a comprehensive assessment of a deep learning-based, conditional generative adversarial network (cGAN) model for a large ano-rectal cancer cohort. The following challenges were investigated; T2-SPACE MR sequences, patient data from multiple centres and the impact of sex and cancer site on sCT quality. METHOD: RT treatment position CT and T2-SPACE MR scans, from two centres, were collected for 90 ano-rectal patients. A cGAN model trained using a focal loss function, was trained and tested on 46 and 44 CT-MR ano-rectal datasets, paired using deformable registration, respectively. VMAT plans were created on CT and recalculated on sCT. Dose differences and gamma indices assessed sCT dosimetric accuracy. A linear mixed effect (LME) model assessed the impact of centre, sex and cancer site. RESULTS: A mean PTV D95% dose difference of 0.1% (range: -0.5% to 0.7%) was found between CT and sCT. All gamma index (1%/1 mm threshold) measurements were >99.0%. The LME model found the impact of modality, cancer site, sex and centre was clinically insignificant (effect ranges: -0.4% and 0.3%). The mean dose difference for all OAR constraints was 0.1%. CONCLUSION: Focal loss cGAN models using T2-SPACE MR sequences from multiple centres can produce generalisable, dosimetrically accurate sCTs for ano-rectal cancers.

Bacterial Community Structure Dynamics in Meloidogyne incognita-Infected Roots and Its Role in Worm-Microbiome Interactions.

Plant parasitic nematodes such as Meloidogyne incognita have a complex life cycle, occurring sequentially in various niches of the root and rhizosphere. They are known to form a range of interactions with bacteria and other microorganisms that can affect their densities and virulence. High-throughput sequencing can reveal these interactions in high temporal and geographic resolutions, although thus far we have only scratched the surface. In this study, we have carried out a longitudinal sampling scheme, repeatedly collecting rhizosphere soil, roots, galls, and second-stage juveniles from 20 plants to provide a high-resolution view of bacterial succession in these niches, using 16S rRNA metabarcoding. Our findings indicate that a structured community develops in the root, in which gall communities diverge from root segments lacking a gall, and that this structure is maintained throughout the crop season. We describe the successional process leading toward this structure, which is driven by interactions with the nematode and later by an increase in bacteria often found in hypoxic and anaerobic environments. We present evidence that this structure may play a role in the nematode's chemotaxis toward uninfected root segments. Finally, we describe the J2 epibiotic microenvironment as ecologically deterministic, in part, due to the active bacterial attraction of second-stage juveniles.IMPORTANCE The study of high-resolution successional processes within tightly linked microniches is rare. Using the power and relatively low cost of metabarcoding, we describe the bacterial succession and community structure in roots infected with root-knot nematodes and in the nematodes themselves. We reveal separate successional processes in galls and adjacent non-gall root sections, which are driven by the nematode's life cycle and the progression of the crop season. With their relatively low genetic diversity, large geographic range, spatially complex life cycle, and the simplified agricultural ecosystems they occupy, root-knot nematodes can serve as a model organism for terrestrial holobiont ecology. This perspective can improve our understanding of the temporal and spatial aspects of biological control efficacy.

Infection by cyst nematodes induces rapid remodelling of developing xylem vessels in wheat roots.

Cyst nematodes induce host-plant root cells to form syncytia from which the nematodes feed. Comprehensive histological investigation of these feeding sites is complicated by their variable shape and their positions deep within root tissue. Using tissue clearing and confocal microscopy, we examined thick (up to 150 µm) sections of wheat roots infected by cereal cyst nematodes (Heterodera avenae). This approach provided clear views of feeding sites and surrounding tissues, with resolution sufficient to reveal spatial relationships among nematodes, syncytia and host vascular tissues at the cellular level. Regions of metaxylem vessels near syncytia were found to have deviated from classical developmental patterns. Xylem vessel elements in these regions had failed to elongate but had undergone radial expansion, becoming short and plump rather than long and cylindrical. Further investigation revealed that vessel elements cease to elongate shortly after infection and that they later experience delays in secondary thickening (lignification) of their outer cell walls. Some of these elements were eventually incorporated into syncytial feeding sites. By interfering with a developmental program that normally leads to programmed cell death, H. avenae may permit xylem vessel elements to remain alive for later exploitation by the parasite.

Intravascular ultrasound-guided laparoscopic division of the median arcuate ligament.

Median arcuate ligament syndrome is a rare and poorly understood condition that can have a significant impact on the quality of life of patients. Diagnosis is often difficult and delayed because of the need to exclude other pathologic processes. Treatment strategies traditionally involve open or laparoscopic division of the median arcuate ligament, with or without vascular reconstruction. This report portrays a case of median arcuate ligament syndrome with compression of two visceral arteries and distal embolic complications. A novel hybrid technique is described using intravascular ultrasound technology to aid in laparoscopic median arcuate ligament division. This allowed real-time intravascular visualization of the compressive segment, guided release of the ligament fibers, and demonstrated confirmation of decompression.

A Single, Shared Triploidy in Three Species of Parasitic Nematodes.

The root-knot nematodes of the genus Meloidogyne are important and damaging parasites capable of infecting most flowering plants. Within this genus, several species of the Meloidogyne incognita group show evidence of paleopolyploidy in their genomes. We used our software tool POInT, the Polyploidy Orthology Inference Tool, to phylogenetically model the gene losses that followed that polyploidy. These models, and simulations based on them, show that three of these species (M. incognita, M. arenaria and M. javanica) descend from a single common hybridization event that yielded triplicated genomes with three distinguishable subgenomes. While one of the three subgenomes shows elevated gene loss rates relative to the other two, this subgenome does not show elevated sequence divergence. In all three species, ancestral loci where two of the three gene copies have been lost are less likely to have orthologs in Caenorhabditis elegans that are lethal when knocked down than are ancestral loci with surviving duplicate copies.