WE-G-217BCD-09: Calibration of a DRR Algorithm

PURPOSE

To calibrate an algorithm for digitally reconstructed radiographs (DRRs) such that synthetic projections cast through an object in a fan-beam CT (FBCT) optimally match cone-beam CT projections of the same object.

METHODS

Our DRR algorithm models the transmission of primary photons through an object with a ray-tracing algorithm that samples the CT at small steps along each source-detector pixel path. Sampled CT values are converted to linear attenuation coefficients (LACs), scaled by the step-size, and added to a running sum for each detector pixel. We made attenuation measurements of materials of known CT number to calibrate a CT to LAC conversion function for our FBCT and CBCT systems. DRRs are post- processed to reproduce the tube output, source fluence distribution, and detector response of the CBCT system. In addition, they are modified to account for scatter, beam hardening, and detector veiling glare. Finally, we determined CBCT geometry parameters using a specially designed phantom.

RESULTS

We analyzed the quality of our DRR algorithm by directly comparing synthetic DRRs cast through the FBCT of a Catphan® phantom with actual CBCT projections of the phantom. Line plots comparing the intensity profiles of the DRRs and CBCT projections show that uncorrected DRRs do not align perfectly with the projections. However, when scatter, beam hardening, and veiling glare are modeled there is much closer agreement. Simulations with different geometry phantom shapes and sizes recommend a cylindrical phantom 150 mm in diameter. Computational times under one second per DRR are achieved using a GPU for a simulated 1024×768 pixel detector with a 512×512×281 mm CT volume and 0.5 mm ray step-size.

CONCLUSIONS

Our DRR algorithm is able to closely reproduce actual CBCT projections taken through a test object. It is optimized specifically for the FBCT and CBCT systems in our department. Funded in part by NCI grants R01CA123299 and P01CA116602. The authors report no conflicts of interest.

MO-F-BRA-02: Evaluation of 4D CT to 4D Cone-Beam CT Deformable Image Registration for Lung Cancer Adaptive Radiation Therapy

PURPOSE

To evaluate two deformable image registration (DIR) algorithms for the purpose of contour mapping to support image guided adaptive radiotherapy (IGART) with 4D cone beam CT (4DCBCT).

METHODS

Eleven locally advanced non-small cell lung cancer (NSCLC) patients underwent one planning 4D fan- beam CT (4DFBCT) and seven weekly 4DCBCT scans. Gross tumor volume (GTV) and carina were delineated by a physician in all 4D images. For day to day registration, the end of inspiration 4DFBCT phase was deformably registered to the corresponding phase in each 4DCBCT image. For phase to phase registration, the end of inspiration phase from each 4D image was registered to end of expiration phase. The delineated contours were warped using the resulting transforms and compared to the manual contours through Dice similarity coefficient (DSC), false positive and false negative indices, and, for carina, target registration error (TRE). Two DIR algorithms were tested: 1) small deformation, inverse consistent linear elastic (SICLE) algorithm and 2) Insight Toolkit diffeomorphic demons (DEMONS).

RESULTS

For day to day registrations, the mean DSC was 0.59 ± 0.16 after rigid registration, 0.72 ± 0.13 with SICLE and to 0.66 ± 0.18 with DEMONS. SICLE and DEMONS reduced TRE to 4.1 ± 2.1 mm and 5.8 ± 3.7 mm respectively, from 6.2 ± 3.5 mm; and reduced false positive index to 0.27 and 0.26 respectively from 0.46. Registration with the cone beam as the fixed image resulted in higher DSC than with the fan beam as fixed (p < 0.001). SICLE and DEMONS increased the DSC on average by 10.0% and 8.0% and reduced TRE by 2.8 mm and 2.9 mm respectively for phase to phase DIR.

CONCLUSIONS

DIR achieved more congruent mapping of target structures to delineations than rigid registration alone, although DIR performance varied with algorithm and patient. This work was supported by National Cancer Institute Grant No. P01 CA 116602.

Whole body MRI in the diagnosis of chronic recurrent multifocal osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) is a diagnosis of exclusion primarily in children and adolescents. As part of the essential criteria for the diagnosis of CRMO, multifocal lesions must be identified. We present the case of an 11-year-old boy with CRMO, whose diagnosis was facilitated by the use of whole body magnetic resonance imaging (WBMR), but not isotope bone scanning.

Strategies for improved targeting of therapeutic cells: implications for tissue repair

Multipotent mesenchymal stem cells (MSCs) have been suggested as a suitable cell source for cell-based treatments for diseases such as osteoarthritis due to their ability to differentiate towards chondrogenic and osteogenic lineages. MSCs can be obtained from a variety of tissue sources, are scalable for mass-production and immuno-privileged enabling their use for allogeneic cell therapy. However, recent pre-clinical studies and clinical trials point to the necessity of increasing engraftment and efficacy of MSCs. This review explores how cell surface modification of the cells can improve homing of MSCs and summarises the use of nanoparticles to enable gene delivery by stem cells as well as facilitate in vivo imaging. The use of advanced biomaterials and how they can be applied to reduce the overall dose of MSCs during therapeutic interventions while achieving optimal targeting efficiency of cells to the diseased sites are addressed. Particular attention is paid to methods that improve engraftment of MSCs to cartilage and research describing combinatorial approaches of particle-based cell therapies for improved regeneration of this tissue is reviewed. The use of such approaches will add to the array of potential regenerative therapeutics for treatment of osteoarthritis.

Comparison in maternal body composition between Caucasian Irish and Indian women

The use of body mass index (BMI) for the diagnosis of obesity has limitations, especially when comparing ethnic groups with different body proportions. The aim of this prospective study was to compare maternal body composition in early pregnancy between Caucasian Irish and Indian women. A total of 81 Indian women and 81 Irish Caucasian women were matched for age, parity and BMI. Maternal weight and height were measured, and body composition analysed using bioelectrical impedance. The Irish women were taller and weighed more than the Indian women (p<0.001). At any given BMI, the Indian women had a higher total body fat percentage, visceral fat level and high fat percentage than the Irish women (p=0.024, 0.001 and 0.001, respectively). Our findings suggest that lower BMI cut-offs should be used for screening for gestational diabetes mellitus in Indian women attending our antenatal services.

Palliative and end-of-life care in Newfoundland's deaf community

The deaf community is a distinct cultural and linguistic community (the uppercase D is a cultural identification). Compared to the general population, the deaf community, as a social group, experiences poorer health status. Deaf people seek care less frequently than the general population and have fewer interactions with the health system. Their encounters with the health system are often characterized by communication difficulties, fear, mistrust, and frustration. Qualitative research was used to explore the experiences of family caregivers who provided end-of-life care for a deaf person. Key findings indicate that the deaf community has limited understanding of their options for palliative and end-of-life care. Communication and health literacy are key barriers to accessing appropriate end-of-life care. Pain and symptom management, consideration of physical environments, and limited access to bereavement care are common issues faced by deaf people when caring for loved ones at the end of life.

Surveillance of verocytotoxigenic Escherichia coli in Irish bovine dairy herds

Verocytotoxigenic Escherichia coli (VTEC) are highly significant zoonotic threats to public health, and have been the causative agent implicated in numerous high-profile outbreaks affecting large numbers of people. Serovar O157 is most frequently linked with human illness; however, other serovars, such as O26, O103, O111 and O145, have also been implicated. This study aimed to characterize the prevalence and virulence determinants of these five serovars in Irish dairy farm herds, and their milk. Using real-time PCR (RTi-PCR), bovine rectal faecal swabs and raw milk samples, along with milk filters, were screened for the presence of vt genes. Positive samples were then screened for the five serovars using sero-specific PCR. Serovar-positive samples were subjected to immunomagnetic separation, to isolate viable VTEC strains. These isolates were subsequently screened for four virulence factors: vt1, vt2, eaeA and hlyA. Three hundred and eighty six of the 600 rectal faecal swabs, 85 of the 117 milk-filters and 43 of the 120 bulk-tank milk samples, were positive for vt genes. From these 514 total vt-positive samples, 58 O26, 162 O103, 1 O111, 324 O145 and 26 O157 positives were detected by sero-specific RTi-PCR. Immunomagnetic separation yielded 12 O26, 26 O103, 0 O111, 19 O145 and 10 O157 isolates. Ten of these isolates contained at least one of the four virulence determinants screened for (i.e. vt1, vt2, eaeA and hlyA). Of these 10 isolates, pulsed-field gel electrophoresis showed that two of the O26 isolates from different farms were indistinguishable. Two O157 isolates were also indistinguishable. This study found serovars O103 and O145 to be the most prevalent in samples tested. Apart from the occurrence of VTEC in dairy herds, this study shows a high occurrence of vt genes in the environment, creating the possibility of horizontal gene transfer and emergence of new VTEC strains.

Lateral polarity heterostructures by overgrowth of patterned AlxGa1-xN nucleation layers

In this study thin AlxGa1−xN nucleation layers on sapphire were patterned and overgrown by plasma-induced molecular beam epitaxy (PIMBE) and metalorganic chemical vapor deposition (MOCVD) to obtain adjacent regions of GaN and AlGaN/GaN heterostructures with different polarities. The role of polarity on the structural and electrical properties of epitaxial layers and AlGaN/GaN heterostructures was investigated for samples grown on patterned AlN or GaN nucleation layers. Epitaxial GaN and AlGaN/GaN heterostructures grown on Al-face AlN or N- face GaN nucleation layers were found to be Ga-face or N-face, respectively, independent of the technique used for the overgrowth.

Comparison of adaptive pacing therapy, cognitive behaviour therapy, graded exercise therapy, and specialist medical care for chronic fatigue syndrome (PACE): a randomised trial

BACKGROUND

Trial findings show cognitive behaviour therapy (CBT) and graded exercise therapy (GET) can be effective treatments for chronic fatigue syndrome, but patients' organisations have reported that these treatments can be harmful and favour pacing and specialist health care. We aimed to assess effectiveness and safety of all four treatments.

METHODS

In our parallel-group randomised trial, patients meeting Oxford criteria for chronic fatigue syndrome were recruited from six secondary-care clinics in the UK and randomly allocated by computer-generated sequence to receive specialist medical care (SMC) alone or with adaptive pacing therapy (APT), CBT, or GET. Primary outcomes were fatigue (measured by Chalder fatigue questionnaire score) and physical function (measured by short form-36 subscale score) up to 52 weeks after randomisation, and safety was assessed primarily by recording all serious adverse events, including serious adverse reactions to trial treatments. Primary outcomes were rated by participants, who were necessarily unmasked to treatment assignment; the statistician was masked to treatment assignment for the analysis of primary outcomes. We used longitudinal regression models to compare SMC alone with other treatments, APT with CBT, and APT with GET. The final analysis included all participants for whom we had data for primary outcomes. This trial is registered at http://isrctn.org, number ISRCTN54285094.

FINDINGS

We recruited 641 eligible patients, of whom 160 were assigned to the APT group, 161 to the CBT group, 160 to the GET group, and 160 to the SMC-alone group. Compared with SMC alone, mean fatigue scores at 52 weeks were 3·4 (95% CI 1·8 to 5·0) points lower for CBT (p = 0·0001) and 3·2 (1·7 to 4·8) points lower for GET (p = 0·0003), but did not differ for APT (0·7 [-0·9 to 2·3] points lower; p = 0·38). Compared with SMC alone, mean physical function scores were 7·1 (2·0 to 12·1) points higher for CBT (p = 0·0068) and 9·4 (4·4 to 14·4) points higher for GET (p = 0·0005), but did not differ for APT (3·4 [-1·6 to 8·4] points lower; p=0·18). Compared with APT, CBT and GET were associated with less fatigue (CBT p = 0·0027; GET p = 0·0059) and better physical function (CBT p=0·0002; GET p<0·0001). Subgroup analysis of 427 participants meeting international criteria for chronic fatigue syndrome and 329 participants meeting London criteria for myalgic encephalomyelitis yielded equivalent results. Serious adverse reactions were recorded in two (1%) of 159 participants in the APT group, three (2%) of 161 in the CBT group, two (1%) of 160 in the GET group, and two (1%) of 160 in the SMC-alone group.

INTERPRETATION

CBT and GET can safely be added to SMC to moderately improve outcomes for chronic fatigue syndrome, but APT is not an effective addition.

FUNDING

UK Medical Research Council, Department of Health for England, Scottish Chief Scientist Office, Department for Work and Pensions.

Sharing and borrowing prescription medication: a survey of Irish college students

BACKGROUND

Prescription medicine borrowing and sharing has received not much attention in the research literature, despite serious potential health risks. Although this behaviour is prevalent across all ages, it appears to be particularly high amongst young adults.

AIMS

To determine the prevalence and the characteristics of sharing and borrowing medicines amongst students in an Irish University.

METHOD

Web survey of University College Cork 18-25-year-old undergraduates.

RESULTS

A total of 343 completed the questionnaire. A quarter (26%) reported borrowing, 20% reported sharing and 12% reported both sharing and borrowing prescription drugs, primarily to avoid the cost (37%), the inconvenience of going to a doctor (22%) and not feeling sick enough to see a medical professional (14%). Participants borrowed medicines from family (51.2%) and friends (18.2%). Those who borrowed or shared prescription drugs believed they were at a lesser risk of side effects from taking other people's medicines (p < 0.0005, χ(2) test).

CONCLUSION

Sharing and borrowing prescription drugs appear to be a common practice amongst Irish college students, who may underestimate the risks associated with taking these medicines.

Comparative acaricidal efficacy of the topically applied combinations fipronil/(S)-methoprene, permethrin/imidacloprid and metaflumizone/ amitraz against Dermacentor reticulatus, the European dog tick (ornate dog tick, Fabricius, 1794) in dogs

The acaricidal efficacy against Dermacentor reticulatus in dogs of the commercial topical combinations fipronil/(S)-methoprene (FRONTLINE Combo spot-on dog), imidacloprid/permethrin (Advantix) and metaflumizone/amitraz (ProMeris Duo) was evaluated and compared. Three treatment groups and one untreated control group of six adult Beagle dogs each were randomly formed. Each treatment was administered topically once on Day-0, according to the recommended label dose and instructions for use. All dogs were infested weekly with approximately 50 adult unfed D. reticulatus over a period of seven weeks. Ticks were removed and counted approximately 48 hours after each infestation. The percent reduction in numbers of ticks for fipronil/(S)-methoprene was > or = 97% compared to untreated controls for all seven weekly infestations. The percent reductions for imidacloprid/permethrin and metaflumizone/amitraz were satisfactory initially but fell and stayed below 90 % after three weeks. From the third week onwards, fipronil/(S)-methoprene treated dogs had significantly fewer ticks than imidacloprid/permethrin or metaflumizone/amitraz treated dogs (p < 0.05).

Quantifying the lag time to detect barriers in landscape genetics

Understanding how spatial genetic patterns respond to landscape change is crucial for advancing the emerging field of landscape genetics. We quantified the number of generations for new landscape barrier signatures to become detectable and for old signatures to disappear after barrier removal. We used spatially explicit, individual-based simulations to examine the ability of an individual-based statistic [Mantel's r using the proportion of shared alleles' statistic (Dps)] and population-based statistic (FST ) to detect barriers. We simulated a range of movement strategies including nearest neighbour dispersal, long-distance dispersal and panmixia. The lag time for the signal of a new barrier to become established is short using Mantel's r (1-15 generations). FST required approximately 200 generations to reach 50% of its equilibrium maximum, although G'ST performed much like Mantel's r. In strong contrast, FST and Mantel's r perform similarly following the removal of a barrier formerly dividing a population. Also, given neighbour mating and very short-distance dispersal strategies, historical discontinuities from more than 100 generations ago might still be detectable with either method. This suggests that historical events and landscapes could have long-term effects that confound inferences about the impacts of current landscape features on gene flow for species with very little long-distance dispersal. Nonetheless, populations of organisms with relatively large dispersal distances will lose the signal of a former barrier within less than 15 generations, suggesting that individual-based landscape genetic approaches can improve our ability to measure effects of existing landscape features on genetic structure and connectivity.