A review of segmentation and deformable registration methods applied to adaptive cervical cancer radiation therapy treatment planning

Objective: Manual contouring and registration for radiotherapy treatment planning and online adaptation for cervical cancer radiation therapy in computed tomography (CT) and magnetic resonance images (MRI) are often necessary. However manual intervention is time consuming and may suffer from inter or intra-rater variability. In recent years a number of computer-guided automatic or semi-automatic segmentation and registration methods have been proposed. Segmentation and registration in CT and MRI for this purpose is a challenging task due to soft tissue deformation, inter-patient shape and appearance variation and anatomical changes over the course of treatment. The objective of this work is to provide a state-of-the-art review of computer-aided methods developed for adaptive treatment planning and radiation therapy planning for cervical cancer radiation therapy. Methods: Segmentation and registration methods published with the goal of cervical cancer treatment planning and adaptation have been identified from the literature (PubMed and Google Scholar). A comprehensive description of each method is provided. Similarities and differences of these methods are highlighted and the strengths and weaknesses of these methods are discussed. A discussion about choice of an appropriate method for a given modality is provided. Results: In the reviewed papers a Dice similarity coefficient of around 0.85 along with mean absolute surface distance of 2-4. mm for the clinically treated volume were reported for transfer of contours from planning day to the treatment day. Conclusions: Most segmentation and non-rigid registration methods have been primarily designed for adaptive re-planning for the transfer of contours from planning day to the treatment day. The use of shape priors significantly improved segmentation and registration accuracy compared to other models

Genome-wide association study of school grades identifies genetic overlap between language ability, psychopathology and creativity

Cognitive functions of individuals with psychiatric disorders differ from that of the general population. Such cognitive differences often manifest early in life as differential school performance and have a strong genetic basis. Here we measured genetic predictors of school performance in 30,982 individuals in English, Danish and mathematics via a genome-wide association study (GWAS) and studied their relationship with risk for six major psychiatric disorders. When decomposing the school performance into math and language-specific performances, we observed phenotypically and genetically a strong negative correlation between math performance and risk for most psychiatric disorders. But language performance correlated positively with risk for certain disorders, especially schizophrenia, which we replicate in an independent sample (n = 4547). We also found that the genetic variants relating to increased risk for schizophrenia and better language performance are overrepresented in individuals involved in creative professions (n = 2953) compared to the general population (n = 164,622). The findings together suggest that language ability, creativity and psychopathology might stem from overlapping genetic roots

The role of magnetic resonance imaging (MRI) in external beam radiotherapy treatment planning (RTP) for cervical cancer

BackgroundAccurate delineation of treatment volumes for radiotherapy is a crucial step in radiationtreatment, but can be associated with considerable uncertainty and variability.Magnetic resonance imaging (MRI) has a proven benefit in the staging of cervical cancerand for image guided adaptive brachytherapy; however there is a paucity of data for the roleof MRI in delineating external beam radiotherapy treatment volumes.Aims1) Quantify the proportion of women with cervical cancer in whom there is evidence tosupport the use of MRI for radiotherapy planning (RTP),2) Evaluate the effect of an educational intervention on MRI consistency of volumedelineation for external beam target volumes, and3) Assess volume delineation for external beam radiotherapy on MRI compared to thecurrent standard of care, computer tomography (CT) imaging.MethodsData from an Australian model for estimating the optimal radiotherapy utilization rate forcervical cancer were used and a literature review was performed for each patient group toassess the evidence for the use of MRI for RTP.To evaluate the second aim contours from eleven clinicians were analysed before and afteran educational intervention.For the third aim, twenty patients with locally advanced cervical cancer underwent adedicated MR simulation with a 3T Skyra MRI following CT simulation, four cliniciansindependently contoured each CT and MRI dataset. The Dice Similarity Co-efficient (DSC)and Mean Average Surface Distance (MASD) was calculated for each structure.ResultsThe use of an MRI for radiotherapy planning is supported in 49% of women overall withcervical cancer.The educational intervention resulted in an improvement in contouring the gross tumour,however a variable response for the other target volumes was observed.MRI contouring was associated with less variability between clinicians compared to CTcontouring for most structures including the gross tumour, uterus and parametria. Theoverall target volume demonstrated a high level of contouring consistency on both CT andMRI, with a small improvement in the MASD seen for MRI contouring.ConclusionMRI simulation for external beam radiotherapy in cervical cancer reduces target volumevariability compared to CT

Dedicated MRI simulation for cervical cancer radiation treatment planning: Assessing the impact on clinical target volume delineation

Introduction: Magnetic Resonance Imaging (MRI) provides excellent soft tissue definition of pelvic tumours and organs. The aim of this study was to quantify differences in delineated clinical target volumes (CTVs) between computed tomography (CT) and MRI. Methods: Twenty patients with locally advanced gynaecological malignancies were recruited. Patients underwent dedicated MRI simulation following CT simulation. Four clinicians independently contoured each CT and MRI. CTV structures were contoured using the Radiation Therapy Oncology Group (RTOG) guidelines and lymph node CTV (LN‐CTV) according to published guidelines. Interobserver variability was analysed using the dice similarity coefficient (DSC) and mean absolute surface distance (MASD). Results: Gross tumour volume delineation was more consistent on MRI compared to CT, the DSC improved from 0.77 on CT to 0.81 on MRI, P \u3c 0.01. GTV volumes were significantly smaller on MRI compared to CT (MRI 92 cc vs. CT 117 cc, P \u3c 0.01). The LN‐CTV and combined CTV volumes were both significantly smaller on MRI compared to CT (LN‐CTV: MRI 324 cc vs CT 354 cc, P \u3c 0.01 and combined CTV: MRI 560 cc vs CT 600 cc, P \u3c 0.01). The LN‐CTV DSC was 0.75 for both MRI and CT, and the combined CTV DSC was 0.81 for MRI and 0.80 for CT, P = 0.27. Vagina and parametria volumes exhibited more variability compared to other structures. Conclusions: Magnetic Resonance Imaging contouring resulted in smaller and more consistently delineated volumes when compared to CT for most CTV structures. An MRI contouring atlas is provided to complement the existing RTOG contouring guidelines

Dedicated MRI

Introduction: Magnetic Resonance Imaging (MRI) provides excellent soft tissue definition of pelvic tumours and organs. The aim of this study was to quantify differences in delineated clinical target volumes (CTVs) between computed tomography (CT) and MRI. Methods: Twenty patients with locally advanced gynaecological malignancies were recruited. Patients underwent dedicated MRI simulation following CT simulation. Four clinicians independently contoured each CT and MRI. CTV structures were contoured using the Radiation Therapy Oncology Group (RTOG) guidelines and lymph node CTV (LN‐CTV) according to published guidelines. Interobserver variability was analysed using the dice similarity coefficient (DSC) and mean absolute surface distance (MASD). Results: Gross tumour volume delineation was more consistent on MRI compared to CT, the DSC improved from 0.77 on CT to 0.81 on MRI, P \u3c 0.01. GTV volumes were significantly smaller on MRI compared to CT (MRI 92 cc vs. CT 117 cc, P \u3c 0.01). The LN‐CTV and combined CTV volumes were both significantly smaller on MRI compared to CT (LN‐CTV: MRI 324 cc vs CT 354 cc, P \u3c 0.01 and combined CTV: MRI 560 cc vs CT 600 cc, P \u3c 0.01). The LN‐CTV DSC was 0.75 for both MRI and CT, and the combined CTV DSC was 0.81 for MRI and 0.80 for CT, P = 0.27. Vagina and parametria volumes exhibited more variability compared to other structures. Conclusions: Magnetic Resonance Imaging contouring resulted in smaller and more consistently delineated volumes when compared to CT for most CTV structures. An MRI contouring atlas is provided to complement the existing RTOG contouring guidelines

The impact of a radiologist-led workshop on MRI target volume delineation for radiotherapy

Introduction: Magnetic resonance imaging (MRI) is increasingly used for target volume delineation in radiotherapy due to its superior soft tissue visualisation compared to computed tomography (CT). The aim of this study was to assess the impact of a radiologist-led workshop on inter-observer variability in volume delineation on MRI. Methods: Data from three separate studies evaluating the impact of MRI in lung, breast and cervix were collated. At pre-workshop evaluation, observers involved in each clinical site were instructed to delineate specified volumes. Radiologists specialising in each cancer site conducted an interactive workshop on interpretation of images and anatomy for each clinical site. At post-workshop evaluation, observers repeated delineation a minimum of 2 weeks after the workshops. Inter-observer variability was evaluated using dice similarity coefficient (DSC) and volume similarity (VOLSIM) index comparing reference and observer volumes. Results: Post-workshop primary gross tumour volumes (GTV) were smaller than pre-workshop volumes for lung with a mean percentage reduction of 10.4%. Breast clinical target volumes (CTV) were similar but seroma volumes were smaller post-workshop on both supine (65% reduction) and prone MRI (73% reduction). Based on DSC scores, improvement in inter-observer variability was seen for the seroma cavity volume on prone MRI with a reduction in DSC score range from 0.4-0.8 to 0.7-0.9. Breast CTV demonstrated good inter-observer variability scores (mean DSC 0.9) for both pre- and post-workshop. Post-workshop observer delineated cervix GTV was smaller than pre-workshop by 26.9%. Conclusion: A radiologist-led workshop did not significantly reduce inter-observer variability in volume delineation for the three clinical sites. However, some improvement was noted in delineation of breast CTV, seroma volumes and cervix GTV

Cuadernos de arquitectura y urbanismo : publicación del Colegio Oficial de Arquitectos de Cataluña y Baleares

Objective: Manual contouring and registration for radiotherapy treatment planning and online adaptation for cervical cancer radiation therapy in computed tomography (CT) and magnetic resonance images (MRI) are often necessary. However manual intervention is time consuming and may suffer from inter or intra-rater variability. In recent years a number of computer-guided automatic or semi-automatic segmentation and registration methods have been proposed. Segmentation and registration in CT and MRI for this purpose is a challenging task due to soft tissue deformation, inter-patient shape and appearance variation and anatomical changes over the course of treatment. The objective of this work is to provide a state-of-the-art review of computer-aided methods developed for adaptive treatment planning and radiation therapy planning for cervical cancer radiation therapy. Methods: Segmentation and registration methods published with the goal of cervical cancer treatment planning and adaptation have been identified from the literature (PubMed and Google Scholar). A comprehensive description of each method is provided. Similarities and differences of these methods are highlighted and the strengths and weaknesses of these methods are discussed. A discussion about choice of an appropriate method for a given modality is provided. Results: In the reviewed papers a Dice similarity coefficient of around 0.85 along with mean absolute surface distance of 2-4. mm for the clinically treated volume were reported for transfer of contours from planning day to the treatment day. Conclusions: Most segmentation and non-rigid registration methods have been primarily designed for adaptive re-planning for the transfer of contours from planning day to the treatment day. The use of shape priors significantly improved segmentation and registration accuracy compared to other models

Patterns of practice survey for brachytherapy for cervix cancer in Australia and New Zealand

Introduction: The purpose of this survey was to explore the current patterns of practice for brachytherapy in cervix cancer in Australia and New Zealand. The survey was also intended to explore clinician attitudes towards image-guided adaptive brachytherapy (IGABT) and identify barriers to the implementation of IGABT. Methods: Electronic surveys were sent to all radiotherapy centres in Australia and New Zealand under collaboration with Australia New Zealand Gynaecology and Oncology Group (ANZGOG), in order to identify patterns of radiotherapy practice. The survey was sent out in December 2013, with a reminder in February 2014. Results: Of the 75 radiotherapy centres in Australia and New Zealand, 23 centres replied (31% response rate). Twenty-two responding departments treat cervix cancer with external beam radiation (EBRT) (22/23; 96%). Fourteen responses were from departments that also use intracavitary brachytherapy (14/22; 64%). The remaining eight departments who do not offer intracavitary brachytherapy referred their patients on to other centres for brachytherapy. Ultrasound was used by 86% for applicator guidance. CT and MRI were used by 79%, and 50% respectively for planning. Optimisation was based on organs at risk (93%) and target volumes (64%). Conclusions: Brachytherapy remains an integral component of definitive treatment for cervix cancer in Australia and New Zealand. There was increased use of soft tissue imaging modalities with emphasis on verification; high rates of volumetric planning, and adherence to a defined overall treatment period. Brachytherapy was not substituted with other EBRT modalities. Despite this, there remain barriers to implementation of image-guided brachytherapy

Impact of dosimetric differences between CT and MRI derived target volumes for external beam cervical cancer radiotherapy

OBJECTIVES: The use of MRI is becoming more prevalent in cervical cancer external beam radiotherapy (RT). The aim of this study was to investigate the impact of dosimetric differences between CT and MRI-derived target volumes for cervical cancer external beam RT. METHODS: An automated planning technique for volumetric modulated arc therapy was developed. Two automated planning plans were generated for 18 cervical cancer patients where planning target volumes (PTVs) were generated based on CT or MRI data alone. Dose metrics for planning target volumes and organs at risk (OARs) were compared to analyse any differences based on imaging modality. RESULTS: All treatment plans were clinically acceptable. Bladder doses (V40) were lower in MRI-based plans (p = 0.04, 53.6 ± 17.2 % vs 60.3 ± 13.1 % for MRI vs CT, respectively). The maximum dose for left iliac crest showed lower doses in CT-based plans (p = 0.02, 47.8 ± 0.7 Gy vs 47.4 ± 0.4 Gy MRI vs CT, respectively). No significant differences were seen for other OARs. CONCLUSIONS: The dosimetric differences of CT- and MRI-based contouring variability for this study was small. CT remains the standard imaging modality for volume delineation for these patients. ADVANCES IN KNOWLEDGE: This is the first study to evaluate the dosimetric implications of imaging modality on target and OAR doses in cervical cancer external beam RT

DNA metabarcoding : Guidelines to monitor phytoplankton diversity and distribution in marine and brackish waters

We present guidelines for using environmental DNA metabarcoding, together with conventional techniques, to monitor the taxonomic diversity of phytoplankton in marine and brackish waters. The focus is on eukaryotic and prokaryotic phytoplankton using 18S and 16S rRNA primers and high-throughput sequencing. Information and recommendations on sampling, sample processing, molecular biological work, quality control, bioinformatics, data storage and management and cost estimates are included so that the method can be used to complement standardized light microscopy. A scientific literature review, discussion on future perspectives, reference databases and standardization are included. Using eDNA metabarcoding to complement standardized light microscopy advances conventional monitoring and research on phytoplankton communities to assess biodiversity and the state of the marine environment