Validating a Simple Urethra Surrogate Model to Facilitate Dosimetric Analysis to Predict Genitourinary Toxicity

PURPOSE/OBJECTIVE(S)

The urethra may be a critical structure in prostate radiotherapy planning as some studies have shown that higher urethral dose correlates with worse genitourinary (GU) toxicity. Identifying the urethra requires an MRI planning scan or foley catheter insertion at CT planning. Most surrogates have been developed and validated against the urethra identified by a foley catheter. However, the urethral position can shift with catheter placement. We, therefore, aim to validate a simple urethra surrogate model against MRI-defined urethra. The surrogate model can be used to correlate urethra dose-volume parameters (DVP) with late GU toxicity and to apply urethral constraints in those with a CT-only based workflow.

MATERIALS/METHODS

Thirty-nine MRI-defined urethras from patients in the PACE-C trial were assessed to determine the average position of the urethra in the midline sagittal prostate plane along the ¼ gland, midgland, ¾ gland, apex and 3mm below apex. Using these average positions, a Python script was developed, which places a 10mm diameter circle in the 1/4 gland, midgland, ¾ gland, apex and 3mm below the apex. The observer manually contours a 10mm circle at the prostate base (prostate-bladder neck interface) to infer the urethra position and interpolates the contours. The urethra surrogate model was compared against 20 MRI-defined urethras (within the treatment PTV) in patients treated with 36.25Gy in 5 fractions as part of the PACE-B trial. To assess the surrogate's geometric performance, the Dice similarity coefficient (DSC), Hausdorff distance (HD), mean surface distance to agreement (MDTA) and the percentage of MRI-defined urethra outside the surrogate (UOS) were calculated. The surrogate model's dosimetric performance was assessed by comparing the mean D99, D98, average dose, D50, D2 and D1 using a paired t-test. The D(n) is the dose (Gy) to (n)% of the urethra.

RESULTS

The median results were: DSC 0.36 (IQR 0.28-0.42), HD 0.88cm (IQR, 0.70-1.04), MDTA 0.24cm (IQR, 0.21-0.28), UOS 29% (IQR, 17-52%). When comparing DVP between the MRI-defined urethra and surrogate urethra, the mean D99, D98 and D95 as 38.8Gy vs 39.1Gy (p = 0.17), 39.3Gy vs 39.5Gy (p = 0.23), 40.1Gy vs 40.4Gy (p = 0.21), respectively. The mean D50, average dose, D2 and D1 was 41.8Gy vs 41.9Gy (p = 0.03), 41.7 vs 41.8Gy (p = 0.04), 42.9Gy vs 43.0Gy (p = 0.05) and 43.0Gy vs 43.1Gy (p = 0.03), respectively.

CONCLUSION

While there were geometric differences between the surrogate urethra and MRI-defined urethra, there was no statistically significant difference between most urethral dose-volume parameters (D99, D98, D95, and D1). Similarly, the actual differences in urethra DVP were not clinically significant. This surrogate model could be validated in a larger cohort and then used to estimate the urethra position on CT planning scans for dosimetric analysis in those without an MRI planning scan or urinary catheter.

IMG-11. A COMPUTERISED CLINICAL DECISION SUPPORT SYSTEM FOR DIAGNOSING CHILDREN’S BRAIN TUMOURS USING FUNCTIONAL IMAGING AND MACHINE LEARNING

INTRODUCTION: Magnetic resonance imaging is a key investigation in the diagnosis of childhood solid tumours. Advanced techniques such as diffusion weighted imaging (DWI), magnetic resonance spectroscopy (MRS) and perfusion imaging probe the underlying cellular, chemical and vascular nature of the disease. Coupled with machine learning these scanning methods show improvement in diagnostic accuracy compared with conventional imaging. Advanced image analysis is not routinely available in hospitals. We present a clinical decision support system (CDSS) developed for advanced MR analysis and interpretation. METHOD: The CDSS was developed in house. The Children’s Cancer and Leukaemia Group Functional Imaging Group (CCLGFIG) Database, a national resource, was used to provide a repository of cases together with their advanced imaging and machine learning diagnostic classifiers. A new case is displayed alongside cases in the repository with known diagnoses, including summary statistics for relevant diagnostic categories. The CDSS was made available to radiologists, in their clinical environment for technical and clinical evaluation. Structured interviews were undertaken. The CDSS was developed as a computer app for multi-centre distribution. RESULTS: 436 MRS, 240 DWI and 85 perfusion cases were available for building repositories. Machine learning classifiers showed diagnostic accuracies for the major childhood brain tumour types of 85-95%. Comparison of MRS with a data repository was found to improve non-invasive diagnosis. Results from the CDSS can be uploaded to the CCLGFIG to support multicentre research. Positive feedback on the CDSS from clinicians included: ready access to advanced analysis; simple and efficient integration into clinical workflow; and assisted interpretation of advanced analysis. DISCUSSION: Advanced MR analysis techniques provide improved non-invasive diagnostic accuracy but are difficult to implement on clinical systems due to technical, infrastructure and training limitations. CONCLUSION: We have successfully released a CDSS for paediatric cancer within the hospital environment and assessed its suitability for clinical use.

IMG-10. Determining brain tumour grade non-invasively using a simplified MRI perfusion protocol: single-bolus, leakage-corrected dynamic susceptibility-contrast MRI

INTRODUCTION: Perfusion is associated with grade and survival in children’s brain tumours. Dynamic susceptibility-contrast (DSC-) MRI measures perfusion non-invasively, estimating relative cerebral blood volume (rCBV). We previously showed significant differences between pre-treatment rCBV in low- and high-grade tumours in a multicentre study. Contrast agent leakage from tumour vessels during acquisition affects rCBV accuracy. A contrast agent pre-bolus can be given but this can be challenging in a clinical environment, introducing variability. Alternatively, a single bolus can be administered with leakage correction applied when processing the data. We investigated pre-treatment rCBV values in a multicentre study without pre-bolus administration. METHODS: Thirty-six patients underwent pre-treatment DSC-MRI scans at 2 centres on 4 different scanners. Protocols were variable. Pixel-by-pixel contrast agent concentration time courses were analysed. Maps of uncorrected (rCBVuncorr) and leakage-corrected rCBV (rCBVcorr) were produced. Whole-tumour regions-of-interest were defined and median whole-tumour DSC-MRI parameters calculated. Patients subsequently underwent surgery / biopsy. Tumours were classified and graded. RESULTS: Twelve tumours were classified as low-grade; 24 as high-grade. Median whole-tumour rCBVuncorr was significantly higher in high-grade tumours than in low-grade tumours (1.628 vs -0.167, p<0.001). Median rCBV significantly increased in low-grade tumours following leakage correction (-0.167 to 1.072, p=0.007); there was no significant change for high-grade tumours. Using the median rCBVuncorr of 1.19 to differentiate between low- and high-grade tumours resulted in sensitivity and specificity of 75% and 100%, respectively; median 1.45 for rCBVcorr resulted in sensitivity and specificity of 67% and 100%, respectively. DISCUSSION: DSC-MRI measures of perfusion can distinguish between low- and high-grade paediatric brain tumours. Contrast agent leakage correction is essential for accurate measurement of rCBV. This is robust across multiple centres despite using multiple protocols. CONCLUSION: Pre-treatment multicentre perfusion MRI acquired with a single-bolus and contrast agent leakage correction can aid with differentiating between high- and low-grade paediatric brain tumours.

Combining multi-site magnetic resonance imaging with machine learning predicts survival in pediatric brain tumors

Brain tumors represent the highest cause of mortality in the pediatric oncological population. Diagnosis is commonly performed with magnetic resonance imaging. Survival biomarkers are challenging to identify due to the relatively low numbers of individual tumor types. 69 children with biopsy-confirmed brain tumors were recruited into this study. All participants had perfusion and diffusion weighted imaging performed at diagnosis. Imaging data were processed using conventional methods, and a Bayesian survival analysis performed. Unsupervised and supervised machine learning were performed with the survival features, to determine novel sub-groups related to survival. Sub-group analysis was undertaken to understand differences in imaging features. Survival analysis showed that a combination of diffusion and perfusion imaging were able to determine two novel sub-groups of brain tumors with different survival characteristics (p < 0.01), which were subsequently classified with high accuracy (98%) by a neural network. Analysis of high-grade tumors showed a marked difference in survival (p = 0.029) between the two clusters with high risk and low risk imaging features. This study has developed a novel model of survival for pediatric brain tumors. Tumor perfusion plays a key role in determining survival and should be considered as a high priority for future imaging protocols.

IMG-06. PREDICTING SURVIVAL FROM PERFUSION AND DIFFUSION MRI BY MACHINE LEARNING

INTRODUCTION

Magnetic Resonance Imaging (MRI) is routinely used in the assessment of children’s brain tumours. Reduced diffusion and increased perfusion on MRI are commonly associated with higher grade but there is a lack of quantitative data linking these parameters to survival. Machine learning is increasingly being used to develop diagnostic tools but its use in survival analysis is rare. In this study we combine quantitative parameters from diffusion and perfusion MRI with machine learning to develop a model of survival for paediatric brain tumours. METHOD: 69 children from 4 centres (Birmingham, Liverpool, Nottingham, Newcastle) underwent MRI with diffusion and perfusion (dynamic susceptibility contrast) at diagnosis. Images were processed to form ADC, cerebral blood volume (CBV) and vessel leakage correction (K2) parameter maps. Parameter mean, standard deviation and heterogeneity measures (skewness and kurtosis) were calculated from tumour and whole brain and used in iterative Bayesian survival analysis. The features selected were used for k-means clustering and differences in survival between clusters assessed by Kaplan-Meier and Cox-regression.

RESULTS

Bayesian analysis revealed the 5 top features determining survival to be tumour volume, ADC kurtosis, CBV mean, K2 mean and whole brain CBV mean. K-means clustering using these features showed two distinct clusters (high- and low-risk) which bore significantly different survival characteristics (Hazard Ratio = 5.6).

DISCUSSION AND CONCLUSION

Diffusion and perfusion MRI can be used to aid the prediction of survival in children’s brain tumours. Tumour perfusion played a particularly important role in predicting survival despite being less routinely measured than diffusion.

Predictors of Satisfying and Impactful Clinical Shadowing Experiences for Underrepresented Minority High School Students Interested in Healthcare Careers

INTRODUCTION

Diversity among healthcare professionals lags behind the increasing racial and ethnic diversity of the United States' population. Increasing diversity of the health professional workforce may be one strategy to influence healthcare disparities. This study sought to understand factors associated with highly satisfying and impactful clinical shadowing experiences among underrepresented minority (URM) students in a health professional development program for urban high school students.

METHODS

We analyzed data from students' summer clinical shadowing experiences in 2016 and 2017. We sought to determine if preceptor factors (e.g. racial and gender concordance with students), or patient related variables (e.g. racial concordance with students, the volume of patients per session) were associated with overall satisfaction with shadowing, the desire to pursue a similar career as their preceptor, and viewing their preceptor as a role model. After each shadowing experience, students completed evaluation forms. Chi-square tests were used for data analysis.

RESULTS

Over two summers, 65 high school juniors participated in an average of 14 half-day clinical shadowing sessions; 59 of these students identify as URMs. Among URM students, racial/ethnic concordance between preceptor and student was significantly associated with viewing the preceptor as a role model (p = 0.028). Witnessing a greater number of patient-provider encounters (≥five patients per session) was associated with higher satisfaction with the experience (p = 0.0002), and viewing the preceptor as a role model (p = 0.04).

CONCLUSION

To increase diversity of the healthcare workforce, URM students need high volume patient-provider encounters. Racial and/or ethnic concordance of URM students and preceptors may provide for preferable role models.

Utilising functional imaging to predict survival in paediatric brain tumours

Introduction

Brain tumours are a common cause of death in the paediatric population. We have previously shown that MR imaging and spectroscopy can be used to non-invasively differentiate between tumour types. Here, we demonstrate that functional imaging can be highly predictive of survival and grade in a paediatric cohort.

Methods

Perfusion (PWI) and diffusion weighted imaging (DWI) were performed in a multi-site (Birmingham Children’s Hospital, Royal Victoria Infirmary, Alder Hey, Nottingham) cohort ([grade, 5-year survival alive:dead number] = [I,15:1],[II, 5:1],[III,2:3],[IV,8:11]). ROIs were drawn on T2 imaging and functional imaging features (mean, standard deviation, skewness, and kurtosis) were derived. Supervised machine learning was used to predict 5-year survival and tumour grade from features. ANOVA and post-hoc tests were used to assess differences in features between grade and 5-year survival status.

Results

5-year survival was predicted with 89%, 85%, and 87% accuracy with all imaging, perfusion, or diffusion features, respectively.

A significant difference in perfusion was found between surviving and diseased participants (1.71 ± 0.82 vs 2.62 ± 1 mL/100g/min, respectively, p < 0.05). A significant difference in ADC (mm2 s-1) between tumour grades was found (1 vs 4 (1533 ± 458 vs 857 ± 239), 4 vs 3 (857 ± 239 vs 1197 ± 137), 4 vs 2 (857 ± 239 vs 1440 ± 557), corrected p < 0.05).

Conclusion

We have shown that perfusion and diffusion imaging features can be used to non-invasively assess tumour grade and estimate 5-year survival status in a cohort of paediatric brain tumours.

Multicentre study of perfusion magnetic resonance imaging in paediatric brain tumours

Studies in adults have shown that brain tumour perfusion correlates with grade. These studies are dominated by gliomas grade II to IV which are rare in children. The standard method, Dynamic Susceptibility Contrast MRI, provides estimates of relative cerebral blood volume (rCBV) but contrast agent leakage affects rCBV accuracy. The majority of perfusion studies have been conducted at single centres and variation in acquisition protocols makes the generalizability of results questionable. The aim of this study was to compare leakage-corrected rCBV with grade in paediatric brain tumours at multiple centres. Scans were analysed from 85 patients at 4 centres on 6 scanners prior to treatment. MRI protocols varied between centres. Histological diagnoses including grade were obtained. Whole-tumour median rCBV was significantly higher in the 45 high grade than the 40 low grade tumours (2.54 ± 1.63 ml/100ml vs 1.68 ± 1.36 ml/100ml, p=0.010). Low grade tumours, particularly pilocytic astrocytomas (grade I), displayed more contrast agent leakage consistent with their appearance on contrast enhanced images and required more leakage correction than high grade tumours. This finding differs from that in adults where contrast agent uptake is usually associated with higher grade. A cut-off of 1.70 ml/100ml for rCBV gave sensitivity and specificity of 76% and 65% respectively for discriminating grade. In summary, perfusion MRI can be used to help distinguish between low and high grade paediatric brain tumours. This finding is robust across multiple centres and acquisition protocols but correction should be made for leakage of contrast agent from the vessels.

Visuospatial and technical ability in the selection and assessment of higher surgical trainees in the London deanery

INTRODUCTION

Despite awareness of the limitations of current selection and competency assessments, there is little consensus and alternatives have not been readily accepted. Essential surgical skills include visuospatial and technical ability. The aim of this study was to survey current methods of higher surgical trainee selection and assessment. We suggest ways to improve the process.

MATERIALS AND METHODS

Nine surgical training programmes in the London deanery were surveyed through questionnaires to programme directors, existing trainees and examination of deanery publications.

RESULTS

Testing of visuospatial and technical ability was piloted at selection only in a single general surgical department. Practical skills were assessed in 3/9 (33%) specialties (ENT, plastic and general surgery). Once selected, no specialty tested visuospatial and technical ability. Practical skills were tested in only 1/9 (11%) specialties (plastic surgery). The remaining 8/9 (89%) were 'assessed' by interview.

CONCLUSIONS

Lack of visuospatial and technical ability assessment was identified at selection and during higher surgical training. Airlines have long recognised early identification of these qualities as critical for efficient training. There is a need for more objective methods in this area prior to selection as time to assess surgical trainees during long apprenticeships is no longer available. We advocate a suitably validated competency-based model during and at completion of training.

Diagnostic fine-needle aspiration in postoperative wound infections is more accurate at predicting causative organisms than wound swabs

INTRODUCTION

Postoperative wound infections are common. Antibiotics are often prescribed empirically, usually in the absence of any microbiological sensitivity data. This study demonstrates the role of fine-needle aspiration microbiology (FNAM) in determining the causative organisms in these wounds compared to wound swabs taken from the same patients.

PATIENTS AND METHODS

A total of 20 patients with clinical signs of soft tissue infection were tested using wound swabs and fine-needle aspiration.

RESULTS

Six of the wound swabs yielded a single organism but 16 out 20 of the FNAM group yielded a single organism (P = 0.002).

CONCLUSIONS

The FNAM approach allows antibiotic sensitivities to be obtained enabling specific antimicrobial therapy to be implemented early. FNAM also has a higher yield of cultures than wound swabs. Cellulitic areas can be sampled even when use of wound swabs is not possible.

A Portal to Validated Websites on Cosmetic Surgery

There has recently been an increase in the usage of the Internet as a source of patient information. It is very difficult for laypersons to establish the accuracy and validity of these medical websites. Although many website assessment tools exist, most of these are not practical.A combination of consumer- and clinician-based website assessment tools was applied to 200 websites on cosmetic surgery. The top-scoring websites were used as links from a portal website that was designed using Microsoft Macromedia Suite.Seventy-one (35.5%) websites were excluded. One hundred fifteen websites (89%) failed to reach an acceptable standard.The provision of new websites has proceeded without quality controls. Patients need to be better educated on the limitations of the Internet. This paper suggests an archetypal model, which makes efficient use of existing resources, validates them, and is easily transferable to different health settings.

Eleven-year survival from an intra-dermal melanoma

Stage IV metastatic malignant melanoma of unknown primary (TxNxM1a) is known to have a poor prognosis. However, some patients suffering from cutaneous disease originally thought to represent metastasis have fared much better than expected. We report a patient who has survived 11 years following such a diagnosis. Due to the prolonged survival and absence of an identified primary, it is unlikely that the lesion was metastatic but may represent one of a number of other possibilities. A small number of similar cases in the literature suggest a need for awareness of this unusual group of patients.

Hyperbaric oxygen as adjuvant therapy in the management of necrotizing fasciitis

BACKGROUND

Necrotizing fasciitis (NF) is an uncommon but serious infection of fascia and skin associated with considerable morbidity and mortality. One modality proposed for improving the outcome of this condition is hyperbaric oxygen (HBO) therapy. This is a form of medical treatment that involves intermittent inhalation of 100% oxygen under pressures exceeding the atmosphere. The aim of this article is to review current practice and evidence for the use of HBO as adjunctive therapy in the management of NF.

METHODS

A survey of published English literature through searches of Medline and PubMed was carried out using the following key words: "necrotizing fasciitis," "Fournier's gangrene," "necrotizing soft tissue infections," "hyperbaric oxygen therapy," "and hyperbaric oxygen chambers."

RESULTS

The results of studies on the use of HBO therapy in NF are inconsistent. Some studies have demonstrated that HBO can improve patient survival and decrease the number of debridements required to achieve wound control, whereas others have failed to show any beneficial effect.

CONCLUSIONS

Encouraging results have been achieved with the addition of HBO therapy to standard treatment regimes, thus justifying further research in this field. More robust evidence by way of a prospective randomized trial is necessary before widespread and routine use of HBO in the management of NF can be recommended.

Bacteriophages--potential for application in wastewater treatment processes

Bacteriophages are viruses that infect and lyse bacteria. Interest in the ability of phages to control bacterial populations has extended from medical applications into the fields of agriculture, aquaculture and the food industry. Here, the potential application of phage techniques in wastewater treatment systems to improve effluent and sludge emissions into the environment is discussed. Phage-mediated bacterial mortality has the potential to influence treatment performance by controlling the abundance of key functional groups. Phage treatments have the potential to control environmental wastewater process problems such as: foaming in activated sludge plants; sludge dewaterability and digestibility; pathogenic bacteria; and to reduce competition between nuisance bacteria and functionally important microbial populations. Successful application of phage therapy to wastewater treatment does though require a fuller understanding of wastewater microbial community dynamics and interactions. Strategies to counter host specificity and host cell resistance must also be developed, as should safety considerations regarding pathogen emergence through transduction.

One hundred cases of endoscopic brow lift

The senior author's experience of using the endoscopic brow lift for rejuvenation of the upper third of the face is presented. One hundred patients underwent endoscopic brow elevation. In 98 cases this was done in combination with other aesthetic procedures. Patient follow-up ranged from 4 months to 53 months (mean: 17 months). No major complications were experienced, although a patient questionnaire identified a number of troublesome but transient minor complications. Levels of patient satisfaction were found to be high. The continuing evolution of this technique is reviewed, particularly relating to methods of brow fixation.

The use of a lymphatic bridge in the management of head and neck lymphoedema

Severe progressive lymphoedema of the whole of the head and neck is almost always due to the combined effects of surgery and radiotherapy, compounded by repeated infections or recurrent tumour. The condition is difficult to control, and manual lymphatic drainage is the mainstay of management. We present a case of progressive lymphoedema following treatment for an occult squamous carcinoma of the head and neck, and describe the use of a lymphatic bridge to drain the facial tissue.

'Clicking-brain syndrome': a curious cause of insomnia

This case report describes a curious cause of insomnia. A 93-year-old woman presented to our follow-up clinic with the complaint of insomnia secondary to an audible click emanating from her skull. The site of loud biphasic-sound production corresponded to an area of the scalp where a squamous cell carcinoma had been removed 11 years previously.

Longstanding pigmentary changes in paediatric scalds dressed with a non-adherent siliconised dressing

The non-adherent siliconised dressing Mepitel is excellent for burns, especially in children. It provides a moist wound environment, promotes wound healing and is easy and relatively painless to use. However, surgeons should be aware that in black children its use has been associated with pigmentation abnormalities.

Sensory deprivation as a consequence of severe head and neck lymphoedema

We report a case of sensory deprivation that occurred as a consequence of progressive head and neck lymphoedema, following combined surgery and radiotherapy for squamous cell carcinoma. The management of head and neck lymphoedema is discussed and measures are suggested for improving the sensory deprivation experienced by the worst affected patients.

Reducing postoperative morbidity after the insertion of gold weights to treat lagophthalmos

Paralysis of the orbicularis oculi muscle leads to an unopposed action of the levator of the upper eyelid (lagophthalmos) in facial nerve palsy. The resultant exposure of the cornea may lead to keratitis, corneal ulceration, and eventual blindness. Although many surgical options exist in the treatment of lagophthalmos, upper lid loading with a gold weight implant has become one of the preferred methods to reduce the complications that may follow. The problems encountered after gold lid loading and methods to reduce postoperative morbidity are not well documented. The objective of this study was to determine the range of morbidity seen after gold weight insertion and to evaluate the effect of supratarsal fixation on subsequent morbidity. After retrospective reviews by questionnaire and case note analysis, supratarsal fixation was found to noticeably reduce the rate of implant ulceration and extrusion. This study demonstrates upper lid loading to be an effective method for the treatment of lagophthalmos, and it supports fixation of gold weights in reducing surgical morbidity.

The use of the photoplethysmograph to monitor the training of a cross-leg free flap prior to division

The cross-leg free flap is an important, although rarely used, option in the reconstruction of lower limb trauma. We report the use of photoplethysmography in the assessment of such a flap's training and the time of pedicle division.

IS900 PCR to detect Mycobacterium paratuberculosis in retail supplies of whole pasteurized cows' milk in England and Wales

IS900 PCR for Mycobacterium paratuberculosis was applied to cream, whey, and pellet fractions of centrifuged whole cows' milk. The test and simultaneous control reactions gave correct results for spiked milk and for native milk samples obtained directly from M. paratuberculosis-free, subclinically infected, and clinically infected cows. The test was then applied to units of whole pasteurized cows' milk widely obtained from retail outlets throughout central and southern England from September 1991 to March 1993. With peak periods in January to March and in September to November, when up to 25% of units were affected, an overall 22 of 312 samples (7%) tested positive for M. paratuberculosis. In 18 of the 22 positive samples (81%), the PCR signal segregated to the cream or pellet fractions or both, consistent with the presence of intact mycobacteria. Nine of 18 PCR-positive milk samples (50%) and 6 of 36 PCR-negative milk samples (16%) yielded long-term liquid cultures which tested positive for M. paratuberculosis after 13 to 40 months of incubation, despite overgrowth by other organisms. Taken together with data on the prevalence of M. paratuberculosis infection in herds in the United Kingdom, the known secretion of M. paratuberculosis in milk from subclinically infected animals, and the inability of laboratory conditions simulating pasteurization to ensure the killing of all these slowly growing or unculturable organisms, there is a high risk, particularly at peak times, that residual M. paratuberculosis will be present in retail pasteurized cows' milk in England.

Chemical de-bulking of desmoid tumours

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