Detection of vessel bifurcations in CT scans for automatic objective assessment of deformable image registration accuracy.

PURPOSE: Objective assessment of deformable image registration (DIR) accuracy often relies on the identification of anatomical landmarks in image pairs, a manual process known to be extremely time-expensive. The goal of this study is to propose a method to automatically detect vessel bifurcations in images and assess their use for the computation of target registration errors (TREs). MATERIALS AND METHODS: Three image datasets were retrospectively analyzed. The first dataset included 10 pairs of inhale/exhale phases from lung 4DCTs and full inhale and exhale breath-hold CT scans from 10 patients presenting with chronic obstructive pulmonary disease, with 300 corresponding landmarks available for each case (DIR-Lab). The second dataset included six pairs of inhale/exhale phases from lung 4DCTs (POPI dataset), with 100 pairs of landmarks for each case. The third dataset included 28 pairs of pre/post-radiotherapy liver contrast-enhanced CT scans, each with five manually picked vessel bifurcation correspondences. For all images, the vasculature was autosegmented by computing and thresholding a vesselness image. Images of the vasculature centerline were computed, and bifurcations were detected based on centerline voxel neighbors' count. The vasculature segmentations were independently registered using a Demons algorithm between representations of their surface with distance maps. Detected bifurcations were considered as corresponding when distant by less than 5 mm after vasculature DIR. The selected pairs of bifurcations were used to calculate TRE after registration of the images considering three algorithms: rigid registration, Anaconda, and a Demons algorithm. For comparison with the ground truth, TRE values calculated using the automatically detected correspondences were interpolated in the whole organs to generate TRE maps. The performance of the method in automatically calculating TRE after image registration was quantified by measuring the correlation with the TRE obtained when using the ground truth landmarks. RESULTS: The median Pearson correlation coefficients between ground truth TRE and corresponding values in the generated TRE maps were r = 0.81 and r = 0.67 for the lung and liver cases, respectively. The correlation coefficients between mean TRE for each case were r = 0.99 and r = 0.64 for the lung and liver cases, respectively. CONCLUSION: For lungs or liver CT scans DIR, a strong correlation was obtained between TRE calculated using manually picked or landmarks automatically detected with the proposed method. This tool should be particularly useful in studies requiring assessing the reliability of a high number of DIRs.

Is the worst of the COVID-19 global pandemic yet to come? Application of financial mathematics as candidate predictive tools.

The Elliott Wave principle is a time-honored, oft-used method for predicting variations in the financial markets. It is based on the notion that human emotions drive financial decisions. In the fight against the COVID-19 global pandemic, human emotions are similarly decisive, for instance in that they determine one's willingness to be vaccinated, and/or to follow preventive measures including the personal wearing of masks, the application of social distancing protocols, and frequent handwashing. On this basis, we postulated that the Elliott Wave Principle may similarly be used to predict the future evolution of the COVID-19 pandemic. We demonstrated that this method reproduces the data pattern for various countries and the world (daily new cases). Potential scenarios were then extrapolated, from the best-case corresponding to a rapid, full vaccination of the population, to the utterly disastrous case of slow vaccination, and poor adherence to preventive protocols.

Do Pandemics Obey the Elliott Wave Principle of Financial Markets?

The Elliott Wave principle is a time-honored, oft-used method for predicting variations in the financial markets. It is based on the notion that human emotions drive financial decisions. In the fight against COVID-19, human emotions are similarly decisive, for instance in that they determine one's willingness to be vaccinated, and/or to follow preventive measures including the wearing of masks, the application of social distancing protocols, and frequent handwashing. On this basis, we postulated that the Elliott Wave Principle may similarly be used to predict the future evolution of the COVID-19 pandemic. We demonstrated that this method reproduces the data pattern especially well for USA (daily new cases). Potential scenarios were then extrapolated, from the best-case corresponding to a rapid, full vaccination of the population, to the utterly disastrous case of slow vaccination, and poor adherence to preventive protocols.

Cost-effectiveness of consensus guideline based management of pancreatic cysts: The sensitivity and specificity required for guidelines to be cost-effective.

BACKGROUND: Detection of cystic lesions of the pancreas has outpaced our ability to stratify low-grade cystic lesions from those at greater risk for pancreatic cancer, raising a concern for overtreatment. METHODS: We developed a Markov decision model to determine the cost-effectiveness of guideline-based management for asymptomatic pancreatic cysts. Incremental costs per quality-adjusted life year gained and survival were calculated for current management guidelines. A sensitivity analysis estimated the effect on cost-effectiveness and mortality if overtreatment of low-grade cysts is avoided, and the sensitivity and specificity thresholds required of methods of cyst stratification to improve costs expended. RESULTS: "Surveillance" using current management guidelines had an incremental cost-effectiveness ratio of $171,143/quality adjusted life year compared with no surveillance or operative treatment ("do nothing"). An incremental cost-effectiveness ratio for surveillance decreases to $80,707/quality adjusted life year if the operative overtreatment of low-grade cysts was avoided. Assuming a societal willingness-to-pay of $100,000/quality adjusted life year, the diagnostic specificity for high-risk cysts must be >67% for surveillance to be preferred over surgery and "do nothing." Changes in sensitivity alone cannot make surveillance cost-effective. Most importantly, survival in surveillance is worse than "do nothing" for 3 years after cyst diagnosis, although long-term survival is improved. The disadvantage is eliminated when overtreatment of low-grade cysts is avoided. CONCLUSION: Current management of pancreatic cystic lesions is not cost-effective and may increase mortality owing to overtreatment of low-grade cysts. The specificity for risk stratification for high-risk cysts must be greater than 67% to make surveillance cost-effective.

Assessment of setup uncertainty in hypofractionated liver radiation therapy with a breath-hold technique using automatic image registration-based image guidance.

BACKGROUND: Target localization in radiation therapy is affected by numerous sources of uncertainty. Despite measures to minimize the breathing motion, the treatment of hypofractionated liver radiation therapy is further challenged by residual uncertainty coming from involuntary organ motion and daily changes in the shape and location of abdominal organs. To address the residual uncertainty, clinics implement image-guided radiation therapy at varying levels of soft-tissue contrast. This study utilized the treatment records from the patients that have received hypofractionated liver radiation therapy using in-room computed tomography (CT) imaging to assess the setup uncertainty and to estimate the appropriate planning treatment volume (PTV) margins in the absence of in-room CT imaging. METHODS: We collected 917 pre-treatment daily in-room CT images from 69 patients who received hypofractionated radiation therapy to the liver with the inspiration breath-hold technique. For each treatment, the daily CT was initially aligned to the planning CT based on the shape of the liver automatically using a CT-CT alignment software. After the initial alignment, manual shift corrections were determined by visual inspection of the two images, and the corrections were applied to shift the patient to the physician-approved treatment position. Considering the final alignment as the gold-standard setup, systematic and random uncertainties in the automatic alignment were quantified, and the uncertainties were used to calculate the PTV margins. RESULTS: The median discrepancy between the final and automatic alignment was 1.1 mm (0-24.3 mm), and 38% of treated fractions required manual corrections of ≥3 mm. The systematic uncertainty was 1.5 mm in the anterior-posterior (AP) direction, 1.1 mm in the left-right (LR) direction, and 2.4 mm in the superior-inferior (SI) direction. The random uncertainty was 2.2 mm in the AP, 1.9 mm in the LR, and 2.2 mm in the SI direction. The PTV margins recommended to be used in the absence of in-room CT imaging were 5.3 mm in the AP, 3.5 mm in the LR, and 5.1 mm in the SI direction. CONCLUSIONS: Manual shift correction based on soft-tissue alignment is substantial in the treatment of the abdominal region. In-room CT can reduce PTV margin by up to 5 mm, which may be especially beneficial for dose escalation and normal tissue sparing in hypofractionated liver radiation therapy.

Treatment trends and outcomes of small-cell carcinoma of the bladder.

PURPOSE: Treatment for small-cell carcinoma of the bladder is largely guided by case reports, retrospective reviews, and small prospective trials. This study aimed to study outcomes using a large population-based database. METHODS: The Surveillance, Epidemiology, and End Results-Medicare database (1991-2005) was used to analyze how different treatment combinations of specific bladder surgeries, chemotherapy, and radiation affected patient outcomes. Trends in the use of these combinations over time were also analyzed. RESULTS: A total of 533 patients were retrieved from the database. A bladder-sparing approach involving transurethral resection of the bladder tumor (TURBT) combined with chemotherapy and radiation yielded no significant difference in overall survival compared with patients undergoing at least a cystectomy (of whom over 90% received radical cystectomy) with chemotherapy (p > 0.05). The analysis of treatment trends indicated that these two general strategies for cure combined to account for fewer than 20% of patients. A majority of patients (54%) received TURBT as their only surgical treatment, and a subset analysis of these patients indicated that chemotherapy played a role in all stages of disease (p < 0.05) whereas radiation improved overall survival in regional-stage disease (p < 0.05). CONCLUSION: Relatively few patients with small-cell carcinoma of the bladder receive potentially curative therapies. Chemotherapy should be a major component of treatment. Cystectomy and bladder-sparing approaches represent two viable strategies and deserve further investigation to identify the patients who may benefit from organ preservation or not. In addition, the role of radiation in regional-stage disease should be investigated further, because it positively affects survival after TURBT.