GPU Accelerated Viscous-fluid Deformable Registration for Radiotherapy

In cancer treatment organ and tissue deformation betweenradiotherapy sessions represent a significant challenge to op-timal planning and delivery of radiation doses. Recent de-velopments in image guided radiotherapy has caused a soundrequest for more advanced approaches for image registrationto handle these deformations. Viscous-fluid registration isone such deformable registration method. A drawback withthis method has been that it has required computation timesthat were too long to make the approach clinically appli-cable. With recent advances in programmability of graph-ics hardware, complex user defined calculations can now beperformed on consumer graphics cards (GPUs). This pa-per demonstrates that the GPU can be used to drasticallyreduce the time needed to register two medical 3D imagesusing the viscous-fluid registration method. This facilitatesan increased incorporation of image registration in radio-therapy treatment of cancer patients, potentially leading tomore efficient treatment with less severe side effects

Myocardial Work in Patients Hospitalized With COVID‐19:Relation to Biomarkers, COVID‐19 Severity, and All‐Cause Mortality

BACKGROUND: COVID‐19 infection has been hypothesized to affect left ventricular function; however, the underlying mechanisms and the association to clinical outcome are not understood. The global work index (GWI) is a novel echocardiographic measure of systolic function that may offer insights on cardiac dysfunction in COVID‐19. We hypothesized that GWI was associated with disease severity and all‐cause death in patients with COVID‐19. METHODS AND RESULTS: In a multicenter study of patients admitted with COVID‐19 (n=305), 249 underwent pressure‐strain loop analyses to quantify GWI at a median time of 4 days after admission. We examined the association of GWI to cardiac biomarkers (troponin and NT‐proBNP [N‐terminal pro‐B‐type natriuretic peptide]), disease severity (oxygen requirement and CRP [C‐reactive protein]), and all‐cause death. Patients with elevated troponin (n=71) exhibited significantly reduced GWI (1508 versus 1707 mm Hg%; P=0.018). A curvilinear association to NT‐proBNP was observed, with increasing NT‐proBNP once GWI decreased below 1446 mm Hg%. Moreover, GWI was significantly associated with a higher oxygen requirement (relative increase of 6% per 100–mm Hg% decrease). No association was observed with CRP. Of the 249 patients, 37 died during follow‐up (median, 58 days). In multivariable Cox regression, GWI was associated with all‐cause death (hazard ratio, 1.08 [95% CI, 1.01–1.15], per 100–mm Hg% decrease), but did not increase C‐statistics when added to clinical parameters. CONCLUSIONS: In patients admitted with COVID‐19, our findings indicate that NT‐proBNP and troponin may be associated with lower GWI, whereas CRP is not. GWI was independently associated with all‐cause death, but did not provide prognostic information beyond readily available clinical parameters. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04377035

Evaluation of a New Prognostic Tumor Score in Locally Advanced Cervical Cancer Integrating Clinical Examination and Magnetic Resonance Imaging

Purpose: The integral results of clinical examination and magnetic resonance imaging (MRI) of patients with locally advanced cervical cancer may provide prognostic information that cannot readily be placed in current staging systems, such as proximal versus distal parametrial invasion, unilateral versus bilateral involvement, or organ infiltration on MRI. The aim was to develop and investigate the performance of a simple but comprehensive tumor score for reporting and prognostication. Methods and Materials: In the present study, 400 consecutive patients with locally advanced cervical cancer treated 2005 to 2018 with chemoradiation and image guided adaptive brachytherapy (IGABT) were analyzed. The diagnostic workup included clinical examination, positron emission tomography/computed tomography, and MRI. International Federation of Gynecology and Obstetrics 2009 stage distribution was IB to IIA 9%, IIB 61%, and III to IV 30%. Involvement of 8 anatomic locations (cervix, left parametrium, right parametrium, vagina, bladder, ureter, rectum, and uterine corpus) was scored according to a ranked ordinal scale with 0 to 3 points. The total sum of points constituted the tumor score (T-score). Results: The median T-score was 6 (range, 0-20). Based on the frequency distribution of the T-score, 4 equally sized groups were formed: 0 to 4, 5 to 6, 7 to 9, and >9 points. The T-score grouping was highly significant in both univariate and multivariable analysis and outperformed International Federation of Gynecology and Obstetrics stage for both survival and local control enabling also intrastage prognostication. Used as a linear variable, the T-score was correlated with IGABT target volume (high-risk clinical target volume, CTVHR), use of interstitial needles, dose (D90 of CTVHR), and total reference air kerma. Conclusions: The T-score is a simple instrument for combining clinical findings and imaging into a powerful prognostic factor for survival and local control with capabilities surpassing traditional staging. In addition, the T-score may already at diagnosis predict essential IGABT parameters and may be used for audit and comparison of results in multicenter settings

PTV margins should not be used to compensate for uncertainties in 3D image guided intracavitary brachytherapy

The planning target volume (PTV) concept has been created within the context of external beam radiotherapy (EBRT). It would be ideal to have a similar approach in brachytherapy (BT) to compensate for uncertainties. However, the BT and EBRT dose distributions are profoundly different, and the role of a PTV concept in BT needs a distinct discussion. The EBRT PTV concept is based on expanding the dose distribution into a homogeneous plateau reaching beyond the CTV. According to basic BT physics, there are significant dose gradients around radioactive source positions, and it is impossible to create homogeneous dose plateaus. This means that PTV margins cannot be directly applied in BT. Application of PTV margins in lateral and anterior-posterior directions can even lead to a significant and overall dose escalation (∼8% per mm margin applied) for the individual patient and for the entire patient population. In the specific direction along the intrauterine tandem, safety margins can partly account for uncertainties, though. In conclusion, safety margins can only be partially applied in intracavitary BT, and it is not recommended to perform PTV delineation. The PTV seems not to be useful for dose reporting, and dose normalisation to PTV is strongly discouraged since it can lead to dose escalation. © 2010 Elsevier Ireland Ltd. All rights reserved

Anal cancer brachytherapy: From radon seeds to interstitial Papillon technique in a century. What does the future hold?

Evidence from studies which combined 2D-3D external beam radiotherapy (EBRT) ± chemotherapy with 2D brachytherapy (BT) for anal cancer suggest favorable outcomes when compared with chemo-EBRT alone. Further improvement of results can be expected in the era of intensity modulated EBRT and MRI-guided adaptive BT. Despite this, BT is not discussed as a therapeutic option in the prominent international guidelines and its use remains limited to selected institutions. Special skills, complexity, equipment, cost and reimbursement policies have been highlighted as barriers for its wider implementation. However, these factors are relevant for modern radiotherapy in general. Therefore, it can be argued that the role of BT as a component of chemoradiation should be redefined. We describe the historical evolution and current role of BT boost for anal cancer and outline its potential in the context of combined intensity modulated EBRT, chemotherapy and MRI-guided adaptive BT