Errors detected during physics plan review for external beam radiotherapy.

Background and purpose: Risk management in radiotherapy is of high importance. There is not much data published on errors occurring in the treatment planning process of external beam techniques. The aim of this study was to investigate errors occurring during physics plan review in external beam radiotherapy. Materials and methods: Over a period of 14 months errors observed during the physical review process are reported. The errors were grouped and evaluated regarding treatment machine, technique, and treatment site. In addition, a correlation between frequency of errors and staff shortage was analyzed. Results: Subgroups of grave errors (g-errors) and slight errors (s-errors) were defined to consider the different impact on the patient and clinical workflow of the errors. In 1056 plans reviewed, 110 errors (41 g-errors, 69 s-errors) were detected. The most common g-errors and s-errors were "Wrong gantry angle at setup field" (n = 19) and "Wrong field label" (n = 24), respectively. A correlation of number of errors and treatment machine, technique, or anatomical site could not be found. No correlation between staff shortage and number of errors was observed. Conclusions: The process of reviewing treatment plans is a relevant topic to consider in risk analysis of the radiotherapy workflow. The review process could be improved by enhancements in the treatment planning systems, use of digital dose prescription, and treatment planning templates.

Comparison of Machine Learning Computed Tomography-Based Fractional Flow Reserve and Coronary CT Angiography-Derived Plaque Characteristics with Invasive Resting Full-Cycle Ratio.

BACKGROUND: The aim is to compare the machine learning-based coronary-computed tomography fractional flow reserve (CT-FFRML) and coronary-computed tomographic morphological plaque characteristics with the resting full-cycle ratio (RFRTM) as a novel invasive resting pressure-wire index for detecting hemodynamically significant coronary artery stenosis. METHODS: In our single center study, patients with coronary artery disease (CAD) who had a clinically indicated coronary computed tomography angiography (cCTA) and subsequent invasive coronary angiography (ICA) with pressure wire-measurement were included. On-site prototype CT-FFRML software and on-site CT-plaque software were used to calculate the hemodynamic relevance of coronary stenosis. RESULTS: We enrolled 33 patients (70% male, mean age 68 ± 12 years). On a per-lesion basis, the area under the receiver operating characteristic curve (AUC) of CT-FFRML (0.90) was higher than the AUCs of the morphological plaque characteristics length/minimal luminal diameter4 (LL/MLD4; 0.80), minimal luminal diameter (MLD; 0.77), remodeling index (RI; 0.76), degree of luminal diameter stenosis (0.75), and minimal luminal area (MLA; 0.75). CONCLUSION: CT-FFRML and morphological plaque characteristics show a significant correlation to detected hemodynamically significant coronary stenosis. Whole CT-FFRML had the best discriminatory power, using RFRTM as the reference standard.

Correlation of machine learning computed tomography-based fractional flow reserve with instantaneous wave free ratio to detect hemodynamically significant coronary stenosis.

BACKGROUND: Fractional flow reserve based on coronary CT angiography (CT-FFR) is gaining importance for non-invasive hemodynamic assessment of coronary artery disease (CAD). We evaluated the on-site CT-FFR with a machine learning algorithm (CT-FFRML) for the detection of hemodynamically significant coronary artery stenosis in comparison to the invasive reference standard of instantaneous wave free ratio (iFR®). METHODS: This study evaluated patients with CAD who had a clinically indicated coronary computed tomography angiography (cCTA) and underwent invasive coronary angiography (ICA) with iFR®-measurements. Standard cCTA studies were acquired with third-generation dual-source computed tomography and analyzed with on-site prototype CT-FFRML software. RESULTS: We enrolled 40 patients (73% males, mean age 67 ± 12 years) who had iFR®-measurement and CT-FFRML calculation. The mean calculation time of CT-FFRML values was 11 ± 2 min. The CT-FFRML algorithm showed, on per-patient and per-lesion level, respectively, a sensitivity of 92% (95% CI 64-99%) and 87% (95% CI 59-98%), a specificity of 96% (95% CI 81-99%) and 95% (95% CI 84-99%), a positive predictive value of 92% (95% CI 64-99%), and 87% (95% CI 59-98%), and a negative predictive value of 96% (95% CI 81-99%) and 95% (95% CI 84-99%). The area under the receiver operating characteristic curve for CT-FFRML on per-lesion level was 0.97 (95% CI 0.91-1.00). Per lesion, the Pearson's correlation between the CT-FFRML and iFR® showed a strong correlation of r = 0.82 (p < 0.0001; 95% CI 0.715-0.920). CONCLUSION: On-site CT-FFRML correlated well with the invasive reference standard of iFR® and allowed for the non-invasive detection of hemodynamically significant coronary stenosis.

Stereotactic body radiotherapy for ventricular tachycardia (cardiac radiosurgery) : First-in-patient treatment in Germany.

PURPOSE: Single-session cardiac stereotactic body radiotherapy, called cardiac radiosurgery (CRS) or radioablation (RA), may offer a potential treatment option for patients with refractory ventricular tachycardia (VT) and electrical storm who are otherwise ineligible for catheter ablation. However, there is only limited clinical experience. We now present the first-in-patient treatment using (CRS/RA) for VT in Germany. METHODS: A 78-year-old male patient with dilated cardiomyopathy and significantly reduced ejection fraction (15%) presented with monomorphic VT refractory to poly-anti-arrhythmic medication and causing multiple implantable cardioverter-defibrillator (ICD) interventions over the course of several weeks, necessitating prolonged treatment on an intensive care unit. Ultra-high-resolution electroanatomical voltage mapping (EVM) revealed a re-entry circuit in the cardiac septum inaccessible for catheter ablation. Based on the EVM, CRS/RA with a single session dose of 25 Gy (83% isodose) was delivered to the VT substrate (8.1 cc) using a c-arm-based high-precision linear accelerator on November 30, 2018. RESULTS: CRS/RA was performed without incident and dysfunction of the ICD was not observed. Following the procedure, a significant reduction in monomorphic VT from 5.0 to 1.6 episodes per week and of ICD shock interventions by 81.2% was observed. Besides periprocedural nausea with a single episode of vomiting, no treatment-associated side effects were noted. Unfortunately, the patient died 57 days after CRS/RA due to sepsis-associated cardiac circulatory failure after Clostridium difficile-associated colitis developed during rehabilitation. Histopathologic examination of the heart as part of a clinical autopsy revealed diffuse fibrosis on most sections of the heart without apparent differences between the target area and the posterior cardiac wall serving as a control. CONCLUSION: CRS/RA appears to be a possible treatment option for otherwise untreatable patients suffering from refractory VT and electrical storm. A relevant reduction in VT incidence and ICD interventions was observed, although long-term outcome and consequences of CRS/RA remain unclear. Clinical trials are strongly warranted and have been initiated.

Coronary CT angiography derived plaque markers correlated with invasive instantaneous flow reserve for detecting hemodynamically significant coronary stenoses.

PURPOSE: The study aimed to compare morphological and anatomic plaque markers derived from coronary computed tomography angiography (cCTA) for the detection of lesion specific ischemia with invasive instantaneous wave free ratio (iFR®) as the reference standard. METHODS: In our prospective study, we enrolled patients with suspected coronary artery disease (CAD), who had undergone cCTA, using a low-dose third-generation dual-source CT and invasive coronary angiography (ICA) with iFR® measurement. Various plaque markers were assessed on cCTA. Discriminatory power of these markers for the detection of ischemia-inducing coronary artery disease was evaluated against invasive iFR®. RESULTS: Our study cohort included 39 patients (66.6 ± 12.0 years, 72 % male). Among 54 vessel-specific lesions, 15 lesions (28 %) were characterized as hemodynamically significant by iFR® ≤0.89. The area under the curve (AUC) of lesion length/ minimal luminal diameter4 (LL/MLD4) (0.84) was greater than the AUC of minimal luminal area (MLA) (0.82), MLD (0.81), the degree of luminal diameter stenosis (0.81), corrected coronary opacification (CCO) (0.79), remodeling index (RI) (0.75), and percentage aggregate plaque volume (%APV) (0.72). LL, vessel volume (VV), total plaque volume (TPV), calcified and non-calcified plaque volume (CPV and NCPV) did not reach statistical significance and were unable to discriminate between vessels with and without ischemia-inducing coronary stenosis. CONCLUSION: LL/MLD4, MLA, MLD, the degree of luminal diameter stenosis, CCO, RI, and %APV derived from cCTA can support the detection of hemodynamically significant coronary stenosis as compared with iFR®, with LL/MLD4 showing the greatest discriminatory power.

Imaging of implant needles for real-time HDR-brachytherapy prostate treatment using biplane ultrasound transducers.

Ultrasound imaging is becoming increasingly important in prostate brachytherapy. In high-dose-rate (HDR) real-time planning procedures the definition of the implant needles is often performed by transrectal ultrasound. This article describes absolute measurements of the visibility and accuracy of manual detection of implant needle tips and compares measurement results of different biplane ultrasound systems in transversal and longitudinal (i.e., sagittal) ultrasound modes. To obtain a fixed coordinate system and stable conditions the measurements were carried out in a water tank using a dedicated marker system. Needles were manually placed in the phantom until the observer decided by the real-time ultrasound image that the zero position was reached. A comparison of three different ultrasound systems yielded an offset between 0.8 and 3.1 mm for manual detection of the needle tip in ultrasound images by one observer. The direction of the offset was discovered to be in the proximal direction, i.e., the actual needle position was located more distally compared to the ultrasound-based definition. In the second part of the study, the ultrasound anisotropy of trocar implant needles is reported. It was shown that the integrated optical density in a region of interest around the needle tip changes with needle rotation. Three peaks were observed with a phase angle of 120 degrees. Peaks appear not only in transversal but also in longitudinal ultrasound images, with a phase shift of 60 degrees. The third section of this study shows results of observer dependent influences on needle tip detection in sagittal ultrasound images considering needle rotation. These experiments were carried out using the marker system in a water tank. The needle tip was placed exactly at the position z=0 mm. It was found that different users tend to differently interpret the same ultrasound images. The needle tip was manually detected five times in the ultrasound images by three experienced observers at positions (+/- standard deviation) -0.53 +/- 0.16, -0.16 +/- 0.14, and -0.30 +/- 0.16 mm using a gain of 15 dB. The minus sign indicates that the needle tips were detected more proximally than the actual position of the needle tip. When using a gain of -15 dB the mean values of two observers resulted in -0.62 +/- 0.08 and -0.51 +/- 0.12 mm. Additionally an alternative approach to the direct needle tip definition was investigated. Two observers detected the solid part of the needle tip in sagittal images. This solid part, often named as "dead space end," is the distance between the needle tip and the beginning of the hollow part of the implant needle. The dead space end is 6.2 mm for the investigated needle type. Two users found mean values of -6.70 +/- 0.16 and -7.00 +/- 0.06 mm, respectively, for 15 dB gain and -6.90 +/- 0.09 and -7.02 +/- 0.06 mm using the -15 dB gain setting. The results show that ultrasound-based needle tip definition in sagittal viewing mode is accurate. The inter- and intraobserver errors should, however, be taken into account. A lower gain setting of the ultrasound system reduces the intraobserver error.