The value of 18F-fluorodeoxyglucose positron-emission-tomography-computed tomography (FDG-PET/CT) for staging patients with (very) high-risk non-muscle invasive bladder cancer (NMIBC) is unknown.... Show moreThe value of 18F-fluorodeoxyglucose positron-emission-tomography-computed tomography (FDG-PET/CT) for staging patients with (very) high-risk non-muscle invasive bladder cancer (NMIBC) is unknown. In this study among NMIBC patients referred for RC, FDG-PET/CT detected metastases that were not detected by CT, leading to treatment changes in 10% of patients. However, the use of FDG-PET/CT should be weighed against its disad-vantages, including false-positive lesions. Introduction and Objectives: 18F-fluorodeoxyglucose positron-emission tomography-computed tomography (FDG-PET/CT) is increasingly used in the preoperative staging of patients with muscle-invasive bladder cancer. The clinical added value of FDG-PET/CT in high-risk non-muscle invasive bladder cancer (NMIBC) is unknown. In this study, the value of FDG-PET/CT in addition to contrast enhanced (CE)-CT was evaluated in high-risk NMIBC before radical cystec-tomy (RC). Materials and Methods: This is a retrospective analysis of consecutive patients with high risk and very-high risk urothelial NMIBC scheduled for RC in a tertiary referral center between 2011 and 2020. Patients underwent staging with CE-CT (chest and abdomen/pelvis) and FDG-PET/CT. We assessed the clinical disease stage before and after FDG-PET/CT and the treatment recommendation based on the stage before and after FDG-PET/CT. The accuracy of CT and FDG-PET/CT for identifying metastatic disease was defined by the receiver-operating curve using a reference -standard including histopathology/cytology (if available), imaging and follow-up. Results: A total of 92 patients were identified (median age: 71 years). In 14/92 (15%) patients, FDG-PET/CT detected metastasis (12 suspicious lymph nodes and 4 distant metastases). The disease stage changed in 11/92 (12%) patients based on additional FDG-PET/CT findings. FDG-PET/CT led to a different treatment in 9/92 (10%) patients. According to the reference standard, 25/92 (27%) patients had metastases. The sensitivit y, specificit y and accuracy of FDG-PET/CT was 36%, 93% and 77% respectively, versus 12%, 97% and 74% of CE-CT only. The area under the ROC curve was 0.643 for FDG-PET/CT and 0.545 for CT, P = .036. Conclusion: The addition of FDG-PET/CT to CE-CT imaging changed the treatment in 10% of patients and proved to be a valuable diagnostic tool in a selected subgroup of NMIBC patients scheduled for RC. Show less
MR fingerprinting (MRF) is a promising method for quantitative characterization of tissues. Often, voxel-wise measurements are made, assuming a single tissue-type per voxel. Alternatively, the... Show moreMR fingerprinting (MRF) is a promising method for quantitative characterization of tissues. Often, voxel-wise measurements are made, assuming a single tissue-type per voxel. Alternatively, the Sparsity Promoting Iterative Joint Non-negative least squares Multi-Component MRF method (SPIJN-MRF) facilitates tissue parameter estima-tion for identified components as well as partial volume segmentations. The aim of this paper was to evaluate the accuracy and repeatability of the SPIJN-MRF parameter estimations and partial volume segmentations. This was done (1) through numerical simulations based on the BrainWeb phantoms and (2) using in vivo acquired MRF data from 5 subjects that were scanned on the same week-day for 8 consecutive weeks. The partial volume segmen-tations of the SPIJN-MRF method were compared to those obtained by two conventional methods: SPM12 and FSL. SPIJN-MRF showed higher accuracy in simulations in comparison to FSL-and SPM12-based segmentations: Fuzzy Tanimoto Coefficients (FTC) comparing these segmentations and Brainweb references were higher than 0.95 for SPIJN-MRF in all the tissues and between 0.6 and 0.7 for SPM12 and FSL in white and gray matter and between 0.5 and 0.6 in CSF. For the in vivo MRF data, the estimated relaxation times were in line with literature and minimal variation was observed. Furthermore, the coefficient of variation (CoV) for estimated tissue volumes with SPIJN-MRF were 10.5% for the myelin water, 6.0% for the white matter, 5.6% for the gray matter, 4.6% for the CSF and 1.1% for the total brain volume. CoVs for CSF and total brain volume measured on the scanned data for SPIJN-MRF were in line with those obtained with SPM12 and FSL. The CoVs for white and gray mat-ter volumes were distinctively higher for SPIJN-MRF than those measured with SPM12 and FSL. In conclusion, the use of SPIJN-MRF provides accurate and precise tissue relaxation parameter estimations taking into account intrinsic partial volume effects. It facilitates obtaining tissue fraction maps of prevalent tissues including myelin water which can be relevant for evaluating diseases affecting the white matter. Show less
Vargas, C.S.; Bauwens, M.; Pooters, I.N.A.; Pomme, S.; Peters, S.M.B.; Segbers, M.; ... ; Wierts, R. 2020
BackgroundPersonalized molecular radiotherapy based on theragnostics requires accurate quantification of the amount of radiopharmaceutical activity administered to patients both in diagnostic and... Show moreBackgroundPersonalized molecular radiotherapy based on theragnostics requires accurate quantification of the amount of radiopharmaceutical activity administered to patients both in diagnostic and therapeutic applications. This international multi-center study aims to investigate the clinical measurement accuracy of radionuclide calibrators for 7 radionuclides used in theragnostics: Tc-99m, In-111, I-123, I-124, I-131, Lu-177, and Y-90.MethodsIn total, 32 radionuclide calibrators from 8 hospitals located in the Netherlands, Belgium, and Germany were tested. For each radionuclide, a set of four samples comprising two clinical containers (10-mL glass vial and 3-mL syringe) with two filling volumes were measured. The reference value of each sample was determined by two certified radioactivity calibration centers (SCK CEN and JRC) using two secondary standard ionization chambers. The deviation in measured activity with respect to the reference value was determined for each radionuclide and each measurement geometry. In addition, the combined systematic deviation of activity measurements in a theragnostic setting was evaluated for 5 clinically relevant theragnostic pairs: I-131/I-123, I-131/I-124, Lu-177/In-111, Y-90/Tc-99m, and Y-90/In-111.ResultsFor Tc-99m, I-131, and Lu-177, a small minority of measurements were not within 5% range from the reference activity (percentage of measurements not within range: Tc-99m, 6%; I-131, 14%; Lu-177, 24%) and almost none were outside +/- 10% range. However, for In-111, I-123, I-124, and Y-90, more than half of all measurements were not accurate within +/- 5% range (In-111, 51%; I-123, 83%; I-124, 63%; Y-90, 61%) and not all were within +/- 10% margin (In-111, 22%; I-123, 35%; I-124, 15%; Y-90, 25%). A large variability in measurement accuracy was observed between radionuclide calibrator systems, type of sample container (vial vs syringe), and source-geometry calibration/correction settings used. Consequently, we observed large combined deviations (percentage deviation > +/- 10%) for the investigated theragnostic pairs, in particular for Y-90/In-111, I-131/I-123, and Y-90/Tc-99m.Conclusions Our study shows that substantial over- or underestimation of therapeutic patient doses is likely to occur in a theragnostic setting due to errors in the assessment of radioactivity with radionuclide calibrators. These findings underline the importance of thorough validation of radionuclide calibrator systems for each clinically relevant radionuclide and sample geometry. Show less
Automated revenue management systems with complex and protected algorithms have significantly changed the revenue management profession. Hotels have become increasingly reliant on advanced computer... Show moreAutomated revenue management systems with complex and protected algorithms have significantly changed the revenue management profession. Hotels have become increasingly reliant on advanced computer systems that continually reforecast hotel demand. However, performance of these systems is not flawless, and revenue managers adjust their computer system forecasts using their professional judgment. These judgmental adjustments can improve accuracy, but if performed poorly, can result in a cascade of suboptimal decisions. This dissertation explores the influence of judgmental adjustments on the accuracy of system-generated hotel occupancy forecasts. To this purpose, three studies have been conducted. The dissertation first evaluated whether it matters which measure is used to assess the forecast accuracy. It was then investigated whether the timing of judgmental adjustments influenced the forecast accuracy. Finally, the characteristics of judgmental adjustments (e.g., direction, size, frequency) and their effects on forecast accuracy were analyzed. The dissertation shows that (1) the choice of accuracy measure is complex and important, (2) the accuracy of occupancy forecasts improves considerably as the forecast horizon becomes shorter, and (3) the effect of judgmental adjustments differs and differs per hotel. Using a disaggregated reforecasting perspective, this dissertation improves understanding of how judgmental adjustments impact the accuracy of system-generated occupancy forecasts. Show less
Objective: The reliability of the electrically evoked compound action potential (eCAP) threshold depends on its precision and accuracy. The precision of the eCAP threshold reflects its variability,... Show moreObjective: The reliability of the electrically evoked compound action potential (eCAP) threshold depends on its precision and accuracy. The precision of the eCAP threshold reflects its variability, while the accuracy of the threshold shows how close it is to the actual value. The objective of this study was to determine the test/retest variability of the eCAP threshold in Advanced Bionics cochlear implant users, which has never been reported before. We hypothesized that the test/retest variability is dependent on the presence of random noise in the recorded eCAP waveforms. If this holds true, the recorded error should be reduced by approximately the square-root of the number of averages. As secondary objectives, we assessed the effects of the slope of the amplitude growth function (AGF), cochlear location, and eCAP threshold on eCAP threshold precision. We hypothesized that steeper slopes should result in better precision of the linearly extrapolated eCAP threshold. As other studies have shown that apical regions have steeper slopes and larger eCAPs, we recorded eCAPs in three different cochlear locations. The difference of the precision between two commonly applied stimulus-artifact reduction paradigms on eCAP threshold precision was compared, namely averaging of alternating stimulus polarities (AP averaging) and forward masking (FM). FM requires the addition of more waveforms than AP averaging, and hence we expected FM to have lower precision than AP.Design: This was an unmasked, descriptive, and observational study with a cross-over (repeated measures) design that included 13 subjects. We recorded eCAPs on three electrode contacts: in the base, middle, and apex of the cochlea at 10 stimulus intensities. Per stimulus level, 256 eCAP waveforms were recorded. eCAP thresholds were determined by constructing AGFs and linear extrapolation to zero-amplitude. The precision of the eCAP threshold was calculated as the SD using a Monte Carlo simulation, as a function of the number of waveform averages.Results: The SD of the eCAP threshold was reduced by approximately the square root of two when the number of averages in the eCAP waveforms was doubled. The precision was significantly better when the slope of the AGF was steeper and was more favorable in the cochlear base than in the apex. Precision was better when AP averaging was used. Absolute eCAP threshold did not significantly affect precision. At the default number of 32 waveform averages in the Advanced Bionics system, we report a median SD of the eCAP threshold of 2 to 3 mu A, with a range of 1 to 11 mu A across the cochlea. Previous studies have shown that the total error, based on the 95% confidence bounds of the linear extrapolation, can be as high as -260 to +120 mu A.Conclusions: The median variability in the eCAP threshold proved to be small compared with the total variability introduced by the linear extrapolation method. Yet there was substantial intersubject variability. Therefore, we recommend monitoring the SD during eCAP recording to facilitate informed decisions when to terminate waveform collection. From a precision perspective, AP averaging is preferable over FM as it has better precision, while fewer recordings are needed, making it the more time-efficient method of the two. Show less
Purpose: To assess the reliability of magnetic resonance imaging (MRI) for evaluation of craniocaudal tumour extension by comparing the craniocaudal tumour extension on the pre-operative MRI and... Show morePurpose: To assess the reliability of magnetic resonance imaging (MRI) for evaluation of craniocaudal tumour extension by comparing the craniocaudal tumour extension on the pre-operative MRI and postoperative hysterectomy specimen in patients with early stage uterine cervical cancer.Materials and methods: After approval of the institutional review board was acquired, pre-operative MRI and hysterectomy specimen of 21 women with early stage cervical cancer were re-evaluated. The craniocaudal extension on MRI was measured separately by two experienced radiologists and compared with corresponding measurements from the hysterectomy specimen, which were re-evaluated by an experienced pathologist.Results: Median craniocaudal extension of uterine cervical cancer on MRI was slightly smaller compared to histopathology (2.1 cm vs. 2.5 cm). The median underestimation was 0.4 cm (range -0.6 cm to 2.2 cm, mean 0.4 cm, standard deviation (SD) +/- 0.7 cm); Pearson's correlation was 0.83 (p < 0.001). In two patients (9%) MRI underestimated tumour craniocaudal extension by more than 1.8 cm.Conclusion: MRI represents the histopathological craniocaudal tumour extension in the majority of patients with early stage uterine cervical cancer, but with a systematic small underestimation of the real craniocaudal tumour extension. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license Show less
The studies in this thesis concentrate on memory for an emotional event, with a specific focus on completeness, consistency and accuracy of emotional memories and their predictors. In doing so,... Show moreThe studies in this thesis concentrate on memory for an emotional event, with a specific focus on completeness, consistency and accuracy of emotional memories and their predictors. In doing so, both field and laboratory studies were conducted. The results show that overall, memory for emotional events is fairly complete and consistent over time. Still, the human memory is sometimes incomplete and prone to inaccuracies and inconsistencies. Maybe an elephant never forgets, people occasionally do! Emotional state, psychiatric status and psychological variables, with the exception of (peri) traumatic dissociation, did not have a strong influence on completeness, consistency and accuracy of memory for emotional events. Show less
