Which Localizing Strategy is the Most Cost-Effective in Reoperative Primary Hyperparathyroidism?

INTRODUCTION: 2%-10% of patients with primary hyperparathyroidism (PHPT) who undergo parathyroidectomy develop persistent/recurrent disease. The aim of this study was to determine which preoperative localization method is most cost-effective in reoperative PHPT. METHODS: Clinical decision analytic models comparing cost-effectiveness of localizing studies in reoperative PHPT were constructed using TreeAge Pro. Cost and probability assumptions were varied via Probabilistic Sensitivity Analysis (PSA) to test the robustness of the base case models. RESULTS: Base case analysis of model 1 revealed ultrasound (US)-guided fine-needle aspiration with PTH assay as most cost-effective after localizing US. This was confirmed on PSA of model 1. Model 2 showed four-dimensional computed tomography (4D-CT) as most cost-effective after negative US. If not localized by US, on PSA, 4D-CT was the next most cost-effective test. CONCLUSIONS: US-guided FNA with PTH is the most cost-effective confirmatory test after US localization. 4D-CT should be considered as the next best test after negative US.

4D Monte Carlo dose reconstructions using surface motion measurements.

PURPOSE: To investigate the feasibility of a 4D Monte Carlo based dose reconstruction method to study the dosimetric impact of respiratory motion using surface motion measurements for patients undergoing VMAT treatments for Non-Small Cell Lung Cancer. METHODS: The 4Ddefdosxyznrc/EGSnrc algorithm was used to reconstruct VMAT doses delivered to the patients using machine log files and respiratory traces measured with the RADPOS 4D dosimetry system. The RADPOS sensor was adhered to the patient's abdomen prior to each treatment fraction and its position was used as a surrogate for tumour motion. Treatment log files were synchronized with the patient respiratory traces. Patient specific respiratory models were generated from deformable registration of the inhale and exhale 4DCT images and the respiratory traces. The reconstructed doses were compared to planned doses calculated with DOSXYZnrc/EGSnrc on the average-intensity and the exhale phase CT images. RESULTS: Respiratory motion measurements and log files were acquired for 2 patients over 5 treatment fractions each. The motion was predominantly along the anterior/posterior direction (A/P). The average respiratory amplitudes were 8.7 ± 2.7 mm and 10.0 ± 1.2 mm for Patient 1 and 2, respectively. Both patients displayed inter- and intra-fractional variations in the baseline position. Small inter-fractional differences were observed in the reconstructed doses for each patient. Differences between the reconstructed and planned doses were attributed to differences in organ volumes. CONCLUSION: The 4D reconstruction method was successfully implemented for the two patients studied. Small differences between the planned and reconstructed doses were observed due to the small tumour motion of these patients.

The preoperative assessment of thoracic wall adhesions using four-dimensional computed tomography.

OBJECTIVE: Pleural adhesions are challenging during lung cancer surgery and may be associated with a long surgery time and excessive blood loss due to pleural adhesiolysis. We used preoperative four-dimensional computed tomography to quantitatively assess parietal pleural adhesions and determine its diagnostic accuracy. METHODS: A total of 216 patients with lung cancer underwent four-dimensional computed tomography during the study period. Pleural adhesions were subsequently confirmed by surgery in 85 of these patients, whereas 126 patients had no adhesions. The movements of the tumor or target vessels (α) was tracked. Receiver-operating characteristic curve analysis was used to identify the relationship between adhesions and (α). RESULTS: The movement of (α) was smaller in patients with adhesions than in those without adhesions. The greater the adhesion, the shorter the movement distance (p < 0.001). Receiver-operating characteristic curve analysis demonstrated an area under the curve for the moving (α) point at 0.71 (95% confidence interval: 0.62-0.80) in the upper lung field and at 0.75 (95% confidence interval: 0.64-0.85) in the lower field. To identify adhesions, a cut off of 11.3 mm (sensitivity = 43.6%, specificity = 93.2%) in the upper lung field and a cut off of 41.2 mm (sensitivity = 71.4%, specificity = 66.0%) in the lower lung field were established. CONCLUSIONS: Four-dimensional computed tomography is a novel and helpful modality for predicting the presence of parietal pleural adhesions. To obtain robust evidence, further accumulation of cases and re-examination of the analysis methods are needed.

Clinical 3D/4D cumulative proton dose assessment methods for thoracic tumours with large motion.

PURPOSE: Despite the anticipated clinical benefits of intensity-modulated proton therapy (IMPT), plan robustness may be compromised due to its sensitivity to patient treatment uncertainties, especially for tumours with large motion. In this study, we investigated treatment course-wise plan robustness for intra-thoracic tumours with large motion comparing a 4D pre-clinical evaluation method (4DREM) to our clinical 3D/4D dose reconstruction and accumulation methods. MATERIALS AND METHODS: Twenty patients with large target motion (>10 mm) were treated with five times layered rescanned IMPT. The 3D-robust optimised plans were generated on the averaged planning 4DCT. Using multiple 4DCTs, treatment plan robustness was assessed on a weekly and treatment course-wise basis through the 3D robustness evaluation method (3DREM, based on averaged 4DCTs), the 4D robustness evaluation method (4DREM, including the time structure of treatment delivery and 4DCT phases) and 4D dose reconstruction and accumulation (4DREAL, based on fraction-wise information). RESULTS: Baseline target motion for all patients ranged from 11-17 mm. For the offline adapted course-wise dose assessment, adequate target dose coverage was found for all patients. The target volume receiving 95% of the prescription dose was consistent between methods with 16/20 patients showing differences < 1%. 4DREAL showed the highest target coverage (99.8 ± 0.6%, p < 0.001), while no differences were observed between 3DREM and 4DREM (99.3 ± 1.3% and 99.4 ± 1.1%, respectively). CONCLUSION: Our results show that intra-thoracic tumours can be adequately treated with IMPT in free breathing for target motion amplitudes up to 17 mm employing any of the accumulation methods. Anatomical changes, setup and range errors demonstrated a more severe impact on target coverage than motion in these patients treated with fractionated proton radiotherapy.

Experimental validation of 4D log file-based proton dose reconstruction for interplay assessment considering amplitude-sorted 4DCTs.

PURPOSE: The unpredictable interplay between dynamic proton therapy delivery and target motion in the thorax can lead to severe dose distortions. A fraction-wise four-dimensional (4D) dose reconstruction workflow allows for the assessment of the applied dose after patient treatment while considering the actual beam delivery sequence extracted from machine log files, the recorded breathing pattern and the geometric information from a 4D computed tomography scan (4DCT). Such an algorithm capable of accounting for amplitude-sorted 4DCTs was implemented and its accuracy as well as its sensitivity to input parameter variations was experimentally evaluated. METHODS: An anthropomorphic thorax phantom with a movable insert containing a target surrogate and a radiochromic film was irradiated with a monoenergetic field for various 1D target motion forms (sin, sin4 ) and peak-to-peak amplitudes (5/10/15/20/30 mm). The measured characteristic film dose distributions were compared to the respective sections in the 4D reconstructed doses using a 2D γ-analysis (3 mm, 3%); γ-pass rates were derived for different dose grid resolutions (1 mm/3 mm) and deformable image registrations (DIR, automatic/manual) applied during the 4D dose reconstruction process. In an additional analysis, the sensitivity of reconstructed dose distributions against potential asynchronous timing of the motion and machine log files was investigated for both a monoenergetic field and more realistic 4D robustly optimized fields by artificially introduced offsets of ±1/5/25/50/250 ms. The resulting dose distributions with asynchronized log files were compared to those with synchronized log files by means of a 3D γ-analysis (1 mm, 1%) and the evaluation of absolute dose differences. RESULTS: The induced characteristic interplay patterns on the films were well reproduced by the 4D dose reconstruction with 2D γ-pass rates ≥95% for almost all cases with motion magnitudes ≤15 mm. In general, the 2D γ-pass rates showed a significant decrease for larger motion amplitudes and increase when using a finer dose grid resolution but were not affected by the choice of motion form (sin, sin4 ). There was also a trend, though not statistically significant, toward the manually defined DIR for better quality of the reconstructed dose distributions in the area imaged by the film. The 4D dose reconstruction results for the monoenergetic as well as the 4D robustly optimized fields were robust against small asynchronies between motion and machine log files of up to 5 ms, which is in the order of potential network latencies. CONCLUSIONS: We have implemented a 4D log file-based proton dose reconstruction that accounts for amplitude-sorted 4DCTs. Its accuracy was proven to be clinically acceptable for target motion magnitudes of up to 15 mm. Particular attention should be paid to the synchronization of the log file generating systems as the reconstructed dose distribution may vary with log file asynchronies larger than those caused by realistic network delays.

Implementation of a 4-dimensional computed tomography protocol for parathyroid adenoma localization.

PURPOSE: To present the results of our implementation of a four-dimensional computed tomography- (4DCT) based parathyroid localization protocol for primary hyperparathyroidism at a safety net hospital. METHODS: We performed a retrospective review of all patients who underwent parathyroidectomy for primary hyperparathyroidism at Elmhurst Hospital Center from June 2016 - September 2019. Patients treated prior to the implementation of 4DCT during October 2018 served as historical controls for comparison. Imaging-related costs and hospital charges were obtained from the Radiology Department for each patient. RESULTS: Forty-two patients underwent parathyroid surgery during the study period. Twenty patients had undergone 4DCT while 22 had nuclear medicine studies with or without ultrasonography. The sensitivity and specificity of 4DCT was 90.4% and 100% respectively, compared to 63% and 93.7% for nuclear imaging studies and 41% and 95% for ultrasound. The mean number of glands explored was significantly less in the 4DCT group, 1.8 ± 1.19 versus 2.77 ± 1.26 (p = 0.01). There was no increase in infrastructure or personnel costs associated with 4DCT implementation. CONCLUSIONS: 4DCT represents an increasingly common imaging modality for pre-operative parathyroid localization. Here we demonstrate that 4DCT is associated with a reduction in the number of glands explored and enables minimally invasive parathyroid surgery. 4DCT is a cost-effective and clinically sound localization study for parathyroid localization in an urban safety-net hospital.

Lung 4D CT Image Registration Based on High-Order Markov Random Field.

To solve the problem that traditional image registration methods based on continuous optimization for large motion lung 4D CT image sequences are easy to fall into local optimal solutions and lead to serious misregistration, a novel image registration method based on high-order Markov Random Field (MRF) is proposed. By analyzing the effect of the deformation field constraint of the potential functions with different order cliques in MRF model, energy functions with high-order cliques form are designed separately for 2D and 3D images to preserve topology of the deformation field. In order to preserve the topology of the deformation field more effectively, it is necessary to apply a smooth term and a topology preservation term simultaneously in the energy function and use logarithmic function to impose a penalty on the Jacobian matrix with high-order cliques in the topology preservation term. For the complexity of the designed energy function with high-order cliques form, Markov Chain Monte Carlo (MCMC) algorithm is used to solve the optimization problem of the designed energy function. To address the high computational requirements in lung 4D CT image registration, a multi-level processing strategy is adopted to reduce the space complexity of the proposed registration method and promotes the computational efficiency. In the DIR-lab dataset with 4D CT images and the COPD (Chronic Obstructive Pulmonary Disease) dataset with 3D CT images, the average target registration error (TRE) of our proposed method can reach 0.95 mm respectively.

Comparison of the dose on specific 3DCT images and the accumulated dose for cardiac structures in esophageal tumors radiotherapy: whether specific 3DCT images can be used for dose assessment?

BACKGROUND: Cardiac activity could impact the accuracy of dose assessment for the heart, pericardium and left ventricular myocardium (LVM). The purpose of this study was to explore whether it is possible to perform dose assessment by contouring the cardiac structures on specific three-dimensional computed tomography (3DCT) images to reduce the impact of cardiac activity. METHODS: Electrocardiograph-gated 4DCT (ECG-gated 4DCT) images of 22 patients in breath-hold were collected. MIM Maestro 6.8.2 (MIM) was used to reconstruct specific 3DCT images to obtain the Maximal intensity projection (MIP) image, Average intensity projection (AIP) image and Minimum intensity projection (Min-IP) image. The heart, pericardium and LVM were contoured in 20 phases of 4DCT images (0, 5%... 95%) and the MIP, AIP and Min-IP images. Then, a radiotherapy plan was designed at the 0% phase of the 4DCT images, and the dose was transplanted to all phases of 4DCT to acquire the dose on all phases, the accumulated dose of all phases was calculated using MIM. The dose on MIP, AIP and Min-IP images were also obtained by deformable registration of the dose. The mean dose (Dmean), V5, V10, V20, V30 and V40 for the heart, pericardium and LVM in MIP, AIP and Min-IP images were compared with the corresponding parameters after dose accumulation. RESULTS: The mean values of the difference between the Dmean in the MIP image and the Dmean after accumulation for the heart, pericardium and LVM were all less than 1.50 Gy, and the dose difference for the pericardium and LVM was not statistically significant (p > 0.05). For dose-volume parameters, there was no statistically significant difference between V5, V10, and V20 of the heart and pericardium in MIP, AIP, and Min-IP images and those after accumulation (p > 0.05). For the LVM, only in the MIP image, the differences of V5, V10, V20, V30 and V40 were not significant compared to those after dose accumulation (p > 0.05). CONCLUSIONS: There was a smallest difference for the dosimetry parameters of cardiac structures on MIP image compared to corresponding parameters after dose accumulation. Therefore, it is recommended to use the MIP image for the delineation and dose assessment of cardiac structures in clinical practice.

Estimation of effective imaging dose and excess absolute risk of secondary cancer incidence for four-dimensional cone-beam computed tomography acquisition.

This study was conducted to estimate the organ equivalent dose and effective imaging dose for four-dimensional cone-beam computed tomography (4D-CBCT) using a Monte Carlo simulation, and to evaluate the excess absolute risk (EAR) of secondary cancer incidence. The EGSnrc/BEAMnrc were used to simulate the on-board imager (OBI) from the TrueBeam linear accelerator. Specifically, the OBI was modeled based on the percent depth dose and the off-center ratio was measured using a three-dimensional (3D) water phantom. For clinical cases, 15 lung and liver cancer patients were simulated using the EGSnrc/DOSXYZnrc. The mean absorbed doses to the lung, stomach, bone marrow, esophagus, liver, thyroid, bone surface, skin, adrenal glands, gallbladder, heart, intestine, kidney, pancreas and spleen, were quantified using a treatment planning system, and the equivalent doses to each organ were calculated. Subsequently, the effective dose was calculated as the weighted sum of the equivalent dose, and the EAR of the secondary cancer incidence was determined for each organ with the use of the biologic effects of ionizing radiation (BEIR) VII model. The effective doses were 3.9 ± 0.5, 15.7 ± 2.0, and 7.3 ± 0.9 mSv, for the lung, and 4.2 ± 0.6, 16.7 ± 2.4, and 7.8 ± 1.1 mSv, for the liver in the respective cases of the 3D-CBCT (thorax, pelvis) and 4D-CBCT modes. The lung EARs for males and females were 7.3 and 10.7 cases per million person-years, whereas the liver EARs were 9.9 and 4.5 cases per million person-years. The EAR increased with increasing time since radiation exposure. In clinical studies, we should use 4D-CBCT based on consideration of the effective dose and EAR of secondary cancer incidence.

Performance assessment of displacement-field estimation of the human left atrium from 4D-CT images using the coherent point drift algorithm.

BACKGROUND: Cardiac four-dimensional computed tomography (4D-CT) imaging is a standard approach used to visualize left atrium (LA) deformation for clinical diagnosis. However, the quantitative evaluation of LA deformation from 4D-CT images is still a challenging task. We assess the performance of LA displacement-field estimation from 4D-CT images using the coherent point drift (CPD) algorithm, which is a robust point set alignment method based on the expectation-maximization (EM) algorithm. METHOD: Subject-specific LA surfaces at 20 phases/cardiac cycles were reconstructed from 4D-CT images and expressed as sets of triangular elements. The LA surface at the phase that maximized the LA surface area was assigned as the control LA surface and those at the other 19 phases were assigned as observed LA surfaces. The LA displacement-field was estimated by solving the alignment between the control and observation LA surfaces using CPD. RESULTS: Global correspondences between the estimated and observed LA surfaces were successfully confirmed by quantitative evaluations using the Dice similarity coefficient and differences of surface area for all phases. The surface distances between the estimated and observed LA surfaces ranged within 2 mm, except at the left atrial appendage and boundaries, where incomplete data, such as missing or false detections, were included on the observed LA surface. We confirmed that the estimated LA surface displacement and its spatial distribution were anisotropic, which is consistent with existing clinical observations. CONCLUSION: These results highlight that the LA displacement field estimated by CPD robustly tracks global LA surface deformation observed in 4D-CT images.

4D Monte Carlo dose calculations for pre-treatment quality assurance of VMAT SBRT: a phantom-based feasibility study.

Volumetric arc therapy (VMAT) for lung stereotactic body radiotherapy (SBRT) is challenging due to both breathing-induced motion and the dynamic components of the linear accelerator. In this study, a 4D Monte Carlo (4DMC) dose calculation method for VMAT SBRT is proposed and the feasibility of the method is evaluated. A rigidly-moving lung phantom was imaged using four dimensional computed tomography (4DCT). VMAT SBRT plans were generated on the average intensity projection dataset using the internal target volume (ITV) strategy (ITV-plan) and a single phase to simulate a dynamic treatment-couch tracking technique (TRACKING-plan). 4DMC simulations were performed and compared to 3D Monte Carlo (3DMC) and 3D- and 4D- calculations in the treatment planning system using the adaptive convolution (AC) algorithm. Dose metrics calculated for the ITV-plan showed an overestimation with 3D adaptive convolution (3DAC) for D[Formula: see text] (GTV) by 3.5% and by 2.0% for 3DMC, both compared to 4DMC. The TRACKING-plan D[Formula: see text] (GTV) calculated with the 3DAC method overestimated by 2.0% compared with 4DMC. Deviations between the calculation methods for D mean (Lung) and D[Formula: see text] (PTV) were minimal. For both plans, measurements were taken with EBT3 film inside the phantom tumour. EBT3 film profiles showed good agreement with 4DMC for the TRACKING-plan giving a gamma pass rate of 97.2% for 3%/3 mm global and for 3DAC compared with measured, 95.8%. Whereas for the ITV-plan, the 3D profiles varied from film in the ITV periphery region with a pass rates of 50% and 48.6% for 3DAC and 3DMC, respectively. 4DMC agreed more closely to measurements for this plan with a pass rate of 95.8%. We have proposed an accurate method to perform 4D dose calculations for pre-treatment quality assurance of VMAT SBRT. The method was compared to experimental measurements and for both plans, 4DMC dose agreed with measurements more closely than other evaluated dose calculation methods. This study has demonstrated the feasibility of this 4DMC method.

Numerical simulation of novel concept 4D cardiac microtomography for small rodents based on all-optical Thomson scattering X-ray sources.

Accurate dynamic three-dimensional (4D) imaging of the heart of small rodents is required for the preclinical study of cardiac biomechanics and their modification under pathological conditions, but technological challenges are met in laboratory practice due to the very small size and high pulse rate of the heart of mice and rats as compared to humans. In 4D X-ray microtomography (4D µCT), the achievable spatio-temporal resolution is hampered by limitations in conventional X-ray sources and detectors. Here, we propose a proof-of-principle 4D µCT platform, exploiting the unique spatial and temporal features of novel concept, all-optical X-ray sources based on Thomson scattering (TS). The main spatial and spectral properties of the photon source are investigated using a TS simulation code. The entire data acquisition workflow has been also simulated, using a novel 4D numerical phantom of a mouse chest with realistic intra- and inter-cycle motion. The image quality of a typical single 3D time frame has been studied using Monte Carlo simulations, taking into account the effects of the typical structure of the TS X-ray beam. Finally, we discuss the perspectives and shortcomings of the proposed platform.

Preoperative assessment of parietal pleural invasion/adhesion of subpleural lung cancer: advantage of software-assisted analysis of 4-dimensional dynamic-ventilation computed tomography.

OBJECTIVE: To evaluate the accuracy of four-dimensional (4D) dynamic-ventilation computed tomography (CT) scanning coupled with our novel image analysis software to diagnose parietal pleural invasion/adhesion of peripheral (subpleural) lung cancer. METHODS: Eighteen patients with subpleural lung cancer underwent both 4D dynamic-ventilation CT during free breathing and conventional (static) chest CT during preoperative assessment. The absence of parietal pleural invasion/adhesion was surgically confirmed in 13 patients, while the presence of parietal pleural invasion/adhesion was confirmed in 5 patients. Two chest radiologists, who were blinded to patient status, cooperatively evaluated the presence of pleural invasion/adhesion using two different imaging modalities: (i) conventional high-resolution CT images, reconstructed in the axial, coronal, and sagittal directions, and (ii) 4D dynamic-ventilation CT images combined with a color map created by image analysis software to visualize movement differences between the lung surface and chest wall. Parameters of diagnostic accuracy were assessed, including a receiver operating characteristic analysis. RESULTS: Software-assisted 4D dynamic-ventilation CT images achieved perfect diagnostic accuracy for pleural invasion/adhesion (sensitivity, 100%; specificity, 100%; area under the curve [AUC], 1.000) compared to conventional chest CT (sensitivity, 60%; specificity, 77%; AUC, 0.846). CONCLUSION: Software-assisted 4D dynamic-ventilation CT can be considered as a novel imaging approach for accurate preoperative analysis of pleural invasion/adhesion of peripheral lung cancer. KEY POINTS: • 4D dynamic-ventilation CT can correctly assess parietal pleural invasion/adhesion of peripheral lung cancer. • A unique color map clearly demonstrates parietal pleural invasion/adhesion. • Our technique can be expanded to diagnose "benign" pleural adhesions for safer thoracoscopic surgery.

Dynamic assessment of sternoclavicular joint instability using four-dimensional computed tomography.

Chronic post-traumatic sternoclavicular joint (SCJ) instability can be debilitating and result in restriction of normal daily activities. The diagnosis can be difficult to make clinically or with the use of static imaging modalities. Wide-volume dynamic four-dimensional computed tomography (4D CT) can confidently diagnose chronic post-traumatic SCJ instability. This can aid surgeons in pre-operative planning and help to triage patients into surgical or non-surgical candidates. We propose that 4D CT to be a routine pre-operative imaging in patients with chronic post-traumatic SCJ instability.

Vascular assessment after clipping surgery using four-dimensional CT angiography.

Recent advances in computed tomography angiography (CTA) enable repeated imaging follow up for post-clipping surgery. The purpose of this study was to clarify the critical volume and configuration of the aneurysmal clip in the postoperative evaluation using volume rendering (VR) imaging, and present four-dimensional (4D)-CTA for these larger metal artifacts. A total of 44 patients with cerebral aneurysm, treated using clipping surgery, were included in this study. The metal artifact volume was assessed using CTA and the association between the type of clips and its metal artifact volume was analyzed. A VR image and a 4D-CTA were then produced, and the diagnostic accuracy of arteries around the clip or residual aneurysm on these images was evaluated. In the receiver operating characteristic (ROC) curve analysis, the cutoff value for metal artifacts was 2.32 mm3 as determined through a VR image. Patients were divided into two groups. Group 1 included patients with a simple and small clip, and group 2 included patients with multiple, large or fenestrated clips. The metal artifact volume was significantly larger in group 2, and the group incorporated the cutoff value. Post-clipping status on the VR image was significantly superior in group 1 compared with group 2. In group 2, the imaging quality of post-clipping status on 4D-CTA was superior in 92.9% of patients. The metal artifact volume was dependent on the number, size, or configuration of the clip used. In group 2, evaluation using a 4D-CTA eliminated the effect of the metal artifacts.

Cine 4DCT imaging artifacts: Quantification and correlations with scanning parameters and target kinetics.

To study temporal resolved computed tomography imaging (4-Dimensional Computed Tomography: 4DCT) artifacts correlations with scanning parameters and target kinetics and to assess uncertainty introduced by 4DCT in radiotherapy treatment planning. In this work we classified 4DCT artifacts as finite gantry rotation speed related (FGS) and finite sampling frequency related (FSF). We studied FGS artifacts using a respiratory phantom and FSF artifacts using a Monte Carlo simulation of acquisition timing. From our analysis FGS localization error is comparable with image resolution determined by voxel dimensions. Remaining FGS artifacts are correlated with gantry rotation time (Trot), target velocity (v) and their interaction. FSF artifacts occurrence is correlated with sampling ratio (SR), i.e. the ratio of patient respiratory period (Tresp) and sampling time (Ts). In the studied velocity range (0-2 cm/s), using a Trot of 0,5s and a SR higher than 15, FGS and FSF artifacts became comparable with other sources of uncertainty. Our considerations are valid for "ideal" breathing pattern only. When variations from periodical breathing, high target velocity (more than 2 cm/s) or high peak to peak amplitude (more than 2 cm) are present, patient specific images artifacts analysis is recommended.

4D-PET reconstruction using a spline-residue model with spatial and temporal roughness penalties.

4D reconstruction of dynamic positron emission tomography (dPET) data can improve the signal-to-noise ratio in reconstructed image sequences by fitting smooth temporal functions to the voxel time-activity-curves (TACs) during the reconstruction, though the optimal choice of function remains an open question. We propose a spline-residue model, which describes TACs as weighted sums of convolutions of the arterial input function with cubic B-spline basis functions. Convolution with the input function constrains the spline-residue model at early time-points, potentially enhancing noise suppression in early time-frames, while still allowing a wide range of TAC descriptions over the entire imaged time-course, thus limiting bias. Spline-residue based 4D-reconstruction is compared to that of a conventional (non-4D) maximum a posteriori (MAP) algorithm, and to 4D-reconstructions based on adaptive-knot cubic B-splines, the spectral model and an irreversible two-tissue compartment ('2C3K') model. 4D reconstructions were carried out using a nested-MAP algorithm including spatial and temporal roughness penalties. The algorithms were tested using Monte-Carlo simulated scanner data, generated for a digital thoracic phantom with uptake kinetics based on a dynamic [18F]-Fluromisonidazole scan of a non-small cell lung cancer patient. For every algorithm, parametric maps were calculated by fitting each voxel TAC within a sub-region of the reconstructed images with the 2C3K model. Compared to conventional MAP reconstruction, spline-residue-based 4D reconstruction achieved >50% improvements for five of the eight combinations of the four kinetics parameters for which parametric maps were created with the bias and noise measures used to analyse them, and produced better results for 5/8 combinations than any of the other reconstruction algorithms studied, while spectral model-based 4D reconstruction produced the best results for 2/8. 2C3K model-based 4D reconstruction generated the most biased parametric maps. Inclusion of a temporal roughness penalty function improved the performance of 4D reconstruction based on the cubic B-spline, spectral and spline-residue models.

Assessment of dosimetric errors induced by deformable image registration methods in 4D pencil beam scanned proton treatment planning for liver tumours.

PURPOSE: Respiratory impacts in pencil beam scanned proton therapy (PBS-PT) are accounted by extensive 4D dose calculations, where deformable image registration (DIR) is necessary for estimating deformation vector fields (DVFs). We aim here to evaluate the dosimetric errors induced by different DIR algorithms in their resulting 4D dose calculations by using ground truth(GT)-DVFs from 4DMRI. MATERIALS AND METHODS: Six DIR methods: ANACONDA, Morfeus, B-splines, Demons, CT Deformable, and Total Variation, were respectively applied to nine 4DCT-MRI liver data sets. The derived DVFs were then used as input for 4D dose calculation. The DIR induced dosimetric error was assessed by individually comparing the resultant 4D dose distributions to those obtained with GT-DVFs. Both single-/three-field plans and single/rescanned strategies were investigated. RESULTS: Differences in 4D dose distributions among different DIR algorithms, and compared to the results using GT-DVFs, were pronounced. Up to 40 % of clinically relevant dose calculation points showed dose differences of 10 % or more between the GT. Differences in V95(CTV) reached up to 11.34 ±â€¯12.57 %. The dosimetric errors became in general less substantial when applying multiple-field plans or using rescanning. CONCLUSION: Intrinsic geometric errors by DIR can influence the clinical evaluation of liver 4D PBS-PT plans. We recommend the use of an error bar for correctly interpreting individual 4D dose distributions.

Can multiphase dynamic CT angiography provide a better assessment of aortic dissection compared with the standard triphasic protocol?

Background Acute aortic dissection (AD) is a life-threatening medical emergency. It has been debated whether the multiphase dynamic computed tomography angiography (CTA) protocol is superior to the standard triphasic protocol for revealing the characteristics of AD. Purpose To examine two multiphase dynamic protocols, Dynamic four-dimensional (4D) CTA using the shuttle mode and Flash 4D CTA using the high-pitch mode for the assessment of AD and to compare them with the standard triphasic protocol. Material and Methods A total of 54 consecutive patients were randomly and equally assigned to three groups and scanned with a second-generation DSCT scanner. Groups A, B, and C were assessed with the Dynamic 4D CTA in the shuttle mode, the Flash 4D CTA in the high-pitch mode, and the standard triphasic acquisition protocol, respectively. Image quality of all patients was evaluated. The effective radiation dose (ED) was recorded. Results In 54 patients, CTA images could display the true and false lumens, the intimal flap, the entry tear, and branch vessel involvement in the AD. Compared with group C, additional diagnostic information was obtained in groups A and B, including the dynamic enhancement delay between the true and false lumens (A = 18, B = 18); the presence of membrane oscillation (A = 8, B = 14); dynamic ejection of the contrast material from the true lumen into the false lumen (A = 6, B = 7); and the dynamic obstruction of the left renal artery (B = 2). The ED in these three groups was significantly different ( P < 0.05). Conclusion Compared to the standard triphasic protocol, the multiphase dynamic CTA protocol is feasible and is able to reveal additional diagnostic information. Therefore, we recommend using the high-pitch, dual-source multiphase dynamic CTA to assess ADs.

Epidemiology of acute kidney injury in patients with stroke: a retrospective analysis from the neurology ICU.

Acute kidney injury (AKI) is proven to be an independent risk factor for adverse clinical outcomes in patients with stroke, but data about the epidemiology of AKI in these patients are not well characterized. Therefore, we investigated the incidence, risk factors, and the impact of AKI on the clinical outcomes in a group of Chinese patients with stroke. We retrospectively recruited 647 stroke patients from the neurology ICU between 2012 and 2013. AKI was identified according to the 2012 KDIGO criteria. Baseline estimated glomerular filtration rate (eGFR) was calculated using modified Chronic Kidney Disease Epidemiology Collaboration equation for Chinese patients. National Institutes of Health Stroke Scale (NIHSS) score was assessed for the stroke severity. A total of 135 (20.9%) patients developed AKI. Patients with AKI stages from 1 to 3 were 84 (62.2%), 26 (19.3%), and 25 (18.5%), respectively. Logistic regression analysis showed that independent risk factors for AKI were higher NIHSS score (OR, 1.027; 95% CI 1.003-1.051), lower baseline eGFR (OR, 0.985; 95% CI 0.977-0.993), the presence of hypertension (OR, 1.592; 95% CI 1.003-2.529), and infectious complications (OR, 3.387; 95% CI 1.997-5.803) (P < 0.05 for all). AKI patients were also significantly associated with all-cause mortality in the neurology ICU [OR and 95% CI of AKI-stage 1, AKI-stage 2, and AKI-stage 3 were 4.961 (2.191-11.232), 19.722 (6.354-61.217), and 48.625 (17.616-134.222), respectively (P < 0.001 for all)]. AKI is common among patients with stroke and is associated with worse clinical outcomes after stroke. Prevention of AKI seems to be very important among these patients, because they are exposed to many risk factors for developing AKI.