Cranial-caudal Research Articles

Experimental demonstration of real-time cardiac physiology-based radiotherapy gating for improved cardiac radioablation on an MR-linac.

Cardiac radioablation is a noninvasive stereotactic body radiation therapy (SBRT) technique to treat patients with refractory ventricular tachycardia (VT) by delivering a single high-dose fraction to the VT isthmus. Cardiorespiratory motion induces position uncertainties resulting in decreased dose conformality. Electocardiograms (ECG) are typically used during cardiac MRI (CMR) to acquire images in a predefined cardiac phase, thus mitigating cardiac motion during image acquisition. We demonstrate real-time cardiac physiology-based radiotherapy beam gating within a preset cardiac phase on anMR-linac. MR images were acquired in healthy volunteers (n = 5, mean age = 29.6 years, mean heart-rate (HR) = 56.2 bpm) on the 1.5 T Unity MR-linac (Elekta AB, Stockholm, Sweden) after obtaining written informed consent. The images were acquired using a single-slice balance steady-state free precession (bSSFP) sequence in the coronal or sagittal plane (TR/TE = 3/1.48 ms, flip angle = 48 , SENSE = 1.5, , voxel size = , partial Fourier factor = 0.65, frame rate = 13.3 Hz). In parallel, a 4-lead ECG-signal was acquired using MR-compatible equipment. The feasibility of ECG-based beam gating was demonstrated with a prototype gating workflow using a Quasar MRI4D motion phantom (IBA Quasar, London, ON, Canada), which was deployed in the bore of the MR-linac. Two volunteer-derived combined ECG-motion traces (n = 2, mean age = 26 years, mean HR = 57.4 bpm, peak-to-peak amplitude = 14.7 mm) were programmed into the phantom to mimic dose delivery on a cardiac target in breath-hold. Clinical ECG-equipment was connected to the phantom for ECG-voltage-streaming in real-time using research software. Treatment beam gating was performed in the quiescent phase (end-diastole). System latencies were compensated by delay time correction. A previously developed MRI-based gating workflow was used as a benchmark in this study. A 15-beam intensity-modulated radiotherapy (IMRT) plan ( Gy) was delivered for different motion scenarios onto radiochromic films. Next, cardiac motion was then estimated at the basal anterolateral myocardial wall via normalized cross-correlation-based template matching. The estimated motion signal was temporally aligned with the ECG-signal, which were then used for position- and ECG-based gating simulations in the cranial-caudal (CC), anterior-posterior (AP), and right-left (RL) directions. The effect of gating was investigated by analyzing the differences in residual motion at 30, 50, and 70% treatment beam duty cycles. ECG-based (MRI-based) beam gating was performed with effective duty cycles of 60.5% (68.8%) and 47.7% (50.4%) with residual motion reductions of 62.5% (44.7%) and 43.9% (59.3%). Local gamma analyses (1%/1 mm) returned pass rates of 97.6% (94.1%) and 90.5% (98.3%) for gated scenarios, which exceed the pass rates of 70.3% and 82.0% for nongated scenarios, respectively. In average, the gating simulations returned maximum residual motion reductions of 88%, 74%, and 81% at 30%, 50%, and 70% duty cycles, respectively, in favor of MRI-basedgating. Real-time ECG-based beam gating is a feasible alternative to MRI-based gating, resulting in improved dose delivery in terms of high rates, decreased dose deposition outside the PTV and residual motion reduction, while by-passing cardiac MRIchallenges.

A phantom to simulate organ motion and its effect on dose distribution in carbon ion therapy for pancreatic cancer

Objective. Carbon ion radiotherapy is a promising radiation technique for malignancies like pancreatic cancer. However, organs’ motion imposes challenges for achieving homogeneous dose delivery. In this study, an anthropomorphic Pancreas Phantom for Ion-beam Therapy (PPIeT) was developed to simulate breathing and gastrointestinal motion during radiotherapy. Approach. The developed phantom contains a pancreas, two kidneys, a duodenum, a spine and a spinal cord. The shell of the organs was 3D printed and filled with agarose-based mixtures. Hounsfield Units (HU) of PPIeTs’ organs were measured by CT. The pancreas motion amplitude in cranial-caudal (CC) direction was evaluated from patients’ 4D CT data. Motions within the obtained range were simulated and analyzed in PPIeT using MRI. Additionally, GI motion was mimicked by changing the volume of the duodenum and quantified by MRI. A patient-like treatment plan was calculated for carbon ions, and the phantom was irradiated in a static and moving condition. Dose measurements in the organs were performed using an ionization chamber and dosimetric films. Main results. PPIeT presented tissue equivalent HU and reproducible breathing-induced CC displacements of the pancreas between (3.98 ± 0.36) mm and a maximum of (18.19 ± 0.44) mm. The observed maximum change in distance of (14.28 ± 0.12) mm between pancreas and duodenum was consistent with findings in patients. Carbon ion irradiation revealed homogenous coverage of the virtual tumor at the pancreas in static condition with a 1% deviation from the treatment plan. Instead, the dose delivery during motion with the maximum amplitude yielded an underdosage of 21% at the target and an increased uncertainty by two orders of magnitude. Significance. A dedicated phantom was designed and developed for breathing motion assessment of dose deposition during carbon ion radiotherapy. PPIeT is a unique tool for dose verification in the pancreas and its organs at risk during end-to-end tests.

MRI-based inter- and intrafraction motion analysis of the pancreatic tail and spleen as preparation for adaptive MRI-guided radiotherapy in neuroblastoma

BackgroundIn pediatric radiotherapy treatment planning of abdominal tumors, dose constraints to the pancreatic tail/spleen are applied to reduce late toxicity. In this study, an analysis of inter- and intrafraction motion of the pancreatic tail/spleen is performed to estimate the potential benefits of online MRI-guided radiotherapy (MRgRT).Materials and methodsTen randomly selected neuroblastoma patients (median age: 3.4 years), irradiated with intensity-modulated arc therapy at our department (prescription dose: 21.6/1.8 Gy), were retrospectively evaluated for inter- and intrafraction motion of the pancreatic tail/spleen. Three follow-up MRIs (T2- and T1-weighted ± gadolinium) were rigidly registered to a planning CT (pCT), on the vertebrae around the target volume. The pancreatic tail/spleen were delineated on all MRIs and pCT. Interfraction motion was defined as a center of gravity change between pCT and T2-weighted images in left-right (LR), anterior-posterior (AP) and cranial-caudal (CC) direction. For intrafraction motion analysis, organ position on T1-weighted ± gadolinium was compared to T2-weighted. The clinical radiation plan was used to estimate the dose received by the pancreatic tail/spleen for each position.ResultsThe median (IQR) interfraction motion was minimal in LR/AP, and largest in CC direction; pancreatic tail 2.5 mm (8.9), and spleen 0.9 mm (3.9). Intrafraction motion was smaller, but showed a similar motion pattern (pancreatic tail, CC: 0.4 mm (1.6); spleen, CC: 0.9 mm (2.8)). The differences of Dmean associated with inter- and intrafraction motions ranged from − 3.5 to 5.8 Gy for the pancreatic tail and − 1.2 to 3.0 Gy for the spleen. In 6 out of 10 patients, movements of the pancreatic tail and spleen were highlighted as potentially clinically significant because of ≥ 1 Gy dose constraint violation.ConclusionInter- and intrafraction organ motion results into unexpected constrain violations in 60% of a randomly selected neuroblastoma cohort, supporting further prospective exploration of MRgRT.

Diaphragm and abdominal organ motion during radiotherapy: a comprehensive multicenter study in 189 children

BackgroundFor accurate thoracic and abdominal radiotherapy, inter- and intrafractional geometrical uncertainties need to be considered to enable accurate margin sizes. We aim to quantify interfractional diaphragm and abdominal organ position variations, and intrafractional diaphragm motion in a large multicenter cohort of pediatric cancer patients (< 18 years). We investigated the correlation of interfractional position variations and intrafractional motion with age, and with general anesthesia (GA).MethodsIn 189 children (mean age 8.1; range 0.4–17.9 years) from six institutes, interfractional position variation of both hemidiaphragms, spleen, liver, left and right kidneys was quantified using a two-step registration. CBCTs were registered to the reference CT relative to the bony anatomy, followed by organ registration. We calculated the group mean, systematic and random errors (standard deviations Σ and σ, respectively) in cranial-caudal (CC), left-right and anterior-posterior directions. Intrafractional right hemidiaphragm motion was quantified using CBCTs on which the breathing amplitude, defined as the difference between end-inspiration and end-expiration peaks, was assessed (N = 79). We investigated correlations with age (Spearman’s ρ), and differences in motion between patients treated with and without GA (N = 75; all < 5.5 years).ResultsInterfractional group means were largest in CC direction and varied widely between patients, with largest variations in the right hemidiaphragm (range -13.0–17.5 mm). Interfractional group mean of the left kidney showed a borderline significant correlation with age (p = 0.047; ρ = 0.17). Intrafractional right hemidiaphragm motion in patients ≥ 5.5 years (mean 10.3 mm) was significantly larger compared to patients < 5.5 years treated without GA (mean 8.3 mm) (p = 0.02), with smaller Σ and σ values. We found a significant correlation between breathing amplitude and age (p < 0.001; ρ = 0.43). Interfractional right hemidiaphragm position variations were significantly smaller in patients < 5.5 years treated with GA than without GA (p = 0.004), but intrafractional motion showed no significant difference.ConclusionIn this large multicenter cohort of children undergoing thoracic and abdominal radiotherapy, we found that interfractional position variation does not depend on age, but the use of GA in patients < 5.5 years showed smaller systematic and random errors. Furthermore, our results showed that breathing amplitude increases with age. Moreover, variations between patients advocate the need for a patient-specific margin approach.

Analysis of heart displacement during thoracic radiotherapy based on electrocardiograph-gated 4-dimensional magnetic resonance imaging.

Periodic cardiac movement may expose the heart to radiation field induced damage, leading to radiation-induced heart disease (RIHD). Studies have proven that delineation of the heart based on planning CT fails to show the real margin of the substructures and a compensatory margin should be applied. The purpose of this study was to quantify the dynamic changes and the compensatory extension range by breath-hold and electrocardiogram gated 4-dimensional magnetic resonance imaging (4D-MRI), which had the advantage of discriminating soft tissues. Eventually, 15 patients with oesophageal or lung cancers were enrolled, including one female and nine males aged from 59 to 77 years from December 10th, 2018, to March 4th, 2020. The displacement of the heart and its substructures was measured through a fusion volume and the compensatory expansion range was calculated by expending the boundary on the planning CT to that of the fusion volume. The differences were tested through the Kruskal-Wallis H test and were considered significant at a two-side P<0.05. The extent of movement of heart and its substructures during one cardiac cycle were approximately 4.0-26.1 millimetre (mm) in anterior-posterior (AP), left-right (LR), and cranial-caudal (CC) axes, and the compensatory margins should be applied to planning CT by extending the margins by 1.7, 3.6, 1.8, 3.0, 2.1, and 2.9 centimetres (cm) for pericardium; 1.2, 2.5, 1.0, 2.8, 1.8, and 3.3 cm for heart; 3.8, 3.4, 3.1, 2.8, 0.9, and 2.0 cm for interatrial septum; 3.3, 4.9, 2.0, 4.1, 1.1, and 2.9 cm for interventricular septum; 2.2, 3.0, 1.1, 5.3, 1.8, and 2.4 cm for left ventricular muscle (LVM); 5.9, 3.4, 2.1, 6.1, 5.4, and 3.6 cm for antero-lateral papillary muscle (ALPM); and 6.6, 2.9, 2.6, 6.6, 3.9, and 4.8 cm for postero-medial papillary muscle (PMPM) in anterior, posterior, left, right, cranial, and caudal directions, respectively. Periodic cardiac activity causes obvious displacement of the heart and its substructures, and the motion amplitude of substructures differs. Extending a certain margin as the compensatory extension to represent the organs at risk (OAR) and then limiting the dose-volume parameters could be performed in clinical practice.

The effect of respiration-induced target motion on 3D magnetic resonance images used to guide radiotherapy

3D Magnetic Resonance Imaging (MRI) is used in radiation therapy for reference planning and, lately, for adaptive treatments on MR accelerators. This study aimed to investigate the impact of different types of respiratory motion on the apparent target position and extent in such scans. An MRI motion phantom with a 30mm diameter target was used to simulate cranial-caudal (CC) motion and imaged at an MR-Linac using a standard clinically released 3D T2w sequence. Scans were acquired for each combination of functions (sin(t), sin4(t) and sin12(t)), peak-to-peak amplitudes(5, 10, 15 and 20mm), and periods (4, 5 and 6s). Furthermore, respiration CC motion patterns fromtwo patients were used. Motion functions were shifted such that the time average target position would match a static reference scan at 0-position. The target was automatically identified in coronal and sagittal images using k-means clustering. The mean position and area of the target were calculated and compared to the reference scan. Artefacts increased with amplitude and depended on the motion type. Sin(t) and sin4(t) oscillations resulted in a blurring of the target, which led to an increased target area, while sin12(t) motion did not show significant changes in the target area. However, for the sin12(t) motion, the offset in apparent position was prominent, while that was not the case for the sin(t) and sin4(t) motion. The patient respiration motion profiles showed similar trends. In 3D MRI, target motion can change apparent tumour extent and apparent position. The changes increase with motion amplitude and depend on the motion type.

Morphometric comparison of Fisch type A and endoscopic endonasal far-medial supracondylar approaches to the jugular foramen.

The jugular foramen (JF) is one of the most complex and challenging skull base regions to approach surgically. The extreme medial approach to access the JF provides the approach angle from an anterior direction and does not require dissection and sacrifice of the jugular bulb (JB) to reach the pars nervosa. The authors compared the Fisch type A approach to the extreme medial approach to access the JF and evaluated the usefulness of the extreme medial approach. This study was performed at the Anatomical Laboratory for Visuospatial Innovations in Otolaryngology and Neurosurgery of The Ohio State University. For the comparison of surgical maneuverability and visualization, two angles were measured: 1) the angle of attack (AoA), defined as the widest angle of movement achieved with a straight dissector; and 2) the angle of endoscopic exposure (AoEE), defined as the widest angle of movement in the nasal cavity. The differences in eustachian tube (ET) management, approach angle, surgical maneuverability, and surgical application of the Fisch type A approach to the extreme medial approach were compared. There was no difference between ET mobilization and transection regarding cranial-caudal (CC) or medial-lateral (ML) AoA (p = 0.646). The CC-AoA of the Fisch type A approach was significantly wider than the CC-AoA of the extreme medial approach (p = 0.001), and the CC-AoEE was significantly wider than the CC-AoA of the extreme medial approach (p < 0.001). There was no significant difference between the CC-AoA of the Fisch type A approach and the CC-AoEE. The ML-AoA of the Fisch type A approach was significantly wider than the ML-AoA of the extreme medial approach (p = 0.033), and the ML-AoEE was significantly wider than ML-AoA in the extreme medial approach (p < 0.001). The ML-AoEE was significantly wider than the ML-AoA in the Fisch type A approach (p = 0.033). The surgical maneuverability of the extreme medial approach was not inferior to that of the Fisch type A approach. The extreme medial approach can provide excellent surgical field visualization, while preserving the JB. Select cases of chordomas, chondrosarcomas, and JF schwannomas should be considered for an extreme medial approach. These two approaches are complementary, and a case-by-case detailed analysis should be conducted to decide the best approach.

Diagnostic Value of Radiomics Analysis in Contrast-Enhanced Spectral Mammography for Identifying Triple-Negative Breast Cancer.

PurposeTo evaluate the value of radiomics analysis in contrast-enhanced spectral mammography (CESM) for the identification of triple-negative breast cancer (TNBC).MethodCESM images of 367 pathologically confirmed breast cancer patients (training set: 218, testing set: 149) were retrospectively analyzed. Cranial caudal (CC), mediolateral oblique (MLO), and combined models were built on the basis of the features extracted from subtracted images on CC, MLO, and the combination of CC and MLO, respectively, in the tumour region. The performance of the models was evaluated through receiver operating characteristic (ROC) curve analysis, the Hosmer-Lemeshow test, and decision curve analysis (DCA). The areas under ROC curves (AUCs) were compared through the DeLong test.ResultsThe combined CC and MLO model had the best AUC and sensitivity of 0.90 (95% confidence interval: 0.85–0.96) and 0.97, respectively. The Hosmer–Lemeshow test yielded a non-significant statistic with p-value of 0.59. The clinical usefulness of the combined CC and MLO model was confirmed if the threshold was between 0.02 and 0.81 in the DCA.ConclusionsMachine learning models based on subtracted images in CESM images were valuable for distinguishing TNBC and NTNBC. The model with the combined CC and MLO features had the best performance compared with models that used CC or MLO features alone.

Synthesizing high-resolution magnetic resonance imaging using parallel cycle-consistent generative adversarial networks for fast magnetic resonance imaging.

The common practice in acquiring the magnetic resonance (MR) images is to obtain two-dimensional (2D) slices at coarse locations while keeping the high in-plane resolution in order to ensure enough body coverage while shortening the MR scan time. The aim of this study is to propose a novel method to generate HR MR images from low-resolution MR images along the longitudinal direction. In order to address the difficulty of collecting paired low- and high-resolution MR images in clinical settings and to gain the advantage of parallel cycle consistent generative adversarial networks (CycleGANs) in synthesizing realistic medical images, we developed a parallel CycleGANs based method using a self-supervised strategy. The proposed workflow consists of two parallely trained CycleGANs to independently predict the HR MR images in the two planes along the directions that are orthogonal to the longitudinal MR scan direction. Then, the final synthetic HR MR images are generated by fusing the two predicted images. MR images, including T1-weighted (T1), contrast enhanced T1-weighted (T1CE), T2-weighted (T2), and T2 Fluid Attenuated Inversion Recovery (FLAIR), of the multimodal brain tumor segmentation challenge 2020 (BraTS2020) dataset were processed to evaluate the proposed workflow along the cranial-caudal (CC), lateral, and anterior-posterior directions. Institutional collected MR images were also processed for evaluation of the proposed method. The performance of the proposed method was investigated via both qualitative and quantitative evaluations. Metrics of normalized mean absolute error (NMAE), peak signal-to-noise ratio (PSNR), edge keeping index (EKI), structural similarity index measurement (SSIM), information fidelity criterion (IFC), and visual information fidelity in pixel domain (VIFP) were calculated. It is shown that the proposed method can generate HR MR images visually indistinguishable from the ground truth in the investigations on the BraTS2020 dataset. In addition, the intensity profiles, difference images and SSIM maps can also confirm the feasibility of the proposed method for synthesizing HR MR images. Quantitative evaluations on the BraTS2020 dataset shows that the calculated metrics of synthetic HR MR images can all be enhanced for the T1, T1CE, T2, and FLAIR images. The enhancements in the numerical metrics over the low-resolution and bi-cubic interpolated MR images, as well as those genearted with a comparative deep learning method, are statistically significant. Qualitative evaluation of the synthetic HR MR images of the clinical collected dataset could also confirm the feasibility of the proposed method. The proposed method is feasible to synthesize HR MR images using self-supervised parallel CycleGANs, which can be expected to shorten MR acquisition time in clinical practices.

Quantitative analysis of the intra-beam respiratory motion with baseline drift for respiratory-gating lung stereotactic body radiation therapy.

This study aimed to quantitatively clarify the baseline drift for each respiratory cycle in two respiratory-gating methods using the intra-beam respiratory motion data of lung cancer patients. The residual motion and dose distribution were calculated based on intra-beam respiratory motion data with the baseline drift. To quantify the baseline drift n}{}Delta during irradiation, it was defined as the inclination between the detected expiration point and the expiration point in the next cycle in the anterior–posterior (AP), cranial–caudal (CC) and left–right (LR) directions obtained using an in-house programme. The baseline drift value reached up to 0.74 mm/s in the CC direction as per the respiratory motion data of 10 patients. The homogeneity index (HI) of the phase-gating method tended to increase because the target was irradiated even when the amplitude position of the target differed from period to period. In contrast, the amplitude-gating method enabled irradiation considering the amplitude position of the target because the gating window was set considering the amplitude position of the respiratory motion. The respiratory-gating methods and respiratory phase in respiratory-gating lung stereotactic body radiation therapy (SBRT) must be determined based on the respiratory motion of the patients.

Four-Dimensional Computed Tomography Scan Analysis of Liver Tumor Motion Treated With Abdominal Compression During Stereotactic Treatment of Liver

To explore the motion and influencing factors of implanted gold markers in guiding liver stereotactic body radiation therapy using abdominal compression.Twenty patients with oligometastatic colorectal cancer or primary hepatocellular carcinoma from January 2016 to December 2019 were included. All patients were treated with stereotactic body radiation therapy (SBRT) under abdominal compression, with 1-3 gold markers implanted within 2cm of the lesion before positioning, meanwhile four-dimensional computed tomography (4DCT) scan used for treatment planning. The respiratory cycle was divided into 0%-90% respiratory phase image based on the respiratory signal, which were reconstructed by the system as well as CBCT validation images before radiation exposure daily. The liver volume was divided into 3 parts: within 2 cm of the main hepatic portal vein, 2-5 cm of the main hepatic portal vein, and 5 cm outside of the main hepatic portal vein, for evaluating the motion of different tumor locations.The average intrafractional motion amplitude (mean ± standard deviation) was 2.63 ± 2.81 mm in the cranial-caudal (CC), 1.35 ± 1.23 mm in the anterior-posterior (AP), and 0.76 ± 0.88 mm in the left-right (LR) direction, respectively. Meanwhile the average interfractional motion amplitude was 3.45 ± 3.06 mm, 2.64 ± 2.60 mm, and 2.23 ± 2.07 mm, respectively. Whether intra- or interfraction, the motion amplitude showed CC > AP > LR direction (P < 0.001). The motion varied at different tumor location, the further away from the main hepatic portal vein, the larger of the intrafractional motion. To cover the 95% population-based confidence interval, internal target volume was suggested to include the expansion of 3.9 mm, 5.2 mm and 7.9 mm in the LR, AP, and CC direction, while 4.3 mm, 4.4 mm, and 6.1 mm within 2 cm of the main hepatic portal vein, 3.5 mm, 7.3 mm, and 9.7 mm outside 5 cm of the main hepatic portal vein, respectively. The expansion varied significantly depending on tumor location, but motion in CC direction showed the largest no matter where the tumor was. Among the 3 parts of liver volume, while the further of tumor away from the main portal vein, the larger expansion in CC direction, and tumor in 5 cm outside of the main portal vein moved more than other inner parts in AP direction.Different tumor locations of liver require external expansion of internal target volume individually.Y. Zhao: None. Y. Tang: None. W. Liu: None. N. Li: None. Y. Song: None. S. Wang: None. Y. Liu: None. H. Fang: None. N. Lu: None. Y. Tang: None. S. Qi: None. Y. Yang: None. B. Chen: None. Y. LI: None. J. Jin: None.

Evaluation of lung tumor motion in a large sample: Target-related and clinical factors influencing tumor motion based on four-dimensional CT.

Background and purposeWe aimed to analyze the influence of target‐related and clinical factors on lung tumor motion based on four‐dimensional CT (4DCT), and clarify the motion based on subgroups in lung stereotactic body radiation therapy.Materials and methods4DCT image data of 267 tumors from 246 patients were analyzed. The coordinates in the left–right (LR), anterior–posterior (AP), and cranial–caudal (CC) directions of the center of mass (COM) of the gross tumor volumes in 10 phases of 4DCT were measured. The peak‐to‐peak COM displacement in the LR, AP, CC, and 3D directions was calculated. The influence of target‐related and clinical factors on tumor motion was evaluated using multivariate analysis.ResultsThe tumor segment location correlated with the tumor motion in each direction. Tumor size was predictive of tumor motion in the 3D (p = 0.023) and AP directions (p = 0.049). The tumor motion for metastatic tumors was smaller than that for primary tumors in the LR (p = 0.019) and AP directions (p = 0.008). The CC motion for pulmonary surgery recipients (3.8 ± 4.5 mm) was less than that for patients who had not undergone surgery (5.6 ± 5.4 mm), and no significant clinical factor was observed. BSA and BMI were positively correlated with the motion in the CC (p = 0.02) and LR directions (p = 0.002).ConclusionThe tumor segment location was a good predictor of tumor motion. A larger tumor tends to have a smaller motion. Patients with metastatic tumors or those who have undergone pulmonary surgery exhibited smaller and more unpredictable tumor motions, which required individual assessments. Thus, clinical factors can potentially predict tumor motion.

Assessment of breast density in women from different regions of Brazil

In many countries, there is an interest in determining the location of the women with the highest breast density. This investigation is important for optimize screening for breast cancer for women with dense breasts as other imaging modalities since 2D mammography is not very efficient on this type of breast. The objective of this study was to evaluate the variations in breast density in Brazilian women of different regions of Brazil. The mammographic images were taken from four regions of Brazil. The images, in the cranial caudal (CC) projection, were separated into intervals of compressed breast thickness (CBT) and patient age and were analysed by the software VolparaDensity, where volumetric breast density (VBD) calculations were performed. For each interval, null hypothesis tests for the mean difference between the VBD from the four regions of Brazil were performed. The paired tests indicated that there was a significant difference in the VBD of the women in the different regions of Brazil, with variations from 11.05% to 36.73%. Higher VBD was observed for women living in the Southeast region, followed by the Midwest, Northeast, and North regions. The Brazilian IBGE data show that the most urbanised region in Brazil is the Southeast, which coincides with the second highest rate of breast cancer in Brazil, according to the Brazilian National Cancer Institute (INCA). It is also known that breast cancer is strongly related to breast density; therefore, the results of this work support the data presented by federal agencies demonstrating that women living in the most urbanised region of Brazil (e.g., Southeast) present the highest breast density.

Study of Spinal Cord Substructure Expansion Margin in Esophageal Cancer.

Purpose:To analyze the setup errors and residual errors of different spinal cord parts in esophageal cancer patients and to explore the necessity of spinal cord segmental expansion.Methods and Materials:Sixty cases of esophageal cancer were included with 20 patients subdivided into the following groups: neck, chest and abdomen as per the treatment site. The patients underwent intensity modulated radiation therapy (IMRT) between 2017 and 2019. Thermoplastic mask or vacuum bag were utilized for immobilization of different groups. CTVision (Siemens CT-On-Rail system) was used to acquire pre-treatment CT, and 20 consecutive pre-treatment CT datasets were collected for data analysis for each case. Images were exported to MIM (MIM Software Inc.) for processing and data analysis. Dice coefficient, maximum Hausdorff distance and centroid coordinate values between the spinal cord contours in the pre-treatment CTs and the planning CT were calculated and extracted. The contour expansion margin value is calculated as MPRV = 1.3 ∑ total + 0.5 σ total, where ∑ total and σ total are the systematic and random error, respectively.Results:For neck, chest, abdominal segments of the spinal cord, the mean Dice coefficients (± SD) are 0.73 ± 0.06, 0.80 ± 0.06, 0.82 ± 0.06, the maximum Hausdorff distance residual error (± SD) are 4.46 ± 0.55, 3.49 ± 0.53, 3.46 ± 0.69 mm, and the mean centroid coordinate residual error (± SD) are 2.40 ± 0.53, 1.66 ± 0.47, 2.14 ± 0.95 mm, respectively. The calculated margin using residual centroid method in medial-lateral (ML), anterior-posterior (AP), and cranial-caudal (CC) direction of spinal cord in neck, chest, abdominal segments are 3.86, 5.37, 6.36 mm, 3.45, 3.83, 4.51 mm, 4.05, 4.83, 7.06 mm, respectively, and the calculated margin using residual Hausdorff method are 3.10, 5.33 and 6.15 mm, 3.30, 3.77, 4.61 mm, 3.35, 4.76, 6.87 mm, respectively.Conclusion:The setup errors and residual errors are different in each segment of the spinal cord. Different margins expansion should be applied to different segment of spinal cord.

Contrast-Enhanced Spectral Mammography-Based Radiomics Nomogram for Identifying Benign and Malignant Breast Lesions of Sub-1 cm.

ObjectivesTo develop a radiomics nomogram that incorporates contrast-enhanced spectral mammography (CESM)-based radiomics features and clinico-radiological variables for identifying benign and malignant breast lesions of sub-1 cm.MethodsThis retrospective study included 139 patients with the diameter of sub-1 cm on cranial caudal (CC) position of recombined images. Radiomics features were extracted from low-energy and recombined images on CC position. The variance threshold, analysis of variance (ANOVA) and least absolute shrinkage and selection operator (LASSO) algorithms were used to select optimal predictive features. Radiomics signature (Rad-score) was calculated by a linear combination of selected features. The independent predictive factors were identified by ANOVA and multivariate logistic regression. A radiomics nomogram was developed to predict the malignant probability of lesions. The performance and clinical utility of the nomogram was evaluated by receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA).ResultsNineteen radiomics features were selected to calculate Rad-score. Breast imaging reporting and data system (BI-RADS) category and age were identified as predictive factors. The radiomics nomogram combined with Rad-score, BI-RADS category, and age showed better performance (area under curves [AUC]: 0.940, 95% confidence interval [CI]: 0.804–0.992) than Rad-score (AUC: 0.868, 95% CI: 0.711–0.958) and clinico-radiological model (AUC: 0.864, 95% CI: 0.706–0.956) in the validation cohort. The calibration curve and DCA showed that the radiomics nomogram had good consistency and clinical utility.ConclusionsThe radiomics nomogram incorporated with CESM-based radiomics features, BI-RADS category and age could identify benign and malignant breast lesions of sub-1 cm.

Histotripsy Ablations in a Porcine Liver Model: Feasibility of Respiratory Motion Compensation by Alteration of the Ablation Zone Prescription Shape.

Previous human-scale porcine liver model studies of histotripsy have resulted in ablation zones elongated in the cranial-caudal (CC) dimension due to uninterrupted respiratory motion during the ablation procedure. The purpose of this study is to compensate for elongation of hepatic histotripsy ablation zones in the cranial-caudal (CC) dimension caused by respiratory motion by prescribing ellipsoid-shaped ablations. Six female swine underwent 12 hepatic histotripsy ablations using a prototype clinical histotripsy system under general anesthesia. Each animal received two ablation zones prescribed as either an ellipsoid (2.5cm (AP) × 2.5cm (ML) × 1.7cm (CC), prescribed volume = 5.8cc) or a sphere (2.5cm all dimensions, prescribed volume 8.2cc). Ventilatory tidal volume was held constant at 400cc for all ablations. Post-procedure MRI was followed by sacrifice and gross and microscopic histology. Ablations on MRI were slightly larger than prescribed in all dimensions. Ellipsoid plan ablations (2.8 × 3.0 × 3.1cm, volume 13.2cc, sphericity index 0.987) were closer to prescribed volume than spherical plan ablations (2.9 × 3.1 × 3.7cm, volume 17.1cc, sphericity index 0.953). Ellipsoid plan ablations were more spherical than sphere plan ablations, but the difference did not reach statistical significance (p = .0.06). Pathologic analysis confirmed complete necrosis within the center of each ablation zone with no widening of the zone of partial ablation on the superior and inferior as compared to the lateral borders (p = .0.22). Altering ablation zone prescription shape when performing hepatic histotripsy ablations can partially mitigate respiratory motion effects to achieve the desired ablation shape and volume.

Effect of GLCM Texture Features on the Medio-Lateral Oblique (MLO) View of Digital Mammograms for Breast Cancer Detection

Breast cancer is one among the most common cancers in women. The early detection of breast cancer reduces the risk of death. Mammograms are an efficient breast imaging technique for breast cancer screening. Computer aided diagnosis (CAD) systems reduce manual errors and helps radiologists to analyze the mammogram images. The mammogram images are typically in two views, cranial-caudal (CC) and medio lateral oblique (MLO) views. MLO contains pectoral muscles (chest muscles) at the upper right or left corner of the image. In this study, it was removed by using a semi-automated method. All the normal and abnormal images were filtered and enhanced to improve the quality. GLCM (Gray Level Co-occurrence Matrix) texture features were extracted and analyzed by changing the number of features in a feature set. Linear Support Vector Machine (LSVM) was used as classifier. The classification accuracy was improved as the number of features in GLCM feature set increases. Simulation results show an overall classification accuracy of 96.7% with 19 GLCM features using SVM classifiers.

Breast Cancer Lesion Detection From Cranial-Caudal View of Mammogram Images Using Statistical and Texture Features Extraction

Breast cancer is the most common cancer among women in the world today. Mammography screening gives vital information about normal and abnormal regions. The task is to detect the lesion in mammograms using computer-aided diagnosis techniques. The automated detection of cancer decreases the mortality rate and manual error. In this work, the statistical (mean, variance, skewness, kurtosis, energy and entropy) and tamura features (coarseness, contrast and directionality) were extracted from the Cranial-Caudal (CC) view of mammogram images collected from the M.S. Ramaiah Memorial Hospital, Bangalore. The support vector machine was used for classification. Different support vector machine kernels were used and results were tabulated. The highest accuracy was obtained for linear and quadratic kernels with 95.7% with sensitivity of 100% and specificity of 91%.

4DCT-based evaluation of lung tumour motion during the breathing cycle.

The aim of this work was to quantify the variability in pre-treatment lung tumor motion during a single breathing period for 55 non-small cell lung cancer (NSCLC) targets. The influence of breathing on the volume and position of lung tumor was examined by comparing the information about tumor from respiratory-correlated four-dimensional computed tomography (4DCT) and three-dimensional computed tomography (3DCT) obtained without respiratory monitoring. The impact of age, gender, lung volume changes and immobilization device on tumor respiratory motion was evaluated. Based on the performed analysis, the significant differences were found between tumor volumes on 3DCT and 4DCT, although the comparison of volumes between 4DCT bins showed no statistically significant dependency. The significant differences between tumor centre of mass coordinates in the cranial-caudal (CC) and anterior-posterior (AP) directions were found. According to the results of statistical testing, there was no impact of gender and immobilization device on detected tumor respiratory motion. The impact was found for patient's age, lung volume changes, tumor volume and its location in different lung segments. The dominant lung cancer motion was observed for smaller tumors (up to 20 cc) located in posterior, caudal segments. This effect was also associated with a large variation in the lung volume during one respiratory cycle, observed for older patients. The important finding of the study is connected with the description of different patterns of tumor motion in AP and CC directions.

Quantification of Esophageal Tumor Motion and Investigation of Different Image-Guided Correction Strategies

PurposeTo accurately quantify esophageal tumor position variability and to optimize image guided correction strategies. Material and MethodsEsophageal cancer patients receiving chemoradiotherapy (41.4-50.4 Gy in 23-28 fractions combined with carboplatin plus paclitaxel) were included in a prospective cohort study (NCT02139488). Gold fiducial markers were inserted into the esophageal tumors during diagnostic endoscopic ultrasound. Four-dimensional (4D) planning computed tomography (CT) and daily 4D cone beam (CB) CT scans were acquired. Each CBCT was registered to the planning CT using different regions of interest (bone; 3D), and carina, diaphragm, clinical target volume (CTV), and fiducial markers (4D) for alignment and using the fiducial markers as the true tumor position. Subsequently, a planning target volume (PTV) margin accounting for residual uncertainties, including the average respiratory motion, was calculated for each of these registrations. ResultsFifty-six patients with tumors located in the proximal (n = 1), mid (n = 7), or distal esophagus (n = 25) or at the gastroesophageal junction (n = 23) were included. The average peak-to-peak respiratory tumor motion was 0.20, 0.92, and 0.34 cm on the planning CT in left–right (LR), cranial–caudal (CC), and anterior–posterior (AP) directions, respectively. The required PTV margin with average motion amplitude, depending on the correction strategy used for image guidance, ranged from 0.8 cm to 1.0 cm, 1.1 cm to 1.6 cm, and 0.7 cm to 0.9 cm in LR, CC, and AP direction, respectively. A registration based on the CTV resulted in the smallest PTV margins (0.8, 1.1, and 0.7 cm in LR, CC, and AP direction, respectively). For bone registration the calculated PTV margins were 1.0, 1.3, and 0.7 cm in LR, CC, and AP directions, respectively. The registration based on the diaphragm increased PTV margins. ConclusionsSubstantial and anisotropic position variability of esophageal tumors was observed during radiation therapy, and nonuniform margins should be considered. Cranial-caudal PTV margins need to be larger than those commonly used. Target positioning during image-guided radiotherapy could be improved with a CTV registration-based correction strategy.