Craniocaudal Direction Research Articles

Factors Affecting Prostate Displacement During Volumetric Modulated Arc Therapy in Prone Position After High-Dose-Rate Brachytherapy for Prostate Cancer

In irradiating the prostate and pelvic lymph node regions, registration based on bony structures matches the pelvic lymph node regions but not necessarily the prostate position, and it is important to identify factors that influence prostate displacement. Therefore, we investigated factors influencing prostate displacement during volumetric modulated arc therapy after single-fraction high-dose-rate brachytherapy (HDR-BT) for prostate cancer and the trends in displacement for each fraction. Seventy patients who underwent pelvic volumetric modulated arc therapy of 46 Gy in the prone position 15 days after 13 Gy HDR-BT were included. Prostate displacement relative to bony structures was calculated using cone beam computed tomography. Systematic error (SE) and random error (RE) were evaluated in the right-left (RL), craniocaudal (CC), and anteroposterior (AP) directions. The association with clinical and anatomic factors on the planning computed tomography or magneticresonanceimaging was analyzed. Prostate volume change (PVC) was defined as the volume change at 2 days after HDR-BT. Displacement trends were individually examined from the first to 23rd fractions. The mean SE in the RL, CC, and AP directions was -0.01 mm, -2.34 mm, and -0.47 mm, respectively. The root mean square of the RE in the RL, CC, and AP directions was 0.44 mm, 1.14 mm, and 1.10 mm, respectively. SE in the CC direction was independently associated with bladder volume (P=.021, t statistic=2.352) and PVC (P < .001, t statistic=-8.526). SE in the AP direction was independently associated with bladder volume (P=.013, t statistic=-2.553), PVC (P < .001, t statistic=5.477), and rectal mean area (P=.008, t statistic=2.743). RE in the CC direction was independently associated with smoking (P=.035). RE in the AP direction was associated with PVC (P=.043). Gradual displacement caudally and posteriorly occurred during the irradiation period. Anatomic characteristics of the bladder, rectum, and prostate predict SE. Smoking and PVC predict RE. In particular, whether PVC is ≥140% affects setting internal margins.

Quantification of phenobarbital-induced ataxia in dogs with idiopathic epilepsy.

Ataxia is a clinical sign seen in several neurological diseases and has been reported as an adverse effect of anti-seizure medication such as phenobarbital (PB). Efforts to objectify canine ataxia in order to provide appropriate treatment or monitor adverse effects of drugs remain limited. Automated quantitative gait analysis can be useful for the acquisition of objective data for the evaluation and monitoring of ataxia in dogs. The aim of this prospective clinical study was to examine the gait characteristics of dogs with PB induced ataxia and compare them with healthy dogs using a computer- and treadmill-based gait analysis system. Six healthy dogs and five dogs with idiopathic epilepsy (IE) with PB-induced ataxia underwent video- and computer-assisted gait analysis during slow walking (maximum speed of 0.7 m/s) on a treadmill with four ground reaction force plates (one plate per limb). Kinetic and spatio-temporal gait parameters of dogs' locomotion were analyzed, including individually calculated coefficients of variation. Dogs with IE treated with PB showed higher variability in spatio-temporal but not in kinetic gait parameters. Double support phase of gait cycles was increased on the cost of single support and swing phases. Body weight standardized ground reaction forces in vertical, craniocaudal, and mediolateral direction were severely affected by ataxia. Compensatory mechanisms in locomotion of dogs with PB-induced ataxia included spatio-temporal and kinetic gait characteristics, most likely in order to compensate imbalance caused by limb incoordination.

Respiration-controlled radiotherapy in lung cancer: Systematic evaluation of the optimal application practice

Background and purposeDefinitive radiochemotherapy (RCT) for non-small cell lung cancer (NSCLC) in UICC/TNM I–IVA (singular, oligometastatic) is one of the treatment methods with a potentially curative concept. However, tumour respiratory motion during RT requires exact pre-planning. There are various techniques of motion management like creating internal target volume (ITV), gating, inspiration breath–hold and tracking. The primary goal is to cover the PTV with the prescribed dose while at the same time maximizing dose reduction of surrounding normal tissues (organs at risk, OAR). In this study, two standardized online breath–controlled application techniques used alternately in our department are compared with respect to lung and heart dose. Materials and methodsTwenty-four patients who were indicated for thoracic RT received planning CTs in voluntary deep inspiration breath-hold (DIBH) and in free shallow breathing, prospectively gated in expiration (FB-EH). A respiratory gating system by Varian (Real-time Position Management, RPM) was used for monitoring. OAR, GTV, CTV and PTV were contoured on both planning CTs. The PTV margin to the CTV was 5 mm in the axial and 6–8 mm in the cranio-caudal direction. The consistency of the contours was checked by elastic deformation (Varian Eclipse Version 15.5). RT plans were generated and compared in both breathing positions using the same technique, IMRT over fixed irradiation directions or VMAT. The patients were treated in a prospective registry study with the approval of the local ethics committee. ResultsThe PTV in expiration (FB-EH) was on average significantly smaller than the PTV in inspiration (DIBH): for tumours in the lower lobe (LL) 431.5 vs. 477.6 ml (Wilcoxon test for connected samples; p = 0.004), in the upper lobe (UL) 659.5 vs. 686.8 ml (p = 0.005). The intra-patient comparison of plans in DIBH and FB-EH showed superiority of DIBH for UL-tumours and equality of DIBH and FB-EH for LL-tumours. The dose for OAR in UL-tumours was lower in DIBH than in FB-EH (mean lung dose p = 0.011; lungV20, p = 0.002; mean heart dose p = 0.016). The plans for LL-tumours in FB-EH showed no difference in OAR compared to DIBH (mean lung dose p = 0.683; V20Gy p = 0.33; mean heart dose p = 0.929). The RT setting was controlled online for each fraction and was robustly reproducible in FB-EH. ConclusionRT plans for treating lung tumours implemented depend on the reproducibility of the DIBH and advantages of the respiratory situation with respect to OAR. The primary tumour localization in UL correlates with advantages of RT in DIBH, compared to FB-EH. For LL-tumours there is no difference between RT in FB-EH and RT in DIBH with respect to heart or lung exposure and therefore, reproducibility is the dominant criterion. FB-EH is recommended as a very robust and efficient technique for LL-tumours.

Usefulness of cranio-dorsal approach for laparoscopic left lateral sectionectomy.

Most surgeons perform laparoscopic left lateral sectionectomy (Lap LLS) using the caudo-peripheral approach (C-P approach). However, recently, a cranio-dorsal approach (C-D approach) has been applied to various types of hepatectomy owing to its advantage of preventing split injury. No studies yet have compared the perioperative outcomes of Lap LLS using each approach. Therefore, this study aimed to determine whether the C-D approach is useful for Lap LLS by comparing its perioperative outcomes with the C-P approach. Data of patients who underwent Lap LLS in our institution between 2010 and 2022 for liver tumors were retrospectively collected. We compared the perioperative outcomes of Lap LLS using a conventional C-P approach, which transects hepatic parenchyma in the caudo-peripheral direction and a C-D approach, which transects hepatic parenchyma in the cranio-caudal direction. All surgeries were performed only by board-certified expert surgeons to minimize technical bias. Furthermore, the perioperative procedures employed at our institution remained unchanged throughout the study period. A total of 36 patients were included in the study (C-P approach, n = 25; C-D approach, n = 11). The C-D approach showed a significantly shorter operation time than the C-P approach (median, 225min vs. 262min, p = 0.04). In addition, the C-D approach showed significantly lower blood loss than the C-P approach (median, 20mL vs. 100mL, p < 0.01). Other parameters, such as morbidity and hospital stay, were comparable between groups. The C-D approach could offer better surgical outcomes than the conventional C-P approach.

The effect of lifting load on the kinematic characteristics of lumbar spinous process in vivo

BackgroundThere are limited data on the in vivo natural kinematics of the lumbar spinous process. This paper intends to explore the effect of lifting load on the in vivo movement mode of the lumbar spinous process and its biomechanical changes.MethodsTen asymptomatic subjects between the ages of 25 and 39 underwent CT scans of the lumbar spine in the supine position, and 3D models of L3-L5 were constructed. Using a Dual Fluoroscopy Imaging System (DFIS), instantaneous orthogonal fluoroscopic images of each subject's flexion–extension, left–right bending, and left–right rotational movements were taken under different loads (0 kg, 5 kg, 10 kg). The supine CT model was matched, using computer software, to the bony contours of the images from the two orthogonal views, so that the instantaneous 3D vertebral position at each location could be quantified. A Cartesian coordinate system was ultimately constructed at the tip of the spinous process to obtain the 6DOF kinematic data of the spinous process.ResultsIn different postural movements of the trunk, there was no significant difference in the rotation angle and translation range of the lumbar spinous process under different loads (P > 0.05). In flexion to extension motion, spinous processes mainly rotate < 4° along the medial and lateral axes and translate < 4 mm along the craniocaudal direction. In the left–right bending motion, spinous processes mainly rotate < 5° along the anterior and posterior axes, and the translation is mainly coupling < 2 mm. In the rotational motion, the spinous process is mainly coupled motion, the rotation range is less than 3°, and the translation range is less than 2 mm. The distance between spinous processes measured in the supine position was 6.66 ± 2.29 mm at L3/4 and 5.08 ± 1.57 mm at L4/5.ConclusionThe in vivo kinematics of the lumbar spinous process will not change significantly with increasing low load. In complex motion, the spinous process is dominated by coupling motion.

Intrafraction motion analysis in online adaptive radiotherapy for esophageal cancer.

Intrafraction motion during magnetic resonance (MR)-guided dose delivery of esophageal cancer tumors was retrospectively analyzed. Deformable image registration of cine-MR series resulted in gross tumor volume motion profiles in all directions, which were subsequently filtered to isolate respiratory and drift motion. A large variability in intrafraction motion patterns was observed between patients. Median 95% peak-to-peak motion was 7.7 (3.7 - 18.3) mm, 2.1 (0.7 - 5.7) mm and 2.4 (0.5 - 5.6) mm in cranio-caudal, left-right and anterior-posterior directions, relatively. Furthermore, intrafraction drift was generally modest (<5mm). A patient specific approach could lead to very small margins (<3mm) for most patients.

The Effect of Mesh Orientation, Defect Location and Size on the Biomechanical Compatibility of Hernia Mesh

ObjectivesSatisfactory biomechanical compatibility of implants is important for obtaining desired tissue repair efficiency. Here, we investigated the combined effects of three important influencing factors, mesh orientation, defect location and size, on biomechanical compatibility of a typical anisotropic mesh by both computational simulation and animal experiment. MethodsNumerical models of rabbits were developed based on CT images and material constitutive models obtained by uniaxial tests, during which two orientations, two defect locations and two defect sizes were investigated. Corresponding pneumoperitoneum tests on rabbits and non-invasive measurements on the displacement of abdominal wall surface were performed for validation. ResultsNumerical results showed that the displacement of abdominal wall was limited when the stiffest direction of mesh was parallel to the cranio-caudal direction, but the stress in suture area was greatly reduced. When the defect was located at the junction of different muscles, the strain distribution became uneven. In addition, for the defects with smaller size, difference between the results caused by different mesh orientations was smaller. Animal experimental results were in good agreement with the numerical results. Further simulations for a hypothetical mesh orientation showed that the meshes exhibited better biomechanical compatibility when their stiffest direction was consistent with that of oblique muscles for all four different defects. ConclusionThe mesh orientation was the most influential factor and the proper orientation of the mesh was not necessarily consistent with the anisotropy of the defect tissue. In addition, the mesh design with asymmetric stiffness should be considered for defects at the junction of different tissues. Finally, it is possible to align the stiffest direction of the mesh with that of the defect tissue in repairing small defects to achieve better compliance. Our findings could provide some reliable and instructive guidelines for high-performance anisotropic meshes development and their appropriate selection and placement in surgery. And methods proposed in this study could be used to comprehensively and instructively evaluate the biomechanical compatibility of hernia meshes, predict their repair effect, and determine their appropriate positioning before they are put into clinical use.

Evaluation of motion artifacts reduction software that compensate for respiratory movements in the craniocaudal direction during abdominal cone-beam computed tomography

We acquired cone-beam computed tomography (CBCT) images of a locally made contrast-enhanced hepatic artery phantom under various conditions, both with the phantom still, and while moving it from the cranial to the caudal position. All the motion CBCT images were processed with and without motion artifacts reduction software (MARS). We calculated some quantitative similarity indexes between the still CBCT images (no-motion) and the motion CBCT images both processed with MARS (MARS ON) and without MARS (MARS OFF). In addition, the vessel signal values under the same movement conditions of the MARS ON/OFF and no-motion were evaluated. All quantitative similarity indexes between MARS ON and no-motion were significantly higher than between MARS OFF and no-motion in all movement conditions (p < 0.01). The vessel signal values were higher in MARS ON than in MARS OFF (p < 0.01) and closer to no-motion in all movement conditions.

Risk factors for clinical and radiological worsening following Chiari malformation type I surgery in the pediatric population.

Foramen magnum (FM) decompression with or without duraplasty is considered a common treatment strategy for Chiari malformation type I (CM-I). The authors' objective was to determine a predictive model of risk factors for clinical and radiological worsening after CM-I surgery. A retrospective review of electronic health records was conducted at an academic tertiary care hospital from 2001 to 2019. A multivariable Cox proportional hazards regression model was used to determine the risk factors. The Kaplan-Meier estimate was plotted to delineate outcomes based on FM size. FM was measured as the preoperative distance between the basion and opisthion and dichotomized into < 34 mm and ≥ 34 mm. Syrinx was measured preoperatively and postoperatively in the craniocaudal and anteroposterior directions using a T2-weighted MRI sequence. A total of 454 patients (231 females [50.9%]) with a median (range) age of 8.0 (0-18) years were included in the study. The median duration of follow-up was 21.0 months (range 3.0-144.0 years). The model suggested that patients with symptoms consisting of occipital/tussive headache (HR 4.05, 95% CI 1.34-12.17, p = 0.01), cranial nerve symptoms (HR 3.46, 95% CI 1.16-10.2, p = 0.02), and brainstem/spinal cord symptoms (HR 3.25, 95% CI 1.01-11.49, p = 0.05) had higher risk, whereas those who underwent arachnoid dissection/adhesion lysis had 75% lower likelihood (HR 0.25, 95% CI 0.10-0.64, p = 0.004) of clinical worsening postoperatively. Similarly, patients with evidence of brainstem/spinal cord symptoms (HR 7.9, 95% CI 2.84-9.50, p = 0.03), scoliosis (HR 1.04, 95% CI 1.01-2.80, p = 0.04), and preoperative syrinx (HR 16.1, 95% CI 1.95-132.7, p = 0.03) had significantly higher likelihood of postoperative worsening of syrinx. Patients with symptoms consisting of occipital/tussive headache (HR 5.44, 95% CI 1.86-15.9, p = 0.002), cranial nerve symptoms (HR 2.80, 95% CI 1.02-7.68, p = 0.04), and nonspecific symptoms (HR 6.70, 95% CI 1.99-22.6, p = 0.002) had significantly higher likelihood, whereas patients with FM ≥ 34 mm and those who underwent arachnoid dissection/adhesion lysis had 73% (HR 0.27, 95% CI 0.08-0.89, p = 0.03) and 70% (HR 0.30, 95% CI 0.12-0.73, p = 0.008) lower likelihood of reoperation, respectively. The Kaplan-Meier curve showed that patients with FM size ≥ 34 mm had significantly better clinical (p = 0.02) and syrinx (p = 0.03) improvement postoperatively when the tonsils were resected. These results showed that preoperative and intraoperative factors may help to provide better clinical decision-making for CM-I surgery. Patients with FM size ≥ 34 mm may have better outcomes when the tonsils are resected.

Correlation of Pituitary Descent and Diabetes Insipidus After Transsphenoidal Pituitary Macroadenoma Resection.

Endoscopic transsphenoidal surgery remains the technique of choice for resection of pituitary adenoma. Postoperative diabetes insipidus (DI) is most often transient and observed in 1.6% to 34% of patients, whereas permanent DI has been reported in 0% to 2.7% of patients. The proposed mechanism was the transduction of traction forces exerted by the surgeon on the descended diaphragma sellae and through the pituitary stalk. To quantify and correlate the degree of pituitary gland descent with postoperative DI. Of 374 patients who underwent transsphenoidal resection of a pituitary adenoma between 2010 and 2020 at our institution, we report a cohort of 30 patients (Group A) DI. We also report a matched cohort by tumor volume of 30 patients who did not develop DI (Group B). We quantified the tension on the pituitary stalk by calculating pituitary descent interval (PDI) by comparing preoperative and postoperative position of the pituitary gland and using Pythagoras' formula where , with craniocaudal (CC) and anterior-posterior (AP) representing measurements of pituitary translation in respective directions after resection. Patients who developed DI had significantly greater pituitary gland translations in the craniocaudal (23.0 vs 16.3 mm, P = .0015) and anteroposterior (2.4 vs 1.5 mm, P = .0168) directions. Furthermore, Group A had a statistically greater PDI, which was associated with development of DI (23.2 vs 16.6 mm, P = .0017). We were able to quantify pituitary descent and subsequent tension on the pituitary stalk, while also associating it with development of postoperative DI after pituitary adenoma resection.

Adaptations in equine axial movement and muscle activity occur during induced fore- and hindlimb lameness: A kinematic and electromyographic evaluation during in-hand trot.

The inter-relationship between equine thoracolumbar motion and muscle activation during normal locomotion and lameness is poorly understood. To compare thoracolumbar and pelvic kinematics and longissimus dorsi (longissimus) activity of trotting horses between baseline and induced forelimb (iFL) and hindlimb (iHL) lameness. Controlled experimental cross-over study. Three-dimensional kinematic data from the thoracolumbar vertebrae and pelvis, and bilateral surface electromyography (sEMG) data from longissimus at T14 and L1, were collected synchronously from clinically nonlame horses (n= 8) trotting overground during a baseline evaluation, and during iFL and iHL conditions (2-3/5 AAEP), induced on separate days using a lameness model (modified horseshoe). Motion asymmetry parameters, maximal thoracolumbar flexion/extension and lateral bending angles, and pelvis range of motion (ROM) were calculated from kinematic data. Normalised average rectified value (ARV) and muscle activation onset, offset and activity duration were calculated from sEMG signals. Mixed model analysis and statistical parametric mapping compared discrete and continuous variables between conditions (α= 0.05). Asymmetry parameters reflected the degree of iFL and iHL. Maximal thoracolumbar flexion and pelvis pitch ROM increased significantly following iFL and iHL. During iHL, peak lateral bending increased towards the nonlame side (NLS) and decreased towards the lame side (LS). Longissimus ARV significantly increased bilaterally at T14 and L1 for iHL, but only at LS L1 for iFL. Longissimus activation was significantly delayed on the NLS and precipitated on the LS during iHL, but these clear phasic shifts were not observed in iFL. Findings should be confirmed in clinical cases. Distinctive, significant adaptations in thoracolumbar and pelvic motion and underlying longissimus activity occur during iFL and iHL and are detectable using combined motion capture and sEMG. For iFL, these adaptations occur primarily in a cranio-caudal direction, whereas for iHL, lateral bending and axial rotation are also involved.

Interfractional Liver Positional Motion Under Exhaled Breath Holding Based on Cone Beam Computed Tomography.

We measured interfractional liver positional motion in liver stereotactic body radiotherapy (SBRT) with exhaled breath holding (BH) based on kilovoltage (kV) cone-beam computed tomography (CBCT) images. We collected 528 pre-treatment kV-CBCT images from 132 patients who underwent liver SBRT under exhaled BH using the Abches system, a non-electronic contact-based respiratory monitoring device, and analyzed them to investigate interfractional liver positional motion. Planning computed tomography (CT) scans were obtained using the Abches system when the patients were under exhaled BH. Translational 3-degree-of-freedom (DOF) soft-tissue-based image registration was performed using the kV-CBCT images under exhaled BH after 6-DOF vertebral bone image registration. Interfractional liver positional motions in the left-right (LR), anteroposterior (AP), and craniocaudal (CC) directions were defined based on the differences in the position of the liver relative to the vertebral bones. For all fractions, the absolute mean±standard deviation for the interfractional liver positional motion in the LR, AP, and CC directions was 0.7±1.0 mm, 1.0±1.5 mm, and 2.8±3.1 mm, respectively. The liver interfractional systematic/random positional motions in the LR, AP, and CC directions were 0.9/1.2 mm, 1.4/1.8 mm, and 2.9/3.9 mm, respectively. For all fractions, 100.0%, 98.3%, and 86.9% of the interfractional liver positional motions in the LR, AP, and CC directions, respectively, were less than 5 mm. CBCT-guided online correction should be used to correct interfractional liver positions errors present in liver SBRT with exhaled BH.

Incidentalomas Discovered during COVID- 19 Chest CT Screening: A Cross-sectional Study from Andhra Pradesh, India

Introduction: The highly contagious Coronavirus Disease 2019 (COVID-19) virus has spread across the globe. For the aberrant changes in the lung parenchyma, thin-section chest Computed Tomography (CT) is more sensitive than chest radiography and can identify early disease. Increased CT usage and resolution also lead to an increase in the discovery of "incidental" findings, creating questions about additional research, diagnosis, and follow-up with associated financial and emotional costs. Aim: To evaluate the non COVID-19 lung pathologies and other system findings in High Resolution Computed Tomography (HRCT) chest done for COVID-19 screening study. Materials and Methods: This was a cross-sectional study done in the Department of Radiodiagnosis at Dr.Pinnamaneni Siddhartha Institute of Medical Sciences and Research Foundation, Vijayawada, Andhra Pradesh, India, from May 2021 to December 2021. The CT scan was done in a craniocaudal direction with an average exposure time of 4-6 seconds, slice thickness of 5 mm and 1.5 mm in mediastinal and lung windows. A total of 1000 HRCT scans done were examined for covid screening. Data was entered in Microsoft Excel and analysed by using Statistical Package for Social Sciences (SPSS) software. Descriptive statistics were represented with percentages. Results: A total of 348 cases were found with various other pathologies incidentally. Lesions like infectious and inflammatory lesions, metabolic diseases, tumours, metastases of various systems and fractures were found. Among 348 total cases with incidental findings 98 cases (28.1%) showed non COVID-19 lung pathologies, 114 cases (32.7%) had findings in the upper abdomen, 30 cases (8.6%) in the thyroid, and three cases (0.8%) had other findings. Conclusion: The HRCT chest screening for COVID-19 not only provided the status of pulmonary infection but gave a broad view of many other system pathologies like in upper abdomen, musculoskeletal system, thyroid, breast which were found incidentally. Identifying those pathologies and correlating them with history will help in early detection and management.

The influence of electrocardiogram-gated computed tomography reconstruction into 8 or 10 cardiac phases on cardiac-pulsatility-induced motion quantification of stent grafts in the aorta

ObjectiveThe goal of this study was to determine to what extent aortic stent graft motion quantification is comparable between electrocardiogram (ECG)-gated computed tomography (CT) scans with reconstructions into 8 and 10 cardiac phases on CT scanners from two different vendors. MethodsAn experimental setup that induces motion of an aortic stent graft, according to a predefined aortic blood pressure wave, was placed in two CT scanners of different vendors. The stent graft motion was captured using an ECG-gated CT technique and quantified using dedicated analysis algorithms. The calculated motion amplitudes and total traveled path lengths of stent segmentations were compared between scans reconstructed into 8 and 10 phases and between the scanners, after validation with sensor measurements and repeated measurements. ResultsNo difference in motion amplitudes in z-direction (craniocaudal direction) was observed between the reconstructions into 8 and 10 phases (0.02 mm; 95% confidence interval [CI], –0.01 to 0.05 mm; P = .358). The z-amplitudes differed by 0.04 mm (95% CI, 0.01-0.07 mm; P = .003) between the different CT scanners. Path lengths differed 0.07 mm (95% CI, 0.01-to 0.13 mm; P = .013) between the reconstructions into 8 and 10 phases and 0.13 mm (95% CI, 0.06-0.17 mm; P < .001) between the different scanners. ConclusionsThe motion amplitudes can accurately be compared between 8 and 10 phases and between the two scanners, without differences larger than the voxel size of 0.3 × 0.3 × 0.5 mm. Clinical motion analysis results of different ECG-gated CT scans and CT scanners can be compared up to the accuracy of the CT scan.

Rotational Set Up Uncertainly in Non-6D Couch and its Effects in Clinical Target Volume- Planning Target Volume Margin Calculation for Different Sites.

The purpose of this study was to estimate and incorporate rotational error to translational error for clinical target volume (CTV) to planning target volume (PTV) margin calculations for non-6D couch. The study involved cone-beam computed tomography (CBCT) images of the patients who already had treatment in Varian Trilogy Clinac. The different sites studied were brain (70 patients, 406 CBCT images), head and neck (72 patients, 356 CBCT images), pelvis (83 patients, 606 CBCT images), and breast (45 patients, 163 CBCT images). Rotational and translational patient shifts were measured with the help of Varian eclipse offline review. The rotational shift introduces translational shift as it resolved along craniocaudal and mediolateral directions. Both rotational and translational error follow normal distribution and their respective errors were used to calculate CTV-PTV margin using van Herk model. Rotational effect on CTV-PTV margin contribution increases with increase in size of CTV. It also increases with increase in distance between center of mass of CTV and isocenter. These margins were more pronounce in single isocenter supraclavicular fossa-Tangential Breast plans. There is always rotational error in all sites and it causes shift and rotation of the target. Rotational contribution to the CTV-PTV margin depends upon geometric center of CTV and isocenter distance and also on size of CTV. CTV-PTV margins should incorporate rotational error along with transitional error.

Study of Phantom Length Correction for kV-Cone Beam CT Dose Evaluation Method Using Farmer-type Ionization Chamber and Cylindrical Phantom

In this study, we investigated the necessary phantom length for dose evaluation of kV-CBCT mounted on the linear accelerator using a Farmer-type ionization chamber and cylindrical PMMA phantom, which many radiotherapy facilities own. Furthermore, a phantom length correction factor was proposed to compensate for the lack of scattered radiation contributed from the craniocaudal direction due to the inadequate phantom length. The air-absorbed dose at the center of a cylindrical PMMA phantom measured by a Farmer-type ionization chamber indicated that the contribution of scattered radiation saturates when the phantom length is 300 mm or longer. The phantom length correction factor was calculated from an approximate curve showing the relationship of the charge ratio measured using phantoms of 300 mm and 150 mm in length to the X-ray beam width. The air-absorbed dose measured with the 150-mm length phantom, corrected by the phantom length correction factor, showed a 1.61% dose difference from the air-absorbed dose measured with the 300-mm length phantom. In this study, the air-absorbed dose at the center of the phantom could be estimated over a wide X-ray beam width only using a 150-mm length cylindrical PMMA phantom. The method proposed in this study could be used in any radiation therapy facility.

Three-dimensional cephalometric outcome predictability of virtual orthodontic-surgical planning in surgery-first approach

ObjectivesThe aim of this study is to introduce a novel 3D cephalometric analysis (3DCA) and to validate its use in evaluating the reproducibility of virtual orthodontic-surgical planning (VOSP) in surgery-first approach (SF) comparing VOSP and post-operative outcome (PostOp).MethodsThe cohort of nineteen patients underwent bimaxillary orthognathic surgery following the VOSP designed in SimPlant O&O software by processing cone-beam computed tomography (CBCT) scans and intraoral digital scanning of the dental arches. Said records were re-acquired once the post-operative orthodontic treatment was completed. The 3DCA was performed by three expert operators on VOSP and PostOp 3D models. Descriptive statistics of 3DCA measures were evaluated, and outcomes were compared via Wilcoxon test.ResultsIn the comparison between cephalometric outcomes against planned ones, the following values showed significant differences: Wits Index, which suggests a tendency towards skeletal class III in PostOp (p = 0.033); decreased PFH/AFH ratio (p = 0.010); decreased upper incisors inclination (p < 0.001); and increased OVJ (p = 0.001). However not significant (p = 0.053), a tendency towards maxillary retroposition was found in PostOp (A/McNamara VOSP: 5.05 ± 2.64 mm; PostOp: 4.1 ± 2.6 mm). On average, however, when McNamara’s plane was considered as reference, a tendency to biprotrusion was found. Upper incisal protrusion was greater in PostOp as an orthodontic compensation for residual maxillary retrusion (VOSP: 5.68 ± 2.56 mm; PostOp: 6.53 ± 2.63 mm; p = 0.084). Finally, the frontal symmetry in relation to the median sagittal plane decreased in craniocaudal direction.LimitationsA potential limit of studies making use of closest point distance analysis is represented by the complexity that surgeons and orthodontists face in applying this three-dimensional evaluation of SF accuracy/predictability to everyday clinical practice and diagnosis. Also, heterogeneity and limited sample size may impact the results of the study comparison.ConclusionsThe presented 3DCA offers a valid aid in performing VOSP and analysing orthognathic surgery outcomes, especially in SF. Thanks to the cephalometric analysis, we found that surgery-first approach outcome unpredictability is mainly tied to the sagittal positioning of the maxilla and that the transverse symmetry is progressively less predictable in a craniocaudal direction.

Dosimetric evaluation of magnetic resonance imaging-guided adaptive radiation therapy in pancreatic cancer by extent of re-contouring of organs-at-risk.

The safety of online contouring and planning for adaptive radiotherapy is unknown. This study aimed to evaluate the dosimetric difference of the organ-at-risk (OAR) according to the extent of contouring in stereotactic magnetic resonance image-guided adaptive RT (SMART) for pancreatic cancer. We reviewed the treatment plan data used for SMART in patients with pancreatic cancer. For the online contouring and planning, OARs within 2 cm from the planning target volume (PTV) in the craniocaudal direction were re-controlled daily at the attending physician's discretion. The entire OARs were re-contoured retrospectively for data analysis. We termed the two contouring methods the Rough OAR and the Full OAR, respectively. The proportion of dose constraint violation and other dosimetric parameters was analyzed. Nineteen patients with 94 fractions of SMART were included in the analysis. The dose constraint was violated in 10.6% and 43.6% of the fractions in Rough OAR and Full OAR methods, respectively (p = 0.075). Patients with a large tumor, a short distance from gross tumor volume (GTV) to OAR, and a tumor in the body or tail were associated with more occult dose constraint violations-large tumor (p = 0.027), short distance from GTV to OAR (p = 0.061), tumor in body or tail (p = 0.054). No dose constraint violation occurred outside 2 cm from the PTV. More occult dose constraint violations can be found by the Full OAR method in patients with pancreatic cancer with some clinical factors in the online re-planning for SMART. Re-contouring all the OARs would be helpful to detect occult dose constraint violations in SMART planning. Since the dosimetric profile of SMART cannot be represented by a single fraction, patient selection for the Full OAR method should be weighted between the clinical usefulness and the time and workforce required.

Upright patient positioning for pelvic radiotherapy treatments.

Radiotherapy is typically delivered in supine position. However, upright positioning may affect organ volume, positioning, and movement, compared to supine/prone positioning which might have beneficial impacts. In this study, we report patient positioning data in an upright positioning system designed by Leo Cancer Care®. Sixteen patients with pelvic tumors were included in this study. They had 3 setups in an upright position: an initial setup with acquisition of reference optical images, and 2 repositioning setups. The intra-fraction motion was assessed during two 20-minute chair rotation sessions. The patient comfort in supine and upright position was assessed with a 5-point Likert scale questionnaire. Eight women and 8 men treated on regular linacs between October 2021 and June 2022 were included. Their median age and weight were 62.5years (35 to 81years) and 75.1kg (41 to 107kg). The inter-fraction shift means were -0.5mm (SD=2.5), -0.4mm (SD=1.3) and -0.9mm (SD=2.7) in left-right (LR), antero-posterior (AP), and cranio-caudal (CC) directions, respectively. The intrafraction shifts after 20min were 0.0mm (SD=1.5), 0.2mm (SD=1.1) and 0.0mm (SD=0.3) in LR, CC, and AP directions, respectively. Average global comfort was 4.1 (3 to 5) for the upright position and 3.9 (2 to 5) for the supine position. In conclusion, the first study on pelvic cancer patients positioned in upright position on a chair is promising, and it opens a potential new direction for the treatment of cancer patients. Evaluation of thoracic and head and neck tumors is ongoing, and imaging with vertical CT is expected to start soon.

Perfusion imaging heterogeneity during NO inhalation distinguishes pulmonary arterial hypertension (PAH) from healthy subjects and has potential as an imaging biomarker

BackgroundWithout aggressive treatment, pulmonary arterial hypertension (PAH) has a 5-year mortality of approximately 40%. A patient’s response to vasodilators at diagnosis impacts the therapeutic options and prognosis. We hypothesized that analyzing perfusion images acquired before and during vasodilation could identify characteristic differences between PAH and control subjects.MethodsWe studied 5 controls and 4 subjects with PAH using HRCT and 13NN PET imaging of pulmonary perfusion and ventilation. The total spatial heterogeneity of perfusion (CV2Qtotal) and its components in the vertical (CV2Qvgrad) and cranio-caudal (CV2Qzgrad) directions, and the residual heterogeneity (CV2Qr), were assessed at baseline and while breathing oxygen and nitric oxide (O2 + iNO). The length scale spectrum of CV2Qr was determined from 10 to 110 mm, and the response of regional perfusion to O2 + iNO was calculated as the mean of absolute differences. Vertical gradients in perfusion (Qvgrad) were derived from perfusion images, and ventilation-perfusion distributions from images of 13NN washout kinetics.ResultsO2 + iNO significantly enhanced perfusion distribution differences between PAH and controls, allowing differentiation of PAH subjects from controls. During O2 + iNO, CV2Qvgrad was significantly higher in controls than in PAH (0.08 (0.055–0.10) vs. 6.7 × 10–3 (2 × 10–4–0.02), p < 0.001) with a considerable gap between groups. Qvgrad and CV2Qtotal showed smaller differences: − 7.3 vs. − 2.5, p = 0.002, and 0.12 vs. 0.06, p = 0.01. CV2Qvgrad had the largest effect size among the primary parameters during O2 + iNO. CV2Qr, and its length scale spectrum were similar in PAH and controls. Ventilation-perfusion distributions showed a trend towards a difference between PAH and controls at baseline, but it was not statistically significant.ConclusionsPerfusion imaging during O2 + iNO showed a significant difference in the heterogeneity associated with the vertical gradient in perfusion, distinguishing in this small cohort study PAH subjects from controls.