Anterior-posterior Motion Research Articles

Increased hindbrain motion in Chiari I malformation patients measured through 3D amplified MRI (3D aMRI)

Chiari Malformation type 1 (CM-I) is a neurological disorder characterized by morphological defects including excessive cerebellar tonsillar ectopia and associated manifestations. We used 3D amplified MRI on a cohort of healthy and CM-I subjects to investigate the brain’s intrinsic motion, its association with the morphology and patient’s symptomatology, and surgical outcomes. We observed that the regional brain motion in CM-I was significantly higher than that of the healthy subjects, with anterior-posterior (AP) and superior-inferior (SI) displacements in cerebellar tonsils and medulla having the highest differences between the healthy and CM-I (∼45%–∼73% increased motion in the CM-I group). Interestingly, we found the ratio of neural tissue in the foramen magnum to be directly correlated with the SI tonsillar motion (r=0.58). Tonsillar herniation was directly correlated with the AP motion of the tonsils (r=0.61), and AP and medial-lateral (ML) motions of the medulla (r=0.66, and r=0.57). Subjects with higher tonsillar ML motion prior to surgery showed improved outcome (p=0.03, and AUC=0.95). Although we did not observe a significant correlation between the brains motion and morphometrics on the CM-I symptoms (perhaps due to our small sample size), illustrative cases increase our hope for the development of a future tool based on brain biomechanics.

Body mass index associated with respiration predicts motion in resting-state functional magnetic resonance imaging scans.

Decreasing body mass index (BMI) reduces head motion in resting-state fMRI (rs-fMRI) data. Yet, the mechanism by which BMI affects head motion remains poorly understood. Understanding how BMI interacts with respiration to affect head motion can improve head motion reduction strategies. A total of 254 patients with back pain were included in this study, each of whom had two visits (interval time = 13.85 ± 7.81 weeks) during which two consecutive re-fMRI scans were obtained. We investigated the relationships between head motion and demographic and pain-related characteristics-head motion was reliable across scans and correlated with age, pain intensity, and BMI. Multiple linear regression models determined that BMI was the main determinant in predicting head motion. BMI was also associated with two features derived from respiration signal. Anterior-posterior and superior-inferior motion dominated both overall motion magnitude and the coupling between motion and respiration. BMI interacted with respiration to influence motion only in the pitch dimension. These findings indicate that BMI should be a critical parameter in both study designs and analyses of fMRI data.

Motion analysis comparing surface imaging and diaphragm tracking on kV projections for deep inspiration breath hold (DIBH)

BackgroundSurface-guided imaging (SGI) is increasingly utilized to monitor patient motion during deep inspiration breath hold (DIBH) in radiotherapy. Understanding the association between surface and internal motion is crucial for effective monitoring. PurposeTo investigate the relation between motion detected by SGI using surface-guided radiotherapy (SGRT) and internal motion measured through diaphragm tracking on kV projections acquired with DIBH for online CBCT. MethodsBoth SGI and kV were simultaneously acquired for ten patients over a total of 200 breath holds (BH). Diaphragm tracking was performed using second-degree polynomial curve fitting on the derivative images for each kV projection and high-pass filtering at 1/30 Hz to remove rotational effects. The superior-inferior (SI) and anterior-posterior (AP) motions of SGI were then compared to kV tracking using various statistical measures. ResultsThe correlation (individuals’ median: −0.07 to 0.73) was a suboptimal metric for the BH data. The median and 95th percentile absolute differences between SGI-SI and kV were 0.73 mm and 3.46 mm, respectively, during DIBH. For SGI-AP, the corresponding values were 0.55 mm and 2.80 mm. For inter-BH measurements, the contingency table based on a 3 mm threshold indicated surface/diaphragm motion agreement for SGI-SI/kV and SGI-AP/kV was 61 % and 56 %, respectively. ConclusionBoth intra- and inter-BH measurements indicated a limited association between surface and diaphragm motion, with certain constraints noted due to kV tracking and DIBH data. These findings warrant further investigation into the association between surface and internal motion.

THE IMPACT OF PLANTAR OSCILLATION ON SHOOTING ACCURACY: A PRE- AND POST-TEST ANALYSIS OF CENTER OF PRESSURE IN COMPETITIVE SHOOTERS

This study aimed to evaluate the impact of a targeted intervention on plantar oscillation in professional shooters, focusing on both medial-lateral and anterior-posterior foot movements. Thirty professional shooters participated in pre-and post-test assessments of foot oscillation using stabilometric measurements. Paired sample t-tests were conducted to compare oscillations in the left foot, right foot, and both feet combined before and after the intervention. Significant improvements were observed in medial-lateral oscillation for the right foot (p = 0.017) and both feet combined (p = 0.013), indicating enhanced lateral stability post-intervention. However, no significant changes were found in anterior-posterior movements for either foot (p > 0.05). These findings suggest that the intervention successfully improved lateral balance but had a limited impact on forward-backward stability. Future interventions should incorporate additional activities to target anterior-posterior control for improved overall postural stability in shooting performance.

Effect of taping on posture of thoracic region in patients with thoracic kyphosis using acceleration.

In the working environment of modern society, a poor sitting posture for a prolonged time may lead to abnormal spinal alignment such as thoracic kyphosis (TK). This study aimed to evaluate the efficacy of taping for posture correction of patients with TK, providing theoretical and empirical guidance for clinicians attempting to rectify TK posture. The study included 15 subjects aged 30-60years, all with a TK angle of ⩾ 40∘. Subjects were required to ascend and descend a set of three steps (a low step, high step, and second low step) under three different conditions: without tape assistance, with taping assistance using 20% elongation, and with taping assistance using 40% elongation. A triaxial accelerometer was employed to measure and compare the anterior-posterior (AP), vertical (VT), and medial-lateral (MIL) movements of the thoracic vertebrae in the different conditions. There were no significant differences in the MIL (P= 0.903) or AP (P= 0.114) movements between the no tape assistance and 20% elongation taping conditions. However, a significant difference was found in the VT movement (P= 0.017). Comparing the no assistance condition to the 40% elongation taping condition, no significant changes were noted in the MIL movement (P= 0.650), but significant differences were detected in both the VT (P= 0.003) and AP movements (P= 0.016). No significant differences were found in any of the three measurements between 20% and 40% elongation taping. Taping serves as an effective method for immediately improving kyphotic posture. It corrects the position of the scapula and cervicothoracic line and exerts passive retraction on the relevant muscles, thus mitigating trunk imbalance.

The use of dose surface maps as a tool to investigate spatial dose delivery accuracy for the rectum during prostate radiotherapy.

This study aims to address the lack of spatial dose comparisons of planned and delivered rectal doses during prostate radiotherapy by using dose-surface maps (DSMs) to analyze dose delivery accuracy and comparing these results to those derived using DVHs. Two independent cohorts were used in this study: twenty patients treated with 36.25Gy in five fractions (SBRT) and 20 treated with 60Gy in 20 fractions (IMRT). Daily delivered rectum doses for each patient were retrospectively calculated using daily CBCT images. For each cohort, planned and average-delivered DVHs were generated and compared, as were planned and accumulated DSMs. Permutation testing was used to identify DVH metrics and DSM regions where significant dose differences occurred. Changes in rectal volume and position between planning and delivery were also evaluated to determine possible correlation to dosimetric changes. For both cohorts, DVHs and DSMs reported conflicting findings on how planned and delivered rectum doses differed from each other. DVH analysis determined average-delivered DVHs were on average 7.1%±7.6% (p ≤ 0.002) and 5.0±7.4% (p ≤ 0.021) higher than planned for the IMRT and SBRT cohorts, respectively. Meanwhile, DSM analysis found average delivered posterior rectal wall dose was 3.8±0.6Gy (p=0.014) lower than planned in the IMRT cohort and no significant dose differences in the SBRT cohort. Observed dose differences were moderately correlated with anterior-posterior rectal wall motion, as well as PTV superior-inferior motion in the IMRT cohort. Evidence of both these relationships were discernable in DSMs. DSMs enabled spatial investigations of planned and delivered doses can uncover associations with interfraction motion that are otherwise masked in DVHs. Investigations of dose delivery accuracy in radiotherapy may benefit from using DSMs over DVHs for certain organs such as the rectum.

The wear and kinematics of two medially stabilised total knee replacement systems

BackgroundMedially stabilised total knee replacement systems aim to provide a more natural feeling knee replacement by providing increased stability through flexion. The aim of this study was to compare the kinematics and wear of two different medially stabilised total knee replacement systems in an experimental simulation study. The Medial Rotation Knee™ system (MRK) is an early medially stabilised knee (>20 years clinical success); the SAIPH® knee system being a more modern and refined, bone conserving evolution of the original design with a larger size range. MethodsThree SAIPH and three MRK total knee replacements (MatOrtho Ltd, UK) were investigated. The study was performed on a knee simulator with load controlled input kinematic conditions (ISO 14243–1). 6 million cycles of simulation were carried out with the wear of the UHMWPE tibial components assessed gravimetrically. The resulting anterior-posterior translation and tibial rotation position was measured throughout the study. ResultsThe mean UHMWPE wear rate was 0.57 ± 0.71 and 1.24 ± 2.0 mm3/million cycles for SAIPH and MRK total knee replacement systems respectively with no significant difference in wear (p = 0.24). Analysis of simulator output kinematics showed a larger range of anterior-posterior motion for SAIPH total knee replacements compared to MRK. The magnitude of tibial rotation was low for both knee replacement systems. ConclusionThe small magnitude of anterior-posterior displacement and tibial rotation motion demonstrates the inherent stability of this knee system design offered by the constrained medial compartment. This study shows the potential for medially stabilised knee systems as a low polyethylene surface wear solution.

Improvement of postural control in the frail older adults through foot care: A pre- and post-intervention study

Frailty in older adults often leads to foot issues, increasing fall-related fracture risk. Mechanoreceptors, the pressure receptors in the foot sole, are pivotal for postural control. Foot problems can impair mechanoreceptor function, compromising balance. This study aimed to examine the effect of foot care on postural control in frail older adults. Forty-eight participants underwent a five-month monthly foot care intervention. Measurements were taken before and after this intervention. Participants stood for 45 s in a static, open-eyed position on a stabilometer. Center-of-pressure (CoP) analysis included total trajectory length, integrated triangle area, rectangular area, and range of motion in anterior–posterior and medio-lateral directions. Results indicated that foot care significantly increased toe ground contact area by 1.3 times and improved anterior–posterior motion control during static standing. Enhanced postural control resulted from improved skin condition due to foot care that intensified mechanoreceptor signal input and improved postural control output. These findings underscore the potential for reducing fracture risks in older adults through proactive foot care. The study highlights the vital role of foot care in enhancing postural control, with broader implications for aging population well-being and safety.

A Noninvasive Clinical Method to Measure in Vivo Mechanical Strains of the Lamina Cribrosa by OCT

To measure mechanical strain of the lamina cribrosa (LC) after intraocular pressure (IOP) change produced 1 week after a change in glaucoma medication. Cohort study. Adult glaucoma patients (23 eyes, 15 patients) prescribed a change in IOP-lowering medication. Noninvasive OCT imaging of the eye. Deformation calculated by digital volume correlation of OCT scans of the LC before and after IOP lowering by medication. Among 23 eyes, 17 eyes of 12 persons had IOP lowering ≥ 3 mmHg (reduced IOP group) with tensile anterior-posterior Ezz strain= 1.0% ± 1.1% (P= 0.003) and compressive radial strain (Err)=-0.3% ± 0.5% (P= 0.012; random effects models accounting inclusion of both eyes in some persons). Maximum in-plane principal (tensile) strain and maximum shear strain in the reduced-IOP group were as follows: Emax= 1.7% ± 1.0% and Γmax= 1.4% ± 0.7%, respectively (both P < 0.0001 vs. zero). Reduced-IOP group strains Emax and Γmax were significantly larger with greater % IOP decrease (P < 0.0001 and P < 0.0001, respectively). The compliances of the Ezz, Emax, and Γmax strain responses, defined as strain normalized by the IOP decrease, were larger with more abnormal perimetric mean deviation or visual field index values (all P ≤ 0.02). Strains were unrelated to age (all P ≥ 0.088). In reduced-IOP eyes, mean LC anterior border posterior movement was only 2.05 μm posteriorly (P= 0.052) and not related to % IOP change (P= 0.94, random effects models). Only Err was significantly related to anterior lamina depth change, becoming more negative with greater posterior LC border change (P= 0.015). Lamina cribrosa mechanical strains can be effectively measured by changes in eye drop medication using OCT and are related to degree of visual function loss in glaucoma. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

New Nitinol-based Thermomechanically Adjustable IOL Technology.

To evaluate the feasibility of new adjustable intraocular lens (IOL) technology. The foldable adjustable IOL consists of a nitinol mechanism placed in a haptic-optic cradle. Heating actuators on the nitinol mechanism with a continuous green laser achieve controlled movement of the mechanism and optic. Activation occurs in controlled steps: rotation in 1-degree steps over 360 degrees, and anterior posterior movement in 0.25-diopter (D) steps with a range of +1.50 D. The IOL was tested in vitro and in vivo in a rabbit eye. Foldability and unfolding were demonstrated through a 2.6-mm cartridge. The adjustable lens mechanism was successfully tested in vitro and in vivo. Activation resulted in a change in optic position relative to the haptics and the capsular bag. Activation of the lever and ratchet mechanism showed radial advancement of the IOL clockwise and counterclockwise. In vivo rotatory movement was achieved after activation by the argon laser at 1 week after implantation. Anterior to posterior movement was accomplished by activating the circular spring actuator mechanism in the laboratory model. Uneventful folding and unfolding were performed. A new adjustable IOL with a mechanism that responds in measured steps had been shown to move as planned after activation by argon laser. This was successful in the laboratory in both radial and anterior posterior movement. The radial movement was also proven in vivo in an animal model. Further refinement of the prototype is currently being undertaken. [J Refract Surg. 2023;39(10):662-667.].

Reduction of Late Urinary Toxicity from Prostate Cancer Radiotherapy via Intrafractional MV-kV Image Guidance

Prostate cancer localization during radiotherapy is difficult and introduces positional variability during treatment. Here we evaluate the impact on treatment toxicities of an in-house system that uses MV and kV imaging guidance (MKIG) to track implanted fiducials during stereotactic body radiotherapy (SBRT) for localized prostate cancer. A 3D MKIG platform that tracks prostate implanted fiducials in real-time was built and clinically translated to replace a prior commercial approach called intrafraction motion review (IMR), which tracks thefiducials in 2D kV view only. MKIG has been shown to correct both superior-inferior and anterior-posterior (AP) motions that are harmful to critical organs and is superior to IMR for intrafractional motion management, which is less sensitive to AP motions. From 2017 to 2019, 150 patients with localized prostate cancer were treated with SBRT to 40 Gy in 5 fractions. During the delivery of volumetric modulated arc therapy, orthogonal MV-kV pairs were simultaneously acquired at every 20° gantry rotation and rigidly registered to the reference image templates created from the planning CT. Calculated 3D translations of implanted fiducials were used to localize the prostate and alert the therapist to interrupt and reposition the prostate when exceeding a 1.5-2 mm threshold. A comparison cohort of 121 prostate patients was treated from 2015 to 2016 with the same prescription dose and treatment technique but instead managed by IMR, where the therapist interrupted treatment based on a 2mm expansion of the fiducial contours superimposed on the kV images. Statistics of intrafractional interruptions, patient shifts, and overall delivery time were collected to evaluate the efficacy of the clinical workflow. The incidence of late grade ≥2 toxicities was analyzed to assess clinical complications. The median follow-up time was 5.5 years (range of 3.6 to 8.0 years). The MKIG cohort had more interruptions per fraction (1.09 vs. 0.28) and longer average delivery time per fraction (579±205s vs. 357±117s) than IMR. 75% of shifts resulting from MKIG were less than 3mm, compared to 51% in IMR, indicating that MKIG tended to detect and correct smaller deviations (p<0.001). The baseline International Prostate Symptom Score was 7.9 in the MKIG cohort vs. 8.4 in IMR (p = 0.41). The incidence of late grade ≥2 urinary toxicity was lower in the MKIG than IMR cohort: 10.7% vs. 19.8% (p = 0.05). One grade ≥2 rectal toxicity was observed in the IMR cohort but none in MKIG. Wehave demonstrated that MKIG is a clinically practical and effective method for monitoring and correcting prostate positional deviations during SBRT of prostate cancer. MKIG is better suited than 2D IMR to localize the prostate and trigger patient repositioning during treatment. A statistically and clinically significant reduction in urinary toxicity was observed. The potential expansion of MKIG to other clinical sites and translation to other centers should be considered.

Effect of Direction and Frequency of Skull Motion on Mechanical Vulnerability of the Human Brain.

Strain energy and kinetic energy in the human brain were estimated by magnetic resonance elastography (MRE) during harmonic excitation of the head, and compared to characterize the effect of loading direction and frequency on brain deformation. In brain MRE, shear waves are induced by external vibration of the skull and imaged by a modified MR imaging sequence; the resulting harmonic displacement fields are typically "inverted" to estimate mechanical properties, like stiffness or damping. However, measurements of tissue motion from MRE also illuminate key features of the response of the brain to skull loading. In this study, harmonic excitation was applied in two different directions and at five different frequencies from 20 to 90 Hz. Lateral loading induced primarily left-right head motion and rotation in the axial plane; occipital loading induced anterior-posterior head motion and rotation in the sagittal plane. The ratio of strain energy to kinetic energy (SE/KE) depended strongly on both direction and frequency. The ratio of SE/KE was approximately four times larger for lateral excitation than for occipital excitation and was largest at the lowest excitation frequencies studied. These results are consistent with clinical observations that suggest lateral impacts are more likely to cause injury than occipital or frontal impacts, and also with observations that the brain has low-frequency (∼10 Hz) natural modes of oscillation. The SE/KE ratio from brain MRE is potentially a simple and powerful dimensionless metric of brain vulnerability to deformation and injury.

Evaluating motion of pancreatic tumors and anatomical surrogates using cine MRI in 0.35T MRgRT under free breathing conditions.

Treatment tolerability is a significant limitation to pancreatic cancer treatment with radiotherapy due to proximity to highly radiosensitive organs and respiratory motion necessitating expanded target margins. Further, pancreatic tumors are difficult to visualize on conventional radiotherapy systems. Surrogates are often used to locate the tumor but are often inconsistent and do not provide strong positional relations throughout the respiratory cycle. This work utilizes a retrospective dataset of 45 pancreatic cancer patients treated on an MR-Linac system with cine MRI acquired for real-time target tracking. We investigated intra-fraction motion of tumors and two abdominal surrogates, leading to prediction models between the tumor and surrogate. Patient specific motion evaluation and prediction models were generated from 225 cine MRI series acquired during treatment. Tumor contours were used to evaluate the pancreatic tumor motion. Linear regression and principal component analysis (PCA) based models were used to predict tumor position from the anterior-posterior (AP) motion of the abdominal surface, the superior-inferior (SI) motion of the diaphragm, or a combination. Models were evaluated using mean squared error (MSE) and mean absolute error (MAE). Contour analysis showed the average pancreatic tumor motion range was 7.4±2.7mm and 14.9±5.8mm in the AP and SI directions, respectively. The PCA model had MSE of 1.4mm2 and 0.6mm2 , for the SI and AP directions, respectively, with both surrogates as inputs for the models. When only the abdomen surrogate was used, MSE was 1.3mm2 and 0.4mm2 in the SI and AP directions, while it was 0.4mm2 and 1.3mm2 when only the diaphragm surrogate was used. We evaluated intra-fraction pancreatic tumor motion and demonstrated prediction models between the tumor and surrogate. The models calculated the pancreatic tumor position from diaphragm, abdominal, or both contours within standard pancreatic cancer target margin, and the process could be applied to other disease sites in the abdominothoracic cavity.

A Report of Radiotherapy Setup Errors in Pelvic and Mediastinal Tumors

Introduction: Radiation therapy as an important step in treatment of cancer which demands accuracy. Patient setup is a challenging job in the radiation therapy process. The Variation in random setup error for specific sites is different among clinics, even from one radiation therapist technologist to other in a same clinic. The purpose of this study is to investigate and report about the setup margins in the pelvic and mediastinal sites. Method &amp;Material: 34 patients (20 males and 14 females) in the supine and prone positions (24 supine positions and 10 prone positions) were selected. Internal protocol and custom-made positioning devices were utilized. The variation of Anterior-Posterior movements (AP) in daily setup is recorded based on the vertical information which is shown on the arian 2100C/D Linear Accelerators monitor. The correlation between body type, position and treatment cases compares with the mean errors. Conclusion: The highest random error for setup is attributed to mediastinal tumor (=0.3 cm), and the highest systematic error is dedicated to cervix (=1.4 cm). The population systematic error (=1.25) is defined as the standard deviation of means of patients(Σ). In centers with lack of image-guided facilities or centers with high loaded patients the setup process should be accurate enough to limit setup error probabilities.

In Vivo Postoperative Motion of Fixed and Mobile Medial Pivot Knees Under Weight-Bearing Conditions after Cruciate-Sacrificing Total Knee Arthroplasty.

In vivo three-dimensional (3D) motion under weight-bearing conditions was analyzed postoperatively in medial pivot cruciate-substituting (CS) knee systems with fixed and mobile inserts. Tibiofemoral knee kinematics during squatting were captured with X-ray fluoroscopy for 4 patients in each cohort. The 3D motion of implants was analyzed with KneeMotion motion analysis software (LEXI Corporation; Tokyo, Japan). In addition, anterior-posterior (AP) movement of the distal-most points and the angle of axial rotation of the femoral component on the tibial component were assessed in both cohorts. Mean AP movement of the femoral component on the tibial component was 3.8±0.5 mm on the medial side and 9.5±0.5 mm on the lateral side in the cohort with fixed prostheses and 5.9±2.1 mm on the medial side and 10.0±2.5 mm on the lateral side in the cohort with mobile prostheses. The mean angle of axial rotation of the femoral component on the tibial component was 14.4±1.1 degrees and 8.2±2.7 degrees of external rotation for fixed knees and mobile knees, respectively. Postoperative motion analysis confirmed that fixed and mobile CS implants, which have a similar design, guided medial pivot motion under weight-bearing conditions. However, motion differed between these implant types after mid-flexion: bicondylar rollback after medial pivot motion was noted in the mobile cohort.

Impact of rectal gas on the planning target volume margin for pelvic bone and prostate matching in prostate cancer patients receiving volumetric-modulated arc therapy.

We performed daily cone-beam computed tomography (CBCT) to determine the impact of rectal gas on the movements of prostate and seminal vesicles (SVs). We aimed to determine the relationship between planning target volume (PTV) margins and rectal gas. In 30 treatments of 15 prostate cancer patients, excessive rectal gas was removed and CBCT images were analyzed. Image registration between planning CT and daily CBCT images before and after rectal gas removal was performed for pelvic bone and prostate matching. The couch movement distance between each matching was considered the prostate movement. In addition, we measured SV tip movement between each matching. The anterior-posterior movement of the prostate before rectal gas removal (3.1 ± 2.9 mm) was significantly greater than that after rectal gas removal (1.2 ± 1.2 mm; p < 0.01). The left-right and superior-inferior movements were similar regardless of the presence or absence of rectal gas. The SV movement distances before and after rectal gas removal were 11.0 ± 5.8 mm and 4.6 ± 3.8 mm, respectively (p < 0.01), in pelvic bone matching, and 8.0 ± 4.2 mm and 3.8 ± 3.2 mm, respectively (p < 0.01), in prostate matching. After rectal gas removal, the SV position did not differ significantly between each matching. In 26 of the 30 treatments, SV movement distance in the presence of rectal gas was >6 mm, which is the minimum PTV margin at our institution. In comparison, after rectal gas removal and prostate matching, only 6 treatments demonstrated an SV movement distance of >6 mm. In the presence of rectal gas, the SVs require greater PTV margins than the prostate. Rectal gas removal should be considered if the movement distance on prostate matching is greater than the minimum PTV margin at treating institution.

Assessing the impact of intrafraction motion correction on PTV margins and target and OAR dosimetry for single-fraction free-breathing lung stereotactic body radiation therapy.

The objective of this research is to investigate intrafraction motion correction on planning target volume (PTV) margin requirements and target and organ-at-risk (OAR) dosimetry in single-fraction lung stereotactic body radiation therapy (SBRT). Sixteen patients (15 with upper lobe lesions, 1 with a middle lobe lesion) were treated with single-fraction lung SBRT. Cone-beam computed tomography (CBCT) images were acquired before the treatment, between the arcs, and after the delivery of the treatment fraction. Shifts from the reference images were recorded in anterior-posterior (AP), superior-inferior (SI), and lateral (LAT) dimensions. The deviations from the reference image were calculated for 3 clinical scenarios: not applying intratreatment couch shifts and not correcting for pretreatment deviations < 3 mm ( scenario 1), not applying intratreatment couch shifts and correcting for pretreatment deviations < 3 mm ( scenario 2), and applying all pre- and intratreatment couch shifts (scenario 3). PTV margins were determined using the van Herk formalism for each scenario and maximum and average deviations were assessed. The clinical scenarios were modelled in the treatment planning system based on each patient dataset to assess target and OAR dosimetry. Calculated lower-bound PTV margins in the AP, SI, and LAT dimensions were [4.6, 3.5, 2.3] mm in scenario 1, [4.6, 2.4, 2.2] mm in scenario 2, and [1.7, 1.2, 1.0] mm in scenario 3. The margins are lower bounds because they do not include contributions from nonmotion related errors. Average and maximum intrafraction deviations were larger in the AP dimension compared to the SI and LAT dimensions for all scenarios. A unidimensional movement (several mm) in the negative AP dimension was observed in clinical scenarios 1 and 2 but not scenario 3. Average intrafraction deviation vectors were 1.2, 1.1, and 0.3 mm for scenarios 1, 2, and 3, respectively. Modelled clinical scenarios revealed that using scenario 3 yields significantly fewer treatment plan objective failures compared to scenarios 1 and 2 using a Wilcoxon signed-rank test. Intratreatment motion correction between each arc may enable reductions PTV margin requirements. It may also compensate for unidimensional negative AP movement, and improve target and OAR dosimetry.

Considering Lumpectomy Cavity PTV Expansions: Characterization of Intrafraction Lumpectomy Cavity Motion

PurposeAccelerated partial breast irradiation and lumpectomy cavity boost radiation therapy plans generally use volumetric expansions from the lumpectomy cavity clinical target volume to the planning target volume (PTV) of 1 to 1.5 cm, substantially increasing the volume of irradiated breast tissue. The purpose of this study was to quantify intrafraction lumpectomy cavity motion during external beam radiation therapy to inform the indicated clinical target volume to PTV expansion. Methods and MaterialsForty-four patients were treated with a whole breast irradiation using traditional linear accelerator-based radiation therapy followed by lumpectomy cavity boost using magnetic resonance (MR)-guided radiation therapy on a prospective registry study. Two-dimensional cine-MR images through the center of the surgical cavity were acquired during each boost treatment to define the treatment position of the lumpectomy cavity. This was compared with the reference position to quantify intrafraction cavity motion. Free-breathing technique was used during treatment. Clinical outcomes including toxicity, cosmesis, and rates of local control were additionally analyzed. ResultsThe mean maximum displacement per fraction in the anterior-posterior (AP) direction was 1.4 mm. Per frame, AP motion was <5 mm in 92% of frames. The mean maximum displacement per fraction in the superior-inferior (SI) direction was 1.2 mm. Per frame, SI motion was <5 mm in 94% of frames. Composite motion was <5 mm in 89% of frames. Three-year local control was 97%. Eight women (18%) developed acute G2 radiation dermatitis. With a median follow-up of 32.4 months, cosmetic outcomes were excellent (22/44, 50%), good (19/44, 43%), and fair (2/44, 5%). ConclusionsIn approximately 90% of analyzed frames, intrafraction displacement of the lumpectomy cavity was <5 mm, with even less motion expected with deep inspiratory breath hold. Our results suggest reduced PTV expansions of 5 mm would be sufficient to account for lumpectomy cavity position, which may accordingly reduce late toxicity and improve cosmetic outcomes.

Trunk Movement and Sequential Trunk Muscle Activation During Oscillation Exercises Using Flexible Poles.

Oscillatory exercises using flexible poles, such as the Flexi-bar, were recommended as rehabilitation programs to increase trunk muscles strength; however, the strategy to enhance the training effects is under investigations. The aim of this study was to characterize the trunk movements and muscle activation patterns when performing an oscillation exercise with flexible poles in different weights. Twelve healthy male participants performed oscillation exercises with flexible poles of different weights. The center of mass, as well as surface electromyography for 10 trunk muscles were assessed while participants performed oscillation exercises. The participants' trunks showed rhythmic anterior-posterior movement during oscillation exercises using flexible poles. The center-of-mass movement distances were 20.32 (6.73)mm, 25.33 (5.31)mm, 32.40 (9.94)mm, and 37.28 (21.59)mm for the Flexi-bar, light pole, medium pole, and heavy pole, respectively. Erector spinae, internal obliques, multifidus, and external obliques revealed significant activation levels during oscillation exercises. The participants who could perform steady and smooth oscillation with heavy pole for 30seconds revealed phasic sequential muscle activation. The present study suggested that oscillation exercises with flexible poles were associated with a concomitant trunk movement in anterior-posterior direction and an effective activation of trunk muscles.

A Morphometric Fixed-Bearing Unicompartmental Knee Arthroplasty Can Reproduce Normal Knee Kinematics. An In Vitro Robotic Evaluation

BackgroundA new morphometric fixed-bearing unicompartmental knee arthroplasty (UKA) system has been introduced to address the anatomical patient-specific challenges. It was our hypothesis that accurate restoration of the patient-specific anatomy would restore normal knee kinematics after UKA. Therefore, we aimed in this cadaveric study to analyze the impact of a medial morphometric UKA on (1) the varus-valgus and anterior-posterior stability of the knee, (2) the knee kinematics during standardized activities of the daily living, and (3) the patellar tracking, measured using a dedicated robotic testing protocol. MethodsEight human knee specimens underwent full-leg computed tomography CT scanning and comprehensive robotic assessments of tibiofemoral and patellofemoral kinematics. Specimens were tested in the intact state and after implantation of a fixed-bearing medial UKA. Assessments included passive flexion, laxity testing and simulations of level walking, lunge, and stair descent. ResultsMedial and lateral joint laxity after UKA closely resembled intact laxity across the full arc of flexion. Anterior-posterior envelope of motion showed a close match between the intact and UKA groups. Net rollback and average laxity were both not statistically different. Simulation of activities of daily living showed a close match in the anterior-posterior motion profile between the medial condyle and lateral condyle. Patellar tilt and medial-lateral shift during knee flexion matched closely between groups. ConclusionFunctional assessment of this UKA system shows nearly identical behavior to the intact knee. Fixed-bearing UKA with morphometric, compartment-specific geometry and precise mechanical instrumentation replicates complex knee balance and kinematics.