Anterior Locations Research Articles

Evaluating lesion integrity with diamond temp system

Abstract Background Pulmonary vein (PV) isolation by temperature-controlled (TC) radiofrequency ablation (RFA) is regaining popularity due to tissue-temperature feedback from thermocouples attached at the distal tip. The Diamond Temp (DT) ablation catheter system is uniquely able to monitor real time tissue temp during RFAs. The DT catheter tip has a 1.1 mm split tip electrode, allowing precise bipolar pacing during RFA. Loss of capture (LOC) with High output pacing (HOP) has been considered a surrogate to assess lesion transmurality [1]. This study evaluated the utility of DT catheter distal pacing to achieve durable lesions. Standard guidelines for TC ablation recommend achieving target tissue-temperature of 60ºC to produce durable lesions. The purpose of this study was to assess whether LOC is achieved at target tissue-temperature of 60ºC. Objective Pacing during ablation from distal tip micro electrode of the DT catheter and observing the time it takes for LOC at different segments around pulmonary veins. First pass isolation (FPI) percentage was also collected. Methods While target enrollment for this prospective study is 50 patients, these preliminary findings are based on analysis of the first 15 patients enrolled, all of whom had symptomatic, drug-refractory paroxysmal AF. Point-by-point RF lesions were delivered around ipsilateral PVs, divided into 4 segments: superior, inferior, anterior, and posterior. Ablation was performed in a TC mode with max temp setting of 60°C and max power of 50 watts. HOP was performed prior to start of ablation and discontinued once LOC was observed. Time taken to LOC around all 4 segments of PVs were recorded. Intracardiac echocardiography (ICE) was used to guide contact and monitor lesion formation. Results Overall mean time to LOC was 3.32 sec. Anterior sites exceeded this mean. Inferior, superior, and posterior sites generally had shorter times. 92.53% of locations achieved LOC within 2-5 sec of ablation. The right anterior PV had the longest time at 3.73 sec, exceeding the overall mean of 3.32 sec. All patient achieved FPI. Conclusion Reaching target therapeutic temp of 60°C alone may not be sufficient to achieve LOC around PVs. Ablation duration of 4 sec led to LOC in 92.53% of lesions. Certain anatomical regions like anterior locations required prolonged ablation time. Tissue thickness on ICE correlated directly with time required to LOC. This analysis shows that TC ablation with DT is effective; however, a therapeutic stable temperature of 60°C for at least 4 sec may be needed to achieve durable lesions around PVs. Tissue thickness on ICE and stability of temperature appear to be independent variables affecting duration prior to LOC.

Risk Factors Associated With Ventricular Dysfunction in Wolff-Parkinson-White Syndrome

BackgroundWolff-Parkinson-White (WPW) syndrome is associated with ventricular dysfunction in the absence of sustained tachyarrhythmias. Our aim was to determine the prevalence of ventricular dysfunction and to assess risk factors associated with this condition. MethodsA single-centre retrospective analysis of all patients <18 years of age with WPW syndrome and normal cardiac anatomy who underwent an electrophysiology study ablation over a 14-year period was performed. Patients with an ejection fraction <55% were defined as having ventricular dysfunction. ResultsAmong 305 patients, 14 cases (4.5%) with ventricular dysfunction were identified. In 4 of 14 cases (28%), the presenting symptom was heart failure, and only 6 of 14 (43%) had symptoms of palpitations or documented supraventricular tachycardia. The vast majority of patients with dysfunction had right-sided pathways, and only 2 patients had a left-sided pathway locations. Right anteroseptal, anterior, and anterolateral accessory pathway locations were more common in the dysfunction group. The presence of multiple pathways and pathway characteristics assessed during electrophysiology study were comparable between the 2 groups. ConclusionsThe prevalence of ventricular dysfunction in WPW syndrome in children was 4.5%, and this is seen more frequently with right anteroseptal, anterior, and anterolateral pathway locations. Risk analysis identified these pathway locations to be associated with a 4-fold risk of developing ventricular dysfunction (odds ratio: 4.32 [confidence interval: 1.38-14.18], P = 0.012). Because of this rare complication, serial assessment of ventricular function is recommended regardless of arrhythmia burden and an ablation should be considered in the presence of dysfunction.

Comprehensive profiling of migratory primordial germ cells reveals niche-specific differences in non-canonical Wnt and Nodal-Lefty signaling in anterior vs posterior migrants.

Mammalian primordial germ cells (PGCs) migrate asynchronously through the embryonic hindgut and dorsal mesentery to reach the gonads. We previously found that interaction with different somatic niches regulates PGC proliferation along the migration route. To characterize transcriptional heterogeneity of migrating PGCs and their niches, we performed single-cell RNA sequencing of 13,262 mouse PGCs and 7,868 surrounding somatic cells during migration (E9.5, E10.5, E11.5) and in anterior versus posterior locations to enrich for leading and lagging migrants. Analysis of PGCs by position revealed dynamic gene expression changes between faster or earlier migrants in the anterior and slower or later migrants in the posterior at E9.5; these differences include migration-associated actin polymerization machinery and epigenetic reprogramming-associated genes. We furthermore identified changes in signaling with various somatic niches, notably strengthened interactions with hindgut epithelium via non-canonical WNT (ncWNT) in posterior PGCs compared to anterior. Reanalysis of a previously published dataset suggests that ncWNT signaling from the hindgut epithelium to early migratory PGCs is conserved in humans. Trajectory inference methods identified putative differentiation trajectories linking cell states across timepoints and from posterior to anterior in our mouse dataset. At E9.5, we mainly observed differences in cell adhesion and actin cytoskeletal dynamics between E9.5 posterior and anterior migrants. At E10.5, we observed divergent gene expression patterns between putative differentiation trajectories from posterior to anterior including Nodal signaling response genes Lefty1, Lefty2, and Pycr2 and reprogramming factors Dnmt1, Prc1, and Tet1. At E10.5, we experimentally validated anterior migrant-specific Lefty1/2 upregulation via whole-mount immunofluorescence staining for LEFTY1/2 proteins, suggesting that elevated autocrine Nodal signaling accompanies the late stages of PGC migration. Together, this positional and temporal atlas of mouse PGCs supports the idea that niche interactions along the migratory route elicit changes in proliferation, actin dynamics, pluripotency, and epigenetic reprogramming.

Physeal Location on the Distal Femoral Cortical Surface Is Consistently Proximal to Apparent Location on the Perfect Lateral Radiograph: A 3-Dimensional Digitally Reconstructed Radiograph Study.

The perfect knee lateral radiograph visualizes anatomic landmarks on the distal femur for clinical and scientific purposes. However, radiographic imaging is a two-dimensional (2D) representation of a three-dimensional (3D) physis. The aim of this study was to characterize the perceived radiographic projection of the femoral physis using perfect lateral digitally reconstructed radiographs (DRRs) and to evaluate discrepancies from this projection to the physis at the lateral and medial cortices. Pediatric patients from a cohort of CT scans were analyzed. Inclusion criteria were an open physis; exclusion criteria were any implant or pathology affecting the physis. CT scans were imported into 3D imaging software and transformed into lateral DRRs and 3D renderings of the femur. The physis was divided into four equal segments, with fiducial markers placed at the "anterior," "midpoint," and "posterior" points. Lines extended from these points in the lateral and medial direction. The vertical distance from these lines, representing the radiographic projection of the physis, was measured relative to the physis at the lateral and medial cortex of the femur on coronal CT slices. Thirty-one patients were included. On the perfect lateral radiograph DRR, the physis on the medial cortex was located proximal to the visualized physis by 6.64 ± 1.74 mm, 11.95 ± 1.67 mm, and 14.30 ± 1.75 mm at the anterior (25%), midpoint (50%), and posterior (75%) locations, respectively. On the lateral side, the physis on the lateral cortex was proximal to the visualized physis by 2.19 ± 1.13 mm, 3.71 ± 1.19 mm, and 6.74 ± 1.25 mm at the anterior, midpoint, and posterior locations, respectively. In this cohort of pediatric patients, the location of the cortical physis was, in all areas measured, proximal to the projection of the visualized physis as seen on the perfect knee lateral DRR. The distance from radiographic physis to cortical physis was greater at the medial cortex compared with the lateral cortex. Descriptive laboratory study. III, observational radiographic anatomic study.

Central cone design demonstrates greater micromotion compared to keel design in cementless tibial baseplates: A biomechanical analysis.

The purpose of this study was to compare micromotion of two new cementless tibial baseplates to a cementless design with well-published clinical success. Three cementless tibial baseplate designs (fixed-bearing [FB] with keel and cruciform pegs, rotating-platform with porous central cone and pegs, FB with cruciform keel and scalloped pegs) were evaluated on sawbone models. Loading was applied to the baseplate at a rate of 1 Hz for 10,000 cycles, which represents 6-8weeks of stair descent. This time frame also represents the approximate time length for the induction of biologic fixation of cementless implants. Compressive and shear micromotion at the sawbone-implant interface were measured. At the end of the loading protocol, the central cone rotating-platform design exhibited greater micromotion at the anterior (p < 0.001), posterior (p < 0.001)and medial locations (p = 0.049) compared to the other two implants. The central cone design also exhibited greater translational micromotion in the sagittal plane at the medial (p = 0.001) and lateral locations (p = 0.034)and in the coronal plane anteriorly (p = 0.007). The cementless central cone rotating-platform baseplate demonstrated greater vertical and translational micromotion compared to the two FB baseplates with a keel underloading. This may indicate lower initial mechanical stability in implants without a keel, which possibly affects osseointegration. The implication of this is yet unknown and requires further long-term clinical follow-up to correlate these laboratory findings. V (biomechanical study).

A Cross-Sectional Study to Evaluate Diffusion Tensor Imaging Findings of the Brain in End-Stage Renal Disease (ESRD) Patients Undergoing Maintenance Hemodialysis Using Volume of Interest Method

Background: Cerebral small vessel disease (CSVD) is a chronic disorder affecting small vessels within the brain, increasing the risk of stroke in patients with chronic kidney disease (CKD). Diffusion tensor imaging (DTI) is a newer quantitative method for diagnosing CSVD at an early stage of pathogenesis. Objectives: This study compares various DTI parameters in multiple white matter tracts of the brain in CKD patients undergoing maintenance hemodialysis with normal controls in the Indian population using the volume of interest (VOI) method. Additionally, it correlates these DTI parameters with each other at different locations to gain insights into the pathogenesis of CSVD. Methods: After obtaining institutional ethics approval, a cross-sectional study was conducted at a tertiary care hospital over one year (June 2022 to May 2023). The study comprised seventy-five patients in the hemodialysis group and twenty-five controls. All participants underwent MRI brain examinations on a 3 Tesla MRI scanner, and the four DTI parameters - fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) - were reviewed for nine white matter tracts to evaluate statistical differences and correlations. Results: Fractional anisotropy was significantly decreased at anterior locations – corpus callosum genu (P = 0. 357 × 10-7), right anterior corona radiata (P = 0.001), and left anterior corona radiata (P = 0.45 × 10-5). In these locations, FA negatively correlated with RD (R = -0.7904, P &lt; 0.00001), and RD was also significantly increased. Axial diffusivity was significantly increased at posterior locations in the corpus callosum splenium (P = 0.108 × 10-5) and left posterior corona radiata (P = 0.244 × 10-5). However, none of the four DTI parameters showed significant differences between hemodialysis patients and the control group for the subset of patients with normal routine brain MRI features. The intraclass correlation coefficients (ICCs) were high for all four DTI parameters for both patients (0.78 to 0.85) and controls (0.82 to 0.89). Conclusions: This study on CKD patients undergoing maintenance hemodialysis reveals significant differences in some DTI parameters in widespread white matter tracts of the brain using the VOI method, with acceptable to excellent interobserver agreement.

Understanding Spatial Correlation Between Multiparametric MRI Performance and Prostate Cancer.

Multiparametric MRI (mpMRI) has shown a substantial impact on prostate cancer (PCa) diagnosis. However, the understanding of the spatial correlation between mpMRI performance and PCa location is still limited. To investigate the association between mpMRI performance and tumor spatial location within the prostate using a prostate sector map, described by Prostate Imaging Reporting and Data System (PI-RADS) v2.1. Retrospective. One thousand one hundred forty-three men who underwent mpMRI before radical prostatectomy between 2010 and 2022. 3.0 T. T2-weighted turbo spin-echo, a single-shot spin-echo EPI sequence for diffusion-weighted imaging, and a gradient echo sequence for dynamic contrast-enhanced MRI sequences. Integrated relative cancer prevalence (rCP), detection rate (DR), and positive predictive value (PPV) maps corresponding to the prostate sector map for PCa lesions were created. The relationship between tumor location and its detection/missing by radiologists on mpMRI compared to WMHP as a reference standard was investigated. A weighted chi-square test was performed to examine the statistical differences for rCP, DR, and PPV of the aggregated sectors within the zone, anterior/posterior, left/right prostate, and different levels of the prostate with a statistically significant level of 0.05. A total of 1665 PCa lesions were identified in 1143 patients, and from those 1060 lesions were clinically significant (cs)PCa tumors (any Gleason score [GS] ≥7). Our sector-based analysis utilizing weighted chi-square tests suggested that the left posterior part of PZ had a high likelihood of missing csPCa lesions at a DR of 67.0%. Aggregated sector analysis indicated that the anterior or apex locations in PZ had the significantly lowest csPCa detection at 67.3% and 71.5%, respectively. Spatial characteristics of the per-lesion-based mpMRI performance for diagnosis of PCa were studied. Our results demonstrated that there is a spatial correlation between mpMRI performance and locations of PCa on the prostate. 4 TECHNICAL EFFICACY: Stage 2.

Spatial regulation of Drosophila ovarian Follicle Stem Cell division rates and cell cycle transitions.

Drosophila ovarian Follicle Stem Cells (FSCs) present a favorable paradigm for understanding how stem cell division and differentiation are balanced in communities where those activities are independent. FSCs also allow exploration of how this balance is integrated with spatial stem cell heterogeneity. Posterior FSCs become proliferative Follicle Cells (FCs), while anterior FSCs become quiescent Escort Cells (ECs) at about one fourth the frequency. A single stem cell can nevertheless produce both FCs and ECs because it can move between anterior and posterior locations. Studies based on EdU incorporation to approximate division rates suggested that posterior FSCs divide faster than anterior FSCs. However, direct measures of cell cycle times are required to ascertain whether FC output requires a net flow of FSCs from anterior to posterior. Here, by using live imaging and FUCCI cell-cycle reporters, we measured absolute division rates. We found that posterior FSCs cycle more than three times faster than anterior FSCs and produced sufficient new cells to match FC production. H2B-RFP dilution studies supported different cycling rates according to A/P location and facilitated live imaging, showing A/P exchange of FSCs in both directions, consistent with the dynamic equilibrium inferred from division rate measurements. Inversely graded Wnt and JAK-STAT pathway signals regulate FSC differentiation to ECs and FCs. JAK-STAT promotes both differentiation to FCs and FSC cycling, affording some coordination of these activities. When JAK-STAT signaling was manipulated to be spatially uniform, the ratio of posterior to anterior division rates was reduced but remained substantial, showing that graded JAK-STAT signaling only partly explains the graded cycling of FSCs. By using FUCCI markers, we found a prominent G2/M cycling restriction of posterior FSCs together with an A/P graded G1/S restriction, that JAK-STAT signaling promotes both G1/S and G2/M transitions, and that PI3 kinase signaling principally stimulates the G2/M transition.

Pharyngeal airway subdivisions in 3-dimensional analysis: Differences between anterior and posterior anatomic boundaries

This study aimed to evaluate if there were differences between anterior and posterior anatomic boundaries used for the 3-dimensional determination of pharyngeal airway. The sample included 150 cone-beam computed tomography scans from healthy patients divided according to (1) age: 6-11, 12-16, and ≥16 years; (2) sex: female and male; (3) anteroposterior skeletal pattern: Class I, II, and III; (4) vertical pattern: brachyfacial, mesofacial, and dolichofacial; and (5) craniocervical inclination (CCI): natural head posture, head flexion, and head extension. Anatomic regions were created to determine the correspondences between structures anteriorly and posteriorly to the pharyngeal airway. The location of the epiglottis, vallecula, hyoid, C2, and C3 were statistically different according to the CCI, and the location of vallecula, C3, and C4 were different according to sex. However, no statistically significant differences were observed between the frequencies of anterior and posterior anatomic region locations among age and different anteroposterior and vertical skeletal patterns. Posterior landmarks tend to be located below the anterior ones; consequently, the anatomic subregion they define will also be located below. Anterior and posterior structures and vertical and anteroposterior skeletal patterns may determine upper airway limits regardless of age. However, the studies must be paired according to sex, and CCI must be standardized.

Accuracy of CT angiography for detecting ruptured intracranial aneurysms.

Digital subtraction angiography (DSA) is invasive, costly and unavailable in many South African hospitals; however, it remains the gold standard for imaging intracranial aneurysms. CT angiography (CTA) is a non-invasive and readily available screening tool prior to DSA. This study aimed to evaluate the diagnostic performance of CTA in detecting ruptured intracranial aneurysms using DSA as the reference standard and to determine the effect of aneurysm size and location on CTA sensitivity. A retrospective analysis of CTA and DSA data from reports of patients suspected to have aneurysmal subarachnoid haemorrhage (SAH) at Chris Hani Baragwanath Academic Hospital between January 2017 and June 2020. Conventional DSA detected aneurysms in 94 out of 115 patients; while of these, CTA detected 75 and missed 19. The CTA sensitivity, specificity and accuracy was 80%, 43% and 73%, respectively. The CTA sensitivity for aneurysms < 3 mm and 3 mm - 5 mm in size was 30% and 81.5%, respectively (p = 0.024). Sensitivity of CTA for posterior communicating artery (PComm) aneurysms was 56% and lower than other major anterior circulation locations (83% - 91%) (p = 0.045). The CTA diagnostic efficiency was lower than previously reported, with even lower sensitivity for aneurysms < 3 mm and for those arising from the PComm. Thus, CTA should remain a screening tool prior to DSA in all local patients suspected to have aneurysmal SAH. Larger, prospective studies are required to accurately define the role of CTA in diagnosing intracranial aneurysms in a developing country with limited resources.

A Retrospective Cohort Study to Determine Whether the Previous Route of Delivery Affects the Uterine Artery Blood Flow.

In our study, we aimed to investigate the effect of the previous delivery route on uterine artery pulsatility index (PI) and obstetric outcome.We aim to assess the effects of previous cesarean delivery (CD) and placental location on first- and second-trimester uterine artery Doppler indices as well as first-trimester pregnancy-associated plasma protein-A (PAPP-A)multiples of the median (MoM) levels in the subsequent pregnancy. We designed a retrospective cohort study to collect the participants' clinical and uterine artery Doppler.Data regarding pregnant women's first- and second-trimester exams, who were referred to our maternal-fetal medicine unit, were collected from hospital records between June 2015 and December 2019. Uterine artery PI MoM values were not different between the cases with the anterior and non-anterior placental locations. No significant difference was found in the first- and second-trimester uterine artery PI MoMvalues by delivery route (p = 0.57). However, the intrauterine growth restriction rate was higher in the CD group (p < 0.001). In this study, we compared the uterine blood flow indices between the previous cesarean and vaginal delivery groups. We observed no significant difference between the patients with different delivery routes.

Automatic detection of irregular vanishing and reappearing parts of objects in two interwoven sequences: A visual mismatch negativity study.

The cognitive system automatically develops predictions on the basis of regularities of event sequences and reacts to the violation of these predictions. In the visual modality, the electrophysiological signature of this process is an event-related potential component, the visual mismatch negativity (vMMN). So far, we have no data, whether the system underlying vMMN is capable of dealing with more than one event sequence simultaneously. To disclose this aspect of the capacity of the system, in a passive oddball paradigm, we presented two interwoven sequences. The stimuli were objects (diamond patterns with their diagonals), one of the sequences was presented to the left side and the other to the right side of the visual field. From time to time, two parallel lines of the diamonds disappeared (OFF event) and then reappeared (ON event). The frequently vanishing pair of lines on the left side (standard) was identical to the rarely vanishing lines of the objects on the right side (deviant) and vice versa. We found that deviant ON events elicited vMMN only for left-side deviants and deviant OFF events elicited vMMN only for right-side deviants. The standardized low resolution brain electromagnetic tomography (sLORETA) source localization showed vMMN sources both in posterior visual structures and in anterior locations, and activity was stronger in the hemisphere contralateral to the deviant event. According to the results, the system underlying vMMN is capable of dealing with two sequences, but within a sequence, it detected only one type (either OFF or ON) of deviancy.

Evaluation of peripheral anterior synechia formation following gonioscopy-assisted transluminal trabeculotomy surgery.

To quantitatively assess the development of peripheral anterior synechia (PAS) formation rate and PAS locations on gonioscopic examination following gonioscopy-assisted transluminal trabeculotomy (GATT) surgery and investigate the surgical outcomes. A total of 35 eyes from 31 patients with open angle glaucoma who underwent GATT or combined GATT and phacoemulsification surgery were analyzed. Presence of PAS was assessed on gonioscopy in nasal, temporal, superior and inferior quadrants at months 1, 3 and 6 following surgery. Surgical outcomes were also noted. Frequencies of PAS formation were 38.3%, 25.3%, 17.0% and 19.1% at postoperative 1month, 34.0%, 26.4%, 17% and 22.6% at postoperative 3months and 32.3%, 25.8%, 16.1% and 25.8% at postoperative 6months, in nasal, temporal, superior and inferior quadrants, respectively. The highest amount of PAS involvement was 3 clock hours in the study which was identified only in nasal and inferior quadrants. Frequency of PAS formation did not significantly differ between nasal, temporal, superior and inferior quadrants at all time points (p > 0.05). No significant differences of mean IOP levels were observed between patients who developed PAS and who did not develop PAS at postoperative 1month (p = 0.72), 3months (p = 0.21) and 6months (p = 0.59). The mean IOP and mean number of antiglaucoma medications decreased from 31.5 ± 7.2mmHg and 3.6 ± 0.6 at baseline to 13.8 ± 3.1mmHg and 1.6 ± 1.3 at postoperative 6months, respectively (p < 0.001, for both). Cumulative success rate (95% confidence interval) was 74.3% (69.9-78.6%) at the end of the study. Mild to moderate degrees of hyphema occurred in all cases postoperatively. Although PAS formation was observed to be relatively higher in nasal quadrant, PAS frequency was not statistically different between the angle quadrants.

Reductions in regional theta power and fronto-parietal theta-gamma phase-amplitude coupling during gaze processing in bipolar disorder

Impaired social cognition is common in bipolar disorder (BD) and predicts poor functional outcomes. A critical determinant of social cognition is the ability to discriminate others’ gaze direction, and its alteration may contribute to functional impairment in BD. However, the neural mechanisms underlying gaze processing in BD are unclear. Because neural oscillations are crucial neurobiological mechanisms supporting cognition, we aimed to understand their role in gaze processing in BD. Using electroencephalography (EEG) data recorded during a gaze discrimination task for 38 BD and 34 controls (HC), we examined: theta and gamma power over bilateral posterior and midline anterior locations associated with early face processing and higher-level cognitive processing, and theta-gamma phase-amplitude coupling (PAC) between locations. Compared to HC, BD showed reduced midline-anterior and left-posterior theta power, and diminished bottom-up/top-down theta-gamma PAC between anterior/posterior sites. Reduced theta power and theta-gamma PAC related to slower response times. These findings suggest that altered theta oscillations and anterior-posterior cross-frequency coupling between areas associated with higher-level cognition and early face processing may underlie impaired gaze processing in BD. This is a crucial step towards translational research that may inform novel social cognitive interventions (e.g., neuromodulation to target specific oscillatory dynamics) to improve functioning in BD.

Evaluation of anterior tooth-ridge angulation, root position and labial bone perforation using dental cone-beam computed tomography: An observational study.

The objective of this study was to use cone-beam computed tomography (CBCT) scans to measure and correlate the maxillary and mandibular tooth-ridge angulation (TRA) and labial bone perforation (LBP) in anterior teeth. A standardized technique was used to orientate Planmeca CBCT images in 140 patients. On the sagittal section, TRA was defined as the angle between the long axis of the tooth and the alveolar housing of the corresponding tooth. The maxillary and mandibular anterior teeth's sagittal root locations were evaluated. Virtual implant software was used to analyze bone perforations using a predetermined taper implant system. A total of 1680 teeth were scanned for this investigation, and 1338 teeth were selected for further analysis. In comparison to the mandible, the maxilla had a greater TRA. LBP was found to be 4.26% (57 teeth) more common in the mandibular arch (n = 39; 68.42 and) than in the maxillary arch (n = 18; 31.58%). When comparing both the sides, there was no significant difference in LBP. There was a significant relationship between TRA and LBP (P < 0.05). There was a significant association between all parameters. There was no statistically significant difference in TRA, sagittal root position (SRP), and LBP between the right and left teeth. The SRP type 1 is most typically present in the anterior teeth. The maxillary anterior teeth were placed at a 5°-10° angle, while the mandibular incisors were parallel to the alveolar ridge. The LBP was more characteristically present in the mandibular incisors. SRP and TRA were directly correlated with LBP. Clinically, bone perforations may be reduced using taper implants and abutments with a 5°-10° angle in maxillary anterior teeth, while straight implants are preferred in mandibular anterior teeth, which may be recommended.

Anterior vs. posterior position of dispersive patch during radiofrequency catheter ablation: insights from in silico modelling.

To test the hypothesis that the dispersive patch (DP) location does not significantly affect the current distribution around the catheter tip during radiofrequency catheter ablation (RFCA) but may affect lesions size through differences in impedance due to factors far from the catheter tip. An in silico model of RFCA in the posterior left atrium and anterior right ventricle was created using anatomic measurements from patient thoracic computed tomography scans and tested the effect of anterior vs. posterior DP locations on baseline impedance, myocardial power delivery, radiofrequency current path, and predicted lesion size. For posterior left atrium ablation, the baseline impedance, total current delivered, current distribution, and proportion of power delivered to the myocardium were all similar with both anterior and posterior DP locations, resulting in similar RFCA lesion sizes (< 0.2 mm difference). For anterior right ventricular (RV) ablation, an anterior DP location resulted in slightly higher proportion of power delivered to the myocardium and lower baseline impedance leading to slightly larger RFCA lesions (0.6 mm deeper and 0.8 mm wider). An anterior vs. posterior DP location will not meaningfully affect RFCA for posterior left atrial ablation, and the slightly larger lesions predicted with anterior DP location for anterior RV ablation are of unclear clinical significance.

The effect of continuous positive airway pressure on inferior vena cava collapsibility as measured by bedside ultrasound.

The purpose of this study was to determine the impact of progressively increasing continuous positive airway pressure (CPAP) on measurements of the caval index (CI) using bedside ultrasound at the 3 common inferior vena cava (IVC) evaluation sites. This was a prospective, observational trial that included 165 healthy adults over 18 years old enrolled between February 2015 and May 2018. Measurements of the IVC were obtained during normal tidal respirations from the subxiphoid area in the long and short axis and from the right mid-axillary line in the long axis. Measurements were obtained in each of these locations at atmospheric pressure and with CPAP at 5, 10, and 15 cmH2O. The CI was then calculated for each of the 3 selected locations at each level of pressure. As CPAP pressures increased from 0 to 15cmH2O the CI measurements obtained at the lateral mid-axillary line did not show any statistically significant variation. There was a statistically significant difference (P<0.001) when comparing measurements of the CI from the lateral mid-axillary line location to both anterior locations. As CPAP pressures increased, the CI calculated from the subxiphoid area in both the anterior short and anterior long axis orientations initially trended upwards at 5cmH2O, then began to downtrend as the pressures increased to 10 and 15cmH2O. Comparing the CI measurements from the anterior long and anterior short axis at 0, 5, 10, and 15cmH2O, there was no statistically significant difference at any pressure (P>0.05). When evaluating the IVC in a spontaneously breathing patient, measurements from an anterior orientation are preferred as the lateral mid-axillary view can underestimate CI calculations.

Abstract A026: Identifying unique genomic and clinical characteristics of radiation-associated rectal cancer

Abstract Introduction: Prostate cancer patients treated with radiation therapy (RT) are at risk of developing radiation-associated rectal cancer (RARC). Previous literature reports worse overall survival in these patients compared to those with non-radiation associated primary rectal cancer (PRC), yet the genomic and clinical characteristics of RARC are not well understood. We compared molecular profiles of RARC and PRC patients to better understand the mechanism of RARC tumorigenesis and its interplay with clinical outcomes. Methods: We performed a retrospective analysis of 22 patients who had stage I-IV rectal cancer (within 12 cm of the anal verge) and had received previous RT for prostate cancer. Patients were excluded if they had a latency period between cancers of &amp;lt;5 years or additional metachronous cancers. Tumors were profiled using MSK-IMPACT, a targeted DNA-sequencing panel that identifies somatic mutations, copy number changes and fusions in a panel of 341-505 genes using a combination of solid tissue and matched blood specimens. The cohort included patients who had received external beam radiation therapy (EBRT, n=8), brachytherapy (BT, n=7), and combined EBRT-BT (n=7). All the RARC patients were microsatellite stable (MSS). To compare molecular features while accounting for clinical differences, we performed propensity score matching (1:1 ratio) using a background set of 616 patients with MSS PRC who had also been sequenced with MSK-IMPACT. Patients were matched for gender, age at diagnosis, distance from anal verge, tumor size, tumor location (anterior, lateral or posterior) and stage. Results: When compared to the general background set of 616 MSS PRC cases, RARC patients tended to be older at diagnosis (median 74 vs. 54 years, P=&amp;lt;0.0001). RARC tumors were more likely to have size &amp;lt;4cm at diagnosis (70% vs. 36%, P=0.01), to originate in the distal rectum, within 0-4 cm from the anal verge (55% vs. 25%, P=&amp;lt;0.001) and also to develop along the anterior rectal wall (41% vs 22%, P=&amp;lt;0.001). We then compared the genomic features of RARC to the clinically matched PRC set. RARC exhibited lower tumor mutational burden than PRC (median 4.4 vs. 6.0 mut/Mb, P=0.011), but no difference was observed in terms of chromosomal instability measured as the fraction of genome altered by copy number changes [median 0.11 vs. 0.17, P=0.49]. RARC patients also exhibited significantly lower frequency of APC mutations (41% vs. 82%, P=0.012) compared to PRC patients. Conclusion: We have identified clinical and molecular differences between RARC and PRC, including distal and anterior locations as well as lower TMB and lower frequency of APC mutations in RARC patients. The results provide clinically relevant insights into the unique attributes of RARC and may ultimately help to improve prognostication and treatment for this unique population. Citation Format: Dana M. R. Omer, Anisha Luthra, Hannah M. Thompson, Jonathan B. Yuval, Paul B. Romesser, Philip B. Paty, Julio Garcia-Aguilar, Francisco Sanchez-Vega. Identifying unique genomic and clinical characteristics of radiation-associated rectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr A026.

Evaluation of Orthodontic Mini-Implant Placement in the Maxillary Anterior Alveolar Region in 15 Patients by Cone Beam Computed Tomography at a Single Center in South India.

BACKGROUND In this study, we aimed to evaluate orthodontic mini-implant placement in the maxillary anterior alveolar region by cone beam computed tomography (CBCT) in 15 patients at a single center in South India. MATERIAL AND METHODS A total of 15 CBCT scans of orthodontic patients after completion of leveling and aligning stage were included. The thickness of labial alveolar bone, labio-palatal bone, and inter-radicular distance between the maxillary central incisors (U1-U1), maxillary central and lateral incisor (U1-U2), and maxillary lateral incisor and canine (U2-U3) at vertical levels 4 mm, 6 mm, and 8 mm above the interdental cementoenamel junction were measured. Descriptive statistics, ANOVA, and Tukey post hoc tests were done to assess the differences among the groups. An independent t test was done to analyze differences by sex. RESULTS The thickness of cortical bone in the labial region was higher in the U2-U3 site than in the U1-U1 site, at a height of 4 mm. Also, there was a significant difference between 4 mm and 8 mm heights in the U2-U3 region. No significant difference was noted in bone dimensions among men and women and in the labio-palatal bone thickness among the different sites. The inter-radicular distance was the highest between the U2-U3 site, while it was the lowest in the U1-U2 site. CONCLUSIONS The findings from this center showed that when CBCT was used to evaluate orthodontic mini-implant placement in the maxillary anterior alveolar region, the U2-U3 and U1-U1 locations at heights between 6 mm to 8 mm apical to the interdental cementoenamel junction were optimal for placement of the mini-implants.

Placental Location in Women Experienced Cesarean Section using Ultrasonography: A Case-Control Study on Sudanese Women

The objective of this study was to assess the placental location in women with a previous cesarean section (CS) using ultrasonography and the impact of cesarean section (CS) on placenta location. Methods and Results: This case-control study included 205 pregnant women with normal singleton pregnancies (83 women with previous CS [case group] and 122 without previous CS [control group]). The study was conducted at three general hospitals in Khartoum State from August to November 2019. The women were investigated using a Mindary ultrasound machine DP_2200 equipped with 3.5MHz transducers. The anterior placenta location was more prevalent than others: 43.3% and 45.9% for cases and control, respectively. The incidence of placenta previa (PP) and the low-lying placenta (LLP) was 1.2% and 3.6%, respectively, in the case group, and 0.0 and 0.8%, respectively, in the control group. Women with a previous CS were at high risk of the LLP and PP (OR=6.12). Conclusion: Our study concluded that the most common sites of the placenta in women with a previous CS were anterior and posterior locations. The study also concluded that women with a previous history of CS are at high risk for LLP and PP.