Pretreatment Cone-beam Computed Tomography Research Articles

Clinical Implications of Geometric and Dosimetric Uncertainties Due to Inter- and Intra-Fractional Movement During Volumetric Modulated Arc Therapy for Breast Cancer Patients

Compared to conventional radiotherapy (RT) techniques, modern RT with fewer fractions and smaller target volumes requires higher accuracy. This study evaluated the necessity of pre-treatment and intra-fractional cone-beam computed tomography (CBCT) by analyzing inter- and intra-fractional CBCT images of breast cancer patients receiving RT.From 57 patients, 1,206 pre-treatment CBCT and 1,067 intra-fractional CBCT images were collected. After positioning the patient according to the three skin markers drawn during simulation, pre-treatment CBCT images were acquired. During partial-arc volumetric modulated arc therapy, a simultaneous intra-fractional CBCT scan was taken as the gantry rotated around the patient. The change in position between simulation and the actual position of the patient before and during RT was assessed according to the differences in x-, y-, and z-axes. After the difference in each axis was measured, the absolute distance between two CT images was measured. Changes in dosimetric parameters were evaluated in selected patients with extreme intra-fractional movement.For right-sided breast cancer patients, left-sided breast cancer patients treated using deep-inspiration breath hold, and left-sided breast cancer patients treated using continuous positive airway pressure, median inter-fractional deviations were 0.53 (range 0.06-2.98) cm, 0.66 (range 0.08-4.41) cm, and 0.69 (range 0.04-3.80) cm and median intra-fractional deviations were 0.14 (range 0.00-0.62) cm, 0.23 (range 0.02-0.96) cm, and 0.24 (0.00-1.15) cm, respectively. Modified plans reflecting large changes in intra-fractional position in 10 selected cases revealed insufficient target coverage in seven cases and more than 20-fold increase in the volume of heart receiving more than 25 Gy of radiation in two cases.Even though the intra-fractional ROM was minimal in most cases, few cases showed huge variations that could significantly affect the goal of RT; therefore, intra-fractional verification might be necessary as well as inter-fractional verification.

Cone Beam CT-Based Online Evaluation in Two Minutes Using a Commercial Treatment Planning Software for Proton Therapy

Daily online treatment evaluation is essential for proton therapy, which is sensitive to daily anatomy and setup uncertainties. We have developed a program based on a commercial treatment planning system (TPS) to streamline the online evaluation process using pre-treatment cone-beam CT (CBCT) images. Herein, we evaluate the speed and accuracy of the tool based on clinical proton plans.Data from 25 previously treated proton patients (7 HN, 11 lung, and 7 prostate) at our institution were evaluated. Corrected CBCT (cCBCT) images were generated using a research version of the TPS, which removes artifacts and calibrates HU for proton dose calculation. A quality assurance simulation CT (QACT) scanned on the same day as the CBCT is deformed to the cCBCT and used as a reference (dQACT). The cCBCT is deformed to the treatment planning CT (TPCT), and all contours on the initial TPCT were deformed to the cCBCT and then rigidly copied to the dQACT. Original clinical treatment plans were applied to both the cCBCT and dQACT, and the doses were calculated with the GPU-based Monte-Carlo dose calculation engine at 0.5% statistical uncertainty. The entire evaluation time (Eval_time) from importing CBCT image to completing final dose calculation for cCBCT was recorded. Plan parameters, including the number of beams (N_bm), proton spot number (N_sp), dose grid voxel numbers (N_voxel), were collected. Pearson correlation coefficient between the Eval_time and the N_bm, N_sp, and N_vosel were calculated. Dosimetric parameters were calculated for the cCBCT and compared to those calculated from the reference dQACT. Dosimetric parameters of interest included the following: for all, CTV D99, D95, and V100, and plan maximum dose (Dmax); for H&N cases, parotid mean dose (P_Dmean) and V30Gy (P_V30), and oral cavity mean dose (C_Dmean); and for H&N and lung cases, spinal cord max dose (SC_Dmax).Mean online Eval_time is 106.6 ± 24.9s for all patients, with HN as the fastest site 87.9 ± 17.5s for HN, 104.5 ± 15.9s for lung, 128.5 ± 28.0s for prostate, P < 0.01. The corresponding (N_bm, N_sp, N_voxel) were (3.9, 7781, 2.6E6) for HN, (3.3, 11080, 2.4E6) for lung, and (3.0, 10484, 3.8E6) for prostate. Eval_time was significantly correlated to N_sp (P = 0.02), but not to N_bm and N_voxel. The absolute differences for CTV D99, D95, V100, plan Dmax, HN P_Dmean, P_V30, C_Dmean, and SC_Dmax are 0.85 ± 0.60%, 0.39 ± 0.22%, 0.48 ± 0.41%, 0.46 ± 0.48%, 0.08 ± 0.05Gy, 0.05 ± 0.06%, 0.21 ± 0.20 Gy, and 0.57 ± 0.53Gy, respectively.Online evaluation can be achieved within 2 minutes for most clinical proton cases (80% in this study) with the commercial TPS. The speed can be further increased with reduced OAR mapping, fine-tuned deformable registration, optimized and reduced spot number in the initial plans, and upgraded computer server. This proposed method may optimize the efficiency and quality of care for proton radiotherapy.

Minimum Bladder Reference Contour to Guide Bladder Filling for Prostate Radiotherapy

The purpose of this study was to evaluate if a minimum bladder reference contour could help reduce treatment delays and imaging needed for pre-treatment setup in patients undergoing prostate stereotactic body radiation therapy (SBRT).20 patients undergoing 5-fraction SBRT to the prostate and seminal vesicles were included in this pilot study. Patients were simulated with a full bladder (1 cup, 45min prior). The simulated bladder was contoured and then a script automatically generated four possible "min reference contours as a contraction by 1, 2, 3, and 4 cm from the superior bladder border. The smallest reference contour that still met our bladder dose constraints was selected as the min_bladder to be used to guide pre-treatment setup. Radiation therapists and treating physicians were instructed to consider bladder filling sufficient if the volume on the cone-beam CT (CBCT) upon visual inspection appeared larger than the min_bladder reference even if smaller than the simulated bladder. Approved CBCTs were used to evaluate bladder and bowel dosimetry. Treatment time (first kV image to beam-off) and number of CBCTs were compared to 66 consecutive patients treated prior to introducing the min-bladder reference contour.The average simulated bladder, min_bladder, and treated bladder sizes were 398 ± 139cc, 157 ± 54cc and 300 ± 150cc, respectively. There was 1 of 100 total fractions where bladder constraints were exceeded, however the approved CBCT bladder volume was less than the min_bladder reference and the total cumulative bladder dose for this patient was within constraints. Average cumulative max bowel dose was 14.5 Gy in 5 fractions with a maximum cumulative max bowel dose 32.5 Gy in 5 fractions. Compared to our historical average treatment time of 31.5 ± 20 min/fraction, the pilot study average was 26 ± 15 min/fraction (P = 0.003). Average number of CBCTs/fraction also decreased from 1.38 ± 0.69 to 1.24 ± 0.60 (P = 0.048). Based on our annual SBRT treatment volume, we estimate that use of this reference contour will save > 150 hours and > 260 CBCTs per year in our department.Our results suggest that the reference contour accurately predicted the minimum bladder volume needed to avoid exceeding bladder constraints, did not inadvertently overexpose bowel, and significantly reduced treatment time and number of pre-treatment CBCTs. A similar reference contour is now being developed for other prostate definitive and post-op regimens at our institution.

Escalating Tumor Dose via Simultaneous Integrated Boost (SIB) Stereotactic Body Radiation Therapy (SBRT) for Large (> 5 cm) Lung Masses

SBRT treatments of large (> 5.0 cm, diameter) lung masses with ablative dose is challenging due to toxicity. We report on a novel centrally-dose-escalated simultaneous integrated boost (SIB) SBRT technique for fast, safe, and effective method that allow for dose escalation to the tumor core while protecting adjacent organs at risk (OAR).Twelve patients with large (mean = 7.0 cm, range: 5.2-7.8 cm, diameter) lung masses from at least Stage II non-small-cell lung cancer (NSCLC) or oligometastatic lung disease from a separate primary site underwent 50 Gy to the planning target volume (PTV) with a 60 Gy SIB to the volume approximately 1 cm interior to the standard gross tumor volume (GTV) margin in 5 fractions. Highly conformal SIB SBRT plans were generated using 3-6 non-coplanar partial VMAT arcs with 6MV-FFF beam and advanced Acuros-based dose engine for tissues heterogeneity corrections. Treatments were delivered every other day using online conebeam CT guidance. Plan quality and treatment delivery efficiency were reported. Outcomes reported include tumor local control (LC), distant failure (DF), lung and rib toxicity. Median follow-up interval was 8 months (1 to 22 months).Mean GTV and PTV was 92.9 ± 40.0 cc and 188.8 ± 45.4 cc. Mean dose to GTV and PTV was 58.1 ± 1.9 Gy and 55.5 ± 1.2 Gy, translating to the corresponding average biological effective dose (BED10, with α/β = 10Gy) of 125 Gy and 117 Gy, respectively. All SIB SBRT plans met RTOG requirements for intermediate dose fall-off and organs at risk (OAR) sparing. Mean values of V20Gy, V10Gy and mean lung dose were 13.6 ± 3.4%, 22.9 ± 6.8%, and 7.5 ± 1.8Gy, respectively. Average maximal doses to OAR were as follows: spinal cord < 12.5 Gy, heart < 33.9 Gy, esophagus < 17.7 Gy, ribs < 48.2 Gy and skin < 23.9 Gy. Average beam-on time was 3.5 ± 0.3 min. Estimated mean treatment time including pre-treatment conebeam CT imaging and patient repositioning was within 15 min. All patients tolerated the SIB-SBRT treatment. 10 patients demonstrated LC, 1 had definite progression, and 1 had ostensible progression with atelectasis complicating the picture. The three patients with oligometastatic disease from stage IV head and neck or sarcoma progressed elsewhere, although the treated site was well controlled. One patient had evidence of grade 2 chest wall pain and treated with NSAIDS; however, 11 patients showed no evidence of rib fracture or chest wall pain. No patients developed grade 2+ pulmonary toxicity or radiation-induced pneumonitis.Escalating core tumor dose via SIB-SBRT (higher than 100Gy BED10) is safe, fast, and efficacious treatment for large lung masses with promising LC rates and no adverse treatment related toxicity. Fast delivery of SIB SBRT treatment could reduce intrafraction motion error due to coughing or pain, making geographic miss unlikely and improving the patient comfort and clinic workflow. Longer clinical follow up results in a larger patient population treated with this approach is warranted.

Skeletal effects of mini-implant assisted rapid palatal expansion (MARPE) on the sagittal dimensions of the maxilla an in-vivo cone-beam computed tomography (CBCT) study

Introduction -Transverse discrepancies of the maxilla are one of the most prevalent skeletal problems. Due to drawbacks of conventional RPE and invasive surgical expansion methods alternative methods were developed such as Mini Implant-supported rapid maxillary expansion (MARPE).Haas17 , Davis and Kronman18, Akkaya et al19 and many other studies have reported the maxillary response after MARPE on the sagittal dimensions, but their results were inconclusive.&#x0D; Aim - This study analyzed the effects on the maxilla in the sagittal dimension after Mini Implant assisted rapid palatal expansion (MARPE) in adolescents using CBCT.&#x0D; Material and method -A pretreatment CBCT image (T1) was taken as a standard initial record for all patients and post treatment CBCT (T2) was taken after three months in retention. The parameters SNA angle, Frankfort horizontal plane to NA angle, A-N perpendicular, ANS –PNS were measured and calculated for evaluation of the sagittal maxillary changes. Comparisons were then made between the two treatment groups (T1, T2).&#x0D; Result -There was a positive increase in both angular and linear measurements from pretreatment to post treatment measurements showing significant skeletal changes in sagittal dimension.&#x0D; Conclusion -The study concludes that there was statistically significant forward displacement of maxilla after transverse skeletal expansion in patients with transverse problems achieved through MARPE in adolescent patients.

Does the protocol-required uniform margin around the CTV adequately account for setup inaccuracies in whole breast irradiation?

PurposeTo use cone-beam computed tomography (CBCT) imaging to determine the impacts of patient characteristics on the magnitude of geometric setup errors and obtain patient-specific planning target volume (PTV) margins from the correlated patient characteristics in whole breast irradiation (WBI).MethodsBetween January 2019 and December 2019, a total of 97 patients who underwent breast-conserving surgery, followed by intensity-modulated radiation therapy in WBI, were scanned with pre-treatment CBCT for the first three treatment fractions and weekly for the subsequent fractions. Setup errors in the left–right (LR), superior–inferior (SI) and anterior–posterior (AP) directions were recorded and analyzed with patient characteristics—including age, tumor location, body mass index (BMI), chest circumference (CC) and breast volume (BV)—to examine the predictors for setup errors and obtain specific PTV margins.ResultsA total of 679 CBCT images from 97 patients were acquired for analysis. The mean setup errors for the whole group were 2.32 ± 1.21 mm, 3.71 ± 2.21 mm and 2.75 ± 1.56 mm in the LR, SI and AP directions, respectively. Patients’ BMI, CC and BV were moderately associated with setup errors, especially in the SI directions (R = 0.40, 0.43 and 0.22, respectively). Setup errors in the SI directions for patients with BMI > 23.8 kg/m2, CC > 89 cm and BV > 657 cm3 were 4.56 ± 2.59 mm, 4.77 ± 2.42 mm and 4.30 ± 2.43 mm, respectively, which were significantly greater than those of patients with BMI ≤ 23.8 kg/m2, CC ≤ 89 cm and BV ≤ 657 cm3 (P < 0.05). Correspondingly, the calculated PTV margins in patients with BMI > 23.8 kg/m2, CC > 89 cm and BV > 657 cm3 were 4.25/7.95/4.93 mm, 4.37/7.66/5.24 mm and 4.22/7.54/5.29 mm in the LR/SI/AP directions, respectively, compared with 3.64/4.64/5.09 mm, 3.31/4.50/4.82 mm and 3.29/5.74/4.73 mm for BMI ≤ 23.8 kg/m2, CC ≤ 89 cm and BV ≤ 657 cm3, respectively.ConclusionsThe magnitude of geometric setup errors was moderately correlated with BMI, CC and BV. It was recommended to set patient-specific PTV margins according to patient characteristics in the absence of daily image-guided treatment setup.

Retrospective evaluation of planning margins for patients undergoing radical radiation therapy treatment for bladder cancer using volumetric modulated arc therapy and cone beam computed tomography.

IntroductionCurrent contouring guidelines for curative radiation therapy for muscle‐invasive bladder cancer (MIBC) recommend margins of 1.5–2.0 cm, applied to the clinical target volume (CTV). This study assessed whether the use of volumetric modulated arc therapy (VMAT), cone beam computed tomography (CBCT) and strict bladder preparation allowed for a reduced planning target volume (PTV) expansion, resulting in lower doses to surrounding organs at risk (OARs).MethodsDaily CBCT images for 12 patients (382 scans total) were retrospectively reviewed against four potential PTV margins created on and exported with the reference CT scan. To form the PTVs, three isotropic expansions of 0.5, 1.0 and 1.5 cm were applied to the CTV, as well as an anisotropic expansion of 1.5 cm superiorly and 1.0 cm in all other dimensions. Following treatment completion, the CBCTs were visually assessed to determine the margins encapsulating the bladder. For retrospective planning purposes, the 1.0‐cm and anisotropic margins were compared with the previously recommended margins to determine differences in OAR doses.ResultsThe 0.5‐, 1.0‐ and 1.5‐cm isotropic margins (IM) and the anisotropic margin (ANIM) covered the CTV in 46.1, 96.8, 100 and 100% of CBCTs retrospectively. Doses to OARs were significantly lower for the reduced margin plans for the small bowel, rectum and sigmoid.ConclusionBladder planning target volumes may be safely reduced. We endorse a PTV margin of 1.0cm anteriorly, posteriorly and inferiorly with 1.0–1.5 cm superiorly for radical whole bladder cases using strict bladder preparation, VMAT and pretreatment CBCTs.

Cone-beam computed tomography analysis of the nasal morphology among Uyghur nationality adults in Xinjiang for forensic reconstruction

IntroductionFacial reconstruction or approximation is the procedure of rebuilding a face onto an anonymous skull to aid identification in forensic and archaeological or paleobiological cases. In the procedure of facial identification, the relationship between hard and soft tissues of the face needs to be identified. The aim of this study is to investigate the shape variability and sexual dimorphism of the nose by using cone-beam computed tomography (CBCT) scans and establish normal values for the nasal form among Uyghur adults. Materials and methodsA total of 258 pre-treatment CBCT images of Uyghur adults (120 males and 138 females, aged 18–30 years old) were retrospectively retrieved from orthodontic clinical data. The three-dimensional parameters of the nasal soft structures and hard structures were measured. All CBCT images were traced using Dolphin 11.95 software. All statistical analyses were performed using SPSS 22.0. ResultsStatistically significant differences were observed in terms of the nasal length, nasal height, nasal depth, and nasal tip angle between the Uyghur males and females. Uyghur males had longer dorsa and increased vertical distances from the pronasale to the posterior columellar point compared with females. ConclusionsThese results suggest that gender and ethnicity must be considered when establishing normal values for the nasal form and its relationship to the other cranial structures. The clinical significance of this study is that hard and soft tissue relation data from CBCT can be useful for predicting the position of the nose. The values of the nasal form are useful for facial reconstruction and rhinoplasty.

Dosimetric impact of rectum and bladder anatomy and intrafractional prostate motion on hypofractionated prostate radiation therapy.

The objective of this study was to evaluate the dosimetric impact on hypofractionated prostate radiation therapy of two geometric uncertainty sources: rectum and bladder filling and intrafractional prostate motion. This prospective study included 544 images (375 pre-treatment cone-beam CT [CBCT] and 169 post-treatment CBCT) from 15 prostate adenocarcinoma patients. We recalculated the dose on each pre-treatment CBCT once the positioning errors were corrected. We also recalculated two dose distributions on each post-treatment CBCT, either using or not intrafractional motion correction. A correlation analysis was performed between CBCT-based dose and rectum and bladder filling as well as intrafraction prostate displacements. No significant differences were found between administered and planned rectal doses. However, we observed an increase in bladder dose due to a lower bladder filling in 66% of treatment fractions. These differences were reduced at the end of the fraction since the lower bladder volume was compensated by the filling during the treatment session. A statistically significant reduction in target volume coverage was observed in 27% of treatment sessions and was correlated with intrafractional prostate motion in sagittal plane > 4mm. A better control of bladder filling is recommended to minimize the number of fractions in which the bladder volume is lower than planned. Fiducial mark tracking with a displacement threshold of 5mm in any direction is recommended to ensure that the prescribed dose criteria are met.

Clinical Implications of Geometric and Dosimetric Uncertainties of Inter- and Intra-Fractional Movement during Volumetric Modulated Arc Therapy for Breast Cancer Patients.

Simple SummaryRadiotherapy is an essential treatment modality for breast cancer. Compared to conventional radiotherapy techniques, modern radiotherapy with fewer fractions and smaller target volumes requires higher accuracy. Image-guidance using cone-beam computed tomography (CBCT) is one of the most common methods used for positional verification before treatment. This study reports geometric and dosimetric outcomes evaluated by analyzing CBCT images acquired before and during treatments. The positional change and internal movement of the patient were less than 1 cm in most cases without significant deviation in the dosimetric parameters of interest. However, there were cases involving extreme variation, which resulted in insufficient radiation delivered to the target areas and increased radiation exposure to adjacent normal organs. The results of the current study suggest that unexpected intra-fractional motion may occur, prompting for marginal adaptation in selected patients who are deemed to suffer from this kind of event.With the introduction of modern sophisticated radiotherapy (RT) techniques, the significance of accuracy has increased considerably. This study evaluated the necessity of pre-treatment and intra-fractional cone-beam computed tomography (CBCT) by analyzing inter- and intra-fractional CBCT images of breast cancer patients receiving RT. From 57 patients, 1206 pre-treatment CBCT and 1067 intra-fractional CBCT images were collected. Geometric movements of patients were measured quantitively in both inter- and intra-fractional CBCT, and changes in dosimetric parameters were evaluated in selected patients with extreme intra-fractional movement. For right-sided breast cancer patients, left-sided breast cancer patients treated using deep-inspiration breath hold (DIBH), and left-sided breast cancer patients treated using continuous positive airway pressure (CPAP), median inter-fractional deviations were 0.53 (range 0.06–2.98) cm, 0.66 (range 0.08–4.41) cm, and 0.69 (range 0.04–3.80) cm, and median intra-fractional deviations were 0.14 (range 0.00–0.62) cm, 0.23 (range 0.02–0.96) cm, and 0.24 (0.00–1.15) cm, respectively. Modified plans reflecting large changes in intra-fractional position in 10 selected cases revealed insufficient target coverage in seven cases and more than 20-fold increase in the volume of heart receiving at least 25 Gy in two cases. Intra-fractional verification, as well as pre-treatment verification, might be considered in patients using DIBH or CPAP.

Correlation between midpalatal suture stage on cone-beam CT images and its cervical vertebral maturation stage for 1 076 Chinese children and youth

Objective: To investigate the correlation between cone-beam CT (CBCT) morphological stage of midpalatal suture (MPS) and cervical vertebral maturation stage (CS) of Chinese children and youth. Methods: This study was a retrospective observational study. A total of 1 076 CBCT images (male: 401, female: 675, age≥ 6.0 years old and<21.0 years old) taken from January 2013 to April 2018 in Peking University School and Hospital of Stomatology were included. MPS and CS of each sample were recorded according to previous studies. MPS included five stages: MPS 1, MPS 2, MPS 3, MPS 4s1 (substage), MPS 4s2 (substage), and MPS 5. CS included six stages: CS 1-6. Correlation between MPS and CS (ordinal categorical variables) was investigated by Spearman correlation coefficient and diagnostic test analysis. Results: Spearman coefficient between CS and MPS was 0.803. Diagnostic pairs with the best diagnostic performance include: CS 6-MPS 5, CS 5-MPS 4s2, CS 1-MPS 1, CS 4-MPS 4s1, CS 2-MPS 1, CS 3-MPS 3. The 90.9% (309/340) of individuals at CS 1-3 were at MPS 1-3 and 9.1% (31/340) were at MPS 4s1. The 33.0% (107/324) of individuals at CS 4 were at MPS 3 and 46.6% (151/324) were at MPS 4s1. Conclusions: CS has a close relationship with MPS. Individuals at CS 4 are recommended to take pre-treatment CBCT, so as to estimate feasibility of skeletal expansion with traditional tooth-borne rapid maxillary expansion.

Volumetric Evaluation of Pharyngeal Airway after Functional Therapy.

The aim of this study was to evaluate three-dimensional (3D) effects of Twin-block functional appliance (TB) on the pharyngeal airway by using cone beam computed tomography (CBCT). A total of 30 patients (14 females, 16 males; mean age 12.50 ± 1.23 and 12.83 ± 1.17 years, respectively) with skeletal Class II malocclusion were included in this study and were treated with TB. On the pretreatment (T1) and posttreatment (T2) CBCT scans, volumetric changes in the pharyngeal airway; SNA, SNB, and ANB angles; and bilateral effective mandibular (Co-Gn) and midfacial length (Co-A) were also evaluated. The statistical differences were accessed by Wilcoxon signed-rank tests, and Mann-Whitney U tests were used to analyze the scores of male and female subjects. In this study, an increase was observed in SNB and Co-Gn (p < 0.01) while a decrease in ANB and SNA (p < 0.01 and p < 0.05, respectively) was found. However, increase in midfacial length was not statistically significant (p > 0.05). In the evaluation of volumetric pharyngeal airway changes, statistically significant increases (p < 0.01) in the upper and lower division and total airway volume were determined. Gender differences were insignificant for all measurements (p > 0.05). Volumetric changes in the pharyngeal airway after functional therapy can be successfully evaluated by CBCT images. The anterior repositioning of the mandible by TB increases the mandibular length and pharyngeal airway volume in patients with retrognathic mandible.

A cone-beam computed tomographic study evaluating the efficacy of incisor movement with clear aligners: Assessment of incisor pure tipping, controlled tipping, translation, and torque

This retrospective clinical study aimed to evaluate the efficacy of different types of incisor movementswith clear aligners in the sagittal plane. Pretreatment and posttreatment cone-beam computed tomography (CBCT) scans were collected from 69 patients who underwent nonextraction treatment with clear aligners (Invisalign; Align Technology, San Jose, Calif). Integrated 3-dimensional models of the virtual incisor position (ClinCheck; Align Technology) and the posttreatment incisor position (from posttreatment CBCT scans) were superimposed over the pretreatment position (from pretreatment CBCT scans) using Mimics software (Materialise, Leuven, Belgium). On the basis of the location of the rotation center, incisors showing pure tipping (>10°), controlled tipping (>10°), translation (>1mm), or torque (>10°) movements were selected. Efficacy was determined by comparing the predicted and achieved incisor movement, and differences with efficacy were analyzed using Kruskal-Wallis and Shapiro-Wilk tests (α=0.05). In measurements for 231 incisors, the mean efficacy of incisor movements in the sagittal plane was 55.58%. The most and least predictable movements were pure tipping (72.48%) and torque (35.21%), respectively. Labial root movement was significantly more predictable than lingual root movement, and labial movement of the mandibular incisors was significantly easier than that of the maxillary incisors. The type of tooth movement achieved was different from the type designed. The efficacy of incisor movement in the sagittal plane using clear aligners varies with designed movement type, and labial root movement appears to be more accurate than the lingual root movement. The biomechanics of clear aligners remains to be further elucidated to achieve more predictable treatment results.

Evaluation of skeletal changes in mandibular ramus height, corpus length, and mandibular angle changes following twin block appliance therapy using cone-beam computed tomography: A clinical prospective study

Aim and Objectives: This study aims to evaluate the skeletal changes in mandibular ramus height, corpus length, and mandibular angles changes following twin block (TB) functional appliance therapy using cone-beam computed tomography (CBCT).Methodology: Fifteen patients with skeletal Class II, growing of 9–14 years of age with mandibular retrognathism, were treated with TB functional appliance treatment. Pretreatment CBCT and posttreatment CBCT were taken (T0) before treatment and (T1) at the end of the 12 months following TB therapy. The data obtained are analyzed and compared for the skeletal changes in ramus height, corpus length, and mandibular angle changes following therapy. Student's paired t-test was used compare the pre- and post-treatment periods.Results: The test results demonstrate that the Ramus height (mm) in posttreatment period was significantly increased as compared to pretreatment period. The mean increase of 1.23 mm in the ramus height between pre- and post-treatment period was statistically significant at P < 0.001, and that the corpus length (mm) in posttreatment period was significantly increased as compared to pretreatment period. The mean increase of 3.35 mm in the corpus length between pre- and post-treatment period was statistically significant at P < 0.001, and demonstrate that the mean gonial angle (degrees) in posttreatment period was significantly increased as compared to pretreatment period. This mean increase of 3.18° in the gonial angle between pre- and post-treatment period was statistically significant at P < 0.001.Conclusion: TB appliance therapy increases the ramus height, and corpus length stimulating the growth of condyle in backward and upward direction and increases the gonial angle by backward rotation of mandible.

Prediction of treatment response to transarterial radioembolization of liver metastases: Radiomics analysis of pre-treatment cone-beam CT: A proof of concept study

PurposeTo investigate the potential of texture analysis and machine learning to predict treatment response to transarterial radioembolization (TARE) on pre-interventional cone-beam computed tomography (CBCT) images in patients with liver metastases. Materials and MethodsIn this IRB-approved retrospective single-center study 36 patients with a total of 104 liver metastases (56 % male, mean age 61.1 ± 13 years) underwent CBCT prior to TARE and follow-up imaging 6 months after therapy. Treatment response was evaluated according to RECIST version 1.1 and dichotomized into disease control (partial response/stable disease) versus disease progression (progressive disease). After target lesion segmentation, 104 radiomics features corresponding to seven different feature classes were extracted with the pyRadiomics package. After dimension reduction machine learning classifications were performed on a custom artificial neural network (ANN). Ten-fold cross validation on a previously unseen test data set was performed. ResultsThe average administered cumulative activity from TARE was 1.6 Gbq (± 0.5 Gbq). At a mean follow-up of 5.9 ± 0.8 months disease control was achieved in 82 % of metastases. After dimension reduction, 15 of 104 (15 %) texture analysis features remained for further analysis. On a previously unseen set of liver metastases the Multilayer Perceptron ANN yielded a sensitivity of 94.2 %, specificity of 67.7 % and an area-under-the receiver operating characteristics curve of 0.85. ConclusionOur study indicates that texture analysis-based machine learning may has potential to predict treatment response to TARE using pre-treatment CBCT images of patients with liver metastases with high accuracy.

Root dilaceration in maxillary impacted canines and adjacent teeth: A retrospective analysis of the difference between buccal and palatal impaction

This research aimed to analyze the prevalence of root dilaceration in buccally impacted canines (BICs) and palatally impacted canines (PICs) with their adjacent teeth based on a retrospective cone-beam computed tomography (CBCT) investigation. Pretreatment CBCT images of 145 subjects with unilateral maxillary canine impaction and 145 age- and sex-matched subjects without impaction were used. Prevalence of dilaceration (subclassified to root curvature and apical hook based on severity) in canines and adjacent teeth was determined in CBCT records. The root length of maxillary impacted canines was measured for further morphologic evaluations. Impacted canines had a significantly higher prevalence of root dilaceration than the control group and compared with the erupted contralateral canines in the experimental group (P<0.001 for both). A significantly higher prevalence of root dilaceration was found in adjacent lateral incisors of the PICs subgroup than that of the control group (P<0.001). Adjacent premolars had a higher prevalence of dilacerated roots in the PICs subgroup (P<0.001) than the control group, but not for the BICs subgroup. Significantly higher prevalence of curvature (P<0.001 for both) and hook (P=0.008 and P<0.001, respectively) were found in BICs and PICs roots compared with the control group. Both types of impacted canines had significantly shorter roots than the control group (P<0.001 for both). BICs and PICs have a higher tendency to present root dilaceration and shorter roots. Unlike BICs, adjacent teethto PICs were more frequently observed to have root dilaceration.

Chinese morphological stages of midpalatal suture and its correlation with Demirjian dental age

Objective To investigate the correlation between morphological stages of midpalatal suture (MPS) and Demirjian dental age. Methods In this retrospective study, 1 076 cone-beam CT (CBCT) images (female: 675, male: 401; age range: 6.0 to 21.0 years) were included. Horizontal view of each sample's CBCT images was observed, each sample's MPS stage was recorded, and dental age. MPS stage and dental age were ordered with categorical variables. Therefore, their correlation was investigated through Spearman correlation coefficient analysis and diagnostic test analysis. Results (1) For left lower second premolar: 95.2% of those in dental age stage B-D were in MPS 1-2, accounting for the largest proportion. 85.3% of those in dental age stage E were in MPS 1-2, still accounting for the largest proportion. Another 14.7% were in MPS 3.45.1% of those in dental age stage F were in MPS 3, 46.1% in MPS 1-2, and another 8.8% in MPS 4s1.49.8% of those in dental age stage G were in MPS 3.24.9% in MPS 4s1, and 18.9% in MPS 1-2.80.1% of those in dental age stage H were in MPS 4-5. Another 16.3% were in MPS 3. (2) For left lower second molar: 89.7% of those in dental age stage B-D were in MPS 1-2, accounting for the largest proportion. 67.4% of those in dental age stage E were in MPS 1-2, still accounting for the largest proportion. Another 26.1% were in MPS 3.55.3% of those in dental age stage F were in MPS 3, 34.2% in MPS 1-2, and another 10.5% in MPS 4s1.50.7% of those in dental age stage G were in MPS 3, 24.3% in MPS 4s1, and 16.8% in MPS 1-2.83.8% of those in dental age stage H were in MPS 4-5, another 14.2% were in MPS 3. (3) To diagnose MPS stage with dental age, diagnostic pairs with good performance included: Dental age of left lower second molar-MPS: H-4s2, H-5, D-1; Dental age of left lower second premolar-MPS: H-4s2, H-5, G-3. Other diagnostic pairs were of ordinary diagnostic efficiency. (4) For dental age-MPS Spearman correlation analysis, dental age of left lower second molar-MPS had the highest Spearman coefficient (0.68), dental age of left lower second premolar-MPS was the second high (0.64). (5) Dental age stage H of left lower second molar or left lower second premolar indicated that the individual was later than MPS 4s2. Conclusion Dental age's diagnostic efficiency for MPS stage is ordinary on the whole, except for some pairs with good performance. Therefore, pre-treatment CBCT examination should be considered as assistance for evaluating maturation and fusion status of midpalatal suture.

A Qualitative Assessment of Bone Mineral Density in Individuals With Hemifacial Microsomia: A Cone-Beam Computed Tomography Study.

The purpose of this study is to utilize cone-beam computed tomography (CBCT) to compare the bone mineral density (BMD) on the affected versus nonaffected side, among individuals with hemifacial microsomia (HFM). This retrospective study included 9 patients with HFM. Pretreatment CBCT volumes were imported into Invivo5 software, which was used to measure BMD through Hounsfield units (HU) in 3 regions of the mandible; inferior to the lower lateral incisors, inferior to the first molar and at the ramus inferior to the sigmoid notch. Each region was measured at the buccal cortical bone, lingual cortical bone, and cancellous bone. The densities on the right and left sides were compared by Wilcoxon signed-rank test. Overall, the BMD on the affected side tended to show slightly lower values when compared with the nonaffected side. Differences ranged from 14 HU at the lingual cortical plate of the first molar region to 234 HU at the buccal cortical plate of the ramus region. Differences were only statistically significant at the ramus region for the buccal (P = .002) and lingual (P < .001) cortical plates and at the lower incisor region at the buccal cortical plate (P = .016) and cancellous bone (P = .044). The differences, however, did not seem to be clinically significant. The current study shows that the quality of bone on the affected side may be slightly reduced but did not seem to be clinically significant. This should be accounted for during surgical and orthodontic planning for patients with HFM.

The use of tumour markers in oesophageal cancer to quantify setup errors and baseline shifts during treatment

PurposeTo prospectively evaluate the feasibility of solid gold marker placement in oesophageal cancer patients and to quantify inter-fractional and intra-fractional (baseline shift) marker motion during radiation treatment. Radiotherapy target margins and matching strategies were investigated. Materials/methodsThirty-four markers were implanted by echo-endoscopy in 10 patients. Patients received a planning 4D CT, daily pre-treatment cone-beam CT (CBCT) and a post-treatment CBCT for at least five fractions. For fractions with both pre- and post-treatment CBCT, marker displacement between planning CT and pre-treatment CBCT (inter-fractional) and between pre-treatment and post-treatment CBCT (intra-fractional; only for fractions without rotational treatment couch correction) were calculated in left–right (LR), cranio-caudal (CC) and anterior-posterior (AP) direction after bony-anatomy and soft-tissue matching. Systematic/random setup errors were estimated; treatment margins were calculated. ResultsNo serious adverse events occurred. Twenty-three (67.6%) markers were visible during radiotherapy (n = 3 middle oesophagus, n = 16 distal oesophagus, n = 4 proximal stomach). Margins for inter-fractional displacement after bony-anatomy match depended on the localisation of the primary tumour and were 11.2 mm (LR), 16.4 mm (CC) and 8.2 mm (AP) for distal markers. Soft-tissue matching reduced the CC margin for these markers (16.4 mm to 10.5 mm). The mean intra-fractional shift of 12 distal markers was 0.4 mm (LR), 2.3 mm (CC) and 0.7 mm (AP). Inclusion of this shift resulted in treatment margins for distal markers of 12.8 mm (LR), 17.3 mm (CC) and 10.4 mm (AP) after bony-anatomy matching and 12.4 mm (LR), 11.4 mm (CC) and 9.7 mm (AP) after soft-tissue matching. ConclusionThis study demonstrated that the implantation of gold markers was safe, albeit less stable compared to other marker types. Inter-fractional motion was largest cranio-caudally for markers in the distal oesophagus, which was reduced after soft-tissue compared to bony-anatomy matching. The impact of intra-fractional baseline shifts on margin calculation was rather small.

Clinical Utility of Deformable Image Registration in Early Prediction of Rectal Bleeding Risk in Prostate Cancer Radiotherapy

To evaluate the clinical utility of deformable image registration (DIR) in the early prediction of rectal bleeding in prostate cancer radiotherapy. 240 images (24 plan-CT and 216 pretreatment cone-beam CT (CBCT)) from 24 prostate adenocarcinoma patients were prospectively acquired during the first fifteen fractions of their real treatment (76 Gy in 38 fractions). After correlation with a deformable image registration (DIR), doses of a virtual treatment plan (57.3 Gy in 15 fractions) were mapped from each CBCT to the plan-CT, allowing the identification of patients who have exceeded the dose limitation for 50% of the rectum (R50). We classified patients according to whether or not they had fulfilled the R50 constraint and we compared with student t-test their variation rate (VR) = [100 x (dose delivered to R50 - planned dose to R50 / planned dose to R50)] during the first 5 sessions. Using Roc curves, we also studied if during these first fractions a value of VR could reliably predict the risk of not complying with the constraint and therefore the risk of rectal bleeding. 15 patients would have met the R50 limitation and 9 would not. Significant differences in the VR between both subgroups have been found in fractions 1, 3 and 5 (t = - 3.192, p = 0.008; t = - 5.683, p< 0,001; t = - 5,340, p< 0,001). In fraction 1, a value of VR > 0% would have predicted the risk of rectal overdosage with a sensitivity of 66.7% and a specificity of 73.3%. In fractions 3 and 5, a VR value > 1% would have predicted the risk of rectal overdosage in the same way, with a sensitivity of 100% and a specificity of 93.3%. After a median follow-up of 56.5 months there have been three rectal bleeding cases (with endoscopic confirmation), all of them would have been detected in fraction three with the VR value established as predictive of rectal toxicity. This study demonstrated the clinical utility of DIR in establishing already in fraction 3 a VR value (>1%) that reliably predicts the risk of rectal bleeding, even if we use a different schedule than the one used for its calculation.