Pretreatment Cone-beam Computed Tomography Research Articles

A target containing phantom for accuracy assessment of cone-beam CT-guided histotripsy.

Histotripsy is a nonionizing, noninvasive, and nonthermal focal tumor therapy. Cone-beam computed tomography (CBCT) guidance was developed for targeting tumors not visible on ultrasound. This approach assumes cavitation is formed at the geometrical focal point of the therapy transducer. In practice, the exact location might vary slightly between transducers. In this study, we present a phantom with an embedded target to evaluate CBCT-guided histotripsy accuracy and assess the completeness of treatments. Spherical (2.8cm) targets with alternating layers of agar and radiopaque barium were embedded in larger phantoms with similar layers. The layer geometry was designed so that targets were visible on pre-treatment CBCT scans. The actual histotripsy treatment zone was visualized via the mixing of adjacent barium and agar layers in post-treatment CBCT images. CBCT-guided histotripsy treatments of the targets were performed in six phantoms. Offsets between planned and actual treatment zones were measured and used for calibration refinement. To measure targeting accuracy after calibration refinement, six additional phantoms were treated. In a separate investigation, two groups (N=3) of phantoms were treated to assess visualization of incomplete treatments ("undertreatment" group: 2cm treatment within 2.8cm tumor, "mistarget" group: 2.8cm treatment intentionally shifted laterally). Treatment zones were segmented (3D Slicer 5.0.3), and the centroid distance between the prescribed target and actual treatment zones was quantified. In the calibration refinement group, a 2mm offset in the direction of ultrasound propagation (Z) was measured. After calibration refinement, the centroid-to-centroid distance between prescribed and actual treatment volumes was 0.5±0.2mm. Average difference between the prescribed and measured treatment sizes in the incomplete treatment groups was 0.5±0.7mm. In the mistarget group, the distance between prescribed and measured shifts was 0.2±0.1mm. The proposed prototype phantom allowed for accurate measurement of treatment size and location, and the CBCT visible target provided a simple way to detect misalignments for preliminary quality assurance of CBCT-guided histotripsy.

Cone Beam Computed Tomography (CBCT) Aid in the Management of Apical Root Resorption of Impacted Maxillary Canines and Physiologically Erupted Maxillary Canines after Orthodontic Treatment

The aim of this study is to evaluate the effects of orthodontic traction, by means of light and controlled forces, on root length in impacted maxillary canines and physiologically erupted maxillary canines. Disinclusion of impacted maxillary canines is a frequent procedure in orthodontics due to their higher incidence of impaction. The effects of orthodontic traction, by means of light and controlled forces, can lead to a resorption of the root length in impacted and physiologically erupted teeth. Therefore, apical root resorption is a common phenomenon that must be taken into consideration. Apical root resorption measurements were taken using pre-treatment CBCTs and pre-treatment and post-treatment digital panoramic radiographs of 52 patients who underwent fixed-appliance treatment by using light and controlled orthodontic forces. The experimental group consisted of 26 patients with one impacted maxillary canine. The control group consisted of 26 patients without any impaction. Apical root resorption was calculated from root lengths before and after orthodontic treatment. In the experimental group, impacted canines with incomplete apical formation underwent root elongation, while impacted canines with completed root formation went through apical root resorption. The latter showed a slightly greater apical root resorption (0.2 mm) compared to the control group (95% confidence interval; p = 0.04). The extent of root resorption of impacted canines was significantly higher than that of physiologically erupted ones. However, this differential resorption did not compromise the structural and functional integrity of the involved teeth. The orthodontic treatment performed with light and controlled forces is, therefore, a procedure to be considered acceptable and safe.

Prospective Evaluation of the Clinical Benefits of a Novel Tattoo-less Workflow for Nonspine Bone Stereotactic Body Radiation Therapy: Integrating Surface-Guidance With Triggered Imaging Reduces Treatment Time and Eliminates the Need for Tattoos

ObjectiveOligometastatic disease has expanded the indications for non-spine bone stereotactic body radiation therapy (NSB SBRT). We investigated whether optical surface monitoring systems (OSMS) could enable tattoo-less set up and substitute for 2D-3D or cone beam computed tomography (CBCT)-based mid-imaging in NSB SBRT. Materials/MethodsOSMS was incorporated in parallel with an existing workflow using pre-treatment CBCT and mid 2D-3D kV/kV imaging beginning 11/2019. The ability of OSMS to detect out-of-tolerance (>2mm/>2°) and commanded couch shifts was analyzed. A workflow incorporating OSMS reference captures, CBCT for pre-treatment verification and OSMS/triggered imaging (TI) for intrafraction monitoring was developed for rib/sternum SBRT beginning 11/2021 and all NSB SBRT beginning 2/2022. Treatment time and CBCT-related radiation dose between the OSMS and the non-OSMS intrafraction monitoring group was analyzed pre and post-OSMS/TI workflow adoption. All fractions were analyzed through statistical process control (SPC) with use of an XmR chart of treatment time per quarter from 2/2019 to 2/2023. Special cause rules were based on Institute for Healthcare Improvement criteria. ResultsFrom 2/2019 to 2/2023, 1993 NSB SBRT fractions were delivered, including 234 rib, 109 sternum, 214 ilium, and 682 multi-site. Over 20 commanded shifts, OSMS could detect 2mm shifts to within 0.4mm 67% of the time and 0.8mm 95% of time. All NSB SBRT sites showed significant reductions in treatment time, including the greatest improvement in rib total treatment (21.6 to 13.4 minutes, p=1.16*10−17) and beam time (7.9 to 3.2 minutes, p= 7.32*10−27). Significant reductions in CBCT-related radiation were also observed for several NSB sites. These process improvements were associated with OSMS adoption. ConclusionAdoption of a novel NSB SBRT workflow incorporating OSMS/TI for bone intrafraction motion monitoring reduced treatment time and CBCT-related radiation exposure while also allowing for more continuous intrafraction motion monitoring for NSB SBRT. OSMS/TI enabled the transition to a tattoo-less workflow.

Evaluation of kV Triggered Fiducial Tracking for Prostate SBRT Intrafraction Motion Management.

Stereotactic body radiation therapy (SBRT) is a safe and effective treatment for localized prostate cancer. Given the high dose per fraction, a high degree of precision is needed during SBRT treatment delivery. Fiducial marker tracking is a means of monitoring intrafraction motion, ensuring precise treatment delivery and potentially allowing for decreased planning target volume (PTV) margins. We present a 5-year single institution experience to characterize the performance of fiducial tracking. We analyzed 132 consecutive patients treated at our institution with prostate SBRT between July 2017 and November 2022 using fiducial tracking with the TrueBeam Auto Beam Hold feature. Patients were treated using a 5-fraction dose escalation protocol, with many receiving a simultaneous integrated boost to the GTV up to 45 Gy. All patients underwent pre-treatment cone-beam CT and planar kV imaging with rigid registration to the fiducial markers. Cine kV images were acquired every 3-5 seconds during treatment delivery and the beam was paused when a fiducial deviated from a given 4 mm diameter tolerance region. Additional intrafraction 2D or 3D imaging techniques were then used to realign the fiducials. Data was retrieved from the record and verify system including: number and type of intrafraction images, number of treatment interruptions, number of and magnitude of shifts, and total treatment time. The average number of cine kV images acquired per fraction and for the total 5 fraction SBRT course were 86.6 ± 26.8 and 425.6 ± 136.8 respectively. Assuming 1.3 mGy/kV image, the fiducial tracking process delivered an average additional 55.3 cGy over the full treatment course. On average, the beam was paused 5.0 ± 2.5 times per fraction (range 1-21 interruptions) and shifts were applied 4.1 ± 2.1 times (range 0-10.2 times) per fraction. Over the 2560 total shifts applied for all the patients, the average(max) translations were 0.6 (12) mm vrt, 0.7 (22) mm lng, and 0.9 (5) mm lat and the average(max) rotations were 0.19 (5.9)° pitch, 0.01 (2.4)° roll, and 0.16 (6.4)° rtn. Overall, 2.4% of shifts were greater than the 4 mm PTV margin and 4.2% of vertical shifts were greater than the 2.5 mm posterior margin. Average fraction treatment time was 27 ± 9.7 minutes. Fiducial tracking affords the potential to increase daily treatment precision when delivering prostate SBRT. Our data indicate that the beam is typically paused several times during a prostate SBRT fraction, with occasional large shifts required, suggesting the importance of intrafraction motion management. Downsides of kV triggered fiducial tracking include extension of treatment times and delivery of additional radiation dose to the patient. We are investigating if this method of motion management might allow for a reduction in PTV margins to reduce normal tissue dosing.

Reducing CTV to PTV Margins with Daily Adaptive Radiotherapy in the Postoperative Treatment of Endometrial and Cervical Cancer

In the postoperative treatment of endometrial and cervical cancer, a PTV expansion of 1.5cm or greater would be generally recommended to ensure adequate coverage of CTV with no or minimal image guidance. Online adaptive radiotherapy (oART) has demonstrated to be feasible to reduce inter-fractional radiotherapy errors as it re-optimizes treatment plan every fraction. In this study, we hypothesized using daily cone-beam computed tomography (CBCT)-guided oART would reduce CTV to PTV margins in the postoperative treatment of endometrial and cervical cancer. Seven patients from a single-center with postoperative endometrial and cervical cancer treated with daily CBCT-guided oART were retrospectively reviewed. A total dose of 45Gy is prescribed in CTV-vaginal cuff (CTV-V) and CTV- regional lymph nodes (CTV-N) with daily fractions of 1.8Gy for five fractions per week. A total of 175 radiotherapy fractions of daily pre-treatment CBCTs and post-treatment CBCTs scans were uploaded to oART emulator for CTV-V and CTV-N contouring by a single observer. CTVpre to PTVpre margins of 5, 7, 10, 12, 15mm was used in all directions. Each post-treatment CBCT was rigidly registered to the pre-treatment CBCT with respect to bony anatomy. The CTVpost was projected onto the PTVpre and assess required planning margins to encompass the CTVpost. The average total treatment time (post-treatment CBCTs - pre-treatment CBCTs) was 23 min 14s (range: 18min 53s ∼ 28min 53s). For all fractions, the adapted plan was selected, and the volume of the PTV-V and PTV-N receiving 100% of the prescribed dose or more (V100%) was more than required 95%. A uniform three-dimensional CTV-Npre to PTV-Npre margin of 5mm could encompass CTV-Npost in all fractions (100%; 175/175f). A uniform three-dimensional CTV-Vpre to PTV-Vpre margin of 10mm could encompass CTV-Vpost in all fractions (100%; 175/175f) and 5mm could encompass 98% fractions (172/175f). In the fractions of 5mm margins that failed to encompass CTV-Vpost, the volume of CTV missed three times in anterior-posterior directions and once in lateral direction. Compared with scheduled plan, adapted plan with 5mm margins significantly reduced the mean dose to bladder (Dmean: 103.97 cGy vs 107.20 cGy, P<0.05) and rectum (Dmean: 117.82 cGy vs 123.67 cGy, P<0.05), and achieved better PTV-N (V100%: 97.8% vs 90.0%, P<0.05) and PTV-V (V100%:96.8% vs 85.4%, P<0.05) dose coverage in 175 fractions. In this study, 5mm CTV to PTV margins was adequate to encompass 100% fractions of CTV-N and 98% fractions of the CTV-V. Adapted plan with 5mm margins significantly reduced the dose to critical organ at risks while improving target coverage.

Escalating SBRT Dose to Hypoxic Centers of Large Pulmonary Tumors via Simultaneous Integrated Boost Confers Effective Local Control with Minimal Toxicity

Hypoxia confers radio-resistance to tumor cells and drives malignant disease progression. SBRT treatment of large (>5.0 cm) pulmonary tumors pose significant dosimetric challenges in minimizing dose to adjacent organs at risk (OARs). Here, we detail the use of SBRT with simultaneous integrated boost (SIB) to the hypoxic centers of large pulmonary masses with effective local control and minimal normal tissue toxicity. Highly conformal treatment plans utilized 3-4 non-coplanar VMAT arcs with 6MV-FFF (1400 MU/min) and 4D-CT on TrueBeam to deliver 50 Gy in 5 fractions to the planning target volume (PTV). SIB dose of 60 Gy was delivered to a 1-cm internal margin from the gross tumor volume (GTV). Dose was calculated using Acuros-based engine. Pre-treatment Conebeam CT imaging was used for patient setup and verification. Treatments were delivered in < 15 minutes. Patients underwent post-treatment clinical evaluation and CT imaging in 3-month intervals to assess changes in tumor size and post-radiation sequelae. Clinical outcomes reported include treatment response and toxicity. Twenty-six patients with large, centrally (n = 13) or peripherally (n = 13) located tumors were evaluated; this included 16 NSCLC patients with T2-T3N0 disease and 5 with pulmonary metastases from distant sites. One patient had declined surgery, while 25/26 (96.1%) were deemed medically inoperable. All plans met RTOG-0813 requirements for target coverage and dose to OARs. Median follow-up interval was 11 months (0 to 23 months). Twenty-one of 26 (80.7%) patients received post-treatment CT imaging within 6 months of SBRT. Local control was achieved in 20/21 (95.2%) patients; one patient with a peripherally located tumor progressed outside the treatment field. Acute toxicity profile amongst the 25 patients assessed included grade 1 fatigue (n = 2), grade 1 rib pain (n = 1), and grade 2 pulmonary fibrosis (n = 1). Otherwise, 22/25 (88%) patients reported no radiation induced toxicities. Subgroup analysis was performed on patients with centrally located tumors, defined as located <2 cm from the hilum, heart, or bronchial trees. One of 13 (7.6%) patients with central tumors reported grade 1 rib pain; otherwise, no radiation induced adverse effects were observed. All patients with centrally located lung tumors experienced local control on surveillance imaging. SBRT with SIB to the hypoxic centers of large pulmonary masses is a safe, efficacious treatment that confers improved local control while maintaining dose to adjacent OARs. This study demonstrates the feasibility of delivering doses up to 60 Gy to the hypoxic centers of large lung tumors, while decreasing local tumor burden, minimizing treatment mobility, and improving clinic workflow. SBRT with SIB shortens treatment course to 5 fractions (in contrast to the traditional daily 30 fractions), thus improving patient comfort and compliance.

Subregional pharyngeal changes after orthognathic surgery in skeletal Class III patients analyzed by convolutional neural networks-based segmentation

ObjectivesTo evaluate the accuracy of fully automatic segmentation of pharyngeal volume of interests (VOIs) before and after orthognathic surgery in skeletal Class III patients using a convolutional neural network (CNN) model and to investigate the clinical applicability of artificial intelligence for quantitative evaluation of treatment changes in pharyngeal VOIs. Methods310 cone-beam computed tomography (CBCT) images were divided into a training set (n = 150), validation set (n = 40), and test set (n = 120). The test datasets comprised matched pairs of pre- and post-treatment images of 60 skeletal Class III patients (mean age 23.1 ± 5.0 years; ANB<-2⁰) who underwent bimaxillary orthognathic surgery with orthodontic treatment. A 3D U-Net CNNs model was applied for fully automatic segmentation and measurement of subregional pharyngeal volumes of pre-treatment (T0) and post-treatment (T1) scans. The model's accuracy was compared to semi-automatic segmentation outcomes by humans using the dice similarity coefficient (DSC) and volume similarity (VS). The correlation between surgical skeletal changes and model accuracy was obtained. ResultsThe proposed model achieved high performance of subregional pharyngeal segmentation on both T0 and T1 images, representing a significant T1–T0 difference of DSC only in the nasopharynx. Region-specific differences amongst pharyngeal VOIs, which were observed at T0, disappeared on the T1 images. The decreased DSC of nasopharyngeal segmentation after treatment was weakly correlated with the amount of maxillary advancement. There was no correlation between the mandibular setback amount and model accuracy. ConclusionsThe proposed model offers fast and accurate subregional pharyngeal segmentation on both pre-treatment and post-treatment CBCT images in skeletal Class III patients. Clinical significanceWe elucidated the clinical applicability of the CNNs model to quantitatively evaluate subregional pharyngeal changes after surgical-orthodontic treatment, which offers a basis for developing a fully integrated multiclass CNNs model to predict pharyngeal responses after dentoskeletal treatments.

Evaluation of Dental Root Development Regarding Maxillary Canine Eruption Status after Secondary Alveolar Bone Grafting in Patients with Cleft Lip and Palate.

In children born with cleft lip and palate, the timing of the secondary alveolar bone graft (SABG) is crucial to its success; this involves estimating the eruption of the permanent maxillary canine. Altered dental eruption in this patient group gives impetus to the identification of dental developmental factors concerning maxillary canine eruption, which may steer the clinical decision of SABG timing. Records of over nine hundred patients who received SABG with pre- and post-operative cone beam computed tomography (CBCT) scans were analyzed for inclusion and divided into two groups (erupting or non-erupting canine after SABG). Roots of the maxillary canines and premolars were segmented from the cementoenamel junction then linear and volumetric measurements were performed. The pre- and post-operative root length and volume differences were calculated and compared statistically using independent sample tests and paired t-tests. No statistically significant differences were found in the volume change (%), or reciprocal of mean root length in the erupted and unerupted groups in the canine, first premolar, or second premolar roots except for an association between the post-operative dental root length of the canine and the maxillary canine eruption status. Therefore, assessment of root development from pre-treatment CBCT scans was not deemed worthy from a diagnostic perspective.

Using the Finite Element Method to Determine the Odonto-Periodontal Stress for a Patient with Angle Class II Division 1 Malocclusion.

The finite element method (FEM) is a computational method that can solve all biomechanical problems, including the field of orthodontics. The purpose of this virtual experimental study is to determine the behavior of a real orthodontic system subjected to different systems of loads. To analyze the real orthodontic system, we studied the case of a 21-year-old female patient. We used the InVesalius program, which can transform a set of DICOM-type images taken from cone beam computed tomography (CBCT) into three-dimensional structures. These structures were edited, modified, completed, and analyzed from a geometric point of view with the help of the Geomagic software. The final result of these operations must be a three-dimensional model made up of perfectly closed surfaces so that they can be transformed into virtual solids. The model consisting of perfectly closed surfaces is loaded into computer-aided design (CAD) programs. Bracket and tube components, as well as orthodontic wires, can be added to these models, similar to the analyzed patient's tissues. When the model is complete and geometrically correct, it is exported to a program that uses FEM, such as Ansys Workbench. The simulation was performed for the forces of 0.5, 0.6, 0.7, 0.8, 0.9, and 1 N. The intention was to determine the behavior of the entire orthodontic system for these force values. After running the simulations, result maps were obtained that were composed of displacement, strain, and stress diagrams. It was also found that, in addition to the known rigidity, the orthodontic system has some elasticity due to the orthodontic wires, as well as the periodontal ligaments. Thus, a virtual analysis study can be carried out starting from a real patient with pre-treatment CBCT images and the virtual models of the bracket and tube elements and of the orthodontic wires.

Evaluation of changes in the maxillary sinus of orthodontic patients with maxillary molar distalization using cone-beam computed tomography

This study aimed to evaluate the possible effects of maxillary molar distalization on maxillary sinus mucosa thickness and sinus volume in 3-dimensions. The study was conducted with 46 patients: 73.9% (n= 34) females and 26.1% (n= 12) males. The patients had a mean age of 27.89 ± 6.62 years, ranging from 18 to 45 years. The study included patients who were admitted to the Faculty of Dentistry at Van Yüzüncü Yıl University between 2010 and 2021 and underwent cone-beam computed tomography (CBCT) before and after orthodontic treatment for various reasons. The CBCT scans of patients were divided into 2 groups: the first group underwent orthodontic treatment and maxillary molar distalization with Class II elastic, whereas the second group consisted of patients who did not get orthodontic treatment (control). In CBCTs, sinus mucosa thickness was measured on the anterior, posterior, medial, lateral, superior, and inferior walls of the maxillary right and left sinuses. Three-dimensional volume calculations were made using CBCT images taken before and after the treatment of both orthodontic treatment patients and control patients. Statistical significance was set at P<0.05. The orthodontic treatment group had a mean distalization of 2.86 ± 0.27 mm. The mean distalization time was 8.01 ± 0.64 months. When the differences between the pretreatment and posttreatment CBCT scans were examined in terms of sinus mucosa thickness in the anterior, posterior, medial, lateral, and superior walls of the right and left sinuses, there was no statistically significant difference between treatment and control groups (P>0.05). The change in sinus mucosa thickness in the right and left sinus inferior wall from T1 to T2 was significantly higher in the control group than treatment group (P<0.05). In addition, the increase in maxillary sinus volume was statistically significantly higher in the treatment group than in the control group (P<0.05). We observed that maxillary molar distalization caused an increase in maxillary sinus volume. The change in sinus mucosa thickness in the right and left sinus inferior wall was lower in the maxillary molar distalization group.

Comparison of two 3-dimensional user-friendly voxel-based maxillary and 2-dimensional superimposition methods

Cephalometric superimpositions have many uses in orthodontics, including growth evaluation and outcome assessment. However, 2-dimensional (2D) cephalograms can be distorted and yield incomplete 2D data. Cone-beam computed tomography (CBCT) imaging provides a 3-dimensional (3D), undistorted, and more complete patient analysis. CBCT imaging provides many unique advantages to the orthodontic practice and can influence how treatment outcomes are assessed. This study aimed to investigate the validity of 3D maxillary voxel-based superimpositions compared with the 2D method recommended by the American Board of Orthodontists. This retrospective study included pretreatment and posttreatment CBCT images of 30 adolescent patients. The images were superimposed using the 3D voxel-based tools in Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). Two different 3D anatomic registration areas (3DA-3DB) were tested for the validity and reproducibility of the 3D maxillary superimpositions as compared with the 2D method. Linear and angular measurements were used to evaluate the dental changes of the maxillary right central incisor and first molar. Data distribution was normal by the Shapiro-Wilk W test. A mixed model analysis of variance test was done to compare the 3 superimposition types within each subject, followed by pairwise Tukey-Kramer comparisons when indicated. After applying the Benjamini-Hochberg procedure to control the false discovery rate at 0.05 with multiple testing, the U1 vertical difference was statistically significant (P<0.0001) for the superimposition method, though the mean differences were clinically nonsignificant (0.52 mm, 0.76 mm). The U1 angular and U6 vertical differences were not statistically significant for the superimposition method (P= 0.3636 and P= 0.1863, respectively). The 3D voxel-based maxillary superimpositions showed similar results to conventional 2D superimpositions recommended by the American Board of Orthodontists.

Five-Fraction Stereotactic Ablative Radiotherapy to the Pelvis and Prostate with Focal Intra-Prostatic Boost: Outcomes of the 5STAR Trial

<h3>Purpose/Objective(s)</h3> Focal boost of the dominant intraprostatic lesion (DIL) improves oncological outcomes in unfavorable-risk prostate cancer (PCa). We hypothesized that MRI-directed DIL boost could be safely and tolerably integrated with 5-fraction stereotactic ablative radiotherapy (SABR) targeting the prostate and pelvic lymph nodes. <h3>Materials/Methods</h3> This single-institution, phase I/II trial enrolled men with high-risk and unfavorable-intermediate PCa (NCT02911636). Patients underwent MRI to delineate the DIL and planning CT with urethrogram. Treatment consisted of 25 Gy to the elective pelvic lymph nodes & seminal vesicles, 35 Gy to the prostate, and up to 50 Gy DIL boost in 5 weekly fractions. Implanted fiducials, endorectal immobilization (GU-Lok), and pre-treatment cone beam CT were utilized. Patients also received androgen deprivation therapy (ADT, 6-18 months). The primary outcome was grade ≥3 genitourinary (GU) or gastrointestinal (GI) toxicity (CTCAE v4.0). Secondary outcomes included quality of life (QoL) and biochemical failure defined by the Phoenix criteria. <h3>Results</h3> Thirty men (63.3% high-risk, 23% grade group 5) were enrolled between January and August 2017. All patients received ADT. The DIL received a median D90% of 48.3 Gy. At median follow-up of 55.1 months (interquartile range: 52.8-59.5), there were no grade ≥ 3 toxicities. Cumulative incidence of worst acute grade 2 GU & GI toxicity was 56.7% and 16.7%, respectively. Cumulative incidence of late grade 2 GU & GI toxicity was 73.3% and 20.0% with prevalence of 50.0% and 13.3%, respectively. Mean nadir PSA (±standard deviation, SD) was 0.056 ng/mL (±0.096), achieved at a median of 16.7 months (1.9-23.4) post-treatment. At last follow-up, mean PSA was 0.22 ng/mL (±0.31). A single patient experienced biochemical failure (3.3%) in the form of an out-of-field, non-regional nodal recurrence. QoL data collection is ongoing using patient-reported outcomes and will be presented subsequently. <h3>Conclusion</h3> The 5STAR trial met its primary endpoint, demonstrating safety and tolerability of integrated focal DIL boost with pelvic & prostate SABR for unfavorable-risk PCa. Our encouraging oncological efficacy data are among the first to be reported at medium-term (4–5-year follow-up) using this particular treatment strategy. These results support further investigation in a randomized setting.

Medical Imaging Utilization Trends in Radiation Oncology over the Past Decade

<h3>Purpose/Objective(s)</h3> We quantify the increase in use of pre-treatment imaging and verification imaging in radiation oncology over the past decade. We also quantify the trend towards hypofractionation, which has partially led to increased imaging. <h3>Materials/Methods</h3> The pre-treatment and verification imaging data used are from a single, tertiary, university-affiliated cancer center. Pre-treatment imaging was defined as magnetic resonance imaging (MRI), positron emission tomography (PET) and four-dimensional computed tomography (4DCT). Verification imaging was defined as cone-beam computed tomography (CBCT). All treatment approved plans were included from 2012 to 2021. Data extraction was performed using custom scripts interfacing with the treatment planning system (TPS) and patient information system. All registered image-sets of planning CT images with either advanced pre-treatment advanced imaging or verification images in the TPS were included. Hypofractionation sub-analysis was performed according to plans above and below 4 Gy per fraction that received a combination of pre-treatment and verification imaging. <h3>Results</h3> Between 2012 and 2021, a total of 42,214 plans were included. In 2021, MRI, PET, and 4DCT pre-treatment imaging modalities were used for 14%, 5%, and 3% of patients, respectively, which was an increase from 5%, 2%, and 0%, in 2012. In 2021, 55% of patients received CBCT for verification imaging compared to only 2% of patients in 2012. In the sub-analysis, cohort receiving greater than or equal to 4 Gy per fraction from 2012 to 2021, the percent of patients receiving one of MRI or PET for pre-treatment imaging and CBCT guidance for verification imaging increased from 1% to 22%. For the cohort receiving less than 4 Gy per fraction, there was an increase from 2012 to 2021 of 0% to 14% of patients receiving at least one of MRI or PET pretreatment imaging and CBCT for verification imaging. Table 1: Annual use of advanced pre-treatment, verification imaging, hypofractionation, and associated combination imaging shown. Entries indicate the percent (%) of patients per year with the imaging modality used in their treatment. <h3>Conclusion</h3> An increase in the adoption of advanced medical imaging was observed in standard of care treatments over the past 10 years. Imaging utilization continues to increase as clinical trial evidence matures. Further analysis could focus on the gap between desired standard of care for patients and the current offerings as well as the increase in capital and human resource requirement for implementation of these advancements.

An Analysis of PTV Margins for Postoperative Pelvic Nodal Radiotherapy (PNRT) Using a Dose Accumulation Workflow

<h3>Purpose/Objective(s)</h3> PTV margins are created to ensure coverage of the target volume. There is no uniform consensus on the PTV margins for prostate bed radiotherapy. Our institution's PTV margins for prostate bed are 8mm everywhere but posterior - a size that leads to PTVs on the order of 2.5 times the prostate bed. We hypothesized that the current PTV margins for prostate bed is larger than necessary in the context of daily cone-beam CT (CBCT)-guided intensity-modulated arc therapy. <h3>Materials/Methods</h3> Nineteen PCa patients treated with daily CBCT-guided intensity-modulated arc therapy were studied. Patients received 68 Gy to the prostate bed (PTV68) and 52.7 Gy to the elective pelvic nodes (CTV52.7, no PTV margins), all in 34 fractions. Patients followed strict bladder and rectal preparation protocols and had daily pretreatment CBCT images. Patient data, consisting of planning CTs and 7 representative CBCTs (1/week), were anonymized. Using a dose accumulation workflow, synthetic CTs (sCT) were created from the planning CTs and the representative CBCTs. Volumes were deformed to the sCT and checked for consistency. The sCTs were sent to the planning system, and a single fraction of the treatment plan was recalculated on the sCT. These daily dose distributions were used to assess target coverages and OAR doses on a daily/weekly basis. <h3>Results</h3> One hundred and thirty-three CBCTs were assessed. In 100% of the fractions, at least 97% of the prostate bed was covered by the prescription dose. Only 2 patients had a max, mean, and median dose to the prostate bed less than planned (though the mean, max and median doses were all greater than 2Gy/fx) at approximately 1 cGy below a value planned per fraction; the remaining 17 patients were at or above the aforementioned planned doses. Though the CTV52.7 coverage dropped slightly compared to the original plan, in 100% of the fractions the CTV52.7 received a median dose equal to or higher than planned. In 74% of the fractions, at least 95% of CTV52.7 was covered by 95% of the prescription dose. In 100% of the fractions at least 90% of the CTV52.7 received 90% of the planned prescription dose. On average there was a 2% difference in the volumes of OARs at the V40, V65 and maximum dose points. <h3>Conclusion</h3> Our results suggest that, in the context of daily CBCT-guided postoperative RT with strict bladder and rectal preparation protocols, a PTV margin of 8 mm everywhere and 6 mm posteriorly is sufficient if not slightly larger than needed. Further studies on margin reduction and its clinical implications are warranted.

Cone-beam computed tomography assessment of maxillary anterior alveolar bone remodelling in extraction and non-extraction orthodontic cases using stable extra-alveolar reference.

To explore alveolar cortical positional change in response to tooth movement in extraction and non-extraction orthodontic cases, using cone-beam computed tomography (CBCT) and stable extra-alveolar references. The pre-treatment (T1) and post-treatment (T2) CBCT scans of 25 extraction (EXT) and matched 25 non-extraction (Non-EXT) orthodontic cases were imported into Dolphin Imaging 3D, and oriented uniformly. Sagittal and axial CBCT cross-sections were traced using customized software-generated guides. The displacement of teeth and alveolar bone cortices were automatically measured using the palatal plane (PP) and the line perpendicular to PP and passing Sella as reference. Intra- and inter-group differences between T1 and T2 were analysed. Subjects were also superimposed three-dimensionally using Geomagic Control X for qualitative analysis of cortical remodelling. The EXT group showed incisor retraction, while the Non-EXT group exhibited statistically significant incisor anterior tipping (P < .05). In EXT, both the labial and palatal cortices are resorbed. Non-EXT showed labial cortex anterior modelling, and statistically significant palatal cortex resorption (P < .05). In both groups, statistically significant decrease in total and palatal alveolar widths, increase in labial widths, and palatal dehiscence were observed. Comparatively, EXT showed significantly more incisal total and palatal width decrease and palatal vertical bone loss. Labial cortical remodelling was shown to follow anterior tooth movement, but the palatal cortical response to incisor retraction and labial cortical remodelling in general remained inconclusive. Narrowing of the alveolar housing and palatal dehiscence were observed regardless of extraction following orthodontic treatment.

The outcome of endodontic treatment using an enhanced infection protocol in specialist practice.

Objectives This study aims to determine the outcome of primary root canal treatment with specific enhanced infection control protocol. The secondary aim was to compare percentages of successful outcomes in this study with a previous study undertaken by the same operator using both periapical radiograph (PR) and cone beam computed tomography (CBCT).Materials and methods Root canal treatment of 110 teeth in 95 patients carried out by a single operator using an enhanced infection control procedure (disinfection of gutta percha before obturation, changing of gloves after each intraoperative radiograph and also before the start of the root canal obturation). PR and CBCT scans of 94 teeth in 87 patients were assessed 12 months after completion of primary root canal treatment and compared with their respective pre-treatment (diagnostic) PR and CBCT scans. Healing was assessed by a consensus panel consisting of two calibrated examiners. Comparison of the PR and CBCT images for 'healed' and/or 'healing' outcomes was performed using McNemar's test.Results The 'healed' rate (absence of periapical radiolucency) was 89.4% using PR and 78.7% for CBCT (p <0.046). This rate increased to 95.7% for PR and 92.6% for CBCT when the 'healing' group (reduced size of periapical radiolucency) was included (p <0.046).Conclusion The frequent changing of gloves during the course of endodontic treatment and disinfection of gutta percha points before obturation, together with the use of contemporary rotary files, resulted in a high success rate of primary root canal treatment compared to similar clinical studies conducted previously.

Assessment of pharyngeal airway in Korean adolescents according to skeletal pattern, sex, and cervical vertebral maturation: A cross-sectional CBCT study.

ObjectiveTo investigate airway volumes using cone-beam computed tomography (CBCT) by skeletal patterns, sex, and cervical vertebral maturation (CVM) stages in Korean adolescents.MethodsThe sample consisted of pretreatment CBCT and cephalograms of 95 adolescents (aged 12–19) obtained out of 1,611 patients examined for orthodontic treatment from 2018 to 2020 in Kyungpook National University Dental Hospital. The samples were classified into two sex groups; three skeletal pattern groups, four chronological age groups and four CVM stages. Nasopharyngeal volumes (NPV), oropharyngeal volumes (OPV), total pharyngeal airway volume (TAV) and minimum cross-sectional area (MCA) measurements were taken from the CBCT. Multiple linear regression analyses to find out which one of the independent variables are good predictors for airway variables. Significant factors were analyzed by two-way multivariate analysis of variance (MANOVA) then multiple comparisons were analyzed using a t-test, and Fisher least significant difference.ResultsAge, sex, CVM, and Sella-Nasion-B point have significant influence on airway variable. Males and females showed similar patterns of change in chronological age groups 1–3; however, males had larger NPV, OPV, and MCA at CVM in group 4. According to CVM stages, males had larger OPV, TAV, and MCA at CVM stage 6 (p-value 0.019, 0.021, 0.015, respectively) and no sex differences at CVM stages 3, 4, and 5.ConclusionsSkeletal patterns have an effect on airway volume. Sex differences were found in CVM 6.

Reducing ExacTrac intrafraction imaging uncertainty for prostate stereotactic body radiotherapy using a pre-treatment CBCT.

This study evaluated the intrafractional auto-matching uncertainties of prostate-implanted fiducial markers when using the ExacTrac v6.5 (Brainlab, Feldkirchen, Germany) X-ray stereoscopic system. A customised phantom with 3 implanted gold seeds was initially positioned at the isocentre using a cone beam CT (CBCT) prior to intrafractional imaging. Progressive offsets were applied to the phantom in all six directions (3 translational, 3 rotational) of 0mm, 1mm, 2mm, 0°, 1° and 2°. Subsequently, the ability of the ExacTrac image-matching functions to detect and correct these offsets was tested. For comparison, this procedure was repeated, but without a CBCT for pre-treatment positioning. The auto-matching uncertainties when a CBCT was introduced into the workflow were significantly reduced, and overall, the auto-matching statistics using the implanted marker (seeds) matching function was found to be more precise than the bony anatomy function in-phantom. The total standard deviations for the translational shifts using the implanted marker and bony anatomy functions respectively were 0.1mm and 0.3mm vertically, 0.1mm and 0.3mm longitudinally, and 0.1mm and 0.4mm laterally. The standard deviations for the rotational shifts using the implanted marker and bony anatomy matching functions respectively were 0.2° and 1.2° for the yaw (angle vert), 0.3° and 1.1° for the pitch (angle long), and 0.2° and 1.2° for the roll (angle lat) directions. The reduced uncertainties from introducing a CBCT for initial localisation resulted in decreased probability of inhibits due to false positives during treatment.

Operator Performance of the Digital Setup Fabrication for Orthodontic-Orthognathic Treatment: An Explorative Study.

The purpose of this study was to explore the operator performance of the fabrication of digital orthodontic setups integrated into cone beam computed tomography (CBCT) scans. Fifteen patients who underwent a combined orthodontic–orthognathic surgical treatment were included. The pre-treatment digital dental models and CBCT scans were fused, and four operators made virtual setups twice for all patients. Differences between the virtual setups were calculated by recording tooth crown movement from the pre-treatment model to the virtual setup. To examine performance, Pearson’s correlation coefficients, duplicate measurement errors, and inter-operator differences were calculated. For intra-operator performance, correlation values varied among tooth types, with mean correlation values from 0.66 to 0.83 for the maxilla and 0.70 to 0.83 for the mandible. For inter-operator performance, mean correlation values varied from 0.40 to 0.87 for the maxilla and from 0.44 to 0.80 for the mandible. Rotational mean differences exceeded the range of clinical acceptance (>2 degrees) at 18% for the maxilla and 20.8% for the mandible, and translational mean differences exceeded the range of clinical acceptance (0.6 mm) at 9.7% and 26% for the maxilla and mandible, respectively. The intra- and inter-operator performance of digital orthodontic setup construction for virtual three-dimensional orthognathic planning shows significant errors.

Effect of orthodontic maxillary posterior en masse intrusion anchored with miniplates on maxillary sinuses volume. Retrospective CBCT study

ObjectiveTo evaluate, by means of cone beam computed tomography (CBCT), the volume change of maxillary sinuses in patients that underwent orthodontic maxillary posterior en masse intrusion anchored with miniplates. Materials and methodsThe sample consisted of pretreatment (T1) and posttreatment (T2) CBCT scans obtained from 14 patients (4 male and 10 female), with a mean age of 32.4 years, that underwent orthodontic maxillary posterior en masse intrusion anchored with miniplates in the zygomatic crest. The mean treatment duration was 20 months and the mean intrusion movement was 2.4 mm. Maxillary sinus volume was measured by means of the software ITK SNAP (version 3.8.0) in T1 and T2 CBCT scans. The changes in sinuses volume were calculated by T1-T2 values. Data were analyzed statistically with Wilcoxon test at 5% of level of significance and the method error was analyzed with Wilcoxon test, intraclass correlation and Dahlberg's formula. ResultsThe mean difference (T1-T2) was -242.85 mm³ (p = 0.396) for the right sinus and -32.5 mm³ (p = 0.875) for the left sinus. A slight increase in the volume of the sinuses was shown although these results were not statistically significant. ConclusionThe orthodontic maxillary posterior en masse intrusion anchored with miniplates did not influence significantly the maxillary sinus volume.