Craniocaudal Direction Research Articles

Customized implants for acetabular Paprosky III defects may be positioned with high accuracy in revision hip arthroplasty

In revision hip arthroplasty, custom-made implants are one option in patients with acetabular Paprosky III defects. In a retrospective analysis, we identified 11 patients undergoing cup revision using a custom-made implant. The accuracy of the intended position of the implant was assessed on post-operative 3D CT and compared to the pre-operative 3D planning in terms of inclination, anteversion, and centre of rotation. In addition, the accuracy of post-operative plain radiographs for measuring implant position was evaluated in relation to the 3D CT standard. We found a mean deviation between the planned and the final position of the custom-made acetabular implant on 3D CT of 3.6° ± 2.8° for inclination and of - 1.2° ± 7.0° for anteversion, respectively. Restoration of center of rotation succeeded with an accuracy of 0.3mm ± 3.9mm in the mediolateral (x) direction, - 1.1mm ± 3.8mm in the anteroposterior (y) direction, and 0.4mm ± 3.2mm in the craniocaudal (z) direction. The accuracy of the post-operative plain radiographs in measuring the position of the custom-made implant in relation to 3D CT was 1.1° ± 1.7° for implant inclination, - 2.6° ± 1.3° for anteversion and 1.3mm ± 3.5mm in the x-direction, and - 0.9mm ± 3.8mm in the z-direction for centre of rotation. Custom-made acetabular implants can be positioned with good accuracy in Paprosky III defects according to the pre-operative planning. Plain radiographs are adequate for assessing implant position in routine follow-up.

Elective nodal irradiation or involved-field irradiation in definitive chemoradiotherapy for esophageal squamous cell cancer: a retrospective analysis in clinical N0 patients.

We compared failure patterns and survival after elective nodal irradiation (eni) or involved-field irradiation (ifi) in patients with thoracic esophageal squamous cell carcinoma (escc), clinical stage T2-4N0M0, to determine whether ifi is feasible for such patients. Between 2005 and 2015, 126 patients with clinical stage T2-4N0M0 thoracic escc who received definitive concurrent chemoradiotherapy in Shandong Cancer Hospital and Institute and who had complete data, were analyzed retrospectively. Of those patients, 49 received ifi, and 77 received eni. In the ifi group, the radiation field included the primary tumour, with a 3-cm to 4-cm margin in the craniocaudal direction, and the elective irradiation was delivered to the adjacent regional lymphatics according to the location of the primary tumour. Patterns of failure were classified using the first site of failure, which included primary tumour failure, regional lymph node failure, and distant metastasis. Median progression-free survival was 20 months [95% confidence interval (ci): 7.87 months to 39.2 months] in the ifi group and 30 months (95% ci: 17.4 months to 44.6 months) in the eni group (p = 0.580). Median overall survival (os) was 36 months (95% ci: 21.9 months to 50.1 months) in the ifi group and 38 months (95% ci: 26.1 months to 49.9 months) in the eni group (p = 0.761). The estimated 1-year, 3-year, and 5-year os rates were, respectively, 87.8%, 49.4%, and 32.3% for the ifi patients and 92.2%, 52.0%, and 28.9% for the eni patients. Disease persistence and primary lesion recurrence after complete remission (cr) were the most frequent causes of treatment failure in the patients overall (83 of 124, 66.9%). Of the 66 patients achieving a clinical cr, 25 experienced recurrence of the primary lesion, 12 experienced distant relapse, 10 experienced regional nodal failure, and 2 experienced an isolated recurrence. No significant differences in the pattern of failure or in the incidences of grade 3 or greater treatment-related myelosuppression or esophagitis were found between the ifi and eni groups. In patients with thoracic escc clinical stage T2-4N0M0 receiving definitive chemoradiotherapy, failure patterns and os were similar with either eni or ifi. Large prospective randomized studies are needed to further investigate and verify those results in this subgroup of patients.

Descriptive study of ultrasound images of the upper airway obtained after insertion of laryngeal mask

Abstract Objective To evaluate clinical usefulness of ultrasound images of the upper airway in order to check correct laryngeal mask placement. Material and methods A prospective observational study was conducted on patients scheduled for abdominal surgery under general anaesthesia, in whom the patency of the upper airway was ensured using an Ambu®AuraGain™ laryngeal mask. An ultrasound scan was performed of the upper-airway in the cranio-caudal direction and with longitudinal scans in the anterior midline and parasagittal axis, in three moments: before, after inserting and after removing the mask. All recorded images were evaluated for a second time by an expert radiologist in upper-airway ultrasound. Subsequently, the ultrasound data were related to the clinical difficulty of the insertion and presence of air leaks. Results Data were collected from 30 patients (20 females and 10 males) being operated on for abdominal hysterectomy (15), eventroplasty (6), uterine myomectomy (3), and umbilical (4) and inguinal herniorrhaphy (2). The blind insertion of the masks did not present difficulties in 24 (80%) patients. Air leakage was detected in eight (26.7%) patients, which was moderate in seven cases and severe in one. The ultrasound findings confirmed good mask placement in 22 (73.3%) patients. Anatomical airway changes after laryngeal mask extraction were only observed in three (12%) patients, all of them minor. There was a statistically significant association (p Conclusions Upper-airway ultrasound is a useful diagnostic method to evaluate laryngeal mask placement. Laryngeal oedema was not observed after removal of the device.

Comparison of Different Registration Methods on Patient Set-Up Error During Volumetric Modulated Arc Therapy Using Cone-Beam CT Imaging for Lung Cancer

Background: The three-dimensional image-guided radiation therapy is very important in volumetric modulated arc therapy (VMAT) to enhance accuracy throughout the course of a patient's radiation treatment. The image guidance can ensure the safe administration of prescribed radiation dose to the patient. Aim: This study investigated patient set-up uncertainties based on three different registration methods in cone bean CT (CBCT) using volumetric modulated arc therapy (VMAT) for different clinical sites. Methods: A total of 396 CBCT performed for lung VMAT plan for patient set-up verification as per institution image guidance protocol. The approved CT images were transferred from treatment planning system (TPS) to x-ray volumetric imaging system (XVI) for reference image registration. The set-up errors in mediolateral (ML), craniocaudal (CC) and anterioposterior (AP) direction were determined using grayscale matching between the reference CT image and onboard CBCT images. For the current study, patient set-up verification was performed based on clip-box registration (CBR) for image matching. By considering clip-box registration as a reference, other two registration methods of mask registration (MR) and dual registration (DR) (clip-box and mask) were performed for comparison. To compare three registration methods, systematic error (∑), random error (σ), mean displacement, mean set-up error and maximum error were analyzed. Results: The systemic and random errors were less in clip-box registration as compared with other two registration ( P > 0.05). Similarly, maximum error, mean displacement error and mean set-up errors were observed less in clip-box registration as compared with mask and dual registration ( P > 0.05). However, statically no significant difference was observed between three different registration methods ( P > 0.05). Conclusion: All three registration methods can be used for patient set-up accuracy for lung VMAT plan. However, the current study suggested that clip-box method will be more efficient as compared with mask and dual registration methods.

Predicting tumour motion during the whole radiotherapy treatment: a systematic approach for thoracic and abdominal lesions based on real time MR

IntroductionAim of this study was to investigate the ability of pre-treatment four dimensional computed tomography (4DCT) to capture respiratory-motion observed in thoracic and abdominal lesions during treatment. Treatment motion was acquired using full-treatment cine-MR acquisitions. Results of this analysis were compared to the ability of 30 seconds (s) cine Magnetic Resonance (MR) to estimate the same parameters. MethodsA 4DCT and 30 s cine-MR (ViewRay, USA) were acquired on the simulation day for 7 thoracic and 13 abdominal lesions. Mean amplitude, intra- and inter-fraction amplitude variability, and baseline drift were extracted from the full treatment data acquired by 2D cine-MR, and correlated to the motion on pre-treatment 30 s cine-MR and 4DCT.Using the full treatment data, safety margins on the ITV, necessary to account for all motion variability from 4DCT observed during treatment, were calculated.Mean treatment amplitudes were 2 ± 1 mm and 5 ± 3 mm in the anteroposterior (AP) and craniocaudal (CC) direction, respectively. Differences between mean amplitude during treatment and amplitude on 4DCT or during 30 s cine-MR were not significant, but 30 s cine-MR was more accurate than 4DCT. Intra-fraction amplitude variability was positively correlated with both 30 s cine-MR and 4DCT amplitude. Inter-fraction amplitude variability was minimal. ResultsMean baseline drift over all fractions and patients equalled 1 ± 1 mm in both CC and AP direction, but drifts per fraction up to 16 mm (CC) and 12 mm (AP) were observed. Margins necessary on the ITV ranged from 0 to 8 mm in CC and 0 to 5 mm in AP direction. Neither amplitude on 4DCT nor during 30 s cine MR is correlated to the magnitude of drift or the necessary margins in both directions. ConclusionLesions moving with small amplitude show limited amplitude variability throughout treatment, making passive motion management strategies seem adequate. However, other variations such as baseline drifts and shifts still cause significant geometrical uncertainty, favouring real-time monitoring and an active approach for all lesions influenced by respiratory motion.

A novel tibial tuberosity advancement technique with cranial implant fixation (TTA CF): a pilot study in sheep

BackgroundCranial cruciate ligament rupture is the most frequent orthopedic disorder in human and animals. An array of surgical techniques have been described to stabilize the stifle joint in dogs, including intraarticular stabilization, extraarticular stabilization, and tibial osteotomy techniques. Tibial plateau leveling osteotomy and tibial tuberosity advancement with a lot of modifications are the most common. In this study we report the possibility of fixing the novel titanium implant for tibial tuberosity advancement with two screws in a craniocaudal direction. The aim of our study was to improve the clinical benefit of the tibial tuberosity advancement surgical technique where an attempt was made to reduce the number of screws and obtain a strong implant fixation with minimal bone traumatization. This way of attachment allows to distribute the forces evenly on medial and lateral side of osteotomy gap.ResultsTibial tuberosity advancement with cranial implant fixation was performed in four sheep. Complete radiographic and clinical follow up was recorded. All four sheep had a complete osteotomy line healing at a mean of 10 weeks postoperative (range 8–12 weeks). None of the animals had osteotomy gap healing grades of poor. Minor complication included the minimally cracked Maquet hole on the postoperative radiographs, without displacement of the tibial crest which occurred in 2 sheep. Major complication grade 1, major complication grade 2 and catastrophic were not found.ConclusionsThe novel surgical technique for tibial tuberosity advancement with cranial implant fixation is technically comparable to the recent trend in tuberosity advancement techniques, where partial osteotomy of the cranial tibial tuberosity crest is performed. A cranial implant fixation allows to distribute the forces evenly on medial and lateral side of osteotomy gap, which may result in less number of major complications in dogs. A novel titanium implant decreases the tibial traumatisation by reducing the number of screws.

P132] Robust proton CSI planning in proteusone

Purpose This work studies the craniospinal irradiation (CSI) with pencil beam scanning proton therapy in an IBA Proteus® ONE gantry. Robust optimization can be used to create gradient-shaped field-junctions if robustness against setup uncertainties is considered in all dimensions. However, the number of scenarios to compute increases exponentially with the number of beams. In the case of Proteus® ONE, where the maximum field size is 20 × 24 cm2; at least four beams are typically needed to cover the whole craniospinal axis. This results in too many scenarios to be computed (7203 if 5 beams are used) and the optimization is not viable. In this work we investigated two possible solutions: (i) we limited the robust optimization to setup uncertainties in the craniocaudal direction only and (ii) we implemented the ancillary beam technique (ABT) proposed by Farace et al. (Acta Oncol 2015:54:1075–8). Methods Plans were generated with RayStation 6 on computed tomography images of two patients in supine position. Two lateral beams were used for brain irradiation, whereas three posterior beams were used to cover the spine. Approach 1 was optimized on the clinical target volume (CTV), considering robustness against setup uncertainties in the craniocaudal direction only (3 mm) and range uncertainties (3%). These settings reduced the number of scenarios to be computed to 729. For Approach 2, a planning target volume (PTV) was created as a 3-mm isotropic expansion of the CTV, and the ABT was implemented. The robustness of all plans was evaluated by simulating setup and range errors. Results Both approaches yielded an optimal nominal plan. For approach 1 a dose gradient was obtained through the junction, but the dose distribution for each individual beam was highly inhomogeneous in the anterior-posterior and left–right directions. Therefore, the plan was not robust to setup uncertainties in those directions. On the other hand, the ancillary beam method, together with the PTV, offered a homogeneous and robust dose distribution throughout the whole craniospinal axis. Conclusions The ancillary beam technique offered a superior plan quality and it is therefore the recommended solution to plan CSI irradiations in a Proteus® ONE proton therapy gantry.

Evaluation of Setup Errors at the Skin Surface Position for Whole Breast Radiotherapy of Breast Cancer Patients.

We used image-processing software to analyze the setup errors at the skin surface position of breast cancer patients (n=66) who underwent post-operative whole breast irradiation at our hospital in 2014-2015. The sixty-six digital reconstructed radiographs (DRR) were created at the treatment planning for each patient. The lineacgraphies (n=377) were taken after the patients' setup during radiotherapy. The lineacgraphies and DRR were superimposed at the skin surface position for each patient with the image-processing software. We measured the deviations of the isocenters for the nipple-lung (X) direction and craniocaudal (Y) direction and the deviation of the rotation angle of the XY axes between the lineacgraphy and DRR on the superimposed images. The systematic error (μ, Σ) and random error (σ) were calculated from the X and Y deviations and rotation angle deviation. The μ of X, Y, and rotation angle were 0.01 mm, -1.2 mm, and 0.05°, respectively. The Σ of X, Y, and rotation angle were 1.8 mm, 1.5 mm, and 0.9°, respectively. The σ of X, Y, and rotation angle were 2.0 mm, 1.5 mm, and 1.0°, respectively. Our analyses thus revealed that evaluations using image-processing software at the skin surface position in routine breast radiotherapy result in sufficiently small setup errors.

Quantification of variations in intra-fraction motion of esophageal tumors over the course of neoadjuvant chemoradiotherapy based on cine-MRI

To noninvasively quantify variation in intra-fraction motion of esophageal tumors over the course of neoadjuvant chemoradiotherapy (nCRT) using 2D cine-magnetic resonance imaging (MRI) series.Patients treated with nCRT for esophageal cancer underwent six MRI scans. Scans were acquired prior to the start of nCRT, followed by weekly MRI scans during nCRT. Cine-MRI series were acquired in the coronal and sagittal plane (≈1.6 Hz). To be able to quantify intra-fraction motion over a longer time period, a second cine-MRI series was performed after 10 min. Tumor motion was assessed in cranio–caudal (CC), anterior–posterior (AP) and left–right (LR) direction. Motion patterns were analyzed for the presence of deep inhales and tumor drift.A total of 232 cine-MRI series of 20 patients were analyzed. The largest tumor motion was found in CC direction, with a mean peak-to-peak motion of 12.7 mm (standard deviation [SD] 5.6), followed by a mean peak-to peak motion in AP direction of 3.8 mm (SD 2.0) and in LR direction of 2.7 mm (SD 1.3). The CC intra-fraction tumor motion can differ extensively between and within patients. Deep inhales were present in six of 232 scans (3%). After exclusion of these scans, mean CC peak-to-peak motion was12.3 mm (SD 5.2). Correction for tumor drift showed a further reduction to 11.0 mm (SD 4.6). Despite correction for tumor drift, a large variation in tumor motion occurred within patients during treatment. Mean tumor drift during the 10 min interval between the two series was 1.5 mm (SD 1.8), with a maximum of 11.6 mm.Intra-fraction tumor motion was found to be highly variable between and within patients with esophageal cancer over the course of nCRT. Correction for deep inhales and tumor drift reduced peak-to-peak motion. The stochastic nature of both deep inhales and tumor drift indicates that real-time tumor motion management during radiotherapy is a prerequisite to safely reduce treatment margins.

Amount of skin shrinkage affecting tumor versus grossly normal marginal skin of dogs for cutaneous mast cell tumors excised with curative intent.

OBJECTIVE To assess differences in skin shrinkage between grossly visible tumor and grossly normal marginal skin of dogs for cutaneous mast cell tumors (MCTs) excised with curative intent and to determine an equation to estimate postexcisional gross tumor margins from preexcisional measurements and vice versa. SAMPLE 19 cytologically confirmed and surgically excised cutaneous MCTs obtained from dogs. PROCEDURES Tumors were measured in craniocaudal and dorsoventral directions before excision, immediately after excision, and after fixation in formalin. Both grossly visible tumor and surrounding grossly normal skin that comprised the surgical margin were measured at each time point. Percentage of shrinkage was compared among time points and between the tumor and surrounding grossly normal skin. Patient and histopathologic variables were correlated to skin shrinkage. RESULTS Overall shrinkage was 17.70%. The amount of shrinkage within the grossly visible tumor (4.45%) was less than that within the surrounding grossly normal skin (24.42%). Most of the shrinkage occurred immediately after excision. There was no effect of age, sex, completeness of excision, or degree of edema. Accuracy of an equation to estimate postexcisional margins from preexcisional measurements was only 18.4%. CONCLUSIONS AND CLINICAL RELEVANCE Grossly evident MCTs of dogs shrunk less than did the grossly normal surrounding skin. Although an equation to estimate postexcisional margins from preexcisional measurements could be derived, it likely would need to contain additional variables not included in the study reported here. Until such an equation exists, care must be used when extrapolating surgical margins from histologic margins and vice versa.

Imágenes ultrasonográficas de vía aérea superior tras la inserción de mascarilla laríngea: estudio descriptivo y utilidad clínica

ObjectiveTo evaluate clinical usefulness of ultrasound images of the upper airway in order to check correct laryngeal mask placement. Material and methodsA prospective observational study was conducted on patients scheduled for abdominal surgery under general anaesthesia, in whom the patency of the upper airway was ensured using an Ambu®AuraGainTM laryngeal mask. An ultrasound scan was performed of the upper-airway in the cranio-caudal direction and with longitudinal scans in the anterior midline and parasagittal axis, in three moments: before, after inserting and after removing the mask. All recorded images were evaluated in a second time by a radiologist-expert in upper airway ultrasound. Subsequently, the ultrasound data were related to the clinical difficulty of the insertion and presence of air leaks. ResultsData was collected from 30 patients (20 females and 10 males) being operated on for abdominal hysterectomy (15), eventroplasty (6), uterine myomectomy (3), and umbilical (4) and inguinal herniorrhaphy (2). The blind insertion of the masks did not present difficulties in 24 (80%) patients. Air leakage was detected in 8 (26.7%) patients, which was moderate in 7 cases and severe in one of them. The ultrasound findings confirmed good mask placement in 22 (73.3%) patients. Anatomical airway changes after laryngeal mask extraction were only observed in 3 (12%) patients, all of them minor. There was a statistically significant association (P<.05) between difficulty in inserting the device and the level of air leakage. ConclusionsUpper airway ultrasound is a useful diagnostic method to evaluate laryngeal mask placement. Laryngeal oedema was not observed after removal of the device.

Head-mounted display augmented reality to guide pedicle screw placement utilizing computed tomography.

Augmented reality has potential to enhance surgical navigation and visualization. We determined whether head-mounted display augmented reality (HMD-AR) with superimposed computed tomography (CT) data could allow the wearer to percutaneously guide pedicle screw placement in an opaque lumbar model with no real-time fluoroscopic guidance. CT imaging was obtained of a phantom composed of L1-L3 Sawbones vertebrae in opaque silicone. Preprocedural planning was performed by creating virtual trajectories of appropriate angle and depth for ideal approach into the pedicle, and these data were integrated into the Microsoft HoloLens using the Novarad OpenSight application allowing the user to view the virtual trajectory guides and CT images superimposed on the phantom in two and three dimensions. Spinal needles were inserted following the virtual trajectories to the point of contact with bone. Repeat CT revealed actual needle trajectory, allowing comparison with the ideal preprocedural paths. Registration of AR to phantom showed a roughly circular deviation with maximum average radius of 2.5mm. Users took an average of 200s to place a needle. Extrapolation of needle trajectory into the pedicle showed that of 36 needles placed, 35 (97%) would have remained within the pedicles. Needles placed approximated a mean distance of 4.69mm in the mediolateral direction and 4.48mm in the craniocaudal direction from pedicle bone edge. To our knowledge, this is the first peer-reviewed report and evaluation of HMD-AR with superimposed 3D guidance utilizing CT for spinal pedicle guide placement for the purpose of cannulation without the use of fluoroscopy.

Improved Volumetric Modulated Arc Therapy Field Junctions Using In Silico Base Plans: Application to Craniospinal Irradiation

IntroductionField junctions present a major challenge for planning craniospinal irradiation (CSI) using volumetric modulated arc therapy (VMAT). In this study, the feasibility of using in silico base dose distributions for planning junctioned VMAT fields for CSI is assessed. MethodsAn in-house computer program was created to generate strategic base plans with controlled linear dose gradients across the junction. The algorithm was generalized to allow user-defined parameters such as number of junctions and junction length. In silico base plans were used to optimize junctioned VMAT CSI plans for a pediatric case and an adult case. Throughout optimization, dose to the eyes, kidneys, lungs, heart, and liver were minimized. Final plan quality was evaluated using the percent of planning target volume receiving at least 95% prescription dose (V95%), homogeneity index, and conformity number. Final plan robustness to setup error was evaluated using changes in near-minimum, median, and near-maximum doses defined as the most exposed 98%, 50%, and 2% of the planning target volume (D98%, D50%, D2%) within the junction region before and after setup errors of ±3, ±5, and ±7 mm in the craniocaudal direction. ResultsThe program generated ideal in silico dose distributions that were compatible with a commercial treatment planning system for use as base doses during VMAT optimization. VMAT plans, that were optimized with the in silico base plans, had complementary linear dose profiles across the junction. Final pediatric and adult VMAT CSI plans both had V95% ≥98.1% and 98.1%, homogeneity index: 0.09 and 0.10, and conformity number: 0.86, 0.84, respectively. In addition, dose to surrounding organs at risk was acceptably low for both cases. For ±3 mm setup errors, small variations in the junction dose were recorded with ΔD98% ≤2.3%, ΔD50% ≤2.3%, and ΔD2% ≤2.8%. ConclusionsThis is the first demonstration of junctioned VMAT field optimization with a controlled linear dose gradient across the junction without the use of any extra planning contours. Planning junctioned VMAT using in silico base plans is feasible and capable of generating high-quality plans that are robust to clinically expected setup variations.

Microendoscope-assisted posterior lumbar interbody fusion: a technical note.

Various surgical options for lumbar interbody fusion have been reported. Minimally invasive techniques are widely used to reduce soft tissue damage. Here, we report our novel technique of microendoscope-assisted posterior lumbar interbody fusion (ME-PLIF) using an 18-mm tubular retractor system (METRx, Medtronic Sofamor Danek, Memphis, TN, USA) for lumbar spine degeneration treatment. Between January 2011 and December 2011, 48 patients underwent one level ME-PLIF by a surgeon in our hospital. We followed up 46 patients (95.8%). A 20-mm skin incision was made in the craniocaudal direction at the level of the intervertebral disc, 15 mm outside the midline (symptomatic side). The surgeon placed the tubular retractor and performed decompression, thoroughly discarded the intervertebral disc, and then inserted the autologous crushed bone on the opposite side. Subsequently, a cage was inserted using fluoroscopic guidance. Following the end of the microendoscopic operation, pedicle screws (PS) were inserted percutaneously using fluoroscopic guidance. Clinical outcomes were evaluated using the Oswestry Disability Index (ODI) and the Japanese Orthopedic Association (JOA) scores. For radiological outcomes, fusion rates based on the Bridwell fusion grading system were evaluated using plain radiography or a computed tomography scan at the most recent follow-up timepoint. The mean age was 61.4 (range, 36.0-86.0) years, the mean operation time was 102 (range, 59-162) min, and the mean blood loss was 86 (range, small amounts-315) mL. The average pre- and post-operative ODI scores were 22.1 and 9.7, respectively, with an improvement rate of 56.1%, and the pre- and post-operative JOA scores were 9.8 and 16.4, respectively, with an improvement rate of 50%. There were no cases of pseudarthrosis. One case (2.2%) had a deep wound infection that required total removal of the implants. Four (8.7%) cases had a dural tear and required dural sutures under microendoscopy, though they had good recovery. This technique yielded good results. The advantages of using only the microendoscope were: (I) better visual field and (II) higher operability (it was possible to change the tubular retractor to various angles; this was difficult under direct viewing or under a microscope). These features are considered to lead to reduce soft tissue damage. Although long-term follow-up results are needed, this appears to be a safe and minimally invasive treatment option for lumbar spine degeneration.

Proton range shift analysis on brain pseudo-CT generated from T1 and T2 MR

Background: In radiotherapy, MR imaging is only used because it has significantly better soft tissue contrast than CT, but it lacks electron density information needed for dose calculation. This work assesses the feasibility of using pseudo-CT (pCT) generated from T1w/T2w MR for proton treatment planning, where proton range comparisons are performed between standard CT and pCT.Material and methods: MR and CT data from 14 glioblastoma patients were used in this study. The pCT was generated by using conversion libraries obtained from tissue segmentation and anatomical regioning of the T1w/T2w MR. For each patient, a plan consisting of three 18 Gy beams was designed on the pCT, for a total of 42 analyzed beams. The plan was then transferred onto the CT that represented the ground truth. Range shift (RS) between pCT and CT was computed at R80 over 10 slices. The acceptance threshold for RS was according to clinical guidelines of two institutions. A γ-index test was also performed on the total dose for each patient.Results: Mean absolute error and bias for the pCT were 124 ± 10 and −16 ± 26 Hounsfield Units (HU), respectively. The median and interquartile range of RS was 0.5 and 1.4 mm, with highest absolute value being 4.4 mm. Of the 42 beams, 40 showed RS less than the clinical range margin. The two beams with larger RS were both in the cranio-caudal direction and had segmentation errors due to the partial volume effect, leading to misassignment of the HU.Conclusions: This study showed the feasibility of using T1w and T2w MRI to generate a pCT for proton therapy treatment, thus avoiding the use of a planning CT and allowing better target definition and possibilities for online adaptive therapies. Further improvements of the methodology are still required to improve the conversion from MRI intensities to HUs.

MR-guided Gated Stereotactic Radiation Therapy Delivery for Lung, Adrenal, and Pancreatic Tumors: A Geometric Analysis

We implemented magnetic resonance-guided breath-hold stereotactic body radiation therapy in combination with visual feedback using the MRIdian system. Both accuracy of gated delivery and reproducibility of tumor positions were studied. Tumor tracking is realized through repeated magnetic resonance imaging in a single sagittal plane at 4 frames per second with deformable image registration. An in-room monitor allowed visualization of the tracked gross tumor volume (GTV) contour and the planning target volume (PTV) (GTV+3mm), which was the gating boundary. For each delivery, a predefined threshold-region of interest percentage (ROI%)allows a percentage of GTV area to be outside the gating boundary before a beam-hold is triggered. Accuracy of gated delivery and tumor position reproducibility during breath-holds was analyzed for 15 patients (87 fractions) with lung, adrenal, and pancreas tumors. For each fraction, we analyzed (1) reproducibility of system-tracked GTV centroid position within the PTV; (2) geometric coverage of GTV area within the PTV; (3) treatment duty cycle efficiency; (4) effects of threshold ROI% settings on treatment duty cycle efficiency and GTV area coverage; and (5) beam-off latency effect on mean GTV coverage. For lung, adrenal, and pancreatic tumors, grouped 5th to 95th percentile distributions of GTV centroid positions in the dorsoventral direction, relative to PTV-center of mass (COM), were, respectively, -3.3mm to 2.8mm, -2.5mm to 3.7mm, and -4.4mm to 2.9mm. Corresponding distributions in the craniocaudal direction were -2.6mm to 4.6mm, -4.1mm to 4.4mm, and -4.4mm to 4.5mm, respectively. Mean GTV areas encompassed during beam-on for all fractions were 94.6%, 94.3%, and 95.3% for lung, adrenal, and pancreas tumors, respectively. Mean treatment duty cycle efficiency ranged from 67% to 87% for these tumors. Use of higher threshold-ROI% resulted in increased duty cycle efficiency, at the cost of a small decrease in GTV area coverage. The beam-off latency had a marginal impact on the GTV coverage. Gated stereotactic body radiation therapy delivery during breath-hold, real-time magnetic resonance guidance resulted in at least 95% geometric GTV coverage in lung, adrenal, and pancreatic tumors.

An offline technique to evaluate residual motion of the diaphragm during deep inspiratory breath-hold from cone-beam CT datasets.

In radiation therapy, the computer-assisted deep inspiration breath-hold (DIBH) technique is one approach to deal with respiratory motion of tumors in the lung, liver, or upper abdomen. However, inter- and intra-breath-hold deviations from an optimal static tumor position might occur. Anovel method is presented to noninvasively measure the diaphragm position and thus estimate its residual deviation (as surrogate for the tumor position) based on cone-beam computed tomography (CBCT) projection data using active breathing control during acquisition. The diaphragm dome (DD) position relative to the isocenter of alinear accelerator is known from the static (DIBH) planning CT. A ball-bearing phantom (BB) is placed at this position, aCBCT dataset is acquired, and in each projection the position of the projected BB is determined automatically based on thresholding. The position of the DD is determined manually in CBCT projections of apatient. The distance between DD and BB (ideal static setting) in craniocaudal direction is calculated for agiven angle based on the distance in the projection plane and the relative position of the BB referring to the source and the detector. An angle-dependent correction factor is introduced which takes this geometrical setting into account. The accuracy of the method is assessed. The method allows aCBCT projection-based estimation of the deviation between the DD and its optimal position as defined in the planning CT, i.e., the residual motion of the DD can be assessed. The error of this estimation is 2.2 mm in craniocaudal direction. The developed method allows an offline estimation of the inspiration depth (inter- and intra-breath-hold) over time. It will be useful as areference for comparison to other methods of residual motion estimation, e.g., surface scanning.

Respiratory motion of lymph node stations in pancreatic cancer: Analyses using contrast-enhanced four-dimensional computed tomography

Background and purposeData regarding respiratory motion of lymph node (LN) stations in pancreatic cancer is limited. Therefore, we assessed their respiratory motion using contrast-enhanced four-dimensional-computed tomography (CE-4DCT). Material and methodsWe evaluated respiratory motion in 18 pancreatic cancer patients. We selected LN stations around major arteries which were visible on CE-4DCT images. This included the common hepatic, celiac, splenic, and superior mesenteric stations. Two radiation oncologists individually delineated the gross tumor volume (GTV) and the LN stations as observers 1 and 2. ResultsThe respiratory motion of the celiac (median, 3.9 mm each for both observers) and superior mesenteric (median, 4.5 and 5.0 mm for observers 1 and 2, respectively) stations in the craniocaudal (CC) directions was significantly smaller than that of the GTV (median, 8.9 and 7.8 mm for observers 1 and 2, respectively). The respiratory motion of the common hepatic station (median, 3.8 and 3.6 mm for observers 1 and 2, respectively) in the anterior–posterior (AP) direction was significantly larger than that of the GTV (median, 2.8 and 2.2 mm for observers 1 and 2, respectively). ConclusionsWe observed significant differences in respiratory motion between the GTV and the LN stations in pancreatic cancer.

Implementation of a voluntary deep inspiration breath hold technique (vDIBH) using BrainLab ExacTrac infrared optical tracking system.

BackgroundVoluntary deep inspiration breath hold technique (vDIBH) is considered as the key to achieving the widest cardiac sparing in whole breast irradiation. Several techniques have been implemented to achieve a reproducible, fast and friendly treatment. The aim of the present study is to implement vDIBH using the ExacTrac (BrainLAB AG, Germany) monitoring system.MethodsWomen with left-sided breast cancer, younger than 50 years or with cardiac disease, underwent whole breast RT with vDIBH using the ExacTrac (BrainLAB AG, Germany) monitoring system. Simulations were performed with patients positioned supine on a breast board with both arms raised above the head. Five optical markers were placed on the skin around the border of the left breast gland and their position was referenced with ink marking. Each patient received a training session to find the individual deep inspiration level. Finally, a vDIBH CT was taken. All patients were also studied in free breathing (FB) in order to compare the dose distribution for PTV, heart and left anterior descending coronary artery (LAD). Pre-treatment verification was carried out through the ExacTrac (BrainLAB AG, Germany) system and verified with electronic portal imaging (EPI). Moreover, daily real time EPIs in during modality (captured during the beam delivery) were taken in order to check the reproducibility.Results34 patients have been evaluated and 30 were eligible for vDIBH. Most patients showed small setup errors during the treatment course of below 5 mm in 94.9% of the recorded fields. Mean Displacement was less in cranio-caudal direction. Mean intra-fraction displacement was below 3 mm in all directions. vDIBH plans provided better cardiac dosimetry.ConclusionsvDIBH technique using ExacTrac (BrainLAB AG, Germany) monitoring system was applied with good reproducibility.

Plan optimization for mediastinal radiotherapy: Estimation of coronary arteries motion with ECG-gated cardiac imaging and creation of compensatory expansion margins

Background and purposeInadvertent heart and coronary arteries (CA) irradiation may increase the risk of coronary artery disease (CAD) in patients receiving thoracic irradiation. To date, the entity of cardiac-related CA displacement and the possible margins to be used for planning organs at risk volume (PRV) have been poorly described. Aim of this study was to quantify CA displacement and to estimate PRV through the use of ECG-gated computed tomography (CT) scans. Material and methodsEight patients received an ECG-gated intravenous contrast enhanced CT for non-cancer related reasons. Nine data sets were reconstructed over the entire R–R cycle with a dedicated retrospective algorithm and the following structures were delineated: Left main trunk (LM), left anterior descending (LAD), left circumflex (CX) and right coronary artery (RCA). CA displacements across the different cardiac phases were evaluated in left–right (X), cranio-caudal (Y) and anteroposterior (Z) directions using the McKenzie–van Herk formula (1.3 * Σ + 0.5 * σ). ResultsThe following CA displacements were found in X, Y and Z coordinates: 3.6, 2.7 and 2.7 mm for LMT, respectively; 2.6, 5.0 and 6.8 mm for LAD, respectively; 3.5, 4.5 and 3.7 mm for CX, respectively; 3.6, 4.6 and 6.9 mm for RCA, respectively. Based on the mean displacements, we created a PRV of 3 mm for LM, 4 mm for CX and 5 mm for LAD and RCA. ConclusionCA showed relevant displacements over the heart cycle, suggesting the need for a specific PRV margin to accurately estimate the dose received by these structures and optimize the planning process.