Bladder preservation with trimodal therapy (TMT; maximal tumor resection followed by chemoradiation) is an effective paradigm for select patients with muscle invasive bladder cancer. We report our ...institutional experience of a TMT protocol using nonadaptive magnetic resonance imaging–guided radiation therapy (MRgRT) for partial bladder boost (PBB).
A retrospective analysis was performed on consecutive patients with nonmetastatic muscle invasive bladder cancer who were treated with TMT using MRgRT between 2019 and 2022. Patients underwent intensity modulated RT-based nonadaptive MRgRT PBB contoured on True fast imaging with steady state precession (FISP) images (full bladder) followed sequentially by computed tomography–based RT to the whole empty bladder and pelvic lymph nodes with concurrent chemotherapy. MRgRT treatment time, table shifts, and dosimetric parameters of target coverage and normal tissue exposure were described. Prospectively assessed acute and late genitourinary and gastrointestinal (GI) toxicity were reported. Two-year local control was assessed with Kaplan-Meier methods.
Seventeen patients were identified for analysis. PBB planning target volume margins were ≤8 mm in 94% (n = 16) of cases. Dosimetric target coverage parameters were favorable and all normal tissue dose constraints were met. For MRgRT PBB fractions, median table shifts were 0.4 cm (range, 0-3.15), 0.45 cm (0-2.65), and 0.75 cm (0-4.8) in the X, Y, and Z planes, respectively. Median treatment time for MRgRT PBB fractions was 9 minutes (range, 6.9-17.4). We identified 32 out of 100 total MRgRT fractions that may have benefitted from online adaptation based on changes in organ position relative to planning target volume, predominantly because of small bowel (13/32, 41%) or rectum (8/32, 25%). Two patients discontinued RT prematurely. The incidence of highest-grade acute genitourinary toxicity was 1 to 2 (69%) and 3 (6%), whereas the incidence of acute GI toxicity was 1 to 2 (81%) and 3 (6%). There were no late grade 3 events; 17.6% had late grade 2 cystitis and none had late GI toxicity. With median follow-up of 18.2 months (95% CI, 12.4-22.5), the local control rate was 92%, and no patient has required salvage cystectomy.
Nonadaptive MRgRT PBB is feasible with favorable dosimetry and low resource utilization. Larger studies are needed to evaluate for potential benefits in toxicity and local control associated with this approach in comparison to standard treatment techniques.
The recent results from the Nordic-HILUS study indicate stereotactic body radiation therapy (SBRT) is associated with high-grade toxicity for ultracentral (UC) tumors. We hypothesized that magnetic ...resonance-guided SBRT (MRgSBRT) or hypofractionated radiation therapy (MRgHRT) enables the safe delivery of high-dose radiation to central and UC lung lesions.
Patients with UC or central lesions were treated with MRgSBRT/MRgHRT with real-time gating or adaptation. Central lesions were defined as per the Radiation Therapy Oncology Group and UC as per the HILUS study definitions: (1) group A or tumors less than 1 cm from the trachea and/or mainstem bronchi; or (2) group B or tumors less than 1 cm from the lobar bronchi. The Kaplan-Meier estimate and log-rank test were used to estimate survival. Associations between toxicities and other patient factors were tested using the Mann-Whitney U test and Fisher’s exact test.
A total of 47 patients were included with a median follow-up of 22.9 months (95% confidence interval: 16.4–29.4). Most (53%) had metastatic disease. All patients had central lesions and 55.3% (n = 26) had UC group A. The median distance from the proximal bronchial tree was 6.0 mm (range: 0.0–19.0 mm). The median biologically equivalent dose (α/β = 10) was 105 Gy (range: 75–151.2). The most common radiation schedule was 60 Gy in eight fractions (40.4%). Most (55%) had previous systemic therapy, 32% had immunotherapy and 23.4% had previous thoracic radiation therapy. There were 16 patients who underwent daily adaptation. The 1-year overall survival was 82% (median = not reached), local control 87% (median = not reached), and progression-free survival 54% (median = 15.1 mo, 95% confidence interval: 5.1–25.1). Acute toxicity included grade 1 (26%) and grade 2 (21%) with only two patients experiencing grade 3 (4.3%) in the long term. No grade 4 or 5 toxicities were seen.
Previous studies noted high rates of toxicity after SBRT to central and UC lung lesions, with reports of grade 5 toxicities. In our cohort, the use of MRgSBRT/MRgHRT with high biologically effective doses was well tolerated, with two grade 3 toxicities and no grade 4/5.
Radiation therapy (RT) is an effective treatment modality for hepatocellular carcinoma (HCC), but globally, it is underutilized. In Russia, practice patterns with regard to liver-directed radiation ...are unknown. Under the auspices of Russian Society of Clinical Oncology (RUSSCO), our team conducted an IRB-approved contouring workshop for Russian radiation oncologists. Pre- and post-workshop surveys were analyzed to determine baseline clinical experience and patterns of care for liver-directed RT among Russian providers. The effect of the contouring workshop on participants’ knowledge was tested using mixed effects model. Forty pre-workshop and 24 post-workshop questionnaires were analyzable with a 100% response rate. Sixty percent of respondents had never evaluated a patient with HCC and only 8% (3 out of 40) reported treating an HCC patient with liver-directed RT. Nonetheless, 73% of respondents were comfortable offering liver-directed RT prior to the workshop. After the workshop, 85% of respondents felt comfortable treating a patient with HCC with liver-directed RT and 50% were comfortable recommending stereotactic body radiation therapy (SBRT). Measures of knowledge pertaining to evaluation of HCC patients and selection for appropriate liver-directed therapies were dramatically improved after the workshop. Liver-directed RT is not commonly used in Russia in the management of patients with HCC, and few centers are equipped for motion management. Our contouring workshop resulted in dramatically improved understanding of the evaluation and management of HCC patients. We recommend starting with a more protracted fractionated RT and building experience through attendance of additional educational activities, participation in multidisciplinary liver tumor boards, and prospective analysis of treatment toxicity and outcomes.
Quantum noise is common in CT images and is a persistent problem in accurate ventilation imaging using 4D-CT and deformable image registration (DIR). This study focuses on the effects of noise in ...4D-CT on DIR and thereby derived ventilation data. A total of six sets of 4D-CT data with landmarks delineated in different phases, called point-validated pixel-based breathing thorax models (POPI), were used in this study. The DIR algorithms, including diffeomorphic morphons (DM), diffeomorphic demons (DD), optical flow and B-spline, were used to register the inspiration phase to the expiration phase. The DIR deformation matrices (DIRDM) were used to map the landmarks. Target registration errors (TRE) were calculated as the distance errors between the delineated and the mapped landmarks. Noise of Gaussian distribution with different standard deviations (SD), from 0 to 200 Hounsfield Units (HU) in amplitude, was added to the POPI models to simulate different levels of quantum noise. Ventilation data were calculated using the ΔV algorithm which calculates the volume change geometrically based on the DIRDM. The ventilation images with different added noise levels were compared using Dice similarity coefficient (DSC). The root mean square (RMS) values of the landmark TRE over the six POPI models for the four DIR algorithms were stable when the noise level was low (SD <150 HU) and increased with added noise when the level is higher. The most accurate DIR was DD with a mean RMS of 1.5 ± 0.5 mm with no added noise and 1.8 ± 0.5 mm with noise (SD = 200 HU). The DSC values between the ventilation images with and without added noise decreased with the noise level, even when the noise level was relatively low. The DIR algorithm most robust with respect to noise was DM, with mean DSC = 0.89 ± 0.01 and 0.66 ± 0.02 for the top 50% ventilation volumes, as compared between 0 added noise and SD = 30 and 200 HU, respectively. Although the landmark TRE were stable with low noise, the differences between ventilation images increased with noise level, even when the noise was low, indicating ventilation imaging from 4D-CT was sensitive to image noise. Therefore, high quality 4D-CT is essential for accurate ventilation images.
The 4D-CT data used for comparing a patient's ventilation distributions before and after lung radiotherapy are acquired at different times. As a result, an additional variable--the tidal volume ...(TV)--can alter the results. Therefore, in this paper we propose to normalize the ventilation to the same TV to eliminate that uncertainty.
Absolute ventilation (AV) data were generated for 6 stereotactic body radiation therapy (SBRT) cases before and after treatment, using the direct geometric algorithm and diffeomorphic morphons deformable image registration (DIR). Each pair of AV distributions was converted to TV-normalized, percentile ventilation (PV) and low-dose well-ventilated-normalized ventilation (LDWV) distributions. The ventilation change was calculated in various dose regions based on the treatment plans using the DIR-registered before and after treatment data sets. The ventilation change based on TV-normalized ventilation was compared with the AV as well as the data normalized by PV and LDWV.
AV change may be misleading when the TV differs before and after treatment, which was found to be up to 6.7%. All three normalization methods produced a similar trend in ventilation change: the higher the dose to a region of lung, the greater the degradation in ventilation. In low dose regions (<5 Gy), ventilation appears relatively improved after treatment due to the relative nature of the normalized ventilation. However, the LDWV may not be reliable when the ventilation in the low-dose regions varies. PV exhibited a similar ventilation change trend compared to the TV-normalized in all cases. However, by definition, the ventilation distribution in the PV is significantly different from the original distribution.
Normalizing ventilation distributions by the TV is a simple and reliable method for evaluation of ventilation changes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In cancer care, tissue seeding after curative resections is a known potential complication, despite precautions taken during surgical treatment. We present an uncommon case of an abdominal wall ...metastasis along the tract of a surgical drain following gastrectomy for gastric adenocarcinoma. To our knowledge, this is the first case of such an occurrence in the setting of a negative staging peritoneal lavage. Aside from the rarity of such a recurrence, this instance highlights an opportunity to reevaluate best practices with regard to the extent of coverage of postoperative salvage radiotherapy. The oncologic patient provides many challenges and may require multiple catheters for drainage and at times infusion of nutrition or therapeutic agents. These foreign bodies should be scrutinized both clinically and radiographically, as they may create vulnerabilities in keeping malignant diseases contained and controlled. We provide a review of the literature with reasonable treatment options for the benefit of future patients.
Ventilation imaging using 4D CT is a convenient and low‐cost functional imaging methodology which might be of value in radiotherapy treatment planning to spare functional lung volumes. Deformable ...image registration (DIR) is needed to calculate ventilation imaging from 4D CT. This study investigates the dependence of calculated ventilation on DIR methods and ventilation algorithms. DIR of the normal end expiration and normal end inspiration phases of the 4D CT images was used to correlate the voxels between the two respiratory phases. Three different DIR algorithms, optical flow (OF), diffeomorphic demons (DD), and diffeomorphic morphons (DM) were retrospectively applied to ten esophagus and ten lung cancer cases with 4D CT image sets that encompassed the entire lung volume. The three ventilation extraction methods were used based on either the Jacobian, the change in volume of the voxel, or directly calculated from Hounsfield units. The ventilation calculation algorithms used are the Jacobian, ΔV, and HU method. They were compared using the Dice similarity coefficient (DSC) index and Bland‐Altman plots. Dependence of ventilation images on the DIR was greater for the ΔV and the Jacobian methods than for the HU method. The DSC index for 20% of low‐ventilation volume for ΔV was 0.33±0.03(1SD) between OF and DM, 0.44±0.05 between OF and DD, and 0.51±0.04 between DM and DD. The similarity comparisons for Jacobian were 0.32±0.03,0.44±0.05, and 0.51±0.04, respectively, and for HU they were 0.53±0.03,0.56±0.03, and 0.76±0.04, respectively. Dependence of extracted ventilation on the ventilation algorithm used showed good agreement between the ΔV and Jacobian methods, but differed significantly for the HU method. DSC index for using OF as DIR was 0.86±0.01 between ΔV and Jacobian, 0.28±0.04 between ΔV and HU, and 0.28±0.04 between Jacobian and HU, respectively. When using DM or DD as DIR, similar values were obtained when comparing the different ventilation calculation methods. The similarity values for the 20% high‐ventilation volume were close to those found for the 20% low‐ventilation volume. The results obtained with DSC index were confirmed when using the Bland‐Altman plots for comparing the ventilation images. Our data suggest that ventilation calculated from 4D CT depends on the DIR algorithm employed. Similarities between ΔV and Jacobian are higher than between ΔV and HU, and Jacobian and HU.
PACS number: 87.57.nj
. To reduce the magnetic isocenter position variation with gantry rotation on an 0.35 T MRI-guided linac to a practically negligible level.
. Central fRequency (CF) offset, eddy current calibration, ...cross-term calibration, gradient delay, and gradient offsets are tuned for each MR linac installation at every 30° of gantry rotation and stored in a look-up table (LUT). During treatment, the CF is tuned only once in the beginning at an arbitrary gantry angle. After that, imaging paramters are offset based on the stored LUT values for any given gantry angle.
. For the same hardware configuration, the implementation of the gantry-angle-specific parameter corrections reduced the total isocenters range of travel in the transverse plane from 1.1 to 0.3 mm and from 0.8 to 0.2 mm in horizontal and vertical directions, respectively. With the longitudinal shift always being negligible (≤0.2 mm), the radius of the sphere encompassing the isocenter locations was reduced from 0.6 to 0.2 mm. Geometric distortion improved as well; in particular, the gantry-angle-averaged maximum longitudinal distortion within a 35 cm diameter sphere was reduced from 1.4 to 0.8 mm. Since the CF is tuned only once during treatment, imaging may resume promptly after the gantry reaches the next target position.
. The MRI-guided linear accelerator was conceived primarily as an instrument for precision image-guided therapy. Thus, it is important to keep the treatment and imaging isocentres as close as possible while minimizing the geometric distortion. The described solution reduces the walkout of the imaging isocenter to a fraction of 1 mm, while keeping geometric distortion in a substantial volume below 1 mm. The approach is robust and does not increase the overall procedure time.
The main focus of the recommended spatial accuracy tests for the multi‐leaf collimators (MLC) is calibration of the leaf position along the movement direction and overall alignment to the radiation ...isocenter. No explicit attention was typically paid to the alignment of the leaves from the opposing banks in the direction orthogonal to movement. This paper is a case study demonstrating that verification of such alignment at the time of acceptance testing is prudent. The original standard MLC (SMLC) on an MRIdian MRI‐guided linac (ViewRay Inc., Mountain View, CA, USA) was upgraded to a high‐speed MLC (HSMLC), which is supposed to be mechanically identical to the SMLC except for the higher drive screw pitch. The results of the end‐to‐end IMRT tests demonstrated unacceptable dosimetric results exemplified by an average and maximum ion chamber (IC) point dose error in the high‐dose low‐gradient region of 2.5 ± 1.4% and 4.6%, respectively. Before the upgrade, those values were 0.3 ± 0.7% and 0.9%, respectively. An exhaustive analysis of possible failure modes eventually zeroed in on the average misalignment of about 1 mm in the Y (along the couch) direction between the right and left upper MLC banks. The MLC was replaced, reducing the Y‐direction misalignment to 0.4 mm. As a result, the average and maximum IC dose‐errors became acceptable 1.0 ± 0.7% and 1.6%, respectively. Simple film and/or chamber array tests during acceptance testing can easily detect Y‐direction misalignments between opposing leaves banks measuring a fraction of a mm at isocenter. Left undetected, such misalignment can cause nontrivial dosimetric consequences.
Abstract
Background and aims
The role of three-dimensional positron emission tomography/computed tomography (3 D PET/CT) in esophageal tumors that move with respiration and have potential for ...significant mucosal inflammation is unclear. The aim of this study was to determine the correlation between gross tumor volumes derived from 3 D PET/CT and endoscopically placed fiducial markers.
Methods
This was a retrospective, IRB approved analysis of 40 patients with esophageal cancer with fiducials implanted and PET/CT. The centroid of each fiducial was identified on PET/CT images. Distance between tumor volume and fiducials was measured using axial slices. Image features were extracted and tested for pathologic response predictability.
Results
The median adaptively calculated threshold value of the standardized uptake value (SUV) to define the metabolic tumor volume (MTV) border was 2.50, which corresponded to a median 23 % of the maximum SUV. The median distance between the inferior fiducial centroid and MTV was – 0.60 cm (– 3.9 to 2.7 cm). The median distance between the superior fiducial centroid and MTV was 1.25 cm (– 4.2 to 6.9 cm). There was no correlation between MTV-to-fiducial distances greater than 2 cm and the gastroenterologist who performed the fiducial implantation. Eccentricity demonstrated statistically significant correlations with pathologic response.
Conclusions
There was a stronger correlation between inferior fiducial location and MTV border compared to the superior extent. The etiology of the discordance superiorly is unclear, potentially representing benign secondary esophagitis, presence of malignant nodes, inflammation caused by technical aspects of the fiducial placement itself, or potential submucosal disease. Given the concordance inferiorly and the ability to more precisely set up the patient with daily image guidance matching to fiducials, it may be possible to minimize the planning tumor volume (PTV) margin in select patients, thereby, limiting dose to normal structures.
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