Dose-volume Histogram Analysis Research Articles

Comparative assessment of passive scattering and active scanning proton therapy techniques using Monte Carlo simulations

Background: in this study, two proton beam delivery designs, i.e. passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo (MC) particle transport code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements. Method: a water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120–235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including Bragg peak width (BP W50), peak position, range, peak-to-entrance dose ratio, penumbra(90-10)%, penumbra(80-20)%, M 95% and dose volume histogram have been analyzed under the same conditions. Furthermore, the clinical test cases introduced by AAPM TG-119 were simulated in both beam delivery modes to compare the relevant clinical values obtained from Dose Volume Histogram (DVH) analysis. Results: the parametric comparison in the water phantom between the two techniques revealed that the value of peak-to-entrance dose ratio in PSPT is considerably higher than that from PBS by a factor of 8%. In addition, the BP_W50, penumbra(90-10)%, penumbra(80-20)%, and M 95% in PSPT was increased by a factor of 7, 51, 37, and 2.7%, respectively compared to the corresponding value obtained from PBS model. TG-119 phantom simulations showed that the difference of PTV mean dose between PBS and PSPT techniques are up to 1.8% while the difference of max dose to organ at risks (OARs) exceeds 50%. Conclusion: the results of this simulation show that although the passive scattering design method has a slightly higher ability to adjust the dose in target volume, but the active scanning proton therapy systems was superior in dose painting, and lower out-of-field dose compared to passive scattering design.

Compensation for radiotherapy treatment interruptions due to a cyberattack: An isoeffective DVH‐based dose compensation decision tool

Unscheduled interruptions to radiotherapy treatments lead to decreased tumor control probability (TCP). Rapid cell repopulation in the tumor increases due to the absence of radiation dose, resulting in the loss of TCP. Compensation for this loss is required to prevent or reduce an extension of the patient's overall treatment time and regain the original TCP. The cyberattack on the Irish public health service in May 2021 prevented radiotherapy treatment delivery resulting in treatment interruptions of up to 12 days. Current standards for treatment gap calculations are performed using the Royal College of Radiologists (RCR) methodology, using a point‐dose for planning target volume (PTV) and the organs at risk (OAR).An in‐house tool, named EQD2VH, was created in Python to perform treatment gap calculations using the dose–volume histogram (DVH) information in DICOM data extracted from commercial treatment planning system plans. The physical dose in each dose bin was converted into equivalent dose in 2‐Gy fractions (EQD2), accounting for tumor cell repopulation. This EQD2‐based DVH provides a 2D representation of the impact of treatment gap compensation strategies on both PTV and OAR dose distributions compared to the intended prescribed treatment plan. This additional information can aid clinicians’ choice of compensation options. EQD2VH was evaluated using five high‐priority patients experiencing a treatment interruption when the cyberattack occurred. Compensation plans were created using the RCR methodology to evaluate EQD2VH as a decision‐making tool.The EQD2VH method demonstrated that the comparison of compensated treatment plans alongside the original intended treatment plans using isoeffective DVH analysis can be achieved. It enabled a visual and quantitative comparison between treatment plan options and provided an individual analysis of each structure in a patient's plan. It demonstrated potential to be a useful decision‐making tool for finding a balance between optimizing dose to PTV while protecting OARs.

Assessment of dose perturbations for metal stent in photon and proton radiotherapy plans for hepatocellular carcinoma

BackgroundThe present study aimed to investigate the dosimetric impact of metal stent for photon and proton treatment plans in hepatocellular carcinoma.MethodsWith computed tomography data of a water-equivalent solid phantom, dose perturbation caused by a metal stent included in the photon and proton treatment of hepatocellular carcinoma was evaluated by comparing Eclipse and RayStation treatment planning system (TPS) to a Monte Carlo (MC) based dose calculator. Photon and proton plans were created with anterior–posterior/posterior-anterior (AP/PA) fields using a 6 MV beam and AP/PA fields of a wobbling beam using 150 MeV and a 10 cm ridge filter. The difference in dose distributions and dosimetric parameters were compared depending on the stent's positions (the bile duct (GB) and intestinal tract (GI)) and angles (0°, 45°, and 90°). Additionally, the dose variation in the target volume including the stent was comparatively evaluated through dose volume histogram (DVH) analysis. And the comparison of clinical cases was carried out in the same way.ResultsPercentage differences in the dosimetric parameters calculated by MC ranged from − 7.0 to 3.9% for the photon plan and − 33.7 to 4.3% for the proton plan, depending on the angle at which the GB and GI stents were placed, compared to those without the stent. The maximum difference was observed at the minimum dose (Dmin), which was observed in both photon and proton plans in the GB and GI stents deployed at a 90° incidence angle. The parameter differences were greater in the proton plan than in photon plan. The target volume showed various dose variations depending on positions and angles of stent for both beams. Compared with no-stent, the doses within the target volume containing the GI and GB stents for the photon beam were overestimated in the high-dose area at 0°, nearly equal within 1% at 45°, and underestimated at 90°. These doses to the proton beam were underestimated at all angles, and the amount of underdose to the target volume increased with an increase in the stent angle. However, the difference was significantly greater with the proton plan than the photon plan.ConclusionsDose perturbations within the target volume due to the presence of the metal stent were not observed in the TPS calculations for photon and proton beams, but MC was used to confirm that there are dose variations within the target volume. The MC results found that delivery of the treatment beam avoiding the stent was the best method to prevent target volume underdose.

Near-maximum rib dose is the most relevant risk factor for ipsilateral spontaneous rib fracture: adosimetric analysis of breast cancer patients after radiotherapy.

Spontaneous rib fracture (SRF) is acommon late complication in treated breast cancer patients. This study evaluated the incidence and risk factors of ipsilateral SRF after radiotherapy (RT) in breast cancer patients. In addition, we identified dosimetric parameters that were significantly associated with ipsilateral SRF. We retrospectively reviewed 2204patients with breast cancer who underwent RT between 2014 and 2016, and were followed up with bone scans. We evaluated clinical risk factors for ipsilateral SRF. Dose-volume histogram analysis was also performed for patients (n = 538) whose dosimetric data were available. All ipsilateral ribs were manually delineated, and dosimetric parameters of the ribs were converted into the equivalent dose in 2 Gy fractions (EQD2). Most of the patients with SRF (87.3%) were asymptomatic, and the remaining symptomatic patients complained of mild tenderness or chest wall discomfort; these symptoms all resolved within 6months without any treatment. Ipsilateral SRF occurred in 14.5% of patients 3years after RT. The median time to develop ipsilateral SRF was 15months. In dosimetric analysis, near-maximum rib dose (D2cc) best predicted ipsilateral SRF. The cut-off value of D2cc was EQD2 52 Gy, as determined by receiver operating characteristic analysis. In multivariate analysis including dosimetric variables, D2cc EQD2 ≥ 52 Gy was the only significant risk factor for ipsilateral SRF. Our data demonstrated that near-maximum rib dose was the best dosimetric parameter to predict ipsilateral SRF in RT-treated breast cancer patients. In addition, our results suggest that patients who received RT with exceeding rib dose cut-off value and had ipsilateral SRF on bone scan be recommended routine follow-up without additional imaging tests.

Radiobiological analysis of preliminary results of a phase II study of pelvic hypofractionated and accelerated radiotherapy for high-risk prostate cancer patients.

PurposeConventionally fractionated radiotherapy (CRT) is widely applied for the treatment of high-risk prostate cancer. Pelvic node irradiation improves control of the disease. Although the therapeutic guidelines support the use of hypofractionated and accelerated radiotherapy (HypoAR), this is addressed to prostate and seminal vesicles. At the same time, the safety and efficacy of HypoAR for pelvic node irradiation remain obscure.Material and MethodsIn a phase II study, we evaluated the feasibility of pelvic HypoAR in 22 high-risk prostate cancer patients. The RT scheme delivers 14 consecutive fractions of 3.67 Gy (total 51.38 Gy) to the prostate, 3.5 Gy (total 49 Gy) to the seminal vesicles, and 2.7 Gy (total 37.8 Gy) to the lymph nodes, using image-guided volumetric modulated arc therapy. A comparative radiobiological analysis of dose-volume histogram is performed (HypoAR vs. hypothetical equivalent CRT regimens, without and with time correction).ResultsOur clinical experience shows impressively low early and short-term late toxicities, without any grade III events, within a median follow-up of 30 months. Only one biochemical relapse was recorded 30 months after irradiation. In radiobiological analysis, considering an α/β-value of 4 Gy and a λ-value of 0.2 Gy/day for late effects, all comparisons predicted significantly lower toxicity for the HypoAR regimen (p < 0.05). For early toxicities (α/β = 10 Gy), a λ-value lower than 0.4 Gy/day favors the HypoAR regimen, which is along with the clinical results.ConclusionRadiobiological analysis favors HypoAR as a safe and effective regimen for high-risk prostate cancer patients, which is confirmed in the current phase II clinical study.

Effect of dosimetric parameters on postoperative respiratory morbidity in locally advanced esophageal cancer treated with preoperative chemoradiotherapy (CRT).

e16075 Background: Postoperative pulmonary complications are common after neoadjuvant CRT of locally advanced esophageal cancers. Using data from the French multicenter randomized phase II PROTECT trial (NCT02359968), we aimed to evaluate the dosimetric parameters which could be associated with the occurrence of postoperative respiratory morbidities in patients (pts) who underwent preoperative CRT. Methods: Key eligibility criteria for the PROTECT trial were stage II or III resectable adenocarcinoma or squamous cell carcinoma of the esophagus located below the carina. Pts received FOLFOX or Carboplatin-Paclitaxel, combined with radiotherapy (RT): total dose of 41.4 Gy, 5 fractions of 1.8 Gy per week, starting at day 1 of chemotherapy. The patient's position and definition of the target volumes and organs at risk were the same as in the CROSS trial (van Hagen, 2012). Pts were treated using 3D conformal RT or IMRT. Surgery occurred 4 to 8 weeks after completion of CRT through a transthoracic or mini-invasive approach with a two field extended lymphadenectomy. Pts recruited in the PROTECT trial up to Sept. 2019 who underwent surgery after CRT were eligible for this ancillary study. The primary endpoint of our translational study was the occurrence of postoperative respiratory morbidity, of any grade (Clavien-Dindo classification for early morbidity &lt; 31 days; NCI-CTCAE v4 for later events), up to 1 year following surgery, considering disease progression or death as competing events. Cause-specific Cox models were used to model the risk of respiratory morbidity, considering the following factors: performance status, BMI, smoking, histological subtype, tumor site, FEV1, RT technique, time interval between CRT and surgery, and dosimetric parameters derived from the Dose-Volume Histogram analysis (mean lung dose, V10Gy, V20Gy and V30Gy, as other parameters strongly correlated to these 4 ones). Results: Among the 98 pts recruited in the PROTECT trial from Feb. 2015 to Sept. 2019, 78 underwent surgery after CRT and were included in our translational study. Median age was 63.5 years (range 33 to 79). Tumor was located at the middle or lower third of the esophagus for 67% of pts. Mean lung dose was 10.2 Gy (sd = 3.2). Mean PTV volume was 566 cc (sd = 272). A total of 33 pts experienced at least one respiratory morbidity (16 pneumonia, 7 pleural effusion, 4 ARDS, 21 miscellaneous events). The cumulative incidence of respiratory morbidity was 42% one month after surgery (95% CI, 32-54), 44% at 3 months (32-54), and 46% at 6 months (35-57). None of the dosimetric parameters and other studied factors appeared associated with postoperative respiratory morbidity. Conclusions: We did not identify dosimetric factors that could predict the risk of postoperative respiratory morbidity after treatment with preoperative CRT with FOLFOX or Carboplatin-Paclitaxel. Clinical trial information: NCT02359968.

Targeting for stereotactic radiosurgical thalamotomy based on tremor treatment response.

Stereotactic radiosurgery (SRS) treats severe, medically refractory essential tremor and tremor-dominant Parkinson disease. However, the optimal target for SRS treatment within the thalamic ventral intermediate nucleus (VIM) is not clearly defined. This work evaluates the precision of the physician-selected VIM target, and determines the optimal SRS target within the VIM by correlation between early responders and nonresponders. Early responders and nonresponders were assessed retrospectively by Elements Basal Ganglia Atlas autocontouring of the VIM on the pre-SRS-treatment 1-mm slice thickness T1-weighted MRI and correlating the center of the post-SRS-treatment lesion. Using pre- and posttreatment diffusion tensor imaging, the fiber tracking package in the Elements software generated tremor-related tracts from autosegmented motor cortex, thalamus, red nucleus, and dentate nucleus. Autocontouring of the VIM was successful for all patients. Among 23 patients, physician-directed SRS targets had a medial-lateral target range from +2.5 mm to -2.0 mm from the VIM center. Relative to the VIM center, the SRS isocenter target was 0.7-0.9 mm lateral for 6 early responders and 0.9-1.1 mm medial for 4 nonresponders (p = 0.019), and without differences in the other dimensions: 0.2 mm posterior and 0.6 mm superior. Dose-volume histogram analyses for the VIM had no significant differences between responders and nonresponders between 20 Gy and 140 Gy, mean or maximum dose, and dose to small volumes. Tractography data was obtained for 4 patients. For tremor control in early responders, the Elements Basal Ganglia Atlas autocontour for the VIM provides the optimal SRS target location that is 0.7-0.9 mm lateral to the VIM center.

A study to determine the impact of IMPT optimization techniques on prostate synthetic CT image sets dose comparison against CT image sets.

BackgroundThe objective of this study is to determine the impact of intensity modulated proton therapty (IMPT) optimization techniques on the proton dose comparison of commercially available magnetic resonance for calculating attenuation (MRCA T) images, a synthetic computed tomography CT (sCT) based on magnetic resonance imaging (MRI) scan against the CT images and find out the optimization technique which creates plans with the least dose differences against the regular CT image sets.Material and methodsRegular CT data sets and sCT image sets were obtained for 10 prostate patients for the study. Six plans were created using six distinct IMPT optimization techniques including multi-field optimization (MFO), single field uniform dose (SFUD) optimization, and robust optimization (RO) in CT image sets. These plans were copied to MRCA T, sCT datasets and doses were computed. Doses from CT and MRCA T data sets were compared for each patient using 2D dose distribution display, dose volume histograms (DVH), homogeneity index (HI), conformation number (CN) and 3D gamma analysis. A two tailed t-test was conducted on HI and CN with 5% significance level with a null hypothesis for CT and sCT image sets.ResultsAnalysis of ten CT and sCT image sets with different IMPT optimization techniques shows that a few of the techniques show significant differences between plans for a few evaluation parameters. Isodose lines, DVH, HI, CN and t-test analysis shows that robust optimizations with 2% range error incorporated results in plans, when re-computed in sCT image sets results in the least dose differences against CT plans compared to other optimization techniques. The second best optimization technique with the least dose differences was robust optimization with 5% range error.ConclusionThis study affirmatively demonstrates the impact of IMPT optimization techniques on synthetic CT image sets dose comparison against CT images and determines the robust optimization with 2% range error as the optimization technique which gives the least dose difference when compared to CT plans.

Clinical advantage and outcomes of computed tomography-based transvaginal hybrid brachytherapy performed only by sedation without general or saddle block anesthesia.

Three-dimensional image-guided brachytherapy is the standard of care in cervical cancer radiotherapy. In addition, the usefulness of the so-called "hybrid brachytherapy (HBT)" has been reported, which involves the addition of needle applicators to conventional intracavitary brachytherapy for interstitial irradiation. To evaluate the clinical outcomes of CT-based HBT consisting of transvaginal insertion of needle applicators (CT-based transvaginal HBT) and only intravenous sedation without general or saddle block anesthesia. This is a retrospective chart review of patients who received definitive radiotherapy, including CT-based transvaginal HBT, between February 2012 and July 2019. The inclusion criteria were as follows: (i) histologically diagnosed disease, (ii) untreated cervical cancer, (iii) International Federation of Gynecology and Obstetrics (FIGO) stage IB1-IVA disease in the 2008 FIGO staging system, and (iv) patients who underwent CT-based transvaginal HBT at least once in a series of intracavitary brachytherapy. Overall, 54 patients fulfilled the eligibility criteria in the present study. The median follow-up period was 32 (IQR, 19-44) months. No patient complained of symptoms such as persistent bleeding or abdominal pain after the treatment. The 3-year local control (LC), disease-free survival, and overall survival rates for all 54 patients were 86.6%, 60.3%, and 90.7% (95% CI [81.3%-100.0%]), respectively. The 3-year LC rate was 87.7% in patients with FIGO III-IVA and 90.4% in tumor size >6.0cm. The incidence rate of late adverse events, grade ≥3, in the rectum and bladder was 0% and 1.8%, respectively. In the dose-volume histogram analyses, transvaginal HBT increased the dose of HR-CTVD90 by ~7.5% without significantly increasing the dose of organs at risk. Considering the favorable clinical outcomes, CT-based transvaginal HBT may be a good option for treating cervical cancer.

Prospective Evaluation of Prostate and Organs at Risk Segmentation Software for MRI-based Prostate Radiation Therapy.

The segmentation of the prostate and surrounding organs at risk (OARs) is a necessary workflow step for performing dose-volume histogram analyses of prostate radiation therapy procedures. Low-dose-rate prostate brachytherapy (LDRPBT) is a curative prostate radiation therapy treatment that delivers a single fraction of radiation over a period of days. Prior studies have demonstrated the feasibility of fully convolutional networks to segment the prostate and surrounding OARs for LDRPBT dose-volume histogram analyses. However, performance evaluations have been limited to measures of global similarity between algorithm predictions and a reference. To date, the clinical use of automatic segmentation algorithms for LDRPBT has not been evaluated, to the authors' knowledge. The purpose of this work was to assess the performance of fully convolutional networks for prostate and OAR delineation on a prospectively identified cohort of patients who underwent LDRPBT by using clinically relevant metrics. Thirty patients underwent LDRPBT and were imaged with fully balanced steady-state free precession MRI after implantation. Custom automatic segmentation software was used to segment the prostate and four OARs. Dose-volume histogram analyses were performed by using both the original automatically generated contours and the physician-refined contours. Dosimetry parameters of the prostate, external urinary sphincter, and rectum were compared without and with the physician refinements. This study observed that physician refinements to the automatic contours did not significantly affect dosimetry parameters. Keywords: MRI, Neural Networks, Radiation Therapy, Radiation Therapy/Oncology, Genital/Reproductive, Prostate, Segmentation, Dosimetry Supplemental material is available for this article. © RSNA, 2022.

Comparison of dosimetric parameters and three-dimensional dosimetric verification of three intensity-modulated radiotherapy plans for thymoma based on the dose-volume histogram and ArcCHECK-3DVH system

Objective: To compare the dosimetric parameters of step-shoot intensity-modulated radiotherapy (sIMRT), dynamic intensity-modulated radiotherapy (dIMRT), and volume-modulated arc therapy (VMAT) in thymoma and to study the feasibility of the ArcCHECK-3DVH system in three intensity-modulated radiotherapy plans to choose a more appropriate intensity-modulated radiotherapy for thymoma. Materials and Methods: Seventeen patients with thymoma were enrolled in this study. Treatment plans of sIMRT, dIMRT, and VMAT for each patient were based on the Monaco treatment planning system (TPS). Dosimetric verification was performed via the ArcCHECK-3DVH system. We compared and analyzed the 3D γ pass rates of the TPS dose calculation and ArcCHECK-3DVH system dose reconstruction with the three gamma criteria (3 mm/3%, 2 mm/2%, and 1 mm/1%) with a threshold of 10%. Dose-volume histogram analysis was used to compare the dose parameters for target volumes, and organs at risk (OARs), such as D98%, D50%, D2%, Dmax, V20, and V5. Monitor units (MUs) and delivery time were also compared. Results: There were significant differences in the three intensity-modulated radiotherapy plans. For target volume, VMAT showed the highest planning target volume (PTV) D98% and the lowest PTV D50% compared with sIMRT or dIMRT. The PTV D2% of VMAT was lower than that of sIMRT and higher than that of dIMRT, and VAMT demonstrated the highest conformity index and MU, lowest homogeneity index, and shortest treatment delivery time. For the OARs, VMAT is not inferior to sIMRT and dIMRT in OARs protection. For the dosimetric verification, the entire area, PTV, lungs, heart, and spinal cord of VMAT showed the highest γ pass rates than the other two techniques under the gamma 3 mm/3% criteria, which was even more pronounced when the stricter gamma criteria of 2 mm/2% and 1 mm/1% were applied. Conclusion: VMAT can be applied to radiotherapy of thymoma, and the accuracy of treatment plan execution can be guaranteed through the ArcCHECK-3DVH system.

Comparison of Sequential Boost and Simultaneous Integrated Boost Volumetric Modulated Arc Therapy in Treatment of Head and Neck Carcinoma: A Prospective Interventional Study

Introduction: Volumetric Modulated Arc Therapy (VMAT) is a radiotherapy in head and neck cancer can be delivered by two boost techniques: Sequential Boost (SEQ) and Simultaneous Integrated Boost (SIB). There is still limited data comparing these two techniques. Aim: To compare SEQ and SIB planning techniques of VMAT in patients of Head And Neck Squamous Cell Carcinoma (HNSCC) in terms of disease response and acute toxicities. Materials and Methods: A prospective interventional study was conducted at Geetanjali Medical College and Hospital, Udaipur, Rajasthan, India from January 2019 to December 2020. Fifty two patients of HNSCC planned for radical chemoradiation were enrolled into two study arms SEQ-VMAT and SIB-VMAT. Chemotherapy given as weekly cisplatin 40 mg/m2 . Dosimetric comparison was done using Dose Volume Histogram (DVH) analysis. Response evaluation was done as per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 at 8-10 weeks follow-up. Acute toxicity evaluation was done as per Radiation Therapy Oncology Group (RTOG) toxicity grading. Statistical analysis was done using Statistical Package for Social Sciences (SPSS) version 20.0 software. Results: A total of 52 subjects were included in the study, out of which 26 subjects were included in SEB group while 26 subjects in SIB group. No significant difference was observed in demographic data in terms of age 56.2 vs 53.5 years, sex (24 males and 2 females in both the arms), disease site (oropharynx is the most common site 38.5% in both arms)and stage (IVA 69.2% in SEQ arm vs 46.2% in SIB arm and III 30.8% in SEQ arm vs 42.3% in SIB arm). Dosimetric data was comparable between the two arms. SIB-VMAT shows significantly higher incidence of acute dermatitis (grade1 dermatitis at two weeks 69.2% vs 38.5%, p=0.0279 and grade 2 dermatitis at six weeks 84.6% vs 38.5%, p=0.0007) and acute mucositis (grade 1 mucositis at two weeks 84.6% vs 38.5%, p=0.0007) as compared to SEQ-VMAT. SEQVMAT shows significantly higher incidence of dysphagia (grade 1 at four weeks 84.5% vs 50%, p=0.0087). No significant differences were observed in terms of xerostomia and laryngeal toxicity.No significant difference in overall response was observed between SIB vs SEQ (complete response 65.4% vs 53.85% p=0.40). Conclusion: SEQ appears better in terms of acute toxicities but SIB was more convenient as no re-planning was required. For head and neck radiotherapy SIB and Sequential VMAT are comparable in terms of overall response.

Dosimetric Evaluation of 4 Field Three-Dimensional Conformal Radiation Therapy and 7 Field Intensity Modulated Radiation Therapy in Esophageal Cancer Treated with Definitive Chemoradiation

Background: The present study aimed to evaluate dosimetrically and correlate the lung and heart dose volume histogram (DVH) of the 4 Field three-dimensional conformal radiotherapy (3DCRT) with 7 field intensity modulated radiotherapy (IMRT) in patients with oesophageal cancers. Method: This retrospective dosimetric study considered 20 oesophagus cancer patients treated with definitive chemoradiation with IMRT technique. In the 7 field IMRT technique, the first phase delivered a dose of 36Gy/18fr followed by 18Gy/9fr in two weeks in the second phase. In the 3DCRT technique, the first phase was planned with 4 field technique with two parallel opposed and two posterior oblique fields, followed by the 3 field technique in the second phase. The assessments of the techniques were performed using Differential DVH analysis of the right and left lungs, heart, and the spinal cord. The values of the mean dose, V20 (Volume receiving 20 Gy), and V30 (volume receiving 30 Gy) were assessed for any correlations. Results: The DVH of V20 in IMRT showed 5 % less lung volume irradiation compared to the 3DCRT plans and over 20% less V30 for irradiated heart volume. The study demonstrated a statistical advantage of using 7 field IMRT over 4 field 3DCRT in reducing the mean percentage dose to both lungs, heart, and spinal cord. Conclusion: 7 field IMRT is superior to 4 field 3DCRT plans in significantly reducing the average percentage of irradiated volume of both the lung and heart in esophageal cancer radiation therapy.

Effect of a lead block on alveolar bone protection in image-guided high-dose-rate interstitial brachytherapy for tongue cancer: using model-based dose calculation algorithms to correct for inhomogeneity.

PurposeThe purpose of this study was to evaluate the effect of a lead block for alveolar bone protection in image-guided high-dose-rate interstitial brachytherapy for tongue cancer.Material and methodsWe treated 6 patients and delivered 5,400 cGy in 9 fractions using a lead block. Effects of lead block (median thickness, 4 mm) on dose attenuation by distance were visually examined using TG-43 formalism-based dose distribution curves to determine whether or not the area with the highest dose is located in the alveolar bone, where there is a high-risk of infection. Dose re-calculations were performed using TG-186 formalism with advanced collapsed cone engine (ACE) for inhomogeneity correction set to cortical bone density for the whole mandible and alveolar bone, water density for clinical target volume (CTV), air density for outside body and lead density, and silastic density for lead block and its’ silicon replica, respectively.ResultsThe highest dose was detected outside the alveolar bone in five of the six cases. For dose-volume histogram analysis, median minimum doses delivered per fraction to the 0.1 cm3 of alveolar bone (D0.1cm3TG-43, ACE-silicon, and ACE-lead) were 344.3 (range, 262.9-427.4) cGy, 336.6 (253.3-425.0) cGy, and 169.7 (114.9-233.3) cGy, respectively. D0.1cm3ACE-lead was significantly lower than other parameters. No significant difference was observed between CTV-related parameters.ConclusionsThe results suggested that using a lead block for alveolar bone protection with a thickness of about 4 mm, can shift the highest dose area to non-alveolar regions. In addition, it reduced D0.1cm3 of alveolar bone to about half, without affecting tumor dose.

A Dosimetric evaluation of a high dose rate cobalt-60 brachytherapy source using shielded, single and multi-channel cylinder applicators for gynecological cancers.

Vaginal brachytherapy is a standard method for preventing the recurrences of malignancies in the treatment of gynecological cancers. Cylindrical applicators are usually employed in high dose rate cobalt-60 source brachytherapy after abdominal hysterectomy or bilateral salpingo-oophorectomy treatment. The aim of this study is to conduct an assessment of dosimetric properties of single channel, multichannel, and shielded cylinder applicators. This study utilizes a pelvis phantom with three different volumes of bladder and rectum to perform dose measurement around the cylindrical applicators. GAFCHROMIC EBT3 model film was used to measure dose distributions in water phantom around the bladder, rectum, applicator, and CTV. In order to properly compare the performance of the shielded applicator with multichannel and single channel applicators, we consider the both cases of a one-sided CTV and two CTVs placed on both sides of the vagina. Dose-volume histograms analysis shows no statistically significant difference in tumoral region for the two types of CTV between cylindrical applicators. The V120%, V100% and D95% values of target volume were 47.36%. 91.46%, and 3.99Gy for multi-channel cylinder applicator, 60.2%, 95.02%, and 3.99Gy for single channel cylinder applicator, respectively. Statistical analysis reports D0.1cc, D1cc, and D2cc for the multichannel applicator demonstrates a significant dose reduction in bladder compared with single channel. The V120%, V100%, and D95% values of target volume were 55.50%. 97.90%, and 3.91Gy for multi-channel cylinder applicator with four active channels (MCC-4), 41.56%, 92.10%. and 4.13Gy for shielded cylinder applicator, respectively. Statistical analysis reports D0.1cc, D1cc and D2cc for the MCC-4 demonstrates a noticeable dose reduction in bladder and rectum compared with Shielded channel. The results indicate that employing multichannel applicator in vaginal high dose rate cobalt-60 source brachytherapy can reduce the received dose to organs at risk without any significant loss of received dose in CTV, which is contributed to its asymmetric or symmetric dose distribution that depend on which channels are activated.

Determination of differences in dosimetry with and without intravenous contrast media for radiotherapy planning in the anatomical region of the head and neck

In radiotherapy (RT), to determine the tumor volume (TV) and its morphology, computed tomography (CT) is used, acquiring images without and with intravenous iodinated contrast media (CM), where its influence has been poorly studied usually in artificial phantoms. Computerized dosimetries without and with CM from 10 CT of head and neck were analyzed using a before-after design. The same study group served as a control. Point doses and dose-area histogram (DAH) were evaluated, as well as a dose-volume histogram (DVH), using Student's t-test with 5% significance. Before and after administering CM, the average difference between point doses was –0.09% within the confidence interval (CI) 0.27% and –0.45%, with a standard deviation (SD) 0.52%. The average doses using DAH, resulted in a mean difference of 0.02%, within the 0.2% CI and -0.16%, with 0.27% SD. The standard volume within 100% of the dose utilizing DVH analysis resulted in an average of the differences of 0.1%, with CI 1.34% and –1.14% and SD 1.76%. The t-test of difference of means for paired designs, with α=0.05 found that there are no significant differences between the study and control groups for the different dose reading methods.

Deterioration of pancreatic exocrine function in carbon ion radiotherapy for pancreatic cancer

Background and purposeIn radiotherapy (RT) for pancreatic cancer, the pancreas is considered an important organ at risk. However, there are insufficient reports on pancreatic function deterioration after X-ray RT as organ at risk, and there are no reports on those after carbon ion (C-ion) RT. Here, we evaluated pancreatic exocrine insufficiency (PEI) after C-ion RT using dose-volume histogram (DVH) analysis. Materials and methodsData were retrospectively collected from patients who had undergone C-ion RT for pancreatic cancer between July 2013 and June 2019. The prescribed C-ion doses were 55.2 Gy (relative biological effectiveness) in 12 fractions. Serum pancreatic amylase and lipase values were measured before and after C-ion RT. In DVH analysis, we assessed V5Gy–50Gy and V<5Gy–50Gy of pancreatic volume and analyzed whether these DVH parameters involved PEI. ResultsThirty-three patients were included in the analysis. The median follow-up duration after the initiation of C-ion RT in these patients was 15.8 months (range, 4.3–64.8). During and after treatment, 57.6% of patients developed PEI within 13.6 months, defined as pancreatic amylase and lipase deficiencies. In DVH analysis, V<5Gy was the most effective factor for the PEI, and the cutoff value for developing PEI in V<5Gy was 4.57 cm3. ConclusionWe showed that pancreatic exocrine function declined after C-ion RT for pancreatic cancer and that PEI was initiated early in the course of C-ion RT. Additionally, a low dose of DVH parameters, such as V<5Gy, was a prognostic factor of PEI.

Optimisation and validation of an integrated magnetic resonance imaging-only radiotherapy planning solution.

Background and purposeMagnetic resonance imaging (MRI)-only treatment planning is gaining in popularity in radiation oncology, with various methods available to generate a synthetic computed tomography (sCT) for this purpose. The aim of this study was to validate a sCT generation software for MRI-only radiotherapy planning of male and female pelvic cancers. The secondary aim of this study was to improve dose agreement by applying a derived relative electron and mass density (RED) curve to the sCT.Method and materialsComputed tomography (CT) and MRI scans of forty patients with pelvic neoplasms were used in the study. Treatment plans were copied from the CT scan to the sCT scan for dose comparison. Dose difference at reference point, 3D gamma comparison and dose volume histogram analysis was used to validate the dose impact of the sCT. The RED values were optimised to improve dose agreement by using a linear plot.ResultsThe average percentage dose difference at isocentre was 1.2% and the mean 3D gamma comparison with a criteria of 1%/1 mm was 84.0% ± 9.7%. The results indicate an inherent systematic difference in the dosimetry of the sCT plans, deriving from the tissue densities. With the adapted REDmod table, the average percentage dose difference was reduced to −0.1% and the mean 3D gamma analysis improved to 92.9% ± 5.7% at 1%/1 mm.ConclusionsCT generation software is a viable solution for MRI-only radiotherapy planning. The option makes it relatively easy for departments to implement a MRI-only planning workflow for cancers of male and female pelvic anatomy.

Bibliometric analysis of research relating to radiation-induced lung injury [2001-2020

Radiotherapy is one of the common means of cancer treatment, especially in the treatment of lung cancer. However, radiation therapy can cause lung tissue radiation lung injury. The study of this disease can reduce its incidence and avoid the occurrence of radiation pulmonary fibrosis. In the past 20 years, the study of radiation-induced lung injury (RILI) has attracted more attention. This paper extracts the main text information of RILI-related literature from WOSCC database from 2001 to 2020, uses Citespace and VOSviewer for visual analysis, and presents the results. We found that in the past 20 years, there have been 4,665 articles on RILI, and the number of articles published reached a peak in 2017. The United States is the main leader in this research field, among which UNIV Texas MD Anderson Cancer Center has published many research results in this field. The most active author is Liao Zhongxing, and the most influential journal is Int J Radiat Oncol, which provides a platform for scholars in related fields to publish their articles. Current research focuses mainly on randomized controlled trials related to RILI, the relationship between dose-volume histogram analysis and RILI formation, the protection of normal lung tissue, the effect of stereoscopic radiotherapy on RILI and the pathogenesis of RILI. In the study of the formation mechanism of RILI, the main research directions include the apoptosis mechanism of epithelial and endothelial cells, cytokine cascade theory, immune mechanism regulation process, oxidative stress mechanism, etc.

Investigation of optimum minimum segment width on VMAT plan quality and deliverability: A comprehensive dosimetric and clinical evaluation using DVH analysis

PurposeMinimum segment width (MSW) plays a fundamental role in the shaping of optimized apertures and creation of segments of varying sizes and shapes in complex radiotherapy treatment plans. The purpose of this work was to study the effect of MSW on dose distribution in patients planned with VMAT for various treatment sites using dose volume histogram (DVH) analysis.Materials and methodsFor the validation of optimum MSW, 125 clinical treatment plans were evaluated. Five groups were identified (brain, head and neck, thorax, pelvis, and extremity), and five cases were chosen from each group. For each case, five plans were created with different MSW (0.5, 0.8, 1.0, 1.25, and 1.5 cm). The quality of treatment plans created using different MSW were compared using dosimetric indicators such as target coverage (D 98—dose to 98% of the planning target volume (PTV), maximum dose (D 2—maximum dose to 2% of the PTV), monitor units (MU), and DVH parameters related to organs at risk (OAR). The effect of the MSW on delivery accuracy was quantitatively analyzed using the measured fluence utilizing ionization chamber‐based transmission detector and model‐based dose verification system. Traditional global gamma analysis (2%, 2 mm) and dose volume information was gathered for the PTV and organs at risk and compared for different MSWs.ResultsA total of 125 plans were created and compared across five groups. In terms of treatment plan quality, the plans using MSW of 0.5 cm was found to be superior in all groups. PTV coverage (D 98) decreased significantly (p < 0.05) as the MSW increased. Similarly, the maximum dose (D 2) was found to be increased significantly (p < 0.05) as the MSW increased from 0.5 cm, with MSW of 1.5 cm being the least in terms of plan quality for both PTVs and OARs. In terms of plan deliverability using DVH analysis, treatment planning system (TPS) compared to measured fluence, VMAT plans produced with MSW of 0.5 cm showed a better dosimetric index and a smaller deviation for both PTVs and OARs. The deliverability of the plans deteriorated as the MSW increased.ConclusionDose volume histogram (DVH) analysis demonstrated that treatment plans with minimal MSW showed better plan quality and deliverability and provided clinical relevance as compared to gamma index analysis.