Anterior Posterior Fields Research Articles

Dosimetric evaluation of a spinal cord dose-limiting 3D-CRT technique for radiotherapy of spinal metastases.

To evaluate the possible advantages of a simple spinal cord (SC) dose-limiting three-dimensional conformal radiotherapy (3D-CRT) technique in comparison to conventional two-dimensional (2D) techniques and other 3D-CRT techniques for spinal bone irradiation. For 41 spinal target volumes, seven different techniques were evaluated, using a standard schedule of 30Gy in 10 fractions. The SC dose-limiting 3D-CRT technique 1F2S-18MV using a single posterior field (F) supplemented by two anterior segment fields (S) and 18-MV photon beams was compared to two conventional 2D techniques (a single posterior field, PA, and two opposed anterior-posterior fields, APPA), three other 3D-CRT techniques (a single posterior field supplemented by four segment fields, 1F4S; two wedged fields, WD, and the SC dose-limiting variant using 6 MV, 1F2S-6MV) along with the original clinically applied plans. 1F2S-18MV demonstrated notably better results for all target volume parameters compared to the conventional 2D techniques (p<0.001). Limitation of the SC dose was significantly superior with 1F2S-18MV in comparison to PA and APPA (SC Dmean: 28.9±0.4 vs. 30.1±0.6Gy and 30.1±0.4Gy; SC Dmax: 30.9±0.7 vs. 32.5±1.0Gy and 31.8±0.7Gy; SC D1cm3 : 30.1±0.6 vs. 31.7±0.9Gy and 31.1±0.6Gy; p<0.001). Likewise, lower mean SC doses with 1F2S-18MV were observed in comparison to the more treatment time-consuming 3D-CRT techniques (1F4S, WD) and the original plans without relevant compromises on the dose homogeneity in the target volume and the dose exposure to the other OARs. In treatment planning of spinal metastases, simple variants of 3D-CRT-techniques like 1F2S-18MV can offer a significant dose limitation to the SC while providing a sufficient dose coverage of the target volume. Especially in patients with favorable life expectancy and potential need for re-irradiation, such SC dose-limiting 3D-CRT techniques may be a reasonable approach.

A dose planning study for cardiac and lung dose sparing techniques in left breast cancer radiotherapy: Can free breathing helical tomotherapy be considered as an alternative for deep inspiration breath hold?

To investigate the possibility to be able to offer left sided breast cancer patients, not suitable for DIBH, an organ at risk saving treatment. Twenty patients receiving radiotherapy for left breast cancer in DIBH were enrolled in the study. Planning CT scans were acquired in the same supine treatment position in FB and DIBH. 3DCRT_DIBH plans were designed and optimized using two parallel opposed tangent beams (with some additional segments) for the breast and chest wall and anterior-posterior fields for regional lymph nodes irradiation. Additionally, FB helical tomotherapy plans were optimized to minimize heart and lung dose. All forty plans were optimized with at least 95% of the total CTV covered by the 95% of prescribed dose of 50Gy in 25 fractions. HT_FB plans showed significantly better dose homogeneity and conformity compared to the 3DCRT_DIBH specially for regional nodal irradiation. The heart mean dose was almost comparable in 3DCRT_DIBH and HT_FB while the volume (%) of the heart receiving 25Gy had a statistically significant reduction from 7.90±3.33 in 3DCRT_DIBH to 0.88±0.66 in HT_FB. HT_FB was also more effective in left descending artery (LAD) mean dose reduction about 100% from 30.83±9.2Gy to 9.7±3.1. The ipsilateral lung volume receiving 20Gy has a further reduction of 43 % in HT_FB compared with 3DCRT_DIBH. For low dose comparison, 3DCRT_DIBH was superior for contralateral organ sparing compared to the HT_FB due to the limited angle for dose delivery. For patients who cannot be a candidate for DIBH for any reason, HT in free breathing may be a good alternative and provides heart and ipsilateral lung dose sparing, however with the cost of increased dose to contralateral breast and lung.

Using Cherenkov imaging to monitor the match line between photon and electron radiation therapy fields on biological tissue phantoms.

.Significance: Due to patients’ respiratory movement or involuntary body movements during breast cancer radiotherapy, the mismatched adjacent fields in surface exposure regions could result in insufficient dosage or overdose in these regions, which would lead to tissue injury, excessive skin burns, and potential death. Cherenkov luminescence imaging (CLI) could be used to effectively detect the matching information of adjacent radiation fields without extra radiation or invasive imaging.Aim: Our objective was to provide a biological experimental basis for monitoring matching of adjacent radiation fields between photon and electron fields due to introduced shifts during radiotherapy by CLI technique.Approach: A medical accelerator was used to generate photon and electron fields. An industrial camera system was adopted to image the excited CLI signal during irradiation of chicken tissue with yellow (group A and group C experiments) or black color (group B experiment). The following introduced shifts were tested: 10, 5, 2, and 0 mm toward superior or inferior direction. A model was introduced to deal with matching error analysis of adjacent radiation fields due to introduced shifts with adapted plans used to treat neoplasms of the right breast with supraclavicular nodes or internal mammary lymph node.Results: The matching values between photon and electron fields were consistent with the tested introduced shifts during yellow chicken irradiation. In group A, average discrepancies were and for photon fields and electron fields in anterior/posterior (AP) direction, with 87% and 75% of measurement within 1 mm, respectively. In group C, average discrepancies were and for oblique photon field with gantry angles of 330 deg and 150 deg, with 66% and 65% of measurement within 1 mm, respectively. The average discrepancies were for electron field in the AP direction, with 94% of measurement within 1 mm. The matching error introduced by the proposed method was less than 1.5 mm for AP fields and 2 mm for oblique incidence fields. However, the field matching could not be monitored with black chicken tissue irradiation due to a weak CLI signal that could hardly be extracted from background noise in group B.Conclusions: CLI is demonstrated for the quantitative monitoring of the field match line on light biological tissue phantoms and has potential for monitoring of field matching in surface tissue during breast cancer radiotherapy.

Practice Patterns of Pediatric Image-Guided Radiotherapy (IGRT): A Children’s Oncology Group Report

To assess practice patterns of pediatric image-guided radiotherapy (IGRT) within Children’s Oncology Group (COG) member institutions. A survey was directed to 347 COG member radiation oncologists and medical physicists between October and December 2017. Eleven vignettes asked clinicians for recommended treatment modalities [intensity modulation (IMRT), volumetric arc (VMAT), 3-dimensional conformal (3DCRT), anterior-posterior fields (AP/PA), proton (PT)], IGRT preferences [kilovoltage planar imaging (kVi), megavoltage portal imaging (MVi), cone beam computed tomography (CBCT)], and frequency. Technical questions queried physicists about imaging protocol, dose reduction, and adaptive therapy. One hundred sixty-eight responses (48%) were received (105 radiation oncologists and 63 physicists). First vs. second choices for treatment and IGRT modality varied by disease site: ependymoma (52% IMRT/VMAT vs. 36% PT guided by 29% kVi vs. 26% CBCT); craniopharyngioma (51% IMRT/VMAT vs. 38% PT guided by 32% combined CBCT/kVi vs. 24% CBCT); germinoma (59% IMRT/VMAT vs. 29% PT guided by 30% CBCT vs. 24% kVi); medulloblastoma (52% PT vs. 20% IMRT/VMAT guided by 33% kVi vs. 24% combined CBCT/kVi); rhabdomyosarcoma (RMS) (63% IMRT/VMAT vs. 44% PT guided by 34% CBCT vs. 31% combined CBCT/kVi); non-RMS soft tissue sarcoma (58% IMRT/VMAT vs. 31% 3DCRT guided by 34% CBCT vs. 27% combined CBCT/kVi); Ewing sarcoma (70% IMRT/VMAT vs. 29% PT guided by 34% CBCT vs. 34% combined CBCT/kVi); Hodgkin lymphoma (32% IMRT/VMAT vs. 28% 3DCRT guided by 33% kVi vs. 24% CBCT); neuroblastoma (61% IMRT/VMAT vs. 20% 3DCRT guided by 30% combined CBCT/kVi vs. 30% CBCT); Wilms tumor (66% AP/PA vs. 22% 3DCRT guided by 55% kVi vs. 26% MVi); and acute lymphocytic leukemia (ALL) (61% opposed laterals vs. 29% 3DCRT guided by 49% kVi vs. 27% MVi). IGRT frequency was primarily daily for all sites except Wilms tumor (45% daily vs. 35% weekly), Hodgkin lymphoma (58% daily vs. 19% weekly), and ALL (32% daily vs. 45% weekly). The use of IGRT images for making decisions on adaptive replanning was confirmed in 79% responses. Methods to reduce IGRT dose included: lower kV/milliampere-seconds (65%), selecting kV over MV (62%), collimation (48%), and reduced imaging (38%). Responses varied or were neutral (38%) on lowering IGRT doses due to second cancer risk. We report pediatric IGRT practice patterns in COG member institutions. Daily image guidance was used approximately 70% of the time across all sites. Although disease specific, kVi was most common for simple, while CBCT was frequent for complex treatments. Expert guidelines provided by COG Radiation Oncology Discipline for the utilization of IGRT methods are based on these results and existing evidence. Improved institutional technical capabilities should cultivate investigators to propose trials requiring highly precise tumor localization, verified by IGRT.

Evaluation of clinical efficacy and safety of single-channel intracavitary applicator for uterine cervical cancer: early results of a prospective randomized phase II clinical trial

Objective To evaluate whether the self-designed single-channel intracavitary applicator yields equivalent clinical efficacy and safety to the standard Fletcher-type three-channel applicator in the high-dose-rate (HDR) brachytherapy for uterine cervical cancer. Methods From December 2011 to April 2017, patients initially diagnosed with cervical cancer were randomly assigned into the external beam radiotherapy (EBRT)+ single-channel intracavitary applicator group (the patent single-channel group) and EBRT+ the Fletcher applicator group. Whole pelvis irradiation was delivered with 6-MV photons via a four-field box variant or anterior and posterior parallel fields. Five to six fractions of intracavitary brachytherapy were performed at a dose of 7 Gy at point A once a week after 30 Gy (BED at point A: 80-90 Gy). Chemotherapy was given with intravenous injection of cisplatin at a dose of 40 mg/m2 once weekly during EBRT.Clinical efficacy and safety were evaluated after the treatment. Results In total, 150 eligible cases were assigned into the Fletcher applicator group and 149 cases into the patent single-channel group. The short-term clinical efficacy and acute toxicity did not significantly differ between two groups. The response rate was 94.0% in the Fletcher group, and 94.7% in the patent single-channel group. In the Fletcher applicator group, 76(50.7%) patients developed ≥ grade 3 hematologic toxicity and 61(40.9%) in the patent group (P=0.195). Conclusions The self-designed patent single-channel intracavitary applicator yields equivalent clinical efficacy and safety (acute toxicity) to the standard Fletcher-type three-channel applicator in the HDR brachytherapy for uterine cervical cancer. Clincal Trial Registration Chinese Clinical Trial Registry (ChiCTR-TRC-12002321). Key words: Uterine cervical neoplasm/brachytherapy; Clinical trial

2D Dose Reconstruction by Artificial Neural Network for Pretreatment Verification of IMRT Fields

The use of intensity-modulated radiation therapy (IMRT) is developing rapidly in clinical routines. Because of the high complexity and uniqueness of IMRT treatment plans, patient-specific pretreatment quality assurance is generally considered a necessary prerequisite for patient treatment. In this work, we proposed a modified methodology of electronic portal imaging device (EPID)–based dose validation for pretreatment verification of IMRT fields by applying artificial neural networks (ANNs). The ANN must be trained and validated before use for pretreatment dose verification. For this purpose, 20 EPID fluence maps of IMRT prostate anterior-posterior fields were used as an input for ANN (feed forward type) and a dose map of those fluence maps that were predicted by treatment planning system as an output for ANN. After the training and validation of the neural network, the analysis of 10 IMRT prostate anterior-posterior fields showed excellent agreement between ANN output and dose map predicted by the treatment planning system. The average overall fields pass rate was 96.0% ± 0.1% with 3 mm/3% criteria. The results indicated that the ANN can be used as a low-cost, fast, and powerful tool for pretreatment dose verification, based on an EPID fluence map.

Comparison and Evaluation of Different Treatment Plans with IFRT Field and 6 and 18 MV Energies in Hodgkin's Lymphoma Involvement Neck and Mediastinum.

Radiotherapy with large mantle field is an effective technique in increasing the risk of secondary cancers among HL (Hodgkin Lymphoma) patients; therefore, it is essential to choose an effective treatment field including the least medical conditions in radiotherapy. The present study aimed to plan separate fields for neck and mediastinum using various energies, to compare dose distribution with MLC and to block field formation. In this study, 3D conformal treatments, Siemens Oncor accelerator equipped with multi-leaf collimator (MLC) were performed to create anterior-posterior fields. CT-scan data of 18 female patients with neck and mediastinal involvement was imported in TIGRT treatment planning system, and then treatment plans were introduced. Using treatment plan 1, photon 6 MV in neck weighting 1 from interior, 0.5 from posterior, photon 18MV in mediastinum weighting 1 from interior and 0.5 from posterior, it was shown that regarding the common treatment plan used with photon 6 MV, mean dose delivered to breast, lung, esophagus and larynx reduced 6, 7, 41 and 10 percent, respectively and uniformity index improved by 10 percent. Using block compared to MLC in all treatment plans offered improved average dose in all organs under study. To protect breast and lung while using MLC and block in the first treatment plan seemed to be more appropriate; however, using blocks in comparison to MLC increased delivered mean dose in all organs under study. Using separate fields with Pb blocks, though, showed smaller increase.

Low-Dose Splenic Irradiation is Effective for Patients With Hematological Diseases Who Have Symptomatic Splenomegaly

Splenic irradiation was commonly used for symptomatic relief in patients with hematologic disease. In this study, we assessed the response rate and the improvement of hemogram in patients with extramedullary hematopoiesis who received splenic irradiation. We also investigated the adverse effect of splenic irradiation in the same group of tumors. Between June 2004 and July 2016, 23 patients with hematological diseases who received splenic irradiation for symptomatic splenomegaly were included in this study. All patients were treated with splenic irradiation using two anterior-posterior field configurations (3D conformal radiotherapy technique or forward “field in field” intensity modulated radiotherapy technique). The symptom relief and hematological adverse effects were assessed. A total of 23 patients with symptomatic splenomegaly, including 19 cases of myelofibrosis, 3 cases of acute myeloid leukemia, and one with mantle cell lymphoma were analyzed. The radiation prescription dose ranged from 1 Gy to 5 Gy, with a median dose of 4 Gy, in 0.5 to 1 Gy per fraction (twice a week). Splenic irradiation resulted in splenomegaly regression with symptom relief in 21 (91.3%) of 23 cases. Among 21 cases, 3 cases had significant reduction of splenic size 1 week after completing radiotherapy. Grade 3 myelosuppression was observed in four patients, and that the hemogram of these patients improved subsequently after component therapy. Our results indicated that low-dose splenic irradiation with a median of 4 Gy provides an effective and well-tolerated palliative treatment option for symptomatic splenomegaly in patients with hematologic disease.

Effectiveness and toxicity of conventional radiotherapy treatment for painful spinal metastases: a detailed course of side effects after opposing fields versus a single posterior field technique

BackgroundConventional radiotherapy for painful spinal metastases can be delivered with a single posterior-anterior (PA) or two opposed anterior-posterior (APPA) fields. We studied the effectiveness and toxicity of both techniques and studied whether treatment technique was predictive for abdominal and skin toxicity.Patients and methodsWithin the Dutch Bone Metastasis Study, 343 patients received 8 Gray in a single fraction or 24 Gray in six fractions for painful spinal metastases. Treatment technique was not randomized. At baseline and weekly during follow-up, patients reported pain and other physical complaints. Any complaint increasing within 4 weeks after treatment was noted as a side effect. Pain response was calculated according to international standards, taking into account changes in pain score and medication. Repeated measurement analyses and multivariate logistic analyses were performed.ResultsPatients were mainly treated on the thoracic (34%) and lumbar (53%) spine and 73% received a PA field. Pain response was similar between both techniques (74%). In patients treated at the thoraco-lumbar and lumbar spine, with multiple fractions, significantly more abdominal complaints were noticed. In multivariate analysis, radiotherapy technique did not predict for side effects.ConclusionConventional radiotherapy of painful spinal metastases provides limited toxicity. Radiotherapy technique is not an independent predictor of abdominal and skin toxicity of irradiation.

Comparison and Evaluation of Different Treatment Plans with IFRT Field and 6 and 18 MV Energies in Hodgkin’s Lymphoma Involvement Neck and Mediastinum

Background: Radiotherapy with large mantle field is an effective technique in increasing the risk of secondary cancers among HL (Hodgkin Lymphoma) patients; therefore, it is essential to choose an effective treatment field including the least medical conditions in radiotherapy.Objective: The present study aimed to plan separate fields for neck and mediastinum using various energies, to compare dose distribution with MLC and to block field formation.Materials and Methods: In this study, 3D conformal treatments, Siemens Oncor accelerator equipped with multi-leaf collimator (MLC) were performed to create anterior-posterior fields. CT-scan data of 18 female patients with neck and mediastinal involvement was imported in TIGRT treatment planning system, and then treatment plans were introduced.Results and Conclusion: Using treatment plan 1, photon 6 MV in neck weighting 1 from interior, 0.5 from posterior, photon 18MV in mediastinum weighting 1 from interior and 0.5 from posterior, it was shown that regarding the common treatment plan used with photon 6 MV, mean dose delivered to breast, lung, esophagus and larynx reduced 6, 7, 41 and 10 percent, respectively and uniformity index improved by 10 percent. Using block compared to MLC in all treatment plans offered improved average dose in all organs under study. To protect breast and lung while using MLC and block in the first treatment plan seemed to be more appropriate; however, using blocks in comparison to MLC increased delivered mean dose in all organs under study. Using separate fields with Pb blocks, though, showed smaller increase.

Long-term complications of definitive chemoradiotherapy for esophageal cancer using the classical method.

Chemoradiation therapy is widely used to treat both inoperable and operable patients, and is less invasive than surgery. Although the number of long-term survivors who have received chemoradiation therapy is increasing, the long-term toxicity pattern and cumulative incidence of toxicity regarding this modality are poorly understood. Classically, chemoradiation therapy for esophageal cancer consists of an anterior–posterior field and a subsequent oblique boost field. We retrospectively analyzed patients who were treated with definitive chemoradiation therapy for esophageal cancer using this classical method from 1999 to 2008. For the assessment of toxicity, the National Cancer Institute Common Toxicity Criteria Version 3.0 was adopted. A total of 101 patients were analyzed. The median follow-up time was 16 months for all patients and 62 months for the surviving patients. Eleven patients experienced late toxicities of ≥Grade 3. Two patients died of late toxicities. The 3- and 5-year cumulative incidences for the first late cardiopulmonary toxicities of ≥Grade 3 were 17.4% and 20.8%, respectively. Cardiopulmonary effusions were observed within the first 3 years of completion of the initial treatment in seven out of eight patients. Sudden death and cardiac ischemia were observed over a 10-year period. Older age was found to be a risk factor for late toxicity after definitive chemoradiation therapy for esophageal cancer. Substantial toxicities were observed in patients who had received chemoradiation therapy for esophageal cancer using the classical method. To minimize the incidence of late toxicity, more sophisticated radiation techniques may be useful.

NTCP modeling analysis of acute hematologic toxicity in whole pelvic radiation therapy for gynecologic malignancies – A dosimetric comparison of IMRT and spot-scanning proton therapy (SSPT)

PurposeThis treatment planning study was conducted to determine whether spot scanning proton beam therapy (SSPT) reduces the risk of grade ⩾3 hematologic toxicity (HT3+) compared with intensity modulated radiation therapy (IMRT) for postoperative whole pelvic radiation therapy (WPRT). Methods and materialsThe normal tissue complication probability (NTCP) of the risk of HT3+ was used as an in silico surrogate marker in this analysis. IMRT and SSPT plans were created for 13 gynecologic malignancy patients who had received hysterectomies. The IMRT plans were generated using the 7-fields step and shoot technique. The SSPT plans were generated using anterior-posterior field with single field optimization. Using the relative biological effectives (RBE) value of 1.0 for IMRT and 1.1 for SSPT, the prescribed dose was 45Gy(RBE) in 1.8Gy(RBE) per fractions for 95% of the planning target volume (PTV). The homogeneity index (HI) and the conformity index (CI) of the PTV were also compared. ResultsThe bone marrow (BM) and femoral head doses using SSPT were significantly lower than with IMRT. The NTCP modeling analysis showed that the risk of HT3+ using SSPT was significantly lower than with IMRT (NTCP=0.04±0.01 and 0.19±0.03, p=0.0002, respectively). There were no significant differences in the CI and HI of the PTV between IMRT and SSPT (CI=0.97±0.01 and 0.96±0.02, p=0.3177, and HI=1.24±0.11 and 1.27±0.05, p=0.8473, respectively). ConclusionThe SSPT achieves significant reductions in the dose to BM without compromising target coverage, compared with IMRT. The NTCP value for HT3+ in SSPT was significantly lower than in IMRT.

CT Simulation to Evaluate of Pelvic Lymph Node Coverage in Conventional Radiotherapy Fields Based on Bone and Vessels Landmarks in Prostate Cancer Patients.

BackgroundRadiotherapy is the gold standard for treatment of prostrate cancer as it can cover an adequate area of tissues at risk for metastasis.ObjectivesWe evaluated the Pelvic lymph node coverage of conventional radiotherapy fields based on bone and vessels landmarks using computed tomography (CT) simulation in patients with prostate cancer referred to Shohada-e-Tajrish hospital.Patients and MethodsIn this cross sectional study, 40 patients with prostate cancer at the Stage T1c to T3b were studied. Pelvic lymph nodes were contoured by using pelvic vessels as surrogate markers. The distances were measured at different points of anterior-posterior (AP) and lateral fields and distances > 5 mm or more between the contoured nodes and the field borders.ResultsMean and standard deviation of the aortic bifurcation from the superior border was 4.73 ± 1.16 cm, the distance of common iliac bifurcation from the superior border was 1.11 ± 1.25 cm, the mean (SD) distance of right external iliac from the lateral border of AP field was 2.06 ± 0.48 cm and for left external iliac artery was 1.90 ± 0.56 cm. The distance of the external iliac artery from the anterior border of the lateral field was 2.30 ± 0.74 cm. The distance of the external iliac artery from pelvic rim was 0.59 ± 0.59 cm, distance of bifurcation of iliac from sacroiliac joint was 0.82 ± 1.01 cm, the size of the pelvic rim was 12.30 ± 0.64 cm, sacral width was 8.29 ± 1.01 cm, anterior promontory symphysis distance was 12.02 ± 0.92 cm and posterior promontory symphysis distance was 10.98 ± 0.73 cm.ConclusionsWe observed that conventional radiotherapy using CT simulation based on bone and vessels landmarks provided adequate coverage of pelvic lymph nodes in our patients with prostate cancer.

Regional lymph node radiotherapy in breast cancer: single anterior supraclavicular field vs. two anterior and posterior opposed supraclavicular fields.

Background:The treatment of lymph nodes engaged in breast cancer with radiotherapy leads to improved locoregional control and enhanced survival rates in patients after surgery. The aim of this study was to compare two treatment techniques, namely single anterior posterior (AP) supraclavicular field with plan depth and two anterior and posterior opposed (AP/PA) supraclavicular fields. In the study, we also examined the relationships between the depth of supraclavicular lymph nodes (SCLNs) and the diameter of the wall of the chest and body mass index (BMI).Methods:Forty patients with breast cancer were analyzed using computed tomography (CT) scans. In planning target volume (PTV), the SCLNs and axillary lymph nodes (AXLNs) were contoured, and, with the attention to PTV, supraclavicular (SC) depth was measured. The dosage that reached the aforementioned lymph nodes and the level of hot spots were investigated using two treatment methods, i.e., 1) AP/PA and 2) AP with three-dimensional (3D) planning. Each of these methods was analyzed using the program Isogray for the 6 MV compact accelerator, and the diameter of the wall of the chest was measured using the CT scan at the center of the SC field.Results:Placing the plan such that 95% of the target volume with 95% or greater of the prescribed dose of 50 Gy (V95) had ≥95% concordance in both treatment techniques. According to the PTV, the depth of SCLNs and the diameter of the wall of the chest were 3–7 and 12–21cm, respectively. Regression analysis showed that the mean SC depth (the mean Plan depth) and the mean diameter of the wall of the chest were related directly to BMI (p<0.0001, adjusted R2=0.67) and (p<0.0001, adjusted R2=0.71), respectively.Conclusion:The AP/PA treatment technique was a more suitable choice of treatment than the AP field, especially for overweight and obese breast cancer patients. However, in the AP/PA technique, the use of a single-photon, low energy (6 MV) caused more hot spots than usual.

Combined external and intracavitary irradiation in treatment of advanced cervical carcinomas: predictive factors for treatment outcome and early and late radiation reactions.

The objective of this study was to find out predictive factors of tumor control as well as acute and late radiation reactions in treatment of advanced cervical carcinomas. In a series of 134 primary cervical carcinomas in International Federation of Gynecology and Obstetrics stages I to IV treated with combined external pelvic and intraluminal cervical-vaginal brachytherapy, predictive and prognostic factors were analyzed with regard to tumor control, recurrences, survival data, and adverse effects. Concomitant chemotherapy was given to 48 patients (35.8%). The external beam therapy was given with a 4-field technique (50-60 Gy) and brachytherapy was given with a high-dose rate (iridium-192) afterloading technique using a ring applicator set. A computed tomographically based 3-dimensional dose-planning system was used for the external beam therapy and for the brachytherapy planning. The mean age of the patients was 65 years. A total of 110 tumors were squamous cell carcinomas and 24 were adenocarcinomas or adenosquamous carcinomas. A total of 111 tumors were in International Federation of Gynecology and Obstetrics stages I to II; 23 tumors, in stages III to IV. The primary control rate of the complete series was 92.5%. Tumor size, the brachytherapy dose, the combined external and brachytherapy dose, as well as the number of days of interruption (delay) of irradiation were all significant predictive factors for local tumor control. Forty recurrences (30%) were recorded. Early radiation reactions were recorded in 67% (mostly grade 1) and were associated with the widths of the anterior-posterior and lateral pelvic fields. Serious late radiations reactions (grade 3-4) were noted in 11%. The width of the lateral pelvic fields, left point A and B doses, dose to the rectal reference point, as well as asymmetry of the dose distribution were associated with late severe reactions. Prior abdominal and pelvic surgery was also a high-risk factor for late tissue reactions. Concomitant chemotherapy did not increase the risk for acute or late toxicity.

Comparison of Neural Responses to Cat Meows and Human Vowels in the Anterior and Posterior Auditory Field of Awake Cats

For humans and animals, the ability to discriminate speech and conspecific vocalizations is an important physiological assignment of the auditory system. To reveal the underlying neural mechanism, many electrophysiological studies have investigated the neural responses of the auditory cortex to conspecific vocalizations in monkeys. The data suggest that vocalizations may be hierarchically processed along an anterior/ventral stream from the primary auditory cortex (A1) to the ventral prefrontal cortex. To date, the organization of vocalization processing has not been well investigated in the auditory cortex of other mammals. In this study, we examined the spike activities of single neurons in two early auditory cortical regions with different anteroposterior locations: anterior auditory field (AAF) and posterior auditory field (PAF) in awake cats, as the animals were passively listening to forward and backward conspecific calls (meows) and human vowels. We found that the neural response patterns in PAF were more complex and had longer latency than those in AAF. The selectivity for different vocalizations based on the mean firing rate was low in both AAF and PAF, and not significantly different between them; however, more vocalization information was transmitted when the temporal response profiles were considered, and the maximum transmitted information by PAF neurons was higher than that by AAF neurons. Discrimination accuracy based on the activities of an ensemble of PAF neurons was also better than that of AAF neurons. Our results suggest that AAF and PAF are similar with regard to which vocalizations they represent but differ in the way they represent these vocalizations, and there may be a complex processing stream between them.

Evaluation of set-up errors in head and neck radiotherapy using electronic portal imaging

IntroductionThe aim of this study was to evaluate three-dimensional (3D) set-up errors and propose optimum margins for planning target volume (PTV) coverage in head and neck radiotherapy. MethodsThirty-five patients were included in the study. The total number of portal images studied was 632. Population systematic (Σ) and random (σ) errors for the patients with head and neck cancer were evaluated based on the portal images in the caudocranial longitudinal (CC) and left-right lateral (LR) direction measured in the anterior-posterior (AP) field, as well as from the images in the caudocranial longitudinal (CC) and dorsoventral lateral (DV) direction measured in the lateral (LAT) field. The values for the clinical-to-planning target volume (CTV-PTV) margins were calculated using ICRU Report 62 recommendations, along with Stroom's and van Herk's formulae. ResultsThe standard deviations of systematic set-up errors (Σ) ranged from 1.51 to 1.93 mm while the standard deviations of random set-up (σ) errors fell in between 1.77 and 1.86 mm. The mean 3D vector length of displacement was 2.66 mm. PTV margins calculated according to ICRU, Stroom's and van Herk's models were comprised between 1.95 and 6.16 mm in the three acquisition directions. Discussion and conclusionsBased on our results we can conclude that a 6-mm extension of CTV to PTV margin, as the lower limit, is enough to ensure that 90% of the patients treated for head and neck cancer will receive a minimum cumulative CTV dose greater than or equal to 95% of the prescribed dose.

Conventional four field radiotherapy versus computed tomography-based treatment planning in cancer cervix: A dosimetric study

Background:With advancements in imaging, wide variations in pelvic anatomy have been observed, thus raising doubts about adequate target volume coverage by conventional external radiotherapy fields based on bony landmarks. The present study evaluates the need for integrating computed tomography (CT)-based planning in the treatment of carcinoma cervix.Aims:To estimate inadequacies in target volume coverage when using conventional planning based on bony landmarks.Materials and Methods:The study consisted of 50 patients. Target volume delineation was done on planning CT scans, according to the guidelines given in literature. The volume of target receiving 95% of prescribed dose (V95) was calculated after superimposing a conventional four field box on digitally reconstructed radiograph. The geographic miss with conventional four field box technique was compared with the CT-based target volume delineation.Results:In 48 out of 50 patients, the conventional four field box failed to encompass the target volume. The areas of miss were at the superior and lateral borders of the anterior-posterior fields, and the anterior border of the lateral fields. The median V95 for conventional fields marked with bony landmarks was only 89.4% as compared to 93% for target delineation based on CT contouring.Conclusions:Our study shows inadequate target volume coverage with conventional four field box technique. We recommend routine use of CT-based planning for treatment with radiotherapy in carcinoma cervix.

Electronic portal images (EPIs) based position verification for the breast simultaneous integrated boost (SIB) technique

Background and purposeTo develop a method based on electronic portal images (EPIs) for the position verification of breast cancer patients that are treated with a simultaneous integrated boost (SIB) technique. Method3D setup errors of the breast outline and the thoracic wall were determined from EPIs of the tangential treatment fields and anterior posterior (AP) verification field. The method was verified with repeated CT scans of 38 patients with an average setup error larger than 5mm. ResultThe 3D position deviation of the boost volume can best be determined from the position deviation of the breast outline in the ventrodorsal direction and the thoracic wall in the lateral and longitudinal directions from the tangential and AP EPIs. The method gives an average overestimation of the deviation of the boost volume in the ventrodorsal, lateral and longitudinal directions by 28%, 20% and 6%, respectively and an average underestimation of the deviation of the whole breast by 32%, 17% and 39%. ConclusionsThe described method is superior to using tangential EPIs only and is recommended for position verification of breast cancer patients that are treated with a SIB technique if no Cone beam CT (CBCT) or fiducial markers can be used.

Effectiveness of two different HDR brachytherapy regimens with the same BED value in cervical cancer.

PurposeTo analyze the effectiveness of biologically effective dose (BED) in two different regimens of HDR brachytherapy keeping the same total BED to point A and to compare the relationship of overall treatment time in terms of local control and bladder and rectal complications.Material and methodsThe study included two groups comprising a total of 90 cervical cancer patients who underwent external beam radiotherapy (EBRT) followed by HDR intracavitary brachytherapy (ICBT). EBRT treatment was delivered by a Co-60 teletherapy unit to a prescribed dose of 45 Gy with 1.8 Gy per fraction in 25 fractions over a period of five weeks. Parallel opposed anterior–posterior (AP/PA) fields with no central shielding were used, followed by the HDR ICBT dose, to point A, of either two fractions of 9.5 Gy with a gap of 10 days, or three fractions of 7.5 Gy with a gap of 7 days between the fractions. Gemcitabine (dose of 150 mg/m2) was given weekly to all the patients as a radiosensitizer. The calculate BED3 to point A was almost the same in both groups to keep the same late complication rates. The doses, and BED10 and BED3, were calculated at different bladder and rectal point as well as at the lymphatic trapezoid points. During and after treatment patients were evaluated for local control and complications for 24 months.Results and ConclusionsDoses and BEDs at different bladder, rectal and lymphatic trapezoid points, local control, and complications in both HDR ICBT groups did not have statistically significant differences (p > 0.05). Both HDR ICBT schedules are well tolerable and equally effective.