Purpose: VMAT offers continuous dose delivery in the form of arcs while dynamically changing position of collimators and dose rate. The aim of the present study is to investigate the sensitivity of a ...3D‐verification system to different VMAT delivery errors. Methods: Three VMAT plans were generated with MONACO TPS (v2.0, Elekta‐CMS, Maryland Heights, MO) for brain tumor paradigms. With in‐house software, we modified the plans introducing the following errors: (i) One set of leaf bank was opened by 1mm, 2mm and individual leaves were randomly opened (0mm–2mm). (ii) Both sets of leaf banks were shifted by +/−1mm and +/− 2mm. (iii) Gantry angle was shifted by +/−0.5°, +/−1°, +/−2° and randomly shifted (−2° to +2°). All these plans (a total of 45) were delivered to a MatriXX‐based COMPASS system (v2.0, IBA‐Dosimetry,Germany). 3D‐dose distribution was reconstructed onto the patient anatomy based on the measured fluences. Dose—volume parameters for target (D95) and critical organs (Davg) were compared and analyzed. Results: For three reference plans, the maximum dose‐difference (MDD) between MONACO and COMPASS was about 10% (Davg‐lens). However, the absolute dose‐difference (ADD) for the same was 4cGy. For plans with errors in one set of leaf bank, the MDD and ADD were 10% and 13cGy for Davg‐optic nerve, respectively. With errors in both leaf banks, the MDD and ADD were 15% and 21cGy for Davg‐optic nerve, respectively. With gantry angle errors, the MDD and ADD were 50% and 20cGy, respectively. For PTV‐D95, the MDD noticed was 6% and the ADD was 16cGy for different kind of errors. Conclusions: Any increase in aperture size (error in one leaf bank) showed systematic deviations. Shifts in both leaf banks up to 2mm and gantry angle difference (2°) showed considerable deviations. Errors greater than 2mm/2° can be detected with COMPASS system in most of the cases.
IMRT for breast. A planning study Fogliata, A.; Nicolini, G.; Alber, M. ...
Radiotherapy and oncology,
September 2005, 2005-Sep, 2005-9-00, Letnik:
76, Številka:
3
Journal Article
Recenzirano
To evaluate the performance of ten different treatment-planning systems when intensity modulated (IMRT) plans are designed for breast treatments that include the irradiation of the internal mammary ...chain.
A dataset of five patients (CT images and volumes of interest) was distributed to design IMRT plans on the ten systems. To minimise biases, the same geometry and clinical planning aims were imposed on the individual plans. Results were analysed in terms of dose distributions and dose volume histograms.
For target coverage, the volume receiving more than 95% of the prescribed dose ranged from 77% (OTP) to 91% (Eclipse and Pinnacle), the volume receiving more than 107% ranged from 3.3% (Hyperion) to 23.2% (OTP). The mean dose to ipsilateral lung ranged from 13Gy (Eclipse) to 18Gy (OTP). The volume of the contralateral breast receiving more than 10Gy ranged from 3% (Pinnacle) to 26% (Precise). The volume of heart receiving more than 20Gy ranged from 7% (Eclipse) to 47% (Precise), the maximum significant dose to heart ranged from ∼27Gy (XiO) to ∼49Gy (Precise). The maximum significant dose to healthy tissue ranged from ∼51Gy (Eclipse) to ∼62Gy (OTP). It was also possible to show that the treatment geometry proposed here enables to minimise contralateral breast irradiation while keeping minimal ipsilateral lung (or heart) involvement and satisfactory target coverage.
Prolonged administration of temozolomide is widely used in patients with glioblastoma; whereas the treatment of anaplastic glioma differs between neurooncological centres. The safety, feasibility and ...efficacy of prolonged temozolomide administration in patients with anaplastic gliomas was evaluated.
Forty-two patients with primary, recurrent or secondary anaplastic glioma were retrospectively analysed for the course of their disease. Treatment mostly consisted of surgery, followed by radiotherapy with concomitant and adjuvant temozolomide. In five patients with recurrence of primary anaplastic glioma, chemotherapy was initiated without previous surgery. Temozolomide was administered until evidence of tumour recurrence, appearance of serious side-effects or patients' wish to finish chemotherapy.
The median overall survival (OS) was 39 months with a median cycle number of 7.5 (1-42). Treatment with temozolomide was stopped in 12 patients due to side-effects in general, whereas in only three patients (7.1%) treatment had to be discontinued due to haematological side-effects. There was no evidence of treatment related infections or grade IV toxicity. Extent of surgery had a significant influence on OS in anaplastic gliomas, the number of adjuvant temozolomide cycles showed a positive influence as well on time to progression (TTP) and OS.
Prolonged administration of adjuvant temozolomide is safe and can be favorable for patients with anaplastic gliomas.
Radiotherapy is an essential and reliable element of the treatment armamentarium in oncology. Numerous rules, regulations, and protocols minimize the associated risks. It can, however, never be ...excluded that errors in the treatment delivery chain result in inadequate tumor doses or unnecessary damage to organs at risk. A legal framework governs the management of such incidents. The most important European and North American regulations are reported.
Various directives issued by the European Union are differently implemented nationally. This applies particularly to the characterization of incidents that must be reported to authorities. Reporting thresholds, audit systems, and the extent of the integration of voluntary reporting systems vary.
Radiotherapy incidents are dealt with differently on an international level. Changes are to be expected based on the European Basic Safety Standards Directive that is currently being prepared and will have to be implemented nationally in due course.
Interfractional prostate motion during radiotherapy can have deleterious clinical consequences. It has become clinical practice to re-position the patient according to ultrasound or other imaging ...techniques. We investigated the dosimetric consequences of the linear translational position correction (isocenter correction) when a conformal IMRT technique with nine fields was used. Treatment plans of seven patients with empty and distended rectums were analyzed. The reference plans were calculated on the CT with an empty rectum. The treatment plans were transferred to a second CT with a distended rectum for an uncorrected setup of the patient referenced to bony anatomy and a corrected setup after translational position correction of the isocenter. The dosimetric consequences (with and without correction) were analyzed. For single treatment fractions, organ motion decreased the volume of the prostate encompassed by the 95% isodose (V95%) by up to -24%-p (percentage points). The mean rectum dose increased by up to 41%-p. Linear translational correction increased V95% of the prostate by up to 17%-p while the mean rectum dose was reduced by up to -23%-p compared to the uncorrected setup. Linear translational correction can improve radiation treatment accuracy for prostate cancer if geometrical changes are within certain limits.
Zusammenfassung
Ziele und Methodik
Die Strahlentherapie ist eine unverzichtbare und zuverlässige Säule in der Therapie onkologischer Erkrankungen. Zahlreiche Vorgaben zum Qualitätsmanagement, zur ...Qualitätssicherung und zum Strahlenschutz minimieren die Risiken des Verfahrens. Trotzdem ist es möglich, dass bei der Planung oder Durchführung für einzelne Patienten oder Patientengruppen, ungeplant und unbeabsichtigt, das Zielgebiet inadäquat versorgt oder die Risikostrukturen übermäßig geschädigt werden. Verschiedene Rechtsnormen regeln den Umgang mit solchen Ereignissen. Die wesentlichen diesbezüglichen europäischen und nordamerikanischen Regelungen werden vorgestellt.
Ergebnisse
Europäische Rahmenvorgaben werden in den Nationalstaaten unterschiedlich umgesetzt. Dies betrifft insbesondere die Charakterisierung von meldepflichtigen Ereignissen. In diesem Zusammenhang kommen freiwillige Meldesysteme, unterschiedliche Auditsysteme und unterschiedliche Meldeschwellen zum Einsatz.
Schlussfolgerung
Sicherheitsrelevante Ereignisse in der Strahlentherapie werden international unterschiedlich behandelt. Änderungen im europäischen Umgang mit solchen Ereignissen sind durch die in Vorbereitung befindliche „European Basic Safety Standards Directive“ und deren nationale Umsetzungen zu erwarten.
The vaccination route may influence the success of immunization against pathogens. The conventional intramuscular (i.m.) application of a vaccine containing the hepatitis B virus (HBV) surface ...antigen (HBsAg) led to protective anti‐HBs antibody levels in the majority of vaccine recipients. In this study, we vaccinated healthy volunteers and a group of i.m. vaccine nonresponders via the intradermal (i.d.) route and analyzed the HBV‐specific B‐cell response as well as class‐II– and class‐I–restricted T‐cell responses by 3H‐thymidine uptake, enzyme‐linked immunosorbent assay (ELISA) and enzyme‐linked immunospot assay (ELISPOT). The results were then compared with i.m. vaccinated controls. I.d. vaccinations were well tolerated and induced neutralizing anti‐HBs antibodies in all naive vaccine recipients and, importantly, all but one former i.m. nonresponder developed protective anti‐HBs serum antibody levels after 2 or 3 i.d. immunizations. On the cellular level, i.d. vaccine recipients showed significantly higher anti‐HBs producing B‐cell frequencies and more vigorous class‐II–restricted T‐helper (Th) cell responses than i.m. controls. However, although the HBsAg‐specific T cells were characterized by their cytokine release as Th1‐like cells in both groups, human leukocyte antigen (HLA)‐A2+ individuals who received the soluble HBsAg via the i.d. route developed higher peptide‐specific cytotoxic CD8+ T cell precursor (CTLp) frequencies. In conclusion, i.d. HBsAg vaccination is more effective even in former i.m. vaccine nonresponders with respect to antibody induction and specific B‐ and T‐cell responses. The induction of virus‐specific CTLp may provide the rationale to study the i.d. HBsAg vaccine in the treatment of chronic hepatitis B.
