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PubMed1987

[Combination of bilateral pelvic lymphadenectomy, permanent iodine-125 implantation and percutaneous irradiation of localized prostate carcinoma. 1: Methods and results].

Since the beginning of 1981, 32 patients at an age of 52 to 72 years who suffered from a locally confined adenocarcinoma of the prostate were treated by permanent implantation of iodine-125 seeds at the Urologic and Radiotherapeutic Hospital of the University of Erlangen. 25 patients were evaluated after a median observation period of 30 months. The first group consisting of 19 patients was submitted to a combined percutaneous and interstitial treatment, the other six patients were initially treated only by interstitial therapy because of severe complications observed in the meantime. After bilateral pelvic staging lymphadenectomy, permanent iodine-125 seeds were implanted into the patients of stage T1, T2, early T3, and pN0-1, in case of microscopic lymph node manifestation without capsular perforation also into patients of stage pN2 and pN4. Eight weeks later the patients received a moving beam irradiation with 10 MV photons at the linear accelerator. The centre of the prostate was faded out by a specially constructed H absorber in such a way that the prescribed target dose of 36 Gy in four weeks to the 90%-isodose was only applied to a spherical surface around the implant. One patient died perioperatively from an embolism due to phlebothrombosis of the thigh. 22 out of the other 24 patients are in complete remission, one patient had a local recurrence in the right seminal vesicle which appeared 28 months after primary therapy, and one patient developed skeletal metastases. The objective side effects and late complications of our combined treatment are considerable with respect to their incidence as well as their severity: a slight or medium radioproctitis was found after a latent period of one to two years in 28% (5/18) of cases, after a latent time of about 1 1/2 to two years another 28% (5/18) developed subsequently to a proctitis an urethral stricture and an ulcer situated on the anterior rectum wall facing the prostate, and four patients presented finally a prostato-rectal fistula.

Aged↗

PubMed1996

Feasibility study of multileaf collimated electrons with a scattering foil based accelerator.

BACKGROUND AND PURPOSE: There is an ever evolving process to improve the technical aspects of electron beam delivery. Both the foil/applicator and scanning electron beam systems have gone through recent upheavals. Concomitantly, multileaf collimators are now a staple method for collimating photons. We undertook a study of multileaf collimated electron beam (MLCEB) using a dual scattering foil system. MATERIALS AND METHODS: We compared MLCEB with applicator collimated electron beams (AEB) by examining the dosimetric aspects of the two systems using 70 and 80 cm SSDs for the MLCEB, the minimum practical SSDs achievable. Percent depth dose, isodose profiles, output factors, leakage, surface dose, bremstrahlung, effective SSDs, etc. were measured using film and/or ion chamber. Clinical fields, such as posterior neck node (PNN), were compared. We also investigated the use of MLCEB for arc therapy using segments. RESULTS: In all cases, the MLCEB performed inferior, as judged by isodoses, uniformity index (UI) and penumbra analysis. The 80 cm SSD (minimum for PNN), low energy, small fields, was the worst case. For a 6 MeV beam, the UI/penumbra was 0.823/10 mm for the AEB, and 0.561/29 mm for the MLCEB at 80 cm SSD. The PNN multileaf fields exhibited narrow 90% and 80% isodose lines, and wide 20% and 10% lines. CONCLUSIONS: We conclude that multileaf for PNN fields could not be matched to adjacent off-cord photon fields. The "stair-stepping' effect associated with MLC photons was absent for electrons.

Electrons↗

PubMed2004

Results of a one year survey of output for linear accelerators using IMRT and non-IMRT techniques.

This paper presents the results of a one year survey of treated fields for 3 treatment machines at our New Jersey regional center. One machine predominantly treated IMRT prostate patients using a sliding window technique. The others were not equipped to deliver IMRT. Information obtained for each treated field included patient number, modality, monitor units delivered, gantry angle, and time. Data was obtained directly from our record and verify system and analyzed using a spreadsheet. We studied workload (MU/week), patient load, and average MU per patient as a function of time, as well as angular distributions and number of treatment fractions per patient. We also calculated the fraction of time the beam was on during treatments. By the end of the survey year, the workload of the IMRT machine reached approximately 100,000 MU/week and that of the non-IMRT machines was approximately 40-45000 MU/week. This was due predominantly to the higher number of monitor units for IMRT plans. Patient loads were not significantly different for the 3 machines. Duty cycle was 14% and 16% for the non-IMRT machines and 27% for the IMRT machine. The difference in workload for IMRT treatments relative to non-IMRT treatments confirms an earlier study performed at our institution using a much smaller data sample. One needs to consider the increase in leakage associated with this higher workload when designing shielding for an IMRT room.

Data Collection↗

PubMed2004

Three-dimensional conformal setup (3D-CSU) of patients using the coordinate system provided by three internal fiducial markers and two orthogonal diagnostic X-ray systems in the treatment room.

PURPOSE: To test the accuracy of a system for correcting for the rotational error of the clinical target volume (CTV) without having to reposition the patient using three fiducial markers and two orthogonal fluoroscopic images. We call this system "three-dimensional conformal setup" (3D-CSU). METHODS AND MATERIALS: Three 2.0-mm gold markers are inserted into or adjacent to the CTV. On the treatment couch, the actual positions of the three markers are calculated based on two orthogonal fluoroscopies crossing at the isocenter of the linear accelerator. Discrepancy of the actual coordinates of gravity center of three markers from its planned coordinates is calculated. Translational setup error is corrected by adjustment of the treatment couch. The rotation angles (alpha, beta, gamma) of the coordinates of the actual CTV relative to the planned CTV are calculated around the lateral (x), craniocaudal (y), and anteroposterior (z) axes of the planned CTV. The angles of the gantry head, collimator, and treatment couch of the linear accelerator are adjusted according to the rotation of the actual coordinates of the tumor in relation to the planned coordinates. We have measured the accuracy of 3D-CSU using a static cubic phantom. RESULTS: The gravity center of the phantom was corrected within 0.9 +/- 0.3 mm (mean +/- SD), 0.4 +/- 0.2 mm, and 0.6 +/- 0.2 mm for the rotation of the phantom from 0-30 degrees around the x, y, and z axes, respectively, every 5 degrees. Dose distribution was shown to be consistent with the planned dose distribution every 10 degrees of the rotation from 0-30 degrees. The mean rotational error after 3D-CSU was -0.4 +/- 0.4 (mean +/- SD), -0.2 +/- 0.4, and 0.0 +/- 0.5 degrees around the x, y, and z axis, respectively, for the rotation from 0-90 degrees. CONCLUSIONS: Phantom studies showed that 3D-CSU is useful for performing rotational correction of the target volume without correcting the position of the patient on the treatment couch. The 3D-CSU will be clinically useful for tumors in structures such as paraspinal diseases and prostate cancers not subject to large internal organ motion.

Humans↗

PubMed1998

Whole-body dose from tomotherapy delivery.

PURPOSE: To measure whole-body dose in tomotherapy of the head and neck region resulting from internal patient scatter and linear accelerator leakage. METHODS AND MATERIALS: Treatments are performed using a commercial computer-controlled intensity modulated radiation therapy planning and delivery system (Peacock, NOMOS Corp.) and a 6-MV linear accelerator (Clinac 6/100, Varian Corp.). The patient dose outside the treatment field is measured in a water-equivalent phantom using thermoluminescent dosimetry. The whole-body dose components from internal scatter and leakage are separately determined. The use of fixed-portal leakage and scattered radiation measurements to estimate the whole-body dose from tomotherapy is evaluated. RESULTS: The internally scattered dose is significant near the target, but becomes negligible relative to the leakage dose beyond 15 cm from the target. Dose at 10 cm from the target volume, due to internal scatter and leakage, is approximately 2.5% of the total target dose, reducing to 0.5% at 30 cm. The measured dose is relatively uniform throughout the phantom. CONCLUSION: The whole-body dose equivalent from a tomotherapy treatment is greater than that from conventional radiation therapy. Further studies are required to assess the trade-off between improved dose distribution conformality and a possible slight increase in radiation-induced fatal malignancies. The accuracy of using fixed-portal leakage and scattered dose measurements to estimate the whole-body dose from tomotherapy treatments is adequate, if the appropriate fixed-portal field size equivalent is used.

Head↗

PubMed2003

Review of the energy check of an electron-only linear accelerator over a 6 year period: sensitivity of the technique to energy shift.

The calibration and monthly QA of an electron-only linear accelerator dedicated to intra-operative radiation therapy has been reviewed. Since this machine is calibrated prior to every procedure, there was no necessity to adjust the output calibration at any time except, perhaps, when the magnetron is changed, provided the machine output is reasonably stable. This gives a unique opportunity to study the dose output of the machine per monitor unit, variation in the timer error, flatness and symmetry of the beam and the energy check as a function of time. The results show that, although the dose per monitor unit varied within +/- 2%, the timer error within +/- 0.005 MU and the asymmetry within 1-2%, none of these parameters showed any systematic change with time. On the other hand, the energy check showed a linear drift with time for 6, 9, and 12 MeV (2.1, 3.5, and 2.5%, respectively, over 5 years), while at 15 and 18 MeV, the energy check was relatively constant. It is further shown that based on annual calibrations and RPC TLD checks, the energy of each beam is constant and that therefore the energy check is an exquisitely sensitive one. The consistency of the independent checks is demonstrated.

Calibration↗

PubMed1999

Successful conversion from a linear accelerator-based program to a Gamma Knife radiosurgery program: the Cleveland Clinic experience.

From August 1989 to January 1997, 307 treatments in 293 patients were performed with a linear accelerator-based (LINAC) stereotactic radiosurgery system. Because of the program s success, the need for a dedicated radiosurgery unit in Ohio and the desire to treat functional disorders, the Cleveland Clinic Health System (CCHS) obtained the first Gamma Knife in the state of Ohio. Based on the previous volume of patients for radiosurgery, it was estimated that 75-100 patients would be treated during the first year of operation. However, during the first calendar year, 214 treatments were performed on 205 patients, which far exceeded expectations. The success of the CCHS Gamma Knife Center can be attributed to an increase in a number of factors. These included marketing efforts, patient awareness, increased use for functional disorders, physician understanding of radiosurgery, use by qualified nonaffiliated radiation oncologists and neurosurgeons, and outpatient delivery (95% with the Gamma Knife vs <5% with the LINAC). With proper planning, education, and awareness, the opening of a Gamma Knife Center can greatly increase the volume of radiosurgery performed when compared with a LINAC-based program.

Brain Neoplasms↗

PubMed2000

The effects of focus-skin distance and shaping block tray on the calibration factor of in-vivo dosimetry diodes.

PURPOSE: In-vivo dose measurements during conformal treatment require correction factor evaluations for differences in block shapes, field size and source-skin distance (SSD). The aim of this paper is to evaluate a single correction factor, CFentranceSSD, depending only on source-skin distance, which takes into account both shape and size of blocked fields, in pelvic treatments. MATERIALS AND METHODS: A set of measurements was performed to investigate the effects of different block shapes and sizes, source-skin distances and collimator settings on the entrance dose values. For this reason EDP 20 Scanditronix diodes, with 20 mm water-equivalent build-up cap, were irradiated by 2 Varian linear accelerators (Clinac 1800 and Clinac 2100) 18 MV photon beams with 3 different collimator settings. Diodes were calibrated by comparison with a Farmer 2571 ionization chamber at reference conditions (10 cm x 10 cm open field, source-skin distance 100 cm, build-up depth 3.3 cm) in order to convert the semiconductor signal into water absorbed dose. Three sets of different measurements (regarding open beams, tray fields and shaped fields) were performed. Diode responses were compared with the ionization chamber ones, in the same irradiation conditions. RESULTS: The CFentranceSSD trends can be described by linear fits in dependence upon source-skin distance, and the effect with tray alone or with tray and blocks is stronger than in the open field. The observed effects can be interpreted by the influences of a) the different source distances of diode and reference point in the phantom and b) the secondary electron contamination of the photon beam upon the calibration factor of the diode. CONCLUSION: The effects of source-skin distance and of the shaping blocks and tray upon the diode calibration factor can be effectively accounted for by a single CFentranceSSD correction factor.

Calibration↗

PubMed2002

An investigation of energy spectrum and lineal energy variations in mega-voltage photon beams used for radiotherapy.

Megavoltage photon beams are routinely used for external-beam radiotherapy. Recently, new treatment modalities based on dynamic and intensity modulated (IM), beam delivery systems are increasingly used in clinical practice. The purpose of this work is to investigate the energy spectrum and microdosimetric features of these photon beams. A Monte Carlo technique was first used to simulate beam lines of medical accelerators and to compute photon fluence and spectrum per unit dose-to-water inside the irradiated medium. Subsequently, a track structure code was used to compute the lineal energy and its distribution in a 1 micron sphere based on the individual photon spectrum. Results showed that the low energy photon component varied significantly with field size and location within the field due to the presence of the scattered photons. The calculated dose-mean lineal energy ranged from 2.3 keV.micron-1 at a depth of 1.5 cm along the central axis of a 4 cm x 4 cm field, to 3.7 keV.micron-1 at a depth of 20 cm of the field edge in a 10 cm x 10 cm field. In the tested IM fields at a depth of 10 cm, ranged from 2.6 to 3.5 keV.micron-1, which was inversely related to the dose intensity in the field. The values for the clinical photon beams were also significantly greater than that of a reference 60Co beam (1.8 keV.micron-1 from the calculation). The beam quality factor was estimated to vary within 20% due to the change of the energy spectrum for the radiotherapy photon fields.

Cobalt Radioisotopes↗

PubMed2004

Efficacy and safety of stereotactic radiosurgery for glomus jugulare tumors.

OBJECT: Since the mid-1990s the use of radiosurgery for glomus jugulare tumors has grown in popularity. Despite its increased use, follow-up periods for radiosurgery are short and the numbers of patients reported are small. To add to the available information, the authors report their experience with the application of linear accelerator (LINAC) or CyberKnife modalities in 13 patients with 16 tumors. METHODS: All patients were treated with frame-based LINAC or CyberKnife radiosurgery, with doses ranging from 1400 to 2700 cGy. Patients were retrospectively assessed for posttreatment side effects, which included hearing loss, tongue weakness, and vocal hoarseness. The patients' most recent magnetic resonance (MR) images were also assessed for changes in tumor size. The median follow-up duration was 41 months and the mean follow-up period was 60 months. All tumors remained stable or decreased in size on follow-up MR images. All patients had stable neurological symptoms, and one experienced transient ipsilateral tongue weakness and hearing loss, both of which subsequently resolved. One patient experienced transient ipsilateral vocal cord paresis; however, this individual had received previous external-beam radiation therapy. CONCLUSIONS: The authors' findings continue to support radiosurgery as an effective and safe method of treatment for glomus jugulare tumors that results in low rates of morbidity.

Adult↗

PubMed1989

[Stereotactically targeted radiotherapy of cerebral arteriovenous malformations].

A report is given about radiotherapy in 41 patients suffering from cerebral vessel anomalies. A modified linear accelerator was used in a moving field technique with multiple pendulum planes to apply single doses between 8 and 28 Gy by means of stereotaxis into the angiographically determined target volume. The medium follow-up is 23 months. The latency of radiogenic effects is between one and two years. Radiological controls with an interval of more than 18 months after therapy are available in 17 out of 41 patients. Angiographic investigation showed complete obliterations of pathological vessels in six out of these patients and partial obliterations in six patients; five patients remained unchanged. There were no acute complications. Seven patients presented neurological deficiencies with a latency of 6 to 12 months, however, in all cases but one they regressed completely. Even taking into consideration the small number of patients and the short time of observation, a comparison with the results of other radiotherapeutical proceedings allows to draw the conclusion that the presented technique of stereotaxic convergent-beam irradiation represents a relatively simple, reliable and, in case of precise indication, efficient method for the therapy of cerebral arteriovenous malformations.

Adult↗

PubMed2001

Commissioning of Peacock System for intensity-modulated radiation therapy.

The Peacock System was introduced to perform tomographic intensity-modulated radiation therapy (IMRT). Commissioning of the Peacock System included the alignment of the multileaf intensity-modulating collimator (MIMiC) to the beam axis, the alignment of the RTA device for immobilization, and checking the integrity of the CRANE for indexing the treatment couch. In addition, the secondary jaw settings, couch step size, and transmission through the leaves were determined. The dosimetric data required for the CORVUS planning system were divided into linear accelerator-specific and MIMiC-specific. The linear accelerator-specific dosimetric data were relative output in air, relative output in phantom, percent depth dose for a range of field sizes, and diagonal dose profiles for a large field size. The MIMiC-specific dosimetric data were the in-plane and cross-plane dose profiles of a small and a large field size to derive the penumbra fit. For each treatment unit, the Beam Utility software requires the data be entered into the CORVUS planning system in modular forms. These modules were treatment unit information, angle definition, configuration, gantry and couch angles range, dosimetry, results, and verification plans. After the appropriate machine data were entered, CORVUS created a dose model. The dose model was used to create known simple dose distribution for evaluation using the verification tools of the CORVUS. The planned doses for phantoms were confirmed using an ion chamber for point dose measurement and film for relative dose measurement. The planning system calibration factor was initially set at 1.0 and will be changed after data on clinical cases are acquired. The treatment unit was released for clinical use after the approval icon was checked in the verification plans module.

Humans↗

PubMedDate not supplied

[Intraoperative electron radiotherapy (IOERT) in the QUART sequence: a phase I study].

We evaluated the tolerance of a single dose of 800-1500 cGy, delivered with an electron beam from an IOERT-dedicated linear accelerator to the tumour bed in patients with breast cancer undergoing conservative treatment, instead of the traditional boost. We enrolled 27 patients (cT1-2, cN0). The first 6 received a dose of 800 cGy, 6 1000 cGy, 10 1200 cGy and 5 1500 cGy. External beam radiation therapy (EBRT) with a conventional schedule, 4000 cGy total dose, was performed after wound healing. The median gap between IOERT and EBRT was 8 weeks. Three patients with adverse prognostic factors undergoing chemotherapy, including doxorubicin or taxanes, received EBRT after completion of chemotherapy. One patient with a prosthesis implant had yielding of the surgical scar 8 months after IOERT (after 4 cycles of doxorubicin and 4 cycles of CMF complicated by frequent mastitis). Another patient with a large serum collection in the axilla manifested delayed scar formation. In the others no significant increase in healing time or surgery-related morbidity was observed. Another 4 patients developed mastitis. The cosmetic outcome was good in 26/27 patients. This treatment is well tolerated at all IOERT doses delivered. In the follow-up, to date, there have been no local relapses.

Breast Neoplasms↗

PubMed1996

[Radiotherapy of epidural metastases with spinal cord compression].

BACKGROUND: We have evaluated the records of patients who developed epidural metastases with spinal cord compression and underwent X-ray therapy in combination with dexamethasone. The results, prognostic factors and live-tables will be demonstrated. PATIENTS AND METHOD: Between 1984 and 1995 48 patients were treated at the Department of Radiooncology at the University of Münster because of epidural metastases. All but 3 cases were histologically proved. Three patients were irradiated without definitive histology because of clinical symptoms and CT or MR-imaging. Only patients with solid tumors were considered-patients with systemic diseases like leukemia or lymphoma were not analysed. In all of our cases irradiation was combined with systemic steroid application. Radiotherapy was performed with cobalt-60 or with an accelerator with total doses between 25 Gy and 40 Gy. RESULTS: The combination of irradiation and steroids had resulted in pain relief in about 80% of all patients. The ambulatory status after paraparesis was restituted in 35%. Best prognosis had been seen in patients with the following criterions: primary tumor should be breast cancer, no evidence of other tumor manifestation, no signs of paraparesis or paraplegia before the beginning of irradiation or regaining the ambulatory status after therapy. Under these conditions we have calculated a median survival rate of 709 days for these patients with good prognosis. Patients with bronchogenic carcinoma had a very poor prognosis with a median survival rate of only 90 days. CONCLUSIONS: Epidural metastases in cancer led often to a very fatal outcome. Irradiation is useful for pain relief and also for local tumor control. In some cases in patients with good prognostic factors long-time survival could be demonstrated. The results of irradiation are comparable with those after surgery.

Adult↗

PubMed2000

Comparison of dosimetric characteristics of Siemens virtual and physical wedges.

Dosimetric properties of Virtual Wedge (VW) and physical wedge (PW) in 6 and 23 MV photon beams from a Siemens Primus linear accelerator, including wedge factors, depth doses, dose profiles, peripheral doses and surface doses, are compared. While there is a great difference in absolute values of wedge factors, VW factors (VWFs) and PW factors (PWFs) have a similar trend as a function of field size. PWFs have a stronger depth dependence than VWF due to beam hardening in PW fields. VW dose profiles in the wedge direction, in general, match very well with PW, except in the toe area of large wedge angles with large field sizes. Dose profiles in the nonwedge direction show a significant reduction in PW fields due to off-axis beam softening and oblique filtration. PW fields have significantly higher peripheral doses than open and VW fields. VW fields have similar surface doses as the open fields while PW fields have lower surface doses. Surface doses for both VW and PW increase with field size and slightly with wedge angle. For VW fields with wedge angles 45 degrees and less, the initial gap up to 3 cm is dosimetrically acceptable when compared to dose profiles of PW. VW fields in general use less monitor units than PW fields.

Humans↗

PubMed2001

[Technique of Linac radiosurgery for cerebral arteriovenous malformations].

BACKGROUND AND PURPOSE: Description of the irradiation technique used by our group since 1986 for radiosurgery of cerebral arteriovenous malformations using Xrays minibeams from a linear accelerator. Method. The technique was elaborated by O. Betti in the early 80. He used several coronal arcs to irradiate the center of the target with X rays circular minibeams. Their diameter (6 to 20 mm) is chosen according to the size of the nidus. The patient is seated in a specially built armchair. His head is immobilized with the Talairach frame afixed in the calvarium by 4 special screws: they allow to remove the frame after stereotactic angiography and/or CTscan and to replace it to perform the stereotactic irradiation. The frame and the head rotate around an horizontal axis passing by the linac isocenter ie the center of the target volume. The combination of both movements: rotation of the Linac and rotation of the stereotactic frame covers a spherical sector representing the surface of portals of entry of the minibeams. The frame can slide on a plate allowing access to the entire brain. Results. The special seat and the frame are movable on curved rails allowing to avoid or reduce irradiation of the body of the patient. CONCLUSION: We have been using this system of irradiation in the seated position since 1986 to treat more than 900 patients.

Dose Fractionation, Radiation↗

PubMed2003

Performance of different radiotherapy workload models.

PURPOSE: The purpose of this study was to evaluate the performance of different radiotherapy workload models using a prospectively collected dataset of patient and treatment information from a single center. METHODS AND MATERIALS: Information about all individual radiotherapy treatments was collected for 2 weeks from the three linear accelerators (linacs) in our department. This information included diagnosis code, treatment site, treatment unit, treatment time, fields per fraction, technique, beam type, blocks, wedges, junctions, port films, and Eastern Cooperative Oncology Group (ECOG) performance status. We evaluated the accuracy and precision of the original and revised basic treatment equivalent (BTE) model, the simple and complex Addenbrooke models, the equivalent simple treatment visit (ESTV) model, fields per hour, and two local standards of workload measurement. RESULTS: Data were collected for 2 weeks in June 2001. During this time, 151 patients were treated with 857 fractions. The revised BTE model performed better than the other models with a mean [observed -predicted] of 2.62 (2.44-2.80). It estimated 88.0% of treatment times within 5 min, which is similar to the previously reported accuracy of the model. CONCLUSION: The revised BTE model had similar accuracy and precision for data collected in our center as it did for the original dataset and performed the best of the models assessed. This model would have uses for patient scheduling, and describing workloads and case complexity.

Appointments and Schedules↗

PubMed2006

Effect of electron contamination of a 6 MV x-ray beam on near surface diode dosimetry.

In critical organ in vivo x-ray dosimetry, the relative contaminating electron contribution to the total dose and total detector response outside the field will be different to the corresponding contributions at the central axis detector calibration position, mainly due to the effects of shielding in the linear accelerator head on the electron and x-ray energy spectrum. To investigate these contributions, the electron energy response of a Scanditronix PFD diode was measured using electrons with mean energies from 0.45 to 14.6 MeV, and the Monte Carlo code MCNP-4C was used to calculate the electron energy spectra on the central axis, and at 1 and 10 cm outside the edge of a 4 x 4, 10 x 10 and a 15 x 15 cm(2) 6 MV x-ray field. The electron contribution to the total dose varied from about 8% on the central axis of the smallest field to about 76% at 10 cm outside the edge of the largest field. The electron contribution to the total diode response varied from about 7-8% on the central axis of all three fields to about 58% at 10 cm outside the edge of the smallest field. The results indicated that a near surface x-ray dose measurement with a diode outside the treatment field has to be interpreted with caution and requires knowledge of the relative electron contribution specific to the measurement position and field size.

Calibration↗