[Integration of the radiotherapy irradiation planning in the digital workflow]. / Integration der Bestrahlungsplanung in den volldigitalen Workflow.

BACKGROUND AND PURPOSE: At the Clinic of Radiotherapy at the University Hospital Freiburg, all relevant workflow is paperless. After implementing the Operating Schedule System (OSS) as a framework, all processes are being implemented into the departmental system MOSAIQ. Designing a digital workflow for radiotherapy irradiation planning is a large challenge, it requires interdisciplinary expertise and therefore the interfaces between the professions also have to be interdisciplinary. For every single step of radiotherapy irradiation planning, distinct responsibilities have to be defined and documented. All aspects of digital storage, backup and long-term availability of data were considered and have already been realized during the OSS project. METHOD: After an analysis of the complete workflow and the statutory requirements, a detailed project plan was designed. In an interdisciplinary workgroup, problems were discussed and a detailed flowchart was developed. The new functionalities were implemented in a testing environment by the Clinical and Administrative IT Department (CAI). After extensive tests they were integrated into the new modular department system. RESULTS AND CONCLUSION: The Clinic of Radiotherapy succeeded in realizing a completely digital workflow for radiotherapy irradiation planning. During the testing phase, our digital workflow was examined and afterwards was approved by the responsible authority.

Experimental determination of pCo perturbation factors for plane-parallel chambers.

For plane-parallel chambers used in electron dosimetry, modern dosimetry protocols recommend a cross-calibration against a calibrated cylindrical chamber. The rationale for this is the unacceptably large (up to 3-4%) chamber-to-chamber variations of the perturbation factors (pwall)Co, which have been reported for plane-parallel chambers of a given type. In some recent publications, it was shown that this is no longer the case for modern plane-parallel chambers. The aims of the present study are to obtain reliable information about the variation of the perturbation factors for modern types of plane-parallel chambers, and-if this variation is found to be acceptably small-to determine type-specific mean values for these perturbation factors which can be used for absorbed dose measurements in electron beams using plane-parallel chambers. In an extensive multi-center study, the individual perturbation factors pCo (which are usually assumed to be equal to (pwall)Co) for a total of 35 plane-parallel chambers of the Roos type, 15 chambers of the Markus type and 12 chambers of the Advanced Markus type were determined. From a total of 188 cross-calibration measurements, variations of the pCo values for different chambers of the same type of at most 1.0%, 0.9% and 0.6% were found for the chambers of the Roos, Markus and Advanced Markus types, respectively. The mean pCo values obtained from all measurements are [Formula: see text] and [Formula: see text]; the relative experimental standard deviation of the individual pCo values is less than 0.24% for all chamber types; the relative standard uncertainty of the mean pCo values is 1.1%.

Determination of the recombination correction factor kS for some specific plane-parallel and cylindrical ionization chambers in pulsed photon and electron beams.

It has been shown from an evaluation of the inverse reading of the dosemeter (1/M) against the inverse of the polarizing voltage (1/V), obtained with a number of commercially available ionization chambers, using dose per pulse values between 0.16 and 5 mGy, that a linear relationship between the recombination correction factor kS and dose per pulse (DPP) can be found. At dose per pulse values above 1 mGy the method of a general equation with coefficients dependent on the chamber type gives more accurate results than the Boag method. This method was already proposed by Burns and McEwen (1998, Phys. Med. Biol. 43 2033) and avoids comprehensive and time-consuming measurements of Jaffé plots which are a prerequisite for the application of the multi-voltage analysis (MVA) or the two-voltage analysis (TVA). We evaluated and verified the response of ionization chambers on the recombination effect in pulsed accelerator beams for both photons and electrons. Our main conclusions are: (1) The correction factor k(S) depends only on the DPP and the chamber type. There is no influence of radiation type and energy. (2) For all the chambers investigated there is a linear relationship between kS and DPP up to 5 mGy/pulse, and for two chambers we could show linearity up to 40 mGy/pulse. (3) A general formalism, such as that of Boag, characterizes chambers exclusively by the distance of the electrodes and gives a trend for the correction factor, and therefore (4) a general formalism has to reflect the influence of the chamber construction on the recombination by the introduction of chamber-type dependent coefficients.

The use of plane-parallel chambers in electron dosimetry without any cross-calibration.

Current dosimetry protocols from AAPM, DIN and IAEA recommend a cross-calibration for plane-parallel chambers against a calibrated thimble chamber for electron dosimetry. The rationale for this is the assumed chamber-to-chamber variation of plane-parallel chambers and the large uncertainty in the wall perturbation factor (p(wall)60Co)pp at 60Co for plane-parallel chambers. We have confirmed the results of other authors that chamber-to-chamber variation of the investigated chambers of types Roos, Markus, Advanced Markus and Farmer is less than 0.3%. Starting with a calibration factor for absorbed dose to water and on the basis of the three dosimetry protocols AAPM TG-51, DIN 6800-2 (slightly modified) and IAEA TRS-398, values for (p(wall)60Co)Roos of 1.024 +/- 0.005, (p(wall)60Co)Markus of 1.016 +/- 0.005 and (p(wall)60Co)Advanced Markus of 1.014 +/- 0.005 have been determined. In future this will permit electron dosimetry with the above-listed plane-parallel chambers having a calibration factor N(D, w)60Co without the necessity for cross-calibration against a thimble chamber.

Electron dosimetry based on the absorbed dose to water concept: a comparison of the AAPM TG-51 and DIN 6800-2 protocols.

The dosimetry protocols DIN 6800-2 and AAPM TG-51, both based on the absorbed dose to water concept, are compared in their theoretical background and in their application to electron dosimetry. The agreement and disagreement in correction factors and energy parameters used in both protocols will be shown and discussed. Measurements with three different types of ionization chambers were performed and evaluated according to both protocols. As a result the perturbation correction factor P(60Co)wall for the Roos chamber was determined to 1.024 +/- 0.5%.

[Radiotherapy of malignant obstructive jaundice]. / Strahlentherapie beim malignen Verschlussikterus.

Brachytherapy using the afterloading technique with iridium 192 and percutaneous irradiation using 16 MV photons are used for the irradiation of malignant obstructive jaundice. Mostly, however, a combination of both methods can be used to advantage. In bile duct tumors and Klatskin tumors, the endoluminal part can be treated using brachytherapy. The extralumenal growth and, if necessary, all affected regional lymph node areas can be treated by a 3D planned, percutaneous, moving field technique. Intraoperative radiotherapy can be used in a few cases as booster irradiation of tumor conglomerates at the porta hepatis. The decision to use irradiation must be made very carefully since solid tumors are usually involved that require a high target dose, the application of which can lead to unacceptable side effects. The radio-oncological spectrum is therefore confined predominantly to palliative therapy.

[Radiation sensitivity of the normal bile duct during high dose rate afterloading irradiation with Iridium 192. Experimental studies in pigs]. / Strahlenempfindlichkeit des gesunden Gallengangs bei High-dose-rate-Afterloadingbestrahlung mit Iridium 192. Experimentelle Untersuchungen am Schwein.

This animal study was designed to assess the tolerance of the normal bile duct to a single intraluminal high-dose-rate afterloading irradiation. This information is essential for treatment recommendations in irradiation therapy of malignant bile duct stenoses. In 16 pigs bile duct catheters were inserted surgically. Over these devices single intraductal doses of 7.5 Gy and 15 Gy were applied using an iridium-192 source. After a period of two to three months the bile ducts and the surrounding structures were investigated by means of cholangiography, angiography, and macropathological and histological investigations. A single intraductal dose of 7.5 Gy leads to a slightly scarred shrinkage of the bile duct with sclerosis and obliteration of the capillary vessels. Vasculitis and necrosis of the bile duct wall are still evident three months after irradiation. A single dose of 15 Gy leads to severe lesions with widespread necroses of the bile duct wall which tend to bleed, and result in a high degree of shrinkage of the bile duct. The radiation damage is most prevalent near the papilla and in the narrow segments near the liver. Single intraluminal high-dose-rate afterloading doses of 7.5 and 15 Gy cause significant lesions and complications at the bile ducts. As the intact bile duct is the Achilles heel of intraductal therapy, considerably lower single doses are recommended for a fractioned treatment.

Experimental thermoradiotherapy of human tumour xenografts in nude mice; design of the hyperthermia system.

An experimental thermoradiotherapy study was started in 1986. For this study a hyperthermia system was developed for heating human tumours xenotransplanted into nude mice. The treatment device was a four-channel computer-controlled hyperthermia system. Temperature was monitored by microwave radiometry at 3 GHz. Specifications of the radiometer were evaluated first under reference conditions. Subsequently, thermal dosimetry was studied using non-invasive measurement of brightness temperature, TOR. Hyperthermia treatments were simulated in phantom material with radiometric monitor values, TR, of 40 and 41. In conjunction with the parameters of TOR, surface temperature, T0, and water bolus temperature, TW, thermal modelling was performed. Influence of a perfused phantom also was studied on microwave thermometry.

Experimental thermoradiotherapy of human tumour xenografts in nude mice: design of the hyperthermia system.

An experimental thermoradiotherapy study was started in 1986. For this study a hyperthermia system was developed for the heating of human tumours xenotransplanted into nude mice. Our treatment device was a four-channel computer-controlled hyperthermia system. Temperature was monitored by microwave radiometry at 3 GHz. Specifications of the radiometer were first evaluated under reference conditions, then thermal dosimetry was studied using non-invasive measurement of the brightness temperature TOR. Hyperthermia treatments were simulated in phantom material with radiometric monitor values TR of 40 and 41. In conjunction with the parameters of brightness temperature TOR, surface temperature TO and water bolus temperature TW thermal modelling was performed. Finally, we studied the influence of a perfused phantom to the microwave thermometry.

Three-dimensional treatment planning for conformation therapy of a bronchial carcinoma.

Three-dimensional (3-D) radiotherapy planning is applied for the conformation therapy of a bronchial carcinoma. The treatment technique, using dynamically controlled shielding blocks, and the treatment planning procedure are described. The method has now been in clinical routine since 4 years; problems with the patient's positioning are discussed.

[Intracavitary high-dose-rate-afterloading-radiotherapy in the esophagus of the pig]. / Intrakavitäre High-Dose-rate-Afterloading-Strahlentherapie im Schweineösophagus.

The tolerance of sound esophageal mucosa to intracavitary high dose rate afterloading contact therapy with unique doses of 6 Gy and 12 Gy, respectively, was investigated in 15 pigs. Whereas no macroscopic or microscopic alterations of the mucosa are found after 6 Gy, a unique application of 12 Gy produces most severe side effects such as vascular occlusion due to fibrosis of the intima, formation of fistulas, and perforations of the esophagus wall. Future investigations will have to aim at the elaboration of schemes for dosage and fractionation.

[Implantation of 125 iodine seeds in the dog vocal cord. An experimental morphologic study]. / Implantation von 125-Jod-Seeds in die Hundestimmlippe. Eine experimentell-morphologische Studie.

Following the first positive therapeutic results of T1a vocal chord cancer with 125iodine seeds in man (brachytherapy), we were concerned with the effects of this low-energy photon source on healthy laryngeal tissue. In the larynx, changes in the area of the vocal chord and the cartilaginous laryngeal structures were investigated in particular. These experimental studies were performed on the larynx of the dog. Through direct laryngoscopy, two 125iodine seeds were implanted in the anterior third of each vocal chord in 8 dogs; the resulting prick canals were sealed with fibrin glue. During survival the correct position of the seeds was radiologically monitored. After survival periods of 1, 3, 6, and 12 months the larynges were fixed by perfusion, removed, imbedded in paraplast, and stained with H. E., Azan, and E. v. G. After this protracted irradiation with 125iodine seeds only slight and for the most part reversible pathological changes had occurred. One month after implantation, only a perivascular infection was found in the vocal chord. After three months an inhibition of the fibrin organization around the seeds was observed as well as a localized dyschylia with broadening of the gland ducts. Additionally, a circumscribed dysplasia of the squamous epithelium, swelling of the capillary endothelium, atrophy of muscular fibres around the seeds, and telangiectasia of blood vessels were discernable. 6 and 12 months after implantation, only the muscular atrophy and the telangiectasia of the blood vessels remained detectable, in addition to a reduced inhibition of the fibrin organisation by connective tissue.

[A rare complication of interstitial therapy with iodine-125 seeds: embolization of a seed into the lung]. / Eine seltene Komplikation der interstitiellen Therapie mit Jod-125-Spickung: Embolisation eines Seeds in die Lunge.

A case report is given on the embolization of an iodine-125 seed following to interstitial therapy of an anal carcinoma. The problems involved are discussed and possible consequences are indicated.

[Determinants of local tumor control in interstitial radiotherapy of prostatic cancer]. / Determinanten der lokalen Tumorkontrolle in der interstitiellen Strahlentherapie des Prostatakarzinoms.

Clinical followup of 52 patients treated with I-125 implants for localized prostatic cancer demonstrated local control in 85% and failure in 15%. Determining factors for local control or failure were analyzed and underline that homogeneous dose distribution is the most important factor for local control in interstitial radiotherapy. With the use of I-125 seeds this can only be achieved in small-volume (T2) stages with refined technique. For larger tumor volumes (T3) an external boost or the use of other radionuclides is preferable.