Markus Menke

Estimation of pneumonitis risk in three-dimensional treatment planning using dose-volume histogram analysis

PURPOSE Investigations to study correlations between the estimations of biophysical models in three dimensional (3D) treatment planning and clinical observations are scarce. The development of clinically symptomatic pneumonitis in the radiotherapy of thoracic malignomas was chosen to test the predictive power of Lymans normal tissue complication probability (NTCP) model for the assessment of side effects for nonuniform irradiation. METHODS AND MATERIALS In a retrospective analysis individual computed-tomography-based 3D dose distributions of a random sample of 46/20 patients with lung/esophageal cancer were reconstructed. All patients received tumor doses between 50 and 60 Gy in a conventional treatment schedule. Biological isoeffective dose-volume histograms (DVHs) were used for the calculation of complication probabilities after applying Lymans and Kutchers DVH-reduction algorithm. Lung dose statistics were performed for single lung (involved ipsilateral and contralateral) and for the lung as a paired organ. RESULTS In the lung cancer group, about 20% of the patients (9 out of 46) developed pneumonitis 3-12 (median 7.5) weeks after completion of radiotherapy. For the majority of these lung cancer patients, the involved ipsilateral lung received a much higher dose than the contralateral lung, and the pneumonitis patients had on average a higher lung exposure with a doubling of the predicted complication risk (38% vs. 20%). The lower lung exposure for the esophagus patients resulted in a mean lung dose of 13.2 Gy (lung cancer: 20.5 Gy) averaged over all patients in correlation with an almost zero complication risk and only one observed case of pneumonitis (1 out of 20). To compare the pneumonitis risk estimations with observed complication rates, the patients were ranked into bins of mean ipsilateral lung dose. Particularly, in the bins with the highest patient numbers, a good correlation was achieved. Agreement was not reached for the lung functioning as a paired organ. CONCLUSIONS Realistic assessments for the prediction of radiation-induced pneumonitis seem to be possible. In this respect, the implementation of DVH-analysis in 3D planning could be a helpful tool for the evaluation of treatment plans.

Stereotactically guided fractionated radiotherapy: technical aspects.

A system for high precision radiotherapy in the head and neck region has been developed. The components of the system are a head mask connected to a stereotactic frame, a localization unit that can be used during CT- and MR-imaging and a stereotactic target positioner. Conformal precision radiotherapy is planned with a new treatment planning system (Voxelplan-Heidelberg). Three different multi-leaf collimator systems are used. An evaluation of the precision and accuracy of the head fixation system, which was performed with a photogrammetry system, is presented.

Photogrammetric accuracy measurements of head holder systems used for fractionated radiotherapy

PURPOSE We describe how stereo photogrammetry can be used to determine immobilization and repositioning accuracies of head holder systems used for fractionated radiotherapy of intracranial lesions. METHODS AND MATERIALS The apparatus consists of two video cameras controlled by a personal computer and a bite block based landmark system. Position and spatial orientation of the landmarks are monitored by the cameras and processed for the real-time calculation of a target points actual position relative to its initializing position. The targets position is assumed to be invariant with respect to the landmark system. We performed two series of 30 correlated head motion measurements on two test persons. One of the series was done with a thermoplastic device, the other one with a cast device developed for stereotactic treatment at the German Cancer Research Center. Immobilization and repositioning accuracies were determined with respect to a target point situated near the base of the skull. The repositioning accuracies were described in terms of the distributions of the mean displacements of the single motion measurements. RESULTS Movements of the target in the order of 0.05 mm caused by breathing could be detected with a maximum resolution in time of 12 ms. The data derived from the investigation of the two test persons indicated similar immobilization accuracies for the two devices, but the repositioning errors were larger for the thermoplastic device than for the cast device. Apart from this, we found that for the thermoplastic mask the lateral repositioning error depended on the order in which the mask was closed. CONCLUSION The photogrammetric apparatus is a versatile tool for accuracy measurements of head holder devices used for fractionated radiotherapy.

Influence of the positioning error on 3D conformal dose distributions during fractionated radiotherapy.

The influence of patient immobilization error on 3D planned conformal radiation therapy in tumors of the thorax and pelvis was studied. The mean positioning error in 43 patients with carcinomas of the thorax and pelvis undergoing 3D conformal radiotherapy (laser supported alignment, no immobilization device) was measured. A total of 194 portal films were superposed with the corresponding simulator radiographs according to anatomic landmarks and using a subtrascope. x-, y- and z-axis deviation was determined within a coordinate system. Using specialized software including Fourier transformation the mean positioning error was employed to recalculate the dose distributions of all cases under the influence of random (Gaussian) immobilization uncertainty. The mean two-dimensional positioning error using the data from all patients was 5.5 (+/- 3.7) mm. The distribution was Gaussian. Dose volume histograms (DVHs) of each patient with and without consideration of positioning uncertainty were compared on the base of tumor control probability estimations (TCP) using published DVH reduction and TCP algorithms. Inclusion of the positioning error resulted in a mean decrease in TCP (given as the difference between the TCP assuming no positioning error and the TCP modified by the positioning error) of 2% in a series of esophagus carcinomas and of 5% in the prostate carcinomas when looking at gross tumor volume (GTV), only. Planning target volume (PTV) exhibited a relative decrease in TCP of 5% and 11%, respectively.

Renal tolerance to nonhomogenous irradiation: Comparison of observed effects to predictions of normal tissue complication probability from different biophysical models

PURPOSE A patient series was analyzed retrospectively as an example of whole organ kidney irradiation with an inhomogenous dose distribution to test the validity of biophysical models predicting normal tissue tolerance to radiotherapy. METHODS AND MATERIAL From 1969 to 1984, 142 patients with seminoma were irradiated to the paraaortic region using predominantly rotational techniques which led to variable but partly substantial exposure of the kidneys. Median follow up was 8.2 (2.1-21) years and actuarial 10-year survival (Kaplan-Meier estimate) 82.8%. For all patients 3-dimensional dose distributions were reconstructed and normal tissue complication probabilities for the kidneys were generated from the individual dose volume histograms. To this respect different published biophysical algorithms had been introduced in a 3-dimensional-treatment planning system. RESULTS In seven patients clinical manifest renal impairment was observed (interval 10-84 months). An excellent agreement between predicted and observed effects was seen for two volume-oriented models, whereas complications were overestimated by an algorithm based on critical element assumptions. CONCLUSIONS Should these observations be confirmed and extended to different types of organs corresponding algorithms could easily be integrated into 3-dimensional-treatment planning programs and be used for comparing and judging different plans on a more biologically oriented basis.

Rare retinal haemorrhages in translational accidental head trauma in children.

Purpose The characteristic findings in accidental head injury consist of linear skull fracture, epidural haematoma, localized subdural haematoma, or cortical contusion because of a linear or translational impact force. Retinal haemorrhages have been found, although uncommon, in accidental head trauma.Methods We performed a retrospective study of 24 consecutive cases of children with severe head injuries caused by falls. Inclusion criteria were skull fractures and/or intracranial haemorrhages documented by computerized tomography. All patients underwent a careful ophthalmic examination including dilated indirect fundoscopy within the first 48 h following admission.Results No retinal haemorrhages could be found in patients whose accidents were plausible and physical and imaging findings were compatible with reported histories. Excessive bilateral retinal haemorrhages were found in only three children with the typical signs of shaken baby syndrome. In eight children, trauma had led to orbital roof fractures.Conclusions Retinal haemorrhages were not found in any of the patients with accidental trauma despite the severity of their head injuries. Hence, we add more evidence that there are strong differences between the ocular involvement in accidental translational trauma and those in victims of non-accidental trauma. Fall-related injuries carry a very low risk of retinal haemorrhages.

Computer-controlled non-invasive patient positioning in fractionated radiotherapy - a videogrammetric system for automatic patient set-up, fast detection of patient motion and online correction of target point misalignment during therapy

Purpose An integrated videogrammetry based system for high precision fractionated radiotherapy in head and neck region has been developed. Patient setup is performed automatically and patient motion during treatment is detected and compensated. Methods and Materials The system consists of two video cameras controlled by a personal computer, a landmark system with a device for dento-maxillary fixation (DMF) and a computer-controlled motorized tabletop. Individually shaped, the dento-maxillary fixation fits the patients teeth of the upper jaw. The optical measurement system is calibrated relative to the isocenter of the therapy unit. Position and spatial orientation of the landmarks are monitored by the cameras and processed for the real-time calculation of a target points actual position relative to its initial position. Calculated translational misalignments are compensated online by countermovements of a 3D computer-controlled tabletop. Rotational deviations cannot be corrected automatically, but non-isocentric rotations are separeted into isocentric rotations and translations, which are online corrected. Thus the planned target point remains in the isocenter. Results System inaccuracies due to algorithm, calibration, illumination dependence, scale factors for image formation, have been determined in phantom studies. Algorithm and calibration errors are smaller than 0.2 %. Illumination dependence is uncritical for the infrared emitting diodes (IRED) used. Spectrally adapted bandpass filters eliminate interferences, caused by other light sources. The DMF repositioning accuracy has been derived from clinical studies on 11 patients to be 0.280±0.140 mm (mean±std. dev.). Spatial resolution of the optical measurement system is 5 μm for translational and 20 μrad for rotational deviations with a sampling frequency of 15–20 Hz. The maximum speed of the tabletop is 25 mm per second, the spatial resolution is about 10 μm with a default residual motion stop of 50 μm for translational deviations with respect to the initial targetpoint position. In summary, the overall positioning accuracy of the complete system was determined to be 0.6 mm. Conclusion For stereotacically guided radiotherapy in head and neck region the developed patient positioning sensor unit (PPSU) combines the high positioning accuracy, known from invasive stereotactic fixation in single-fraction radiotherapy, together with well known biological advantages for a fractionated regimen. The high positioning accuracy allows to decrease the commonly added safety margins. This leads to an enormous reduction of irradiated tumor-surrounding healthy tissue. The PPSU realizes automatic patient setup, patient motion detection and online movement compensation during therapy.

Diagnose und Therapie okulomotorischer Defizite bei Patienten mit Möbius-Sequenz

ZusammenfassungDer Artikel gibt einen Überblick über das Spektrum möglicher Motilitätseinschränkungen und Stellungsanomalien der Augen bei Patienten mit Möbius-Sequenz. Die augenmuskelchirurgischen Behandlungsoptionen werden diskutiert und es wird ein operatives Stufenschema vorgestellt.AbstractThis article reviews the spectrum of possible motility disorders and ocular misalignment in patients with Möbius sequence. The various options for strabismus surgery are discussed and a stepwise algorithm is presented.This article reviews the spectrum of possible motility disorders and ocular misalignment in patients with Möbius sequence. The various options for strabismus surgery are discussed and a stepwise algorithm is presented.

Diagnose und Therapie okulomotorischer Defizite bei Patienten mit Möbius-Sequenz@@@Diagnosis and treatment of oculomotor deficits in Möbius sequence

ZusammenfassungDer Artikel gibt einen Überblick über das Spektrum möglicher Motilitätseinschränkungen und Stellungsanomalien der Augen bei Patienten mit Möbius-Sequenz. Die augenmuskelchirurgischen Behandlungsoptionen werden diskutiert und es wird ein operatives Stufenschema vorgestellt.AbstractThis article reviews the spectrum of possible motility disorders and ocular misalignment in patients with Möbius sequence. The various options for strabismus surgery are discussed and a stepwise algorithm is presented.This article reviews the spectrum of possible motility disorders and ocular misalignment in patients with Möbius sequence. The various options for strabismus surgery are discussed and a stepwise algorithm is presented.

Diagnosis and treatment of oculomotor deficits in Möbius sequence

ZusammenfassungDer Artikel gibt einen Überblick über das Spektrum möglicher Motilitätseinschränkungen und Stellungsanomalien der Augen bei Patienten mit Möbius-Sequenz. Die augenmuskelchirurgischen Behandlungsoptionen werden diskutiert und es wird ein operatives Stufenschema vorgestellt.AbstractThis article reviews the spectrum of possible motility disorders and ocular misalignment in patients with Möbius sequence. The various options for strabismus surgery are discussed and a stepwise algorithm is presented.This article reviews the spectrum of possible motility disorders and ocular misalignment in patients with Möbius sequence. The various options for strabismus surgery are discussed and a stepwise algorithm is presented.