Jesper Carl

Aalborg University Hospital, Ålborg, North Denmark, Denmark

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Publications (19)49.48 Total impact

  • Journal of Applied Clinical Medical Physics 01/2014; 15(2):4784. · 0.96 Impact Factor
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    ABSTRACT: Background and purpose. Aiming for minimal toxicity after radical prostate cancer (PC) radiotherapy (RT), magnetic resonance imaging (MRI) target delineation could be a possible benefit knowing that clinical target volumes (CTV) are up to 30% smaller, when CTV delineation on MRI is compared to standard computed tomography (CT). This study compares long-term toxicity using CT or MRI delineation before PC RT. Material and methods. Urinary and rectal toxicity assessments 36 months after image-guided RT (78 Gy) using CTC-AE scores in two groups of PC patients. Peak symptom score values were registered. One group of patients (n = 72) had standard CT target delineation and gold markers as fiducials. Another group of patients (n = 73) had MRI target delineation and a nickel-titanium stent as fiducial. Results. At 36 months no difference in overall survival (92% in both groups, p = 0.29) or in PSA-relapse free survival was found between the groups (MRI = 89% and CT = 94%, p = 0.67). A significantly smaller CTV was found in the MRI group (p = 0.02). Urinary retention and frequency were significantly reduced in the MRI group (p = 0.03 in the matter of both). The overall urinary and rectal toxicity did not differ between the two groups. Conclusion. MRI delineation leads to a significantly reduced CTV. Significantly lower urinary frequency and urinary retention toxicity scores were observed following MRI delineation. The study did not find significant differences in overall urinary or rectal toxicity between the two groups. PSA-relapse survival did not differ between the two groups at 36 months.
    Acta oncologica (Stockholm, Sweden) 12/2013; · 2.27 Impact Factor
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    ABSTRACT: Background. The prostate gland is delineated as the clinical target volume (CTV) in treatment planning of prostate cancer. Therefore, an accurate delineation is a prerequisite for efficient treatment. Accurate automated prostate segmentation methods facilitate the delineation of the CTV without inter-observer variation. The purpose of this study is to present an automated three-dimensional (3D) segmentation of the prostate using an active appearance model. Material and methods. Axial T2-weighted magnetic resonance (MR) scans were used to build the active appearance model. The model was based on a principal component analysis of shape and texture features with a level-set representation of the prostate shape instead of the selection of landmarks in the traditional active appearance model. To achieve a better fit of the model to the target image, prior knowledge to predict how to correct the model and pose parameters was incorporated. The segmentation was performed as an iterative algorithm to minimize the squared difference between the target and the model image. Results. The model was trained using manual delineations from 30 patients and was validated using leave-one-out cross validation where the automated segmentations were compared with the manual reference delineations. The mean and median dice similarity coefficient was 0.84 and 0.86, respectively. Conclusion. This study demonstrated the feasibility for an automated prostate segmentation using an active appearance with results comparable to other studies.
    Acta oncologica (Stockholm, Sweden) 09/2013; · 2.27 Impact Factor
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    ABSTRACT: Background. Fiducials can be used as surrogate for target position during radiotherapy. However, fiducial motion could lead to potential position errors when using fiducials in four-dimensional computed tomography (4DCT) treatment planning and for gated image guided radiotherapy (IGRT). Material and methods. One gold marker (GM) and 5, 10 and 15 mm nickel-titanium (NiTi) stents were inserted in a moving phantom for the purpose of fiducial detection in 4DCT and gated IGRT. Fiducial position errors in 4DCT and BrainLAB's gated IGRT were defined as residuals between fiducial detection and the actual physical position at the instance of image acquisition. Results. Fiducials position errors correlate to speed, fiducial type and orientation during 4DCT acquisition. Lower detection accuracy was measured for the 5 mm NiTi-stent relative to the 10 and 15 mm NiTi stents and GM. Fiducials with orientation 45° relative to the scan direction showed a lower detection accuracy relative to parallel and perpendicular orientations. The standard deviation of position errors in 4DCT were up to 2.2 mm with a maximum deviation of 4.0 mm. Using BrainLAB's gated IGRT the fiducials were detected with a standard deviation of 0.6 mm and a maximum deviation of 1.9 mm. For gated IGRT no correlation to fiducial speed was found. Conclusions. Clinical use of fiducials in combination with treatment planning on mid-ventilation CT phase for moving target should include margins up to 5.5 mm due to potential systematic position errors.
    Acta oncologica (Stockholm, Sweden) 08/2013; · 2.27 Impact Factor
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    ABSTRACT: Introduction. Therapy-induced injury to normal brain tissue is a concern in the treatment of all types of brain tumours. The purpose of this study was to investigate if magnetic resonance diffusion tensor imaging (DTI) could serve as a potential biomarker for the assessment of radiation-induced long-term white matter injury. Material and methods. DTI- and T1-weighted images of the brain were obtained in 19 former radiotherapy patients [nine men and 10 women diagnosed with astrocytoma (4), pituitary adenoma (6), meningioma (8) and craniopharyngioma (1), average age 57.8 (range 35-71) years]. Average time from radiotherapy to DTI scan was 4.6 (range 2.0-7.1) years. NordicICE software (NIC) was used to calculate apparent diffusion coefficient maps (ADC-maps). The co-registration between T1 images and ADC-maps were done using the auto function in NIC. The co-registration between the T1 images and the patient dose plans were done using the auto function in the treatment planning system Eclipse from Varian. Regions of interest were drawn on the T1-weighted images in NIC based on isocurves from Eclipse. Data was analysed by t-test. Estimates are given with 95% CI. Results. A mean ADC difference of 4.6(0.3;8.9)× 10(-5) mm(2)/s, p = 0.03 was found between paired white matter structures with a mean dose difference of 31.4 Gy. Comparing the ADC-values of the areas with highest dose from the paired data (dose > 33 Gy) with normal white matter (dose < 5 Gy) resulted in a mean dose difference of 44.1 Gy and a mean ADC difference of 7.87(3.15;12.60)× 10(-5) mm(2)/s, p = 0.003. Following results were obtained when looking at differences between white matter mean ADC in average dose levels from 5 to 55 Gy in steps of 10 Gy with normal white matter mean ADC: 5 Gy; 1.91(-1.76;5.58)× 10(-5) mm(2)/s, p = 0.29; 15 Gy; 5.81(1.53;10.11)× 10(-5) mm(2)/s, p = 0.01; 25 Gy; 5.80(2.43;9.18)× 10(-5) mm(2)/s, p = 0.002; 35 Gy; 5.93(2.89;8.97)× 10(-5) mm(2)/s, p = 0.0007; 45 Gy; 4.32(-0.24;8.89)× 10(-5) mm(2)/s, p = 0.06; 55 Gy; -4.04(-14.96;6.89)× 10(-5) mm(2)/s, p = 0.39. Conclusion. The results indicate that the structural integrity of white matter, assessed by ADC-values based on DTI, undergoes changes after radiation therapy starting as early as total dose levels between 5 and 15 Gy.
    Acta oncologica (Stockholm, Sweden) 08/2013; · 2.27 Impact Factor
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    ABSTRACT: Purpose: In image-guided radiotherapy of prostate cancer defining the clinical target volume often relies on magnetic resonance (MR). The task of transferring the clinical target volume from MR to standard planning computed tomography (CT) is not trivial due to prostate mobility. In this paper, an automatic local registration approach is proposed based on a newly developed removable Ni-Ti prostate stent.Methods: The registration uses the voxel similarity measure mutual information in a two-step approach where the pelvic bones are used to establish an initial registration for the local registration.Results: In a phantom study, the accuracy was measured to 0.97 mm and visual inspection showed accurate registration of all 30 data sets. The consistency of the registration was examined where translation and rotation displacements yield a rotation error of 0.41° ± 0.45° and a translation error of 1.67 ± 2.24 mm.Conclusions: This study demonstrated the feasibility for an automatic local MR-CT registration using the prostate stent.
    Medical Physics 06/2013; 40(6):061907. · 2.91 Impact Factor
  • Dennis Tideman Arp, Jesper Carl
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    ABSTRACT: To evaluate the geometric accuracy of the isocenter of an image-guidance system, as implemented in the exactrac system from brainlab, relative to the linear accelerator radiation isocenter. Subsequently to correct the x-ray isocenter of the exactrac system for any geometric discrepancies between the two isocenters. Five Varian linear accelerators all equipped with electronic imaging devices and exactrac with robotics from brainlab were evaluated. A commercially available Winston-Lutz phantom and an in-house made adjustable base were used in the setup. The electronic portal imaging device of the linear accelerators was used to acquire MV-images at various gantry angles. Stereoscopic pairs of x-ray images were acquired using the exactrac system. The deviation between the position of the external laser isocenter and the exactrac isocenter was evaluated using the commercial software of the exactrac system. In-house produced software was used to analyze the MV-images and evaluate the deviation between the external laser isocenter and the radiation isocenter of the linear accelerator. Subsequently, the deviation between the radiation isocenter and the isocenter of the exactrac system was calculated. A new method of calibrating the isocenter of the exactrac system was applied to reduce the deviations between the radiation isocenter and the exactrac isocenter. To evaluate the geometric accuracy a 3D deviation vector was calculated for each relative isocenter position. The 3D deviation between the external laser isocenter and the isocenter of the exactrac system varied from 0.21 to 0.42 mm. The 3D deviation between the external laser isocenter and the linac radiation isocenter ranged from 0.37 to 0.83 mm. The 3D deviation between the radiation isocenter and the isocenter of the exactrac system ranged from 0.31 to 1.07 mm. Using the new method of calibrating the exactrac isocenter the 3D deviation of one linac was reduced from 0.90 to 0.23 mm. The results were complicated due to routine maintenance of the linac, including laser calibration. It was necessary to repeat the measurements in order to perform the calibration of the exactrac isocenter. The deviations between the linac radiation isocenter and the exactrac isocenter were of an order that may have clinical relevance. An alternative method of calibrating the isocenter of the exactrac system was applied and reduced the deviations between the two isocenters.
    Medical Physics 03/2012; 39(3):1418-23. · 2.91 Impact Factor
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    ABSTRACT: To investigate a novel method for sparing urethra in external beam radiotherapy of prostate cancer and to evaluate the efficacy of such a treatment in terms of tumour control using a mathematical model. This theoretical study includes 20 patients previously treated for prostate cancer using external beam radiotherapy. All patients had a Nickel-Titanium (Ni-Ti) stent inserted into the prostate part of urethra. The stent has been used during the treatment course as an internal marker for patient positioning prior to treatment. In this study the stent is used for delineating urethra while intensity modulated radiotherapy was used for lowering dose to urethra. Evaluation of the dose plans were performed using a tumour control probability model based on the concept of uniform equivalent dose. The feasibility of the urethra dose reduction method is validated and a reduction of about 17% is shown to be possible. Calculations suggest a nearly preserved tumour control probability. A new concept for urethra dose reduction is presented. The method relies on the use of a Ni-Ti stent as a fiducial marker combined with intensity modulated radiotherapy. Theoretical calculations suggest preserved tumour control.
    Radiotherapy and Oncology 12/2011; 103(2):256-60. · 4.52 Impact Factor
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    ABSTRACT: The aim of the present study was to test the feasibility of a Nickel-Titanium (Ni-Ti) stent technique (Memocore™) in a porcine model. The stent is intended as a new fiducial for gated image guided radiotherapy in the lung. The study included test of an improved insertion system and respiratory gated treatments with this new technique. Tests were carried out in a porcine model using Göttingen mini-pigs. The study included 10 animals. Planning CT was performed as 4 dimensional CT (4DCT) using the Varian RPM system. Respiratory gated radiotherapy treatments were simulated using the Brainlab ExacTrac system. Reproducibility of stent position during treatment was analyzed off-line using an experimental version of the ExacTrac software. The experimental version has a dedicated algorithm for segmentation of the stent in the planning CT and subsequent registration to X-ray position images. A total of 23 stents were inserted in the 10 animals. Stents could be placed in all parts of the lungs. No stent migrated within the four weeks the experiment lasted. Stent trajectories in the lung were not reproducible, even though respiration was highly standardized using a respirator. The best accuracy of stent position in the gating window was obtained using gating at the half_max amplitude as reference level. The smallest stent movement within the gating window was observed in the exhale phase. Further success of human application will depend on the possibility to insert the stent within or close to lung tumors. This new technique based on the Memocore™ lung stent used in connection with respiratory gated radiotherapy was demonstrated to be feasible in a porcine model. The study demonstrated lack of reproducibility in lung trajectories of inserted stents. The technique gave the best accuracy when applied to the exhale phase of respiration.
    Radiotherapy and Oncology 12/2011; 102(2):297-302. · 4.52 Impact Factor
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    ABSTRACT: To investigate the accuracy and potential limitations of MV image-based dynamic multileaf collimator (DMLC) tracking in a porcine model on a linear accelerator. A thermo-expandable NiTi stent designed for kilovoltage (kV) X-ray visualization of lung lesions was inserted into the bronchia of three anaesthetized Göttingen minipigs. A four-dimensional computed tomography scan was used for planning a five-field conformal treatment with circular multileaf collimator (MLC) apertures. A 22.5 Gy single fraction treatment was delivered to the pigs. The peak-to-peak stent motion was 3 to 8 mm, with breathing periods of 1.2 to 4 s. Before treatment, X-ray images were used for image-guided setup based on the stent. During treatment delivery, continuous megavoltage (MV) portal images were acquired at 7.5 Hz. The stent was segmented in the images and used for continuous adaptation of the MLC aperture. Offline, the tracking error in beam's eye view of the treatment beam was calculated for each MV image as the difference between the MLC aperture center and the segmented stent position. The standard deviations of the systematic error Σ and the random error σ were determined and compared with the would-be errors for a nontracking treatment with pretreatment image-guided setup. Reliable stent segmentation was obtained for 11 of 15 fields. Segmentation failures occurred when image contrast was dominated by overlapping anatomical structures (ribs, diaphragm) rather than by the stent, which was designed for kV rather than MV X-ray visibility. For the 11 fields with reliable segmentation, Σ was 0.5 mm/0.4 mm in the two imager directions, whereas σ was 0.5 mm/1.1 mm. Without tracking, Σ and σ would have been 1.7 mm/1.4 mm and 0.8 mm/1.4 mm, respectively. For the first time, in vivo DMLC tracking has been demonstrated on a linear accelerator showing the potential for improved targeting accuracy. The study mimicked the envisioned patient workflow of future patient treatments. Clinical implementation of MV image-based tracking would require markers designed for MV visibility.
    International journal of radiation oncology, biology, physics 05/2011; 82(2):e321-7. · 4.59 Impact Factor
  • Radiotherapy and Oncology - RADIOTHER ONCOL. 01/2011; 99.
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    ABSTRACT: Dose escalation in prostate radiotherapy is limited by normal tissue toxicities. The aim of this study was to assess the impact of margin size on tumor control and side effects for intensity-modulated radiation therapy (IMRT) and 3D conformal radiotherapy (3DCRT) treatment plans with increased dose. Eighteen patients with localized prostate cancer were enrolled. 3DCRT and IMRT plans were compared for a variety of margin sizes. A marker detectable on daily portal images was presupposed for narrow margins. Prescribed dose was 82 Gy within 41 fractions to the prostate clinical target volume (CTV). Tumor control probability (TCP) calculations based on the Poisson model including the linear quadratic approach were performed. Normal tissue complication probability (NTCP) was calculated for bladder, rectum and femoral heads according to the Lyman-Kutcher-Burman method. All plan types presented essentially identical TCP values and very low NTCP for bladder and femoral heads. Mean doses for these critical structures reached a minimum for IMRT with reduced margins. Two endpoints for rectal complications were analyzed. A marked decrease in NTCP for IMRT plans with narrow margins was seen for mild RTOG grade 2/3 as well as for proctitis/necrosis/stenosis/fistula, for which NTCP <7% was obtained. For equivalent TCP values, sparing of normal tissue was demonstrated with the narrow margin approach. The effect was more pronounced for IMRT than 3DCRT, with respect to NTCP for mild, as well as severe, rectal complications.
    Medical dosimetry: official journal of the American Association of Medical Dosimetrists 01/2011; 36(2):130-7. · 1.26 Impact Factor
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    ABSTRACT: A clinical feasibility study using a removable prostate stent as fiducial for image-guided radiotherapy (IGRT) of localized prostate cancer (PC). The study included patients with local or locally advanced PC. The clinical target volume (CTV) was outlined on magnetic resonance (MR) images co-registered to planning computer tomography (CT) images. Daily online IGRT was delivered using the stent as fiducial. Risk of migration was estimated using multiple MR. Acute urinary toxicity was scored using the international prostate symptom score (IPSS). Late gastro-intestinal (GI) and genito-urinary (GU) toxicity was scored using the Radio Therapy Oncology Group (RTOG) score, biochemical failure (BF) was defined as an elevation of prostate specific antigen (PSA) above nadir plus 2 ng/ml after radiotherapy. One hundred men were enrolled in the study. Ninety completed radiotherapy with the stent as fiducial. No migration of the stent was seen, but three cases of dislocation of the stent to the bladder were observed. Acute urinary toxicity based on IPSS was comparable to toxicity in patients who had gold markers (GM) as fiducials. Removal of the stent was associated with a high frequency of urinary retention. Late GI and GU toxicity and BF were comparable to those of other studies, but longer observation time is needed. This study reports the first clinical results of using a prostate stent as fiducial. No migration of the stent observed. Dislocation of the stent to the urinary bladder was observed in three cases, requiring removal of the stent and insertion of a new fiducial. Acute toxicity during radiotherapy evaluated from IPSS was comparable to toxicity in patients with GM. Removal of the stent was associated with a high frequency of post procedural urinary retention. Late toxicity and BF were comparable to those of other studies, though longer observation time is needed.
    Acta oncologica (Stockholm, Sweden) 12/2010; 50(4):547-54. · 2.27 Impact Factor
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    ABSTRACT: Fiducial markers based on a removable stent are currently used in image guided radiotherapy. Here it is investigated what the possible dosimetric impact of such a marker could be, if used in proton or carbon ion treatment. The simulations have been done using the Monte Carlo particle transport code FLUKA with its default hadron therapy settings. A 3 cm long stent is approximated in FLUKA by stacking hollow tori. To simulate realistic clinical conditions a field 5 × 5 cm has been used, delivering a 5 cm wide spread out Bragg peak located 5 cm deep for protons and carbon ions. For protons fields mimicking active and passive beam delivery have been investigated. The stent has been arranged perpendicular, turned 45 degrees, and parallel to the beam axis. The position of the 95% dose level shifts for carbon ions 7 mm in proximal direction for the marker perpendicular to the beam and 8 mm if the stent is turned 45 degree for a 1 × 1 cm dose binning on the centre beam axis. For the case where the stent was parallel to beam direction the 95% dose level shifts 26 mm. For active delivered protons, the shift of the 95% dose level is less. The shift for a perpendicular arranged marker is 6 mm, for 45 degrees turned it is 7 mm. For the case where the stent was oriented parallel to the beam, the observed shift is 21 mm. Dose inhomogeneities caused by straggling effects occur only near the distal edge of the field. The results of our investigations show that the Ni-Ti marker has a non negligible impact on the dose distributions for the used radiation types. However if the treatment plan rules out narrow angles between symmetry axis of the stent and the beam direction, this may be compensated.
    Acta oncologica (Stockholm, Sweden) 10/2010; 49(7):1160-4. · 2.27 Impact Factor
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    ABSTRACT: A new fiducial marker for image guided radiotherapy (IGRT) based on a removable prostate stent made of Ni Ti has been developed during two previous clinical feasibility studies. The marker is currently being evaluated for IGRT treatment in a third clinical study. The new marker is used to co-register MR and planning CT scans with high accuracy in the region around the prostate. The co-registered MR-CT volumes are used for delineation of GTV before planning. In each treatment session the IGRT system is used to position the patient before treatment. The IGRT system use a stereo pair of kV images matched to corresponding Digital Reconstructed Radiograms (DRR) from the planning CT scan. The match is done using mutual gray scale information. The pair of DRR's for positioning is created in the IGRT system with a threshold in the Look Up Table (LUT). The resulting match provides the necessary shift in couch coordinates to position the stent with an accuracy of 1-2 mm within the planned position. At the present time 39 patients have received the new marker. Of the 39 one has migrated to the bladder. Deviations of more than 5 mm between CTV outlined on CT and MR are seen in several cases and in anterior-posterior (AP), left-right (LR) and cranial-caudal (CC) directions. Intra-fraction translation movements up to +/- 3 mm are seen as well. As the stent is also clearly visible on images taken with high voltage x-rays using electronic portal images devices (EPID), the positioning has been verified independently of the IGRT system. The preliminary result of an on going clinical study of a Ni Ti prostate stent, potentially a new fiducial marker for image guided radiotherapy, looks promising. The risk of migration appears to be much lower compared to previous designs.
    Acta oncologica (Stockholm, Sweden) 08/2008; 47(7):1358-66. · 2.27 Impact Factor
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    ABSTRACT: A dose compensation method is presented for patients with hip prosthesis based on Dynamic Multi Leaves Collimator (DMLC) planning. Calculations are done from an exit Portal Dose Image (PDI) from 6 MV Photon beam using an Electronic Portal Imaging Device (EPID) from Varian. Four different hip prostheses are used for this work. From an exit PDI the fluence needed to yield a uniform dose distribution behind the prosthesis is calculated. To back-project the dose distribution through the phantom, the lateral scatter is removed by deconvolution with a point spread function (PSF) determined for depths from 10 to 40 cm. The dose maximum, D(max), is determined from the primary plan which delivers the PDI. A further deconvolution to remove the dose glare effect in the EPID is performed as well. Additionally, this calculated fluence distribution is imported into the Treatment Planning System (TPS) for the final calculation of a DMLC plan. The fluence file contains information such as the relative central axis (CAX) position, grid size and fluence size needed for correct delivery of the DMLC plan. GafChromic EBT films positioned at 10 cm depth are used as verification of uniform dose distributions behind the prostheses. As the prosthesis is positioned at the phantom surface the dose verifications are done 10 cm from the prosthesis. The film measurement with 6 MV photon beam shows uniform doses within 5% for most points, but with hot/cold spots of 10% near the femoral head prostheses.
    Radiotherapy and Oncology 06/2008; 88(2):277-84. · 4.52 Impact Factor
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    ABSTRACT: Planning target volumes (PTV) in fractionated radiotherapy still have to be outlined with wide margins to the clinical target volume due to uncertainties arising from daily shift of the prostate position. A recently proposed new method of visualization of the prostate is based on insertion of a thermo-expandable Ni-Ti stent. The current study proposes a new detection algorithm for automated detection of the Ni-Ti stent in electronic portal images. The algorithm is based on the Ni-Ti stent having a cylindrical shape with a fixed diameter, which was used as the basis for an automated detection algorithm. The automated method uses enhancement of lines combined with a grayscale morphology operation that looks for enhanced pixels separated with a distance similar to the diameter of the stent. The images in this study are all from prostate cancer patients treated with radiotherapy in a previous study. Images of a stent inserted in a humanoid phantom demonstrated a localization accuracy of 0.4-0.7 mm which equals the pixel size in the image. The automated detection of the stent was compared to manual detection in 71 pairs of orthogonal images taken in nine patients. The algorithm was successful in 67 of 71 pairs of images. The method is fast, has a high success rate, good accuracy, and has a potential for unsupervised localization of the prostate before radiotherapy, which would enable automated repositioning before treatment and allow for the use of very tight PTV margins.
    Medical Physics 01/2007; 33(12):4600-5. · 2.91 Impact Factor
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    ABSTRACT: A new method for localization of the prostate during external beam radiotherapy is presented. The method is based on insertion of a thermo-expandable Ni-Ti stent. The stent is originally developed for treatment of bladder outlet obstruction caused by benign hyperplasia. The radiological properties of the stent are used for precise prostate localization during treatment using electronic portal images. Patients referred for intended curative radiotherapy and having a length of their prostatic urethra in the range from 25 to 65 mm were included. Pairs of isocentric orthogonal portal images were used to determine the 3D position at eight different treatment sessions for each patient. Fourteen patients were enrolled in the study. The data obtained demonstrated that the stent position was representative of the prostate location. The stent may also improve delineation of the prostate GTV, and prevent obstruction of bladder outlet during treatment. Precision in localization of the stent was less than 1 mm. Random errors in stent position were left-right 1.6 mm, cranial-caudal 2.2 mm and anterior-posterior 3.2 mm. In four of 14 patients a dislocation of the stent to the bladder occurred. Dislocation only occurred in patients with length of prostatic urethra less than 40 mm. A new method for radiological high precision localization of the prostate during radiotherapy is presented. The method is based on insertion of a standard Ni-Ti thermo-expandable stent, designed for treatment of benign prostate hyperplasia.
    Radiotherapy and Oncology 03/2006; 78(2):199-206. · 4.52 Impact Factor
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    Henning Nielsen, Jesper Carl
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    ABSTRACT: This paper deals with the problem of finding precise position and orientation of a titanium coil implant in humans. Analysis of high voltage X-rays stereo images are used to determine the true 3D position. High voltage images inherently presents with poor contrast. Various image processing techniques, such as template matching and grey scale morphology operations were tested. A final solution based on filtering in Fourier domain, greyscale morphology and a new shortest path algorithm is implemented as a set of ImageJ macros. The method has been tested on 100 images. The method correctly determined the position of the titanium wire within less than 1 mm of ground truth determined from manual analysis of the images. This paper presents a technique to detect a titanium coil implant in humans. The implant is a 0.5-0.7 mm thick titanium wire coiled into a diameter of 8 mm and a length of 20-50 mm Figure 1. High voltage x-rays are used to image the individual humans. Each image thus contains a 2D projection of the implant. A material of one hundred images was used for the analysis. The work in this paper assumes that the implant can be translated and rotated in 3D, but always as a rigid object. The goal was to develop an automatic algorithm with a high success rate for detection, with good accuracy.

Publication Stats

44 Citations
49.48 Total Impact Points

Institutions

  • 2008–2013
    • Aalborg University Hospital
      • Department of Oncology
      Ålborg, North Denmark, Denmark
  • 2012
    • Aarhus University Hospital
      • Department of Medical Physics
      Aarhus, Central Jutland, Denmark
  • 2006–2011
    • Aarhus University
      • Department of Medical Physics
      Aarhus, Central Jutland, Denmark