Influence of 4D CT-based respiratory signal acquisition methods on delineation of moving tumor targets / 中国辐射卫生

@#<b>Objective</b> To compare the effects of different respiratory signal acquisition methods on the delineation of moving tumor targets. <b>Methods</b> A cube phantom containing a sphere was placed on a motion platform to simulate respiratory movement by setting motion period, frequency, and direction. Respiratory signal was acquired by real-time position management (RPM) method and GE method independently. Target delineation was conducted using the maximum intensity projection (MIP) sequence. The difference between the reconstructed volume and the theoretical moving volume was compared under the two respiratory signal acquisition methods for cube and sphere targets. <b>Results</b> Under the same respiratory signal acquisition method, the same respiratory amplitude, and different respiratory frequencies, reconstructed volume changes were relatively small. For the sphere target, the deviation between the reconstructed volume and the theoretical moving volume was −1.5% to 5.7% with the RPM method and −1.3% to −13.8% with the GE method (both <i>P</i> < 0.05). For the cube target, the deviation between the reconstructed volume and the theoretical moving volume was 0.2% to 0.9% with the RPM method and −2.6% to 0.9% with the GE method, with no statistical significance. <b>Conclusion</b> For small-volume sphere targets, the target volumes obtained from MIP images by the two respiratory signal acquisition methods are both smaller than the actual moving volume. For large-volume cube targets, there is no significant difference between the reconstructed and theoretical results with any respiratory signal acquisition method. The RPM method produces smaller deviation and better image quality when reconstructing small-volume targets.

Predicting respiratory motion using an Informer deep learning network / 中华放射医学与防护杂志

Objective:To investigate a time series deep learning model for respiratory motion prediction.Methods:Eighty pieces of respiratory motion data from lung cancer patients were used in this study. They were divided into a training set and a test set at a ratio of 8∶2. The Informer deep learning network was employed to predict the respiratory motions with a latency of about 600 ms. The model performance was evaluated based on normalized root mean square errors (nRMSEs) and relative root mean square errors (rRMSEs).Results:The Informer model outperformed the conventional multilayer perceptron (MLP) and long short-term memory (LSTM) models. The Informer model yielded an average nRMSE and rRMSE of 0.270 and 0.365, respectively, at a prediction time of 423 ms, and 0.380 and 0.379, respectively, at a prediction time of 615 ms.Conclusions:The Informer model performs well in the case of a longer prediction time and has potential application value for improving the effects of the real-time tracking technology.

Influence of respiratory motion on image quality of 4D-CBCT / 中华放射肿瘤学杂志

Objective@#To investigate the relationship between the image quality of 4D cone beam CT (4D-CBCT) and the characteristic parameters of respiratory motion.@*Methods@#Catphan 500 was fixed on the Mapcheck XY/4D table by a fixation device. The control platform was utilized to simulate the static and 19 motion states. A synergy accelerator was adopted to perform 4D-CBCT scan of the image quality detection module under different motion states. By analyzing the geometric accuracy, spatial resolution, low-contrast visibility, CT value uniformity and motion position accuracy of the images of the 10 phases of the reconstructed images, the relationship among the image quality of 4D-CBCT, motion direction, amplitude and cycle was analyzed.@*Results@#4D-CBCT images could not be properly reconstructed in the static state or only in the left-right (LR) direction. The image quality was significantly worse than that in the SI direction. The contrast-to-noise ratio (CNR) was decreased as the motion cycle was increased. When the cycle was increased from 2 s to 6 s, the CNR was significantly declined from 3.33 to 1.72(P<0.01), whereas respiratory motion exerted no significant effect upon the geometric accuracy, spatial resolution and sagittal position.@*Conclusions@#The CNR, horizontal and vertical geometric accuracy and motion position accuracy of 4D-CBCT image quality are significantly affected by respiratory motion, whereas spatial resolution and sagittal geometric accuracy are not significantly influenced by respiratory motion.4D-CBCT requires the intervention of periodical motion in the SI direction. Excessively slow or absence of periodical motion can influence the image quality and even the images cannot be accurately reconstructed.4D-CBCT image reconstruction equally requires the intervention of periodical motion in the SI direction. The image quality is simultaneously affected by the amplitude and cycle of respiratory motion. For 4D-CBCT scan, the respiratory cycle of<6 s and an amplitude of>0.75 cm are recommended.

Effect and research progress of respiratory motion on intensity-modulated proton therapy / 中华放射肿瘤学杂志

Compared with intensity-modulated photon therapy, intensity-modulated proton therapy has significant dose advantages. However,the dose gradient of proton Bragg peak is relatively high,and the proton therapy is likely to be affected by range uncertainties,setup uncertainties and antonymic changes,etc. The difference between the planning dose and actual dose caused by respiratory motion hinders the widespread use of intensity-modulated proton therapy in thoracic cancers. In this paper,research progress on the effect of respiratory motion on intensity-modulated proton therapy and how to reduce the effect were summarized,aiming to provide reference for clinicians and researchers.

Respiratory motion correction method based on principal components analysis model for liver contrast-enhanced ultrasound sequences / 医疗卫生装备

Objective To relieve the influences of the respiratory motion on the liver contrast-enhance ultrasound (CEUS) image sequences,to enhance the quantitative analysis accuracy for liver CEUS and to put forward a correction strategy for the respiratory motion in liver CEUS sequences.Methods A principal component analysis (PCA) model of the respiratory motion in liver CEUS sequences was established with 18 cases of rabbit liver VX2 tumors,and a respiratory motion curve was generated based on the principal component with large data proportion,then the images with similar phases to the reference image were analyzed.Resnlts Correction made the mean structural similarity and mean correlation coefficient enhanced significantly to 0.57±0.11 and 0.78±0.11 respectively (P＜0.001),while the average of deviation valve (DV) was decreased to 29.9±7.02 which only was one-third of the original value.Threshold setting could further improve the quality of the selected image sequence.Conchusion The proposed respiratory motion method proves its effectiveness for rabbit liver CEUS image sequences,and thus contributes to enhancing the differential diagnosis rate of benign and malignant liver tumors.

Respiratory motion correction method based on principal components analysis model for liver contrast-enhanced ultrasound sequences / 医疗卫生装备

Objective To relieve the influences of the respiratory motion on the liver contrast-enhance ultrasound (CEUS) image sequences,to enhance the quantitative analysis accuracy for liver CEUS and to put forward a correction strategy for the respiratory motion in liver CEUS sequences.Methods A principal component analysis (PCA) model of the respiratory motion in liver CEUS sequences was established with 18 cases of rabbit liver VX2 tumors,and a respiratory motion curve was generated based on the principal component with large data proportion,then the images with similar phases to the reference image were analyzed.Resnlts Correction made the mean structural similarity and mean correlation coefficient enhanced significantly to 0.57±0.11 and 0.78±0.11 respectively (P＜0.001),while the average of deviation valve (DV) was decreased to 29.9±7.02 which only was one-third of the original value.Threshold setting could further improve the quality of the selected image sequence.Conchusion The proposed respiratory motion method proves its effectiveness for rabbit liver CEUS image sequences,and thus contributes to enhancing the differential diagnosis rate of benign and malignant liver tumors.

Investigation of image guidance strategy for intermittent breath-hold cone beam CT / 中华放射肿瘤学杂志

Objective To develop a practical image acquisition strategy using intermittent breath?hold cone beam computed tomography (CBCT). Methods A breathing phantom was used to simulate the movement of tumor near the diaphragm during free breathing and breath hold and scanned by conventional breath?hold CBCT and type Ⅰ/Ⅱ intermittent breath?hold CBCT. In the conventional breath?hold CBCT, scan paused and free breathing occurred at the break of breath hold and free breathing was not included in the scan. In the intermittent breath?hold CBCT, one scan covered several breath holds separated by free breathing in a ratio of 3 vs1. Image quality and three?dimensional registration accuracy were quantitatively compared between conventional breath?hold CBCT and type Ⅰ/Ⅱ intermittent breath?hold CBCT. Comparison of image quality parameters between conventional breath?hold CBCT and intermittent breath?hold CBCT was made by paired t test. Results Motion artifacts arose in type I and Ⅱ intermittent breath?hold CBCT scans. There were no significant differences in the reconstructed pixel value or uniformity between intermittent breath?hold CBCT and conventional breath?hold CBCT ( P>0. 05, and P= 0. 02, 0. 53 ) . Compared with conventional breath?hold CBCT images, the signal?to?noise ratios of type I andⅡintermittent breath?hold CBCT images were reduced by 30% and 60%, respectively ( P<0. 05 ) . The registration error was up to 0 . 4 cm in the anterior?posterior direction and less than 0 . 1 cm in other directions . Conclusions The phantom study shows that intermittent breath?hold CBCT does not significantly reduce image quality or registration accuracy compared with conventional breath?hold CBCT. The feasibility of intermittent breath?hold CBCT in clinical application needs to be further validated among a large number of patients.

The Effects of Breathing Motion on DCE-MRI Images: Phantom Studies Simulating Respiratory Motion to Compare CAIPIRINHA-VIBE, Radial-VIBE, and Conventional VIBE

OBJECTIVE: To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment. MATERIALS AND METHODS: We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability. RESULTS: With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) (p < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, p < 0.001) and radial-VIBE (from 4.3 to 4.96, p < 0.001) after motion correction. CONCLUSION: CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.

Effect of respiratory amplitude on the dose distribution of volumetric modulated arc therapy / 中华放射医学与防护杂志

Objective To study the effect of the respiratory amplitude on the dose distribution of volumetric modulated arc therapy (VMAT).Methods Respiratory motion simulation phantom (QUASAR) was used to simulate the respiratory movement from head to toe,and a two-dimensional ionization chamber matrix was used to collect the dose distribution in isocenter with different respiratory amplitude.Verisoft software and absolute dose analysis were used to analyze dose distribution,percentage errors of absolute dose in isocenter,passing rates of radiation field for the data collected,and results were compared to planned dosage.Results The effect on isocenter target dose of respiratory motion was below dose tolerance 5％ (t =-22.614--10.756,P ＜ 0.05).The respiratory movement made the dose on the edge of the target area higher,with fewer hot spots and more cold spots in the target area.As the respiratory amplitude increased,the effect of respiratory movement on the overall dose distribution in the target area was greater.The difference of the whole beam γ passing rate between 6,8,10 mm and stationary state was significant (t =3.095,8.685,14.096,P ＜ 0.05).The difference of target γ passing rate between 8,10 mm and stationary state was significant (t =6.081,9.841,P ＜0.05).Conclusions The respiratory movement could cause the dose transmission errors of VMAT,the error increased with increased range of motion.The actual radiation dose for normal tissues along the direction of respiratory movement on the target edge was higher than what was planned.

Evaluating the impact of respiratory motion on lung dosimetry using 4D-CT for non-small cell lung cancer / 中华放射医学与防护杂志

Objective To evaluate the impact of respiratory motion on lung dosimetry using 4D-CT during lung cancer radiotherapy.Methods Ten cases were randomly selected from non-small cell lung cancer (NSCLC) patients treated in our department.The 4D-CT machine was adopted for simulation before treatment and 10 respiratory phases were obtained for each patient.Target volumes were delineated on the maximum intensity projection (MIP) images,and plans were generated on average intensity projection (ALP) images.Plans were transferred to CT images of each respiratory phase,and we calculated the dosage on lungs and subsequently evaluated the volume dosage to lungs and the entire body.Results The mean dosage to lungs are greatly affected by the respiratory phase.This difference also depended on tumor location.When it was inside the lung,the average dosage shows the same trend as the respiratory motion,with the change rate of 2.18％,which was less than the change of lung volume 4.49％ (t =4.189,P ＜ 0.05).When the tumor was located nearby the lung,the mean dosage showed the opposite trend with respiratory motion,with the change rate of 3.76％,which was also less than the change of lung volume 4.49％ (t =25.007,P ＜ 0.05).The effect of respiratory motion on V5,V10,V20 of body was small,and the magnitude of change for whole body dosages were 0.47％,0.28％,0.17％ respectively,which was smaller than the change of lung volume 4.49％ (t =11.371,11.188,11.377,P ＜ 0.05).Volume dose of lung V5,V10,V20 and lung volume change trends were the same,and the magnitude of change for lung volume dosages were 2.39％,1.91％,1.80％ respectively,and were smaller than the change of lung volume 4.49％ (t =2.279,2.298,2.485,P ＜ 0.05).Conclusions The mean dosage to lungs shows a great difference between different respiratory phases.More attention should be paid when evaluating the lung volume during treatment planning.

Numerical simulation on lung tumor motion / 医用生物力学

Objective To investigate the feasibility of simulating the deformation and displacement of lung tumors by simulating the motion of lung tumors during respiration using finite element method (FEM). Methods The CAD (computer-aided design) surfaces of the lung at multiple inhalation phases were reconstructed from 4D CT images of a patient with lung tumor. The finite element model was established according to the surface at the beginning of inhalation. Distributed surface loads were defined by the differences between each individual surface and the surface at the beginning of inhalation, and applied to the surface of the model. The motion and deformation of lung tumors were then simulated using FEM within the inhalation cycle. Results The numerical simulation indicated that the estimated errors for the lung and the tumor’s motion and deformation were less than 2 mm and 1 mm, respectively. The use of linear elastic relationship for tumor with elastic modulus of 50 kPa could achieve higher precision in simulation. Conclusions The deformation of lung and the displacement of lung tumor are possible to be simulated accurately by FEM. This research provides references for the X-ray free lung tumor tracking method based on numerical simulation.

Automatic detection algorithm of the diaphragm motion based on Canny edge detection and wavelet transform / 中华放射医学与防护杂志

Objective To develop a new automatic detection algorithm of the diaphragm motion based on Canny edge detection and wavelet transform.Methods On-line fluoroscopic images under free breathing were enhanced by using the wavelet transform.After the wavelet transform,edge detection was carried out for the enhanced image.Canny edge detection algorithm was used to achieve the diaphragm edge.Programs were written in Matlab to track the position of the diaphragm.The diaphragm movement curves were derived to evaluate the characteristics of patients respiratory motion.Results Under calm free breathing,the amplitude and period of diaphragm motion acquired by means of the wavelet transform and Canny edge detection were in good agreement with manual measurement.There were six to seven respiratory cycles in a XVI MotionViewTM.The magnitude of diaphragm movement was not exactly the same in the cranio-caudal (CC) direction.The magnitude was from 6.7 mm to 8.0 mm with an average of 7.4 mm.The movements of the respiratory motion cycles had little variations in amplitude and period for the same patient between fractions except emotional excitement or cough.Conclusions The automatic diaphragm detection methods developed in this paper are precise,and can effectively reflect the characteristics of the respiratory motion.The method can save much time and improve the measure precision greatly compared with the manual measurement.

Simulation of respiratory motion effect on dose distributions in three-dimensional radiotherapy / 中华放射肿瘤学杂志

Objective To evaluate the effects of respiratory on dose distributions in threedimensional conformal radiotherapy (3 DCRT) and intensity-modulated radiotherapy (IMRT).Methods The dose distributions were measured with a PTW 2D-ARRAY seven29 placed on a home-made moving platform to simulate the respirator.Dosimetric comparisions for 3DCRT and IMRT plans were performed by means of Gamma analysis with 3％ and 3 mm,respectively.Dose distribution measured for static treatment plans.Results The respiratory could reduce the target does and conformal index.The r pass rate (3％3 mm in 3 DCRT was greater than it in IMRT ((53.58 ± 0.74) ％,(30.71 ± 1.00) ％,t =57.91,P ＜ 0.01).The failed points were mainly near the field edge,but located in the whole target volumes for IMRT plans.Conclusions It is undesirable to use IMRT techniques for tumors with large motion amplitude.3DCRT can give a reliable dose distribution by reasonably selecting the PTV margin.

Assessment of gross tumor volume motion and the influence factors during respiration for lung cancer using four-dimensional computed tomography / 中华放射肿瘤学杂志

Objective This study was to assess the three-dimensional gross tumor volume(GTV)motion of lung cancer caused by respiration using four-dimensional computed tomography(4DCT),and to analyze the influenee factors.Methotis Four-DCT scans of 22 lung focuses in 21 patients with lung cancer were analyzed.The gross tumor volume was contoured in all 10 respiration phases of 4DCT scans.The changes in volume of GTV,the 3D motion of the centroid,boundary of GTV and the 3D spatial motion vectors were calculated and the irdluenee factors were analyzed.Results The average change in volume of GTV was+14.3%(0.2%.42.5%)/-8.4%(0.4%-38.6%),the average movement amplitude of GTV centroid and GTV boundary were(0.18±0.12)cm,(0.20±0.16)cm,(0.53±0.59)cm and(0.42±0.23)cm,(0.41±0.22)cm,(0.57±0.70)cm in medio-lateral,vertro-dorsal,cranio-caudal(CC) direction,respectively.The CC movement was larger than other directions(Z=-2.12,P=0.034;Z:-2.10,P=0.035),and no significant difference was observed in 3D motion of GTV boundary(Z=-0.81.P=0.417;Z=-0.86,0.391).The CC motion of GTV eentroid in lower lobe was larger than that in upper lobe[(0.87±0.64)and(0.35±0.49)cm,(t=-2.12,P=0.047)],and no significant difference was found in other directions[(0.23±0.10)and(0.19±0.18)em(t=-0.49,P=0.629),(0.21±0.13)and(0.17±0.11)cm(t=0.76,P=0.460)].There was no correlation of the 3D movement and 3D spatial motion vector of GTV to the volume of GTV(r=-0.306,-0.062,-0.279,-0.300;P=0.189,0.796.0.234,0.199).Conclusions GTV motion of patients with lung cancer is individual,the CC movement is the moat obvious,using 4DCT to assess is comparatively accurate.The motion amplitude of lower lobe focuses is larger.No significant correlation of the GTV motion to the volume was observed.Larger sample study is needed to analyze the influence of adjacency to the GTV motion.

Influencia del movimiento respiratorio sobre el contraste de las lesiones en estudios de perfusión pulmonar: simulación mediante el uso de un fantoma virtual / Respiratory motion on the contrast of pulmonary lesions in lung perfusion scintigraphy: a simulation study with a virtual phantom

El movimiento respiratorio (MR) constituye un factor de degradación de las imágenes con potencial influencia sobre la capacidad de detección de lesiones tromboembólicas en estudios de perfusión pulmonar. El objetivo fue investigar la influencia del MR sobre el contraste de lesiones pulmonares, por medio de simulación con un fantoma virtual. Mediante un fantoma N-CAT se generó un modelo de perfusión pulmonar con SPECT; el modelo fue reconstruido produciendo cortes tomográficos y reproyección de los mismos en tres situaciones: sin MR, simulando MR con desplazamiento diafragmático de 2 cm, y con desplazamiento de 4 cm. Se instalaron en el modelo 7 "lesiones" hipocaptantes simulando la situación del tromboembolismo pulmonar (TEP) en situación superior, media y basal y se calculó el contraste de las lesiones en las 3 situaciones descriptas. Los resultados muestran que el contraste de las lesiones es menor con el MR, que se deteriora más cuanto mayor es la magnitud del MR, y que el MR afecta en mayor grado el contraste de las lesiones de ubicación basal. La corrección de MR podría mejorar la detectabilidad de algunos defectos de perfusión, especialmente los de ubicación basal, incrementando la sensibilidad de la técnica para el diagnóstico de TEP.

Respiratory motion (RM) represents a major factor of image degradation with potential impact on the detection of embolic lesions in lung perfusion scintigraphy. The aim was to investigate the influence of RM on the contrast of pulmonary lesions through a simulation study with a virtual phantom. Using a N-CAT phantom, a SPECT lung perfusion model was generated; the model was reconstructed producing three sets of tomographic slices and image reprojection under different conditions: without RM, RM simulation with 2 cm diaphragmatic displacement, and RM simulation with 4 cm diaphragmatic displacement. Seven "cold" lesions were placed in the model resembling a typical pulmonary embolism (PE) situation in superior, medial and basal locations and image contrast was calculated. Results showed a decrease in lesion contrast proportional to the degree of RM, which was more pronounced for basal lesions. Motion correction could improve the detectability of some perfusión defects, especially those in basal locations, thus incrementing the sensitivity of the technique for the diagnosis of PE.

Four-dimensional computed tomography based assessment and analysis of lung tumor motion during free-breathing respiration / 中华放射肿瘤学杂志

Objective To quantify the amplitudes of lung tumor motion during free-breathing using four dimensional computed tomography (4DCT), and seek the characteristics of tumors with large motion. Methods Respiratory-induced tumor motion was analyzed for 44 tumors from 43 patients. All patients un-derwent 4DCT during free-breathing before treatment. Gross tumor volumes (GTV) on ten respiratory phases were contoured by the same doctor. The eentroids of GTVs were autoplaeed with treatment software (ADAC Pinnacle 7.4f), then the amplitudes of tumor motion were assessed. The various clinical and anatomic fac-tors associated with GTV motion were analyzed. The characteristics of tumors with motion greater than 5 mm in any direction were explored. Results The tumor motion was found to be associated with T stage, GTV size, the superior-inferior (SI) tumor location in the lung, and the attachment to rigid structures such as the chest wall, vertebrae or mediastinum. The motion over 5 mm was observed in ten tumors, which were all lo-cated in the lower or posterior half of the lung, with the greatest motion of 14.4 mm. For 95% of the tumors, the magnitude of motion was less than I 1.8 mm, 4.6 mm and 2.7 mm along the SI, anterior-poste-rior (AP) and lateral directions, respectively. Conclusions Tumor motion due to breathing is associated with tumor location, volume, and T stage. The greatest motion was in the SI direction for unfixed tumor in lower-lobe, followed by tumor in upper-lobe posterior-segment.

Influence of respiratory motion on target dose distribution in radiotherapy for lung tumors / 中华放射肿瘤学杂志

Objective To investigate the influence of respiratory motion on target dose distribution in radiotherapy for patients with lung tumors. Methods The Big Bore Brilliance CT with bellows system was used to gain the 4DCT sets and respiratory frequency information of the patients. The moving ranges of the tumors in left-right (LR), anterior-posterior (AP) and cranial-caudal (CC) directions were measured from the center coordinate values of gross tumor volume of ten time-phase CT sets in the treatment planning sys-tem. Then a breathing model was used to simulate the tumor motions due to respiration. A 4-dimensional motion table was used to mimic the motion of lung tumor in beams-eye-view (BEV). A 2-dimensional semi-conductor beams measurement system was fixed to the table to measure the 2-dimensional dose distribution of static and dynamic targets using the treatment beams at gantry angle of 0°. Finally, the differences of the dose distribution between the static and moving phantom were compared and analyzed with the statistical soft-ware R. Results When the amplitude (half of the moving rang) in the CC direction was 1 cm, the passing ratio of relative dose difference ≤4% in one beam field was minimal (1.1%), and there was 58% maximal relative dose absence. The 4% passing ratios media in the CC direction were 94.7%, 79.4%, 58.6% and 37.1% in <0.25, 0.25-<0.50, 0.50- <0.75 and ≥0.75 mm amplitude (X<'2>=29.20,P=0.000), but were all similar in the AP and LR directions. The mean value of the relative dose change in the high dose area was smaller than the low dose area in the 89% beam fields. When only the CC direction was consid-ered, the 4% passing ratio of 3.6 s and 8.2 s period was 72% and 60%, respectively. Conclusions The amplitude in the CC direction is a factor impacting the dose distribution of the moving target. The influence of respiratory motion on high dose area is more than that on low dose area. When the other respiratory param-eters are fixed, the motion of long period has more influence on the dose than that of short period. Special at-tention should be paid to the patients with tumor of more than 0.5 cm amplitude in the CC direction when planning the intensity modulated radiotherapy.

Motion Correction in PET/CT Images / 핵의학분자영상

PET/CT fused image with anatomical and functional information have improved medical diagnosis and interpretation. This fusion has resulted in more precise localization and characterization of sites of radio-tracer uptake. However, a motion during whole-body imaging has been recognized as a source of image quality degradation and reduced the quantitative accuracy of PET/CT study. The respiratory motion problem is more challenging in combined PET/CT imaging. In combined PET/CT, CT is used to localize tumors and to correct for attenuation in the PET images. An accurate spatial registration of PET and CT image sets is a prerequisite for accurate diagnosis and SUV measurement. Correcting for the spatial mismatch caused by motion represents a particular challenge for the requisite registration accuracy as a result of differences in PET/CT image. This paper provides a brief summary of the materials and methods involved in multiple investigations of the correction for respiratory motion in PET/CT imaging, with the goal of improving image quality and quantitative accuracy.

Evaluation of Real-time Measurement Liver Tumor's Movement and Synchrony(TM) System's Accuracy of Radiosurgery using a Robot CyberKnife / 대한방사선종양학회지

PURPOSE: This study aimed to quantitatively measure the movement of tumors in real-time and evaluate the treatment accuracy, during the treatment of a liver tumor patient, who underwent radiosurgery with a Synchrony Respiratory motion tracking system of a robot CyberKnife. MATERIALS AND METHODS: The study subjects included 24 liver tumor patients who underwent CyberKnife treatment, which included 64 times of treatment with the Synchrony Respiratory motion tracking system (Synchrony(TM)). The treatment involved inserting 4 to 6 acupuncture needles into the vicinity of the liver tumor in all the patients using ultrasonography as a guide. A treatment plan was set up using the CT images for treatment planning uses. The position of the acupuncture needle was identified for every treatment time by Digitally Reconstructed Radiography (DRR) prepared at the time of treatment planning and X-ray images photographed in real-time. Subsequent results were stored through a Motion Tracking System (MTS) using the Mtsmain.log treatment file. In this way, movement of the tumor was measured. Besides, the accuracy of radiosurgery using CyberKnife was evaluated by the correlation errors between the real-time positions of the acupuncture needles and the predicted coordinates. RESULTS: The maximum and the average translational movement of the liver tumor were measured 23.5 mm and 13.9+/-5.5 mm, respectively from the superior to the inferior direction, 3.9 mm and 1.9+/-0.9 mm, respectively from left to right, and 8.3 mm and 4.9+/-1.9 mm, respectively from the anterior to the posterior direction. The maximum and the average rotational movement of the liver tumor were measured to be 3.3degrees and 2.6+/-1.3degrees, respectively for X (Left-Right) axis rotation, 4.8degrees and 2.3+/-1.0degrees, respectively for Y (Cranio-Caudal) axis rotation, 3.9degrees and 2.8+/-1.1degrees, respectively for Z (Anterior-Posterior) axis rotation. In addition, the average correlation error, which represents the treatment's accuracy was 1.1+/-0.7 mm. CONCLUSION: In this study real-time movement of a liver tumor during the radiosurgery could be verified quantitatively and the accuracy of the radiosurgery with the Synchrony Respiratory motion tracking system of robot could be evaluated. On this basis, the decision of treatment volume in radiosurgery or conventional radiotherapy and useful information on the movement of liver tumor are supposed to be provided.

A review on the clinical implementation of respiratorygated radiation therapy

Respiratory-gated treatment techniques have been introduced into the radiation oncology practice to manage target or organ motions. This paper will review the implementation of this type of gated treatment technique where the respiratory cycle is determined using an external marker. The external marker device is placed on the abdominal region between the xyphoid process and the umbilicus of the patient. An infrared camera tracks the motion of the marker to generate a surrogate for the respiratory cycle. The relationship, if any, between the respiratory cycle and the movement of the target can be complex. The four-dimensional computed tomography (4DCT) scanner is used to identify this motion for those patients that meet three requirements for the successful implementation of respiratory-gated treatment technique for radiation therapy. These requirements are (a) the respiratory cycle must be periodic and maintained during treatment, (b) the movement of the target must be related to the respiratory cycle, and (c) the gating window can be set sufficiently large to minimise the overall treatment time or increase the duty cycle and yet small enough to be within the gate. If the respiratory-gated treatment technique is employed, the end-expiration image set is typically used for treatment planning purposes because this image set represents the phase of the respiratory cycle where the anatomical movement is often the least for the longest time. Contouring should account for tumour residual motion, setup uncertainty, and also allow for deviation from the expected respiratory cycle during treatment. Respiratory-gated intensity-modulated radiation therapy (IMRT) treatment plans must also be validated prior to treatment. Quality assurance should be performed to check for positional changes and the output in association with the motion-gated technique. To avoid potential treatment errors, radiation therapist (radiographer) should be regularly in-serviced and made aware of the need to invoke the gating feature when prescribed for selected patients.