Radiotherapy is a vital treatment method for pancreatic cancer. However, the therapeutic effect of radiotherapy is significantly limited by the influence of pancreatic motion. More efficient radiotherapy for pancreatic cancer depends upon the improvement of motion management and high-quality image guidance. The emerging MR-guided radiotherapy (MRgRT) can perform functional imaging with high soft tissue resolution and no additional radiation. Multiple researches have demonstrated that MRgRT has significant advantages in terms of precise delineation of target area and organ at risk, motion management and adaptive radiotherapy, which assists radiotherapy to play a better role in the treatment of pancreatic cancer. In this paper, the application of MRgRT in pancreatic cancer was reviewed and prospected.

Objective To compare the results of three different registration methods in the kilovolt CBCT guided IMRT for nasopharyngeal cancer (NPC).Methods Total 560 CBCT images of 24 NPC patients who received kilovolt CBCT guided IMRT were analyzed off line.Three registration methods were used for alignment between CBCT and planning CT,including translational and rotational errors for bone and grey (BoneT + R,GreyT+ R),only translational errors for grey (GreyT).The registration results were analyzed by mean paired t-test respectively.Results With method BoneT+R,the translational errors on x,y and z axes were (-0.11 ± 1.35) mm,(0.40 ± 2.09) mm and (0.95 ± 1.56) mm and the rotational errors were 1.06° ±0.67°,0.01° ± 1.28° and 0.92° ± 1.00° respectively.With GreyT+R,the translational errors on x,y and z axes were (-0.02 ± 1.06) mm,(0.68 ± 1.92) mm and (0.81 ± 1.46) mm and the rotational errors were 0.85° ±0.61°,-0.05° ± 1.32° and 0.91° ±0.72° respectively.With GreyT,the translational errors on x,y and z axes were (0.58 ± 1.02),(0.52 ± 1.89) and (0.44 ± 1.43) mm.The results of compared mean t-test for different registration methods groups have significant difference (P =0.00-0.01) except for the rotational errors on y and z axes between BoneT+R and GreyT+R (P =0.05,0.62).Conclusions There have different alignment errors when different registration methods used for NPC kilovolt CBCT guided radiotherapy.If there have correct methods for rotation errors,GreyT+R registration method may be a better choice.In opposite,GreyT+R registration method would be used firstly to verify whether the rotational error ＞ 2°or 3°.If the rotational error ＞ 2°or 3°,the patient should be re-setup.If not,according to these alignment results,the GreyT method,manual method would be used to compensate the translational errors.

Stereotactic radiotherapy (SRT), also known as stereotactic ablative radiotherapy (SABR), includes stereotactic radiosurgery and stereotactic body radiotherapy (SBRT). This technique has the characteristics of large single fractional dose, few fractions, high equivalent biological doses, and rapid fall off-target doses. It can be implemented by relatively special equipment such as Gamma knife, Cyberknife, Tomotherapy and Vero 4D RT system, etc. In many cases, SBRT technique is employed based on linear accelerators. SRT differs from conventional radiotherapy in terms of the plan design and plan evaluation. Consequently, it is necessary to discuss the differences and provide guidance for clinical application and research.

Objective To evaluate the image quality and registration accuracy of a three?dimensional ( 3D ) dynamic phantom in four?dimensional computed tomography ( 4DCT ) and four?dimensional cone?beam computed tomography ( 4DCBCT) . Methods The Computerized Imaging Reference Systems Dynamic Thorax Phantom Model 008A was scanned to get 4DCT and 4DCBCT images. Two balls with different diameters ( ?= 1 cm and ?= 2 cm) were used to simulate tumors with different sizes. The motion mode of the balls was 3D sinusoidal motion at 0?25 Hz ( the amplitudes along the x, y, and z axes were ±1?0 cm, ±0?4 cm, and ±0?2 cm, respectively). Gross target volumes (GTVs) from 10?phase bins, internal gross target volumes (IGTV), and target volumes on maximum intensity projection (MIP) and mean intensity projection (MeanIP) images were contoured and calculated. Target volumes on 4DCT or 4DCBCT images were compared with the static and dynamic volumes of the balls ( VS and VD ) . The matching index ( MI) of target volumes between the 4DCT and 4DCBCT images was analyzed after rigid image registration. Results The GTV in each phase of the image was larger than VS . The difference between the average GTV derived from 10 phases of 4DCT or 4DCBCT images and Vs of the small ball was larger than that of the large ball ( 35?03% vs. 22?66%;32?62% vs. 17?00%) . All the IGTVs and target volumes on MIP images were slightly larger than VD , but target volumes on MeanIP images were smaller than VD . The average MI of 10?phase bins of the small ball was smaller than that of the large ball ( 66?76% vs. 82?21%) . Moreover, MIs of IGTV,MIP, and MeanIP of the small ball were also smaller than those of the large ball ( 77?39% vs. 90?29%;75?90% vs. 89?28%;74?47% vs. 82?74%) . Conclusions In the case of a relatively small tumor volume and a relatively large motion amplitude, 4DCT and 4DCBCT should be used with caution for comparison of image registration.

Purpose To explore the significance of three-dimensional reconstruction of fetus based on MRI scan data. Materials and Methods Three woman (more than 39 weeks' gestation) with a strong wish to have natural childbirth and voluntary to take the examination in Nanfang Hospital of Southern Medical University were recruited in the study. Mimics 10.01 software was used to do three-dimensional reconstruction. Results The fetal surface tissue showed low signal on the two-dimensional images, and amniotic fluid and lung, bladder, cerebrospinal fluid showed high signal. The placenta and uterine wall showed moderate to low signal. Those contributed to the clear boundary between fetal surface and other tissue surround. The three-dimensional fetus models were reconstructed successfully, which clearly demonstrated the main surface features and spatial position of the fetus. The fetal morphology and fetal position could be viewed in various directions. Conclusion Fetus surface can be reconstructed into three-dimensional model based on MRI data set, which has advantage of large visual field and can be observed at arbitrary angle. It provides a new method for morphological analysis and prenatal evaluation for fetal development and growth.

To investigate the impact of respiratory movement to determine the target volume on cone beam CT (CBCT) for lung tumor, we used CIRS dynamic thorax phantom (Model-CIRS008) to simulate the sinusoidal motion of lung tumor. With a constant amplitude, the ratio of the time of near-end-expiratory and near-end-inspiratory (E/I) changed when it was scanned with CBCT. We analyzed the contrast changes of target by extracting the CT value of each pixel on the center line of the target movement direction. The targets were contoured with region growing method and compared with the motion volume generated by the tumor trajectory method. The result showed that the contrast of near-end-expiratory increased and the contrast of near-end-inspiratory decreased with increasing E/I. The contoured volume generated by region growing method decreased with increasing E/I. When E/I = 4, the amplitude A = 1 cm, diameter of 1 cm and 3 cm target volumes were reduced by 48.2% and 22.7%. The study showed that CBCT was not suitable to be used to accurately determine the range of lung tumor movement. The internal target volume (ITV) may be underestimated in CBCT images.
Cone-Beam Computed Tomography ; Humans ; Lung Neoplasms ; diagnostic imaging ; Movement ; Phantoms, Imaging ; Respiration

Objective To analyze the displacement of titanium clips for tumor bed localization after breast-conserving surgery for breast cancer and its influential factors.Methods A retrospective analysis was performed on the cone-beam computed tomography (CT) images of 14 patients with breast cancer who received radiotherapy after breast-conserving surgery from April to October,2016.The relative position of the chest wall and the errors of the titanium clips in radiotherapy were measured.A Pearson correlation analysis was used to analyze the correlation of the displacement of titanium clips with the relative position of titanium clips,the breast volume,the vertical distance between the titanium clips and the tangential line of the chest wall,and the maximum thickness of the breast.Results The system errors of the chest wall in left-right,superior-inferior,and anterior-posterior directions were 4.42,3.44,and 5.13 mm,respectively,and the random errors were 3.55,3.07,and 4.54 mm,respectively.The titanium clips had a large displacement relative to the chest wall,mainly in the left-right direction.The maximum system error was 4.39 mm and the random error was 2.42 mm.The displacement of titanium clips was not significantly correlated with the breast volume and the maximum thickness of the breast (P>0.05).However,the relative position of titanium clips in superior-inferior direction was significantly correlated with the displacement of the lowest,the most lateral,the most anterior,and the most posterior titanium clips (P<0.05).As to the uppermost clips,there was a significant difference in displacement between the clips close to the chest wall and the clips far from the chest wall (P=0.02).Conclusions Due to large setup error and displacement of titanium clips during radiotherapy,simultaneous integrated boost is not suitable for patients with breast cancer who are immobilized by vacuum cushion and received radiotherapy.The unstable immobilization may be the major influential factor for the displacement of titanium clips.

The training program of radiation therapists in the United States has been established early, and the mode of training, qualification and continuing education are relatively complete. Literature review was conducted at home and abroad and United States Department of Labor, American Registry of Radiologic Technologists, American Society of Radiologic Technologists as well as Joint Review Committee on Education in Radiologic Technology websites were reviewed. The training mode, qualification, work content, continuing education and employment situation of American radiotherapists were analyzed, aiming to provide some reference and enlightenment for the establishment of a new model for the training of professional radiologists suitable for the national conditions of China Mainland.

BACKGROUND: Integrin α5β1 has been shown to be related to acetabular cartilage degeneration due to developmental dysplasia of the hip.OBJECTIVE: To investigate the expression of integrin α5β1 in differently degenerated cartilage tissues of the knee after knee osteoarthritis.METHODS: Seventy-five degenerated articular cartilage specimens at the weight-bearing surface of femoral lateral and medial condyles were removed from patients with knee osteoarthritis who underwent total knee replacement, and were then allotted to four groups based on Mankin's grading system: normal (n=6), mild degeneration (n=24), moderate degeneration (n=26) and severe degeneration (n=19) groups. The expression of integrin α5β1 in each group was detected using real-time PCR, immunohistochemistry and western blot assay.RESULTS AND CONCLUSION: The detected results were consistent in the three kinds of assays, and the expression level of integrin α5β1 was ranked as follows: severe degeneration group > moderate degeneration group > mild degeneration group > normal group (P < 0.05). To conclude, differential expression levels of integrin α5β1 are found in different degenerative degrees of articular cartilage in knee osteoarthritis. Furthermore, the expression level of integrin α5β1 is increased with the degenerative severity.

Objective:To evaluate the effects of orthogonal magnetic fields on the dose distribution of 6 MeV X-ray in a uniform water and heterogeneous phantoms.Methods:The Monte Carlo simulation software Gate v8.2 was used to investigate the dose distribution of X-ray beams of different field sizes in a uniform water phantom, water-air/bone-water layer phantom and" custom lung model" in the magnetic field strength of 0.0, 0.5, 1.0, 1.5, 3.0 T, respectively. The relationship between the intensity of magnetic field and the dose distribution of X-rays in the phantoms was analyzed.Results:The existence of a magnetic field would cause the X-ray to shorten the built-up area in the water phantom; when the field was 10 cm×10 cm, the maximum dose on the central axis could change by up to 56.22%(3.0 T). The transverse dose distribution of the radiation field in the direction of the vertical magnetic field shifted to one side by up to 43.64%(-44.55%). The average dose of the air layer in the water-air-water phantom could be reduced by 57.4%(3.0 T). In the water-bone-water phantom, the dose at the proximal end of the bone layer was decreased by 16.5%, whereas the dose at the distal end was increased by 22.6%(1.5 T). The dose change in each layer in the customed lung model was positively correlated with the magnetic field strength.Conclusion:The existence of the orthogonal magnetic field will cause the change of X-ray dose distribution on the built-up area and both sides of the radiation field in the phantoms, which is more obvious adjacent to the interface of heterogeneous phantom.