ホウシャセン デ ナオル ビョウキ

Rapid advances in radiation therapy technology have made remotely controlled after loading system, 3 dimensional planning system and intensity modulated radiation therapy system. These technologies have made it possible to deliver ideally distributed radiation to the target three dimensionally with great accuracy, while sparing the adjacent organs. As a result, radiation therapy becomes a treatment method equal to a surgery in local control probability of cancer in various organs. If the cure rate is the same, treatment method with a few functional deficit and adverse effect by a treatment is regarded as a better. Radiation therapy must be always explained to a patient as alternative therapy of a surgery in early cancer of the organ that function preservation is important

ガン ホウシャセン リョウホウ : ギジュツ カクシン ガ モタラス シン ノ チリョウ テキオウ

Technical innovation in radiation therapy symbolized by stereotactic irradiation, intensitymodulated radiation therapy, image-guided radiation therapy, and brachytherapy using remote controlled after-loading system made it possible to deliver ideally distributed radiation dose to the target with great accuracy, while sparing the adjacent organs at risk. The high tumor control ability led by new technology changed radiation therapy into effective and minimally invasive cancer therapy. What we should mention specially for radiation therapy is to have become excellent alternative to surgery for asymptomatic small brain tumors, part of early stage lung cancer or metastatic lung cancer, and low-risk prostate cancer. In locally advanced stage of cancer, randomized controlled trials established the chemoradiation therapy as a standard treatment option for patients with head and neck cancer, lung cancer, esophageal cancer, and gynecological cancer represented by uterine cervical cancer. Radiation therapy has also important role in palliative care and oncologenic emergencies with consistently high response rates. Minimally invasive therapy will come to be emphasized its needs in the background of increased tendency of elderly patients with cancer, and it shows us where the radiation therapy stands and has to go toward. However, much more radiation therapy professions than the present Japanese situation are indispensable to fully demonstrate ability inherent in highly-sophisticated radiation therapy technology. Establishment of an education system for radiation oncologist, radiation therapy technologist, and medical physicists is our current most important issue

サイシン イリョウ ニオケル ホウシャセン チリョウ ノ ヤクワリ

New technologies of radiation therapy such as image-guided radiation therapy, stereotactic irradiation, and brachytherapy using remotely controlled after-loading system have made it possible to deliver ideally distributed radiation dose to the target with great accuracy, while sparing the adjacent organs. As a result, tumor control rate by radiation therapy improved markedly and became excellent alternative to surgery for asymptomatic or mildly symptomatic brain tumors, early stage lung cancer, and low-risk prostate cancer. In locally advanced stage of cancer, randomized controlled trials established the chemoradiation therapy as a standard treatment option for patients with head and neck cancer, lung cancer, esophageal cancer, and cervical cancer. Radiation therapy is also a valuable treatment for palliation of local symptoms caused by cancer with consistently high response rates

Radiation therapy: state of the art and the future

Technical innovation in radiation therapy (RT) such as stereotactic irradiation, intensity modulated RT, image-guided RT, and brachytherapy using remote controlled after-loading system have made it possible to deliver ideally distributed radiation dose to the target with great accuracy, while sparing the adjacent organs at risk. As a result, tumor control rate by RT improved markedly and became excellent alternative to surgery for asymptomatic or mildly symptomatic brain tumors, early stage lung cancer, and low-risk prostate cancer. In locally advanced stage of cancer, randomized controlled trials established the chemoradiation therapy as a standard treatment option for patients with head and neck cancer, lung cancer, esophageal cancer, and cervical cancer. RT is also a valuable treatment for palliation of local symptoms caused by cancer with consistently high response rates. Minimally invasive therapy has come to be emphasized its needs in the background of increased tendency of elderly patients with cancer, and advances in conformal dose delivery technique raise the RT at a more important position in cancer therapy. However, adequate number of RT profession is indispensable to utilize highly-sophisticated RT technology. Substantiality of an education system for radiation oncologist, RT technologist, and medical physicists is our current most important issue

ホウシャセン チリョウ : state of the art and in future

Technical innovation in radiation therapy such as stereotactic irradiation, intensity modulated radiation therapy, image-guided radiation therapy, and brachytherapy using remote controlled after-loading system have made it possible to deliver ideally distributed radiation dose to the target with great accuracy, while sparing the adjacent organs at risk. As a result, tumor control rate by radiation therapy improved markedly and became excellent alternative to surgery for asymptomatic or mildly symptomatic brain tumors, early stage lung cancer, and low-risk prostate cancer. In locally advanced stage of cancer, randomized controlled trials put the chemoradiation therapy forward a standard treatment option for patients with head and neck cancer, lung cancer, esophageal cancer, and uterine cervical cancer. Radiation therapy is also a effective treatment method for palliation of local symptoms caused by cancer with consistently high response rates. Minimmaly invasive therapy has come to be emphasized its needs against the background of increased tendency of elderly patients with cancer, and advances in conformal dose delivery technique raise the radiation therapy at a more important position in the medical care for cancer. However, adequate number of radiation therapy profession is indispensable to manage highlysophisticated radiation therapy technology. It is our current issue to establish the education system bringing up radiation therapy professions including a radiation oncologist, a medical physicist, a dosimetrist, and a radiation therapy technologist

Cervical Cancer Treatment using AI

In cervical cancer treatment, radiation therapy is selected based on the degree of tumor progression, and radiation oncologists are required to delineate tumor contours. To reduce the burden on radiation oncologists, an automatic segmentation of the tumor contours would prove useful. To the best of our knowledge, automatic tumor contour segmentation has rarely been applied to cervical cancer treatment. In this study, diffusion-weighted images (DWI) of 98 patients with cervical cancer were acquired. We trained an automatic tumor contour segmentation model using 2D U-Net and 3D U-Net to investigate the possibility of applying such a model to clinical practice. A total of 98 cases were employed for the training, and they were then predicted by swapping the training and test images. To predict tumor contours, six prediction images were obtained after six training sessions for one case. The six images were then summed and binarized to output a final image through automatic contour segmentation. For the evaluation, the Dice similarity coefficient (DSC) and Hausdorff distance (HD) was applied to analyze the difference between tumor contour delineation by radiation oncologists and the output image. The DSC ranged from 0.13 to 0.93 (median 0.83, mean 0.77). The cases with DSC <0.65 included tumors with a maximum diameter < 40 mm and heterogeneous intracavitary concentration due to necrosis. The HD ranged from 2.7 to 9.6 mm (median 4.7 mm). Thus, the study confirmed that the tumor contours of cervical cancer can be automatically segmented with high accuracy

カンワ ケア ニオケル ホウシャセン チリョウ ノ ヤクワリ

Radiation therapy is a valuable treatment for palliation of local symptoms with consistently high response rates in the relief and control of bone pain, neurological symptom, obstructive symptoms, and tumor hemorrhage. Over than ８０％ of patients who developed bone metastasis and superior vena cava syndrome obtained symptom relief by radiation therapy. Radiation therapy is also well established as an effective treatment for brain metastasis, improving symptoms and preventing progressive neurological deficits, and recently stereotactic irradiation had became a alternative treatment of surgery for small metastatic brain tumors. Both radiation therapy and surgery are effective in the initial treatment of malignant spinal cord compression syndrome, and no advantages of surgery over radiation therapy has been demonstrated in published series when patients have a previously conformed diagnosis of malignant disease and no evidence of vertebral collapse. The outcome of treatment depends primarily upon the speed of diagnosis and neurological status at initiation of treatment. It is very important to start radiation therapy before patient become non-ambulant. Low irradiation dose and short treatment period of palliative radiation therapy can minimize disruption and acute morbidity for the patients with advanced cancer with enabling control of symptoms and palliative radiation therapy is applicable to the patient even in poor general condition

Reproducibility of breath-hold irradiation of lung

Methods to evaluate the positional reproducibility of breath-hold irradiation mostly require manual operation. The purpose of this study is to propose a method to determine the reproducibility of breath-hold irradiation of lung tumors between fractions using non-artificial methods. This study included 13 patients who underwent terminal exhaled breath-hold irradiation for primary and metastatic lung cancer. All subjects received a prescribed dose of 60 Gy/8 fractions. The contours of the gross tumor volume (GTV) were extracted by threshold processing using treatment-planning computed tomography (CT) and cone-beam CT (CBCT), which was done just before the beginning of the treatment. The method proposed in this study evaluates the dice similarity coefficient (DSC) and Hausdorff distance (HD) by comparing two volumes, the GTVCTS (GTV obtained from treatment-planning CT) and GTVCBCT (GTV obtained from CBCT). The reference contours for DSC and HD are represented by GTVCTS. The results demonstrated good visual agreement for cases with a DSC of ~0.7. However, apparent misalignment occurred when the DSC was 2 mm in 3 out of 13 cases, and when the DSC was ~0.7, the HD was ~1 mm. In addition, cases with greater HD also demonstrated more significant variability. It was found that the DSC and HD evaluation methods for the positional reproducibility of breath-hold irradiation proposed in this study are straightforward and can be performed without the involvement of humans. Our study is of extreme significance in the field of radiation studies

Differences in image density adjustment parameters on the image matching accuracy of a floor-mounted kV X-ray image-guided radiation therapy system

This study aimed to investigate the effect of two different image density adjustment parameters on the results of image matching at six degrees of freedom using radiographic images generated by the ExacTrac X-ray system in brain stereotactic radiosurgery (SRS). This study comprised 32 patients who underwent brain SRS at our hospital from January 2020 to December 2020. In this study, (1) the default parameter (an image density parameter between “tissue” and “bone”) was an image density parameter for digitally reconstructed radiograph (DRR) generation used at many facilities, and (2) the bone parameter was the steepest contrast parameter used at our hospital. Of the 32 patients, 24 (75%) had a couch angle of 0.5 mm or more in the translational direction or 0.5° or more in the rotational direction, and 10 (31%) had a couch angle of 1.0 mm or more in the translational direction or 1.0° or more in the rotational direction. Among the 131 cases of all couch angles, 46 (35%) cases had a translational direction of 0.5 mm or more or a rotational direction of 0.5° or more, and 15 (11%) had a translational direction of 1.0 mm or more or a rotational direction of 1.0° or more. The results of this study indicate the usefulness of using appropriate DRR parameters for each case, rather than using the default settings. The use of appropriate DRR parameters can lead to accurate position matching results, leading to fewer image-guided radiation therapy shots and a lower imaging dose

The effect of rectal gas on dose distribution during prostate cancer treatment using full arc and partial arc Volumetric Modulated Arc Therapy (VMAT) treatment plans

Background/AimIn this study, we investigated the effect of rectal gas on the dose distribution of prostate cancer using a volumetric modulated arc therapy (VMAT) treatment planning.Materials and MethodsThe first is the original structure set, clinical target volume (CTV), the rectum, and the bladder used clinically. The second is a structure set (simulated gas structure set) in which the overlapping part of the rectum and PTV is overwritten with Hounsfield Unit −950 as gas. Full arc and limited gantry rotation angle with VMAT were the two arcs. The VMAT of the full arc was 181°–179° in the clockwise (CW) direction and 179°–181° in the counterclockwise (CCW) direction. Three partial arcs with a limited gantry rotation angle were created: 200°–160 °CW and 160°–200 °CCW; 220°–140 °CW and 140°–220 °CCW; and finally, 240°–120 °CW and 120°–240 °CCW. The evaluation items were dose difference, distance to agreement, and gamma analysis.ResultIn the CTV, the full arc was the treatment planning technique with the least effect of rectal gas. In the rectum, when the gantry rotation angle range was short, the pass rate tended to reduce for all evaluation indices. The bladder showed no characteristic change between the treatment planning techniques in any of the evaluation indices.ConclusionsThe VMAT treatment planning with the least effect on dose distribution caused by rectal gas was shown to be a full arc