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HOME Activities Radiology and Radiation Oncology

1.Research Summary

Department of Radiology and Radiation Oncology consists of diagnostic radiology and radiation oncology groups. Both groups are highly active in each area of specialty as well as in a new field conglomerating their specialized abilities in each field. For the details of these research efforts, see the website of the Department of Radiology and Radiation Oncology.

2.Research Groups

  • Diagnostic Radiology Group
  • Radiation Oncology Group

3-1.Diagnostic Radiology Group

Research subjects

Research on diagnostic imaging for lung cancer

A wide range of research encompassing comparisons of clinical, pathological and imaging findings, time-course changes, and relationships between imaging findings and selection of therapies is performed, focusing mainly on lung cancer.

Research on the application of new diagnostic imaging procedures for circulatory disease

Research on the application of various CT and MRI techniques

Research on therapeutic interventions using diagnostic imaging procedures

Research on RI imaging diagnosis and quantitative analysis

Research on diagnostic imaging for central nervous system diseases

addressing imaging characteristics of tumors and other diseases with recently developed technologies, such as high-spatial-resolution MRI, to promote better differential diagnosis.

3-2.Radiation Oncology Group

Research subjects

Research on the optimization of whole-brain radiotherapy in combination with stereotactic radiotherapy for metastatic brain tumors

The combination of stereotactic radiotherapy and whole-brain radiotherapy is effective for local control of brain metastases and preventing brain tumor recurrence, but conventional whole-brain radiotherapy causes the neurocognitive impairment as a late complication. Therefore, research on an optimal whole-brain radiotherapy in combination with stereotactic radiotherapy, such as a reduction in the whole-brain irradiation dose, is being conducted.

Global research on the development of new parameters of neurocognitive function on the treatment for brain tumors

Simplified tests such as the Mini Mental Score Examination have been used for evaluating cognitive function after radiotherapy for brain tumors. For establishing a more precise evaluation method, we are working on the development of a Japanese version of the cognitive function battery combining multiple cognitive function tests.

Research on the change of intratumoral blood flow during the course of stereotactic body radiotherapy for lung tumors

Intratumoral blood flow, i.e., the amount of oxygen supplied, can be estimated by perfusion CT. Perfusion CT scans before and after stereotactic body radiotherapy for lung tumors are evaluated to analyze the correlation between intratumoral oxygen concentrations and treatment response.

Research on endoscopic submucosal dissection + chemoradiotherapy for esophageal cancer

When the depth of invasion is below the mucus membrane after endoscopic submucosal dissection for superficial esophageal cancer, potential lymph node metastasis is a concern. In our department, prophylactic chemoradiotherapy is instituted in such patients to examine the efficacy of recurrence prevention.

Research on outcomes and quality of life (QOL) after intensity modulated radiotherapy and brachytherapy for prostate cancer

In our department, external irradiation (intensity modulated radiotherapy), low-dose-rate (LDR) interstitial irradiation and high-dose-rate (HDR) interstitial irradiation are performed as radiotherapy for prostate cancer. Prospective surveys and research on adverse events and the effects of change of QOL after radiotherapy are carried out.

Research on the improvement of irradiation precision with imaging guidance

In our department, we achieve high-precision irradiation by correcting irradiation positions for each treatment session with imaging guidance using the cone-beam computed tomography (CBCT) system during intensity modulated radiotherapy (IMRT) for prostate cancer and stereotactic body radiotherapy for lung tumors.
We accumulate and evaluate data on shift during treatment and conduct analyses for improving irradiation precision.

4.Research Results

[Area] Radiology (medical diagnostic radiology)

[Research subjects] Research on diagnostic imaging for lung cancer

[Description]
A high serum carcinoembryonic antigen (CEA) level has been reported to be a poor prognostic factor in lung adenocarcinoma; however, the CT features of adenocarcinoma related to high CEA levels have not been thoroughly investigated. Here, we assessed the relationship between CT characteristics of primary tumor and preoperative serum CEA levels in patients with pathological stage I lung adenocarcinoma. In logistic regression analysis, lower tumor shadow disappearance rate (TDR), defined as the ratio of tumor area in mediastinal window to that of lung window, and the presence of bullae or honeycombing around the tumor were significantly associated with high preoperative CEA levels. These CT findings remained statistically significant even after adjusting patient age, gender, and smoking status (Brinkman index). The results suggest that decrease in TDR and presence of bullae or honeycombing are associated with poor prognostic indicator in early-stage lung adenocarcinoma. Further study is necessary as to whether such tumors are likely to indicate recurrence after surgery (Clinical Radiology 2014; 69(6): 559-66).

[Photographs]

Photographs

[Area] Radiology (medical diagnostic radiology)

[Research subjects] Research on the application of new diagnostic imaging procedures for circulatory disease

[Description]
Lung perfusion blood volume (lung PBV) images are generated by dual energy imaging and are used in the diagnosis of PE. Dual-energy imaging enables the selective visualization of the iodine component in tissues on the basis of attenuation differences at different energy levels. An image of lung PBV is a fusion image of an iodine distribution image (iodine map) and a pulmonary CT angiography (CTA) image. Perfusion defect in lung PBV is often not obvious in cases of non-occlusive lesions despite obvious PE in CTA.
Our department visually and quantitatively confirmed by lung PBV that non-occlusive PE do not decrease in blood flow compared with occlusive PE and that there is a dissociation between pulmonary blood flow and distribution of thrombus. In the diagnosis of PE, detection of thrombus by CTA is essential. However, evaluation of pulmonary blood flow should be performed by lung PBV. (European Journal of Radiology 83(12):2260-67, 2014)

[Photographs]

Photographs

[Area] Radiology (Radiation Oncology)

[Research subjects] Research on the respiratory gating intermittent radiation and multi-field radiation for esophageal cancer

[Description]
In radiotherapy for esophageal cancer, some patients suffer from the adverse events. Respiratory gating intermittent radiation and multi-field radiation are the technique to reduce the exposure to the normal tissue. We retrospectively investigated the effect of these technique on the dose-volume histogram (DVH) parameters of organ at risk by comparing some radiation treatment plans for esophageal cancer.
In our study, slightly but significant reduction of the DHV parameters of the lung and heart could be obtained by respiratory gating intermittent radiation technique. By multi-field radiation technique, some DVH parameters are reduced significantly, but some parameters are increased inversely. The DVH parameters are more effected by the number of the radiation fields than the respiratory gating intermittent radiation. (Accepted at the ASTRO 57th Annual Meeting, 2015)

[Photographs]

Photographs

[Area] Medical Physics (Radiation Oncology)

[Research subjects] Evaluation of backscatter dose enhancement around dental alloy in radiation therapy for head and neck cancer

[Description]
In radiation therapy for head and neck cancer, mucositis have been frequently observed adjacent to dental metallic implants. It is due to a local dose enhancement caused by backscatter electrons from high-Z dental alloy located in radiation therapy beams. It is difficult to estimate the dose enhancement accurately with commercially available treatment planning systems. Therefore, we performed measurements with a parallel plate chamber (NACP-02, IBA Dosimetry) and a radiochromic film (GAFCHROMIC EBT3, Ashland ISP Advanced Materials) to estimate the dose enhancement accurately. Monte Carlo calculations (PHITS) were also performed assuming the same geometrical setup as the measurements. As a result, measured and calculated dose enhancements were ranged from 33% to 44% and there was no observed dose enhancement beyond 3-5 mm distance from dental alloy. We proposed a design of dental device to prevent mucositis effectively based on the results of our research. This work is based on the collaboration with the Division of Oral and Maxillofacial Radiology, Niigata University Graduate School of Medical and Dental Sciences and Graduate School of Health Science, Niigata University.

[Figure 1]

Photo1

The experimental setup for measuring dose enhancement. A dental alloy of 1 cm3 was embedded in a Tough Water phantom (Kyoto Kagaku) and a parallel plate chamber or a radiochromic film was placed on it.

[Figure 2]

Photo2

The figure describes a result of Monte Carlo calculation as an example. Target, collimator etc. in linear accelerator were modeled in Monte Carlo calculation code to calculate absorbed dose around dental alloy accurately.

[Figure 3]

Photo3

Rate of dose enhancements (vertical axis) are shown as a function of the distance from the surface of the dental alloy. The red line, the blue line and the green line stand for measured data by parallel plate chamber, radiochromic film and calculated data by Monte Carlo calculations, respectively.


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