Biomedical subjects

Yukio Uchiyama

Publications and source records attributed to Yukio Uchiyama.

4 recordsLinked to original sources

PubMed2006

Stereotactic imaging for radiosurgery: localization accuracy of magnetic resonance imaging and positron emission tomography compared with computed tomography.

Computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) provide complementary information for treatment planning in stereotactic radiosurgery. We evaluated the localization accuracy of MRI and PET compared with CT. Two kinds of phantoms applicable to the Leksell G stereotactic skull frame (Elekta, Tokyo) were developed. Deviations of measured coordinates at target points (x = 50, 100, 150; y = 50, 100, 150) were determined on different axial planes (z = 30-140 for MRI and CT study and Z = 50-120 for PET and CT study). For MRI, the deviations were no more than 0.8 mm in each direction. For PET, the deviations were no more than 2.7 mm. For both imaging modalities studied, accuracy was at or below the imaging resolution (pixel size) and should be considered useful for clinical stereotactic planning purposes.

Fluorodeoxyglucose F18↗

PubMed2005

Long-term results of gamma knife surgery for growth hormone-producing pituitary adenoma: is the disease difficult to cure?

OBJECT: The authors conducted a study to determine the long-term results of gamma knife surgery for residual or recurrent growth hormine (GH)-producing pituitary adenomas and to compare the results with those after treatment of other pituitary adenomas. METHODS: The series consisted of 67 patients. The mean tumor diameter was 19.2 mm and volume was 5.4 cm3. The mean maximum dose was 35.3 Gy and the mean margin dose was 18.9 Gy. The mean follow-up duration was 63.3 months (range 13-142 months). The tumor resolution rate was 2%, the response rate 68.3%, and the control rate 100%. Growth hormone normalization (GH < 1.0 ng/ml) was found in 4.8%, nearly normal (< 2.0 ng/ml) in 11.9%, significantly decreased (< 5.0 ng/ml) in 23.8%, decreased in 21.4%, unchanged in 21.4%, and increased in 16.7%. Serum insulin-like growth factor (IGF)-1 was significantly decreased (IGF-1 < 400 ng/ml) in 40.7%, decreased in 29.6%, unchanged in 18.5%, and increased in 11.1%, which was almost parallel to the GH changes. CONCLUSIONS: Gamma knife surgery was effective and safe for the control of tumors; however, normalization of GH and IGF-1 secretion was difficult to achieve in cases with large tumors and low-dose radiation. Gamma knife radiosurgery is thus indicated for small tumors after surgery or medication therapy when a relatively high-dose radiation is required.

Adenoma↗

PubMed2005

[Survey of patients' impressions of radiotherapy and their need for additional medical information: Japanese domestic survey of 1,529 patients in 2002].

PURPOSE: We clarified the images, impressions, and information about radiotherapy in standard Japanese patients and, at the same time, investigated their need for information about radiotherapy, in order to identify what we, as radiation oncologists, should do to decrease patient anxiety and create good physician-patient relationships. MATERIALS AND METHODS: We handed out 10 questionnaires to 1529 patients from April 2002 through July 2002 in 22 Japanese institutions that were equipped with radiotherapy machines. Questionnaires contained 10 items asking about patients' background, their impression of radiotherapy, frequency of exposure to information about radiotherapy, need to obtain information about radiotherapy, and ideal additional medical informational resources or their content. RESULTS: About 60% of patients had had the opportunity to obtain information about radiotherapy "sometimes" or "often," but 80% of them were not satisfied with the availability of information and answered that it was inadequate. Ten percent responded that they had no idea about radiotherapy. Thirty percent felt unspecified anxiety concerning radiotherapy, and those who had less chance to be exposed to information about radiotherapy felt more anxiety than the others (33.2% vs. 25.2%, p=0.0008). The need for "explanation and information about adverse effects" was the top priority, followed by "explanation of outcome." Although they generally obtained information from their physician (radiation oncologist), they also wanted additional information via written media (662 patients, 43%). However, patients who were over 60 years old most wanted to obtain additional medical information directly from their own radiation oncologist (37.7%). CONCLUSION: Information about radiotherapy given to patients and the general public is still insufficient in Japan. To fully utilize radiotherapy, which is a very effective treatment option against cancer, and to reduce anxiety about radiotherapy among cancer patients, more information is necessary.

Adult↗

PubMed2001

[Three-dimensional conformal radiotherapy with multi-leaf collimator]

In radiation therapy, it is very important to concentrate the high dose to the clinical target volume. For this purpose, S. Takahashi developed the dynamic conformal radiotherapy in 1960. In the first half of 1990' this conformal technique with multi-leaf collimator (MLC) was gradually becoming popular, because the three dimensional extent of the clinical target volume and the surrounding normal tissues was accurately recognized by the use of the serial CT-images, and the 3D-treatment planning was considerably easily obtained by the development of computer-technique. The 3D-CRT (conformal radiation therapy) based on the 3D-treatment planning in a broad sense means the coplanar or non-coplanar irradiation with multi-leaf collimator, and at present it is one of the most reasonable treatment techniques. In order to correspond the high dose region to the clinical target volume as possible, IM (intensity modulation) technique was introduced to the 3D-CRT using MLC in the second half of 1990'. Therefore, the static CRT is routinely used not only in Europe/ USA but also in Japan. But, it is often very difficult to obtain the concave high dose region in static CRT with MLC, even though the IM-technique is applied. At this occasion, the concave high dose region is easily obtained by the use of dynamic CRT such as the hollowed -out technique developed by S. Takahashi in Japan. The dynamic CRT technique is also useful with the static IM-CRT technique. There are two main aims of conformal radiotherapy: First, the protection of the surrounding normal tissues, and second, improvement of the local control rate. Usually the second aim can't be easily achieved, because the tumor control probability curves are often flat. The DVH concept is usually valuable to choose the optimal treatment planning. But, it is difficult to find the optimal dose-distribution, when two DVH-curves cross each other on the middle range of irradiated dose. On that occasion, the NTCP-concept is useful. From the standpoint of the tolerable dose, normal organs are classified into two types: parallel and serial. Therefore, two types of the NTCP-formula should be prepared to apply the NTCP-concept clinically.

Journal Article↗