1994 Fiscal Year Final Research Report Summary
Development of field-within-a-field technique using three-dimensional compensating filter
| Project/Area Number |
05454302
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
Radiation science
|
|---|
| Research Institution | Sinshu University |
|---|
Principal Investigator |
IZUNO Itaru Dept.of Radiology, School of Medicine, Shinshu University, assistant Proffesor, 医学部, 助教授 (80020783)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
OGUCHI Masahiko Dept.of Radiology, School of Medicine, Shinshu University, assistant, 医学部, 助手 (50169257)
SONE Shusuke Dept.of Radiology, School of Medicine, Shinshu University, Proffesor, 医学部, 教授 (80028480)
|
|---|
| Project Period (FY) |
1993 – 1994
|
| Keywords | Radiation terapy / Field within a field technique / compensating filter / 補償フィルタ |
|---|
| Research Abstract |
The radiation fields usually include the primary site and neighboring tissues where tumor invasion is suspected (large field). Additionally, small fields confined to the primary site also may be used for boost therapy. In such a case, the field-within-a-field technique (FFRT) uses both large and small fields in every treatment. Thus FFRT can shorten the overall treatment time. This is advantageous in tumor control probability and decreases burden for a patient. FFRT is adaptable to radiation therapy for nasopharyngeal carcinomas using two opposing lateral fields. Namely, about 60Gy is delivered to the nasopharynx and adjacent tissues through two opposing lateral fields, and dose of 5 to 10Gy is added with smaller fields confined to the nasopharynx. But former FFRT requires much labor to use many portals.
By the way, skin surfaces in the fields are so irregular that dose distribution in the target volume is not uniform. In such a case, it is desirable to use the three-dimensional compensating filter (3DCF) to correct the dose distribution. Our department has developed a system of making 3DCF.Here a numerical-control milling machine carves a mold of 3DCF conforming to the body out-lines of patients from the CT images. If a portion of 3DCF is made thinner, dose for the areas related the portion in the target valume will incrrase. This is the hints of this study. This method enables to irradiate through large and small fields simultaneously.
Daily doses to the nasopharynx and other areas were planned as 2Gy and 1.8Gy, respectively. In the process of making 3DCF,we made the portion of 3DCF related to the nasopharynx thinner than other portion in according to the ratio (2 : 1.8). The effect of 3DCF having FFRT function was assessed by phantom examinations. Clinically, faults of former FFRT were corrected with this new method.
|
