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A method of delivering homogeneous irradiation to small animals
Int. J. Radiation
Oncology
Bid.
Phys..
1976. Vol.
1. pp. 7X5-797’.
Pexgamon Press.
Primed in the U.S.A.
A METHOD OF DELIVERING HOMOGENEOUS IRRADIATION TO SMALL ANIMALS JAY S. COOPER, M.D. and JOSEPH NEWALL, M.D. Division of Radiation Oncology, New York University-Bellevue Avenue, NY 10016, U.S.A.
Medical Center, 566 First
A technique for megnvoftage irmdiatbn of mall odmaJs is described. This te&uique makes it ~1etodellvablghdoseirrrrdiPtiontotbelowerhrrlfofthcbodyofamonsewitblessthan 3%scattertotbeaxfllae.
Megavoltage bmdl8tbn,
Aldmals.
INTRODUCTION
complished easily and machine time generally is available since scheduling is not hampered by the need to treat patients. However, just as in clinical radiotherapeutic practice, megavoltage irradiation does offer distinct advantages in treating animal models. Increased homogeneity of dose, decreased back and side scatter and lessened differential absorption in
Despite the preference for megavoltage quality irradiation in clinical practice, many investigators continue to use superficial or orthovoltage quality irradiation for animal experiments. Undoubtedly, this reflects the technical simplicity of such systems. Portal shaping, immobilization and shielding are ac-
Fig. l(b). Fig. l(a). Fig. 1. (a) The mice are anesthetized and wrapped with paper adhesive tape, (b) placed in pill containers and (c) immersed in a custom-built water bath as described in the text. The irradiating beams are perpendicular to the plane of Fig. l(c). 795
1%
Radiation Oncology 0 Biology 0 Physics
1976, Vol. 1, Number 7 and Number 8
Fig. l(c).
bond vs soft tissue are of the same importance as in human therapy. The following system has been developed as a means of obtaining reproducible, beamdirected megavoltage irradiation of mice. MEZHODS
containers to be inserted by mild and its lucite walls are of sufficient to cause electronic build-up when Radiation is delivered by a 4 MeV
pressure thickness radiated. linear ac-
AND MATERIALS
The method is based on the use of a room temperature water bath. Mice are anesthetized by 0.65 mg Pentobarbital (Nembutai) given intraperitoneally. A single strip of “paper tape” is wrapped around the animal’s abdomen to keep each mouse rigid (Fii. la). The mice are then placed vertically into snugly fitting cylindrical pill containers which have holes drilled in both ends (Fig. lb). The containers are immersed partially in a room temperature custom-built water bath so that the caudal two-thirds of each mouse is below water level (Fig. lc). The inside dimension of the bath is just large enough for the pill Table 1. Average scattered dose measured in axilla (rad)/average delivered dose measured in groin (rad)
Experiment Experiment Experiment Experiment Experiment Experiment
A B C D E F
Run 1
Run 2
Run3
141639 141665 lo/65 1 81627 151644
121657 141650 lo/650 101599 18/660
141613 18/626 141646 111587 151656
131646
161630
171638
Fig. 2. One year old C57BL/6 mouse with radiation-induced caudal hypopigmentation as described in the text.
Delivering homogeneous irradiation to small animals 0 J. S. COOPERand J. NEWALL
celerator using parallel opposed portals. The mice are then towel dried and kept warm until awake.
DOSlMETRY Confirmation of the accuracy of the techniobtained by the following was que experiments. Lithium fluoride thermoluminescent dosimetry rods were implanted into the axillae and groins of 6-7 week old C57BL/6 mice which were then prepared and irradiated as described above. Each of six experiments was performed three times. Table 1 shows that
797
high doses can be delivered to the caudal half of a young mouse with only l-3% scatter to the axillae. The stated doses for each run represents the average of four measurements at each site. All measurements were within 210% of the derived averages. Figure 2 shows a 1 year old C57BL/6 mouse that received caudal hemibody radiation (600 rad/ 1 fraction) as described above when the mouse was 6 weeks old. There is marked depigmentation of the fur within the irradiated field which ends abruptly at the animal’s waist. We conclude that this system permits accurate delivery of megavoltage quality irradiation to specific sites in small animals.
Oncology
Bid.
Phys..
1976. Vol.
1. pp. 7X5-797’.
Pexgamon Press.
Primed in the U.S.A.
A METHOD OF DELIVERING HOMOGENEOUS IRRADIATION TO SMALL ANIMALS JAY S. COOPER, M.D. and JOSEPH NEWALL, M.D. Division of Radiation Oncology, New York University-Bellevue Avenue, NY 10016, U.S.A.
Medical Center, 566 First
A technique for megnvoftage irmdiatbn of mall odmaJs is described. This te&uique makes it ~1etodellvablghdoseirrrrdiPtiontotbelowerhrrlfofthcbodyofamonsewitblessthan 3%scattertotbeaxfllae.
Megavoltage bmdl8tbn,
Aldmals.
INTRODUCTION
complished easily and machine time generally is available since scheduling is not hampered by the need to treat patients. However, just as in clinical radiotherapeutic practice, megavoltage irradiation does offer distinct advantages in treating animal models. Increased homogeneity of dose, decreased back and side scatter and lessened differential absorption in
Despite the preference for megavoltage quality irradiation in clinical practice, many investigators continue to use superficial or orthovoltage quality irradiation for animal experiments. Undoubtedly, this reflects the technical simplicity of such systems. Portal shaping, immobilization and shielding are ac-
Fig. l(b). Fig. l(a). Fig. 1. (a) The mice are anesthetized and wrapped with paper adhesive tape, (b) placed in pill containers and (c) immersed in a custom-built water bath as described in the text. The irradiating beams are perpendicular to the plane of Fig. l(c). 795
1%
Radiation Oncology 0 Biology 0 Physics
1976, Vol. 1, Number 7 and Number 8
Fig. l(c).
bond vs soft tissue are of the same importance as in human therapy. The following system has been developed as a means of obtaining reproducible, beamdirected megavoltage irradiation of mice. MEZHODS
containers to be inserted by mild and its lucite walls are of sufficient to cause electronic build-up when Radiation is delivered by a 4 MeV
pressure thickness radiated. linear ac-
AND MATERIALS
The method is based on the use of a room temperature water bath. Mice are anesthetized by 0.65 mg Pentobarbital (Nembutai) given intraperitoneally. A single strip of “paper tape” is wrapped around the animal’s abdomen to keep each mouse rigid (Fii. la). The mice are then placed vertically into snugly fitting cylindrical pill containers which have holes drilled in both ends (Fig. lb). The containers are immersed partially in a room temperature custom-built water bath so that the caudal two-thirds of each mouse is below water level (Fig. lc). The inside dimension of the bath is just large enough for the pill Table 1. Average scattered dose measured in axilla (rad)/average delivered dose measured in groin (rad)
Experiment Experiment Experiment Experiment Experiment Experiment
A B C D E F
Run 1
Run 2
Run3
141639 141665 lo/65 1 81627 151644
121657 141650 lo/650 101599 18/660
141613 18/626 141646 111587 151656
131646
161630
171638
Fig. 2. One year old C57BL/6 mouse with radiation-induced caudal hypopigmentation as described in the text.
Delivering homogeneous irradiation to small animals 0 J. S. COOPERand J. NEWALL
celerator using parallel opposed portals. The mice are then towel dried and kept warm until awake.
DOSlMETRY Confirmation of the accuracy of the techniobtained by the following was que experiments. Lithium fluoride thermoluminescent dosimetry rods were implanted into the axillae and groins of 6-7 week old C57BL/6 mice which were then prepared and irradiated as described above. Each of six experiments was performed three times. Table 1 shows that
797
high doses can be delivered to the caudal half of a young mouse with only l-3% scatter to the axillae. The stated doses for each run represents the average of four measurements at each site. All measurements were within 210% of the derived averages. Figure 2 shows a 1 year old C57BL/6 mouse that received caudal hemibody radiation (600 rad/ 1 fraction) as described above when the mouse was 6 weeks old. There is marked depigmentation of the fur within the irradiated field which ends abruptly at the animal’s waist. We conclude that this system permits accurate delivery of megavoltage quality irradiation to specific sites in small animals.