Inr J Rndralwn Oncology Bml Phw Vol 20. pp. 605-61 I Pnnkd I” the U.S.A All ri&ts reserved.

0360.3016/91 $3.00 + .oO Copyright 8 1991 Pergamon Press plc

??Technical Innovations and Notes PHYSICAL

ASPECTS OF TOTAL BODY IRRADIATION OF BONE MARROW TRANSPLANT PATIENTS USING 18 MV X RAYS AZAM NIROOMAND-RAD,

PH.D.

Department of Radiation Medicine, Georgetown University Medical Center. 3800 Reservoir Road, N.W., Washington, DC 20007 The physical aspects of a total body irradiation (TBI) treatment are described. Patients seated in a special chair with their legs bent backwards are irradiated anteriorly and posteriorly (AP/PA). The chair reduces patient movement and facilitates positioning patients during 9 fractions of TBI over a 3-day period. The dose to lower extremities are monitored and raised to the total body dose. A conventional linear accelerator in a standard size treatment room is used to deliver 18 MV x-ray beams at a dose rate of approximately 20 cGy/min at a 350 cm treatment distance. Results of dose distribution, field flatness, dose uniformity, in viva and in vitro dosimetry, and boost irradiation techniques are described. Total body irradiation, Patient immobilization

support, Bone marrow transplant.

exposure. They advocate the use of partial lung shielding with electron boost to the chest wall as a means of reducing lung dose ( 18). With hyperfractionated total body photon and electron irradiation, the reported incidence of interstitial pneumonitis by Shank et al. (16) is about 33% less than that reported for any other TBI and BMT treatment regimens. Since 1985 the Department of Radiation Oncology at the Medical College of Wisconsin has followed the recommendations of Peters rt al. (12, 13) and Shank et al. (16, 17) in performing hyperfractionated TBI in preparation for BMT. A total dose of 14.0 Gy is delivered to midline xiphiod in 9 equal fractions at 3 fractions per day for 3 consecutive days while the dose to the lung core and liver is limited to approximately 7.0 and 12.0 Gy, respectively. Since 1985 more than 100 leukemic patients have been treated by this regimen. For the first several years of this program, the TBI treatments were delivered in a standard size treatment room, which necessitated the development of the technique described here. A special chair with no back support was used to support the patient during TBI treatment. Seated patients with their legs bent backwards were irradiated anteriorly and posteriorly (API PA) with 18 MV X rays. The chair reduced patient movement and facilitated TBI treatment with an adequate field size in a standard size treatment room. With this set-up the dose to lower extremities was monitored and raised to the total body dose by additional irradiation. In addition to the photon treatment, the chest wall areas that were shielded by lung blocks were treated with electron beams. The preliminary clinical results for these patients have been reported separately (8, 9).

INTRODUCTION

Total body irradiation (TBI) combined with intensive chemotherapy and bone marrow transplantation (BMT) is used successfully to treat certain types of hemopoietic and immune deficiency disorders such as acute leukemia and aplastic anemia. Total body irradiation involves delivering an adequate immunosuppressive dose before transplantation to achieve a successful marrow graft and to eradicate the malignant cells while avoiding interstitial pneumonitis and damage to other critical organs such as liver, kidneys, heart, CNS, and eye (4). The published results of extensive workshops and review articles indicate disparity of techniques used for TBI, reflecting the complex clinical, biological, physical, dosimetrical, and technical aspects of TBI (1, 2, 5, 7, 14, 15). The clinical and radiobiological bases of TBI with different dose rates and fractionation have been studied by several authors ( 1 1, 12, 13, 2 1). Peters et al. (12, 13) concluded that leukemic cells possess a limited repair capability and that the body’s normal tissue have a greater capacity to repair sublethal damage between the fractions. In fact, Peters et al. ( 12, 13) proposed that increased fractionation of the TBI would yield a better therapeutic ratio with respect to leukemic cell kill and normal tissue tolerance. In an attempt to reduce fatal interstitial pneumonitis while enhancing leukemic cell kill, Shank et al. ( 16, 17) at Memorial Sloan Kettering Cancer Center devised a hyperfractionation regimen for TBI which theoretically yields a greater leukemic cell kill for the same normal tissue tolerance as compared with 10 Gy in a single Accepted for publication

12 September

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Following the guidelines recommended by the American Association of Physicists in Medicine, AAPM Task Group 29 (I), results of dose distribution, field flatness, and dose uniformity. irz ~vivo and in vitro dosimetry. boosting technique are presented. METHODS be-irradiation

AND MATERIALS

technique

Standard anterior-posterior (AP) and lateral chest films, obtained at a distance of 100 cm SSD. were used to determine the outline and thickness of partial lung and liver blocks. Blocks were scaled to an appropriate size and mounted on a lucite plate so that they could be positioned on the patient in a reproducible manner. The 40%-transmission of the lung blocks and the 90%-transmission of the liver block were measured at the TBI treatment distance (350 cm SSD). The outline of lung blocks also was used to determine the outline of cutouts for electron field blocks. The cutouts were shaped as an exact negative impression of the lung blocks with a l-cm overlap margin in all directions. The cutouts were produced using a low-melting lead alloy* and were designed to fit snugly into the trimmer section of the electron cone applicator so that there was minimal leakage between the trimmer and the cutout. The thickness of the cutout was 1 cm for all the electron energies. Standard computerized tomography (CT) scans of the patient thorax were obtained to determine the chest wall thickness; the appropriate electron beam energy and the depth at which the dose from the electron beam was to be delivered were determined. Irradiation

technique

The basic irradiation technique consisted of parallel opposed anterior and posterior fields. A high energy linear accelerator+ was used to treat patients at about 350 cm target-to-skin distance (TSD). This distance, limited by the room size. was about 60 cm from the wall of the room toward which the beam was directed. The gantry was positioned such that the beam axis was almost horizontal. The collimator was opened to its maximum field size of 40 X 40 cm at 1 m from the target: the useful beam dimensions at the treatment distance, about 140 X 140 cm with cutoff edges, were sufficient to accommodate all patients in an upright sitting position. A special “kneeling” chair (Fig. 1) positioned the patient in the beam in a reproducible manner. This chair, which had no back support, rested on the floor next to the wall and the patient sat upright on it. The upper portions of the body were usually flat (within 4 cm of 350 cm TSD). The arms were positioned along the side of the body and the knees were bent backward, in order to fit the patient in the field size available. The legs were spread outward

* Lipowitz’s

metal.

March 1991. Volume 20. Number 3

to reduce the shielding of the lower extremities by the body. The lucite plate with the lung and liver blocks was positioned on the patient chest. Proper alignment of the blocks was facilitated by the marks drawn on the patient’s skin during simulation. The entire lucite-plate with blocks assembly was supported by two nylon cords that passed over two pulleys on a rigid rod. The rod, secured to the wall, hung above the patient’s head. Port films of the chest were obtained during the first fraction to verify the block positions. A large 1 cm thick mobile perpex screen beam spoiler was positioned IO-30 cm from the patient’s skin surface during the large-field photon treatment. We used the same monitor unit (MU) rate setting for our machine for TBI as for the treatments at a standard distance of 100 cm SSD, namely 300 MU per minute. This resulted in a typical dose rate of about 20 cGy per minute at the midline of an average size patient at 350 cm SSD. The total treatment time including the settingup time and occasional interruption was about 20 to 30 minutes per fraction. The treatments were usually scheduled 5 hours apart during the day at 7:00 a.m., 12:00 noon. and 5:00 p.m. On the last 2 days of treatment the chest wall areas shielded by lung blocks were boosted with 7-12 MeV electron beams at standard treatment distance of 100 cm SSD. The electron boost delivered was 7 Gy to the chest wall in two equal fractions on 2 consecutive days. The anterior and posterior cutouts for each lung were inserted one at a time in the electron cone, and the patient was often treated in sitting position on the treatment table. Moreover. since the legs of the patient were bent backwards, the dose to lower extremities was monitored and raised to the total body dose using 6 MV x-ray beam at standard treatment distance of 100 cm SSD. The boost to the lower extremities, if required, was given in one fraction on the last day of TBI treatment. Basic, phantom

dosimetry

The general approach recommended by AAPM Task Group 29 (1) was followed in determining the basic dosimetric quantities for TBI treatment. A water phantom 30 X 40 X 50 cm3 was used to perform dose calibration and to measure the basic dosimetric quantities. The phantom was irradiated under the same geometrical conditions used to treat the patients. Since the TBI treatment field extends beyond the edge of the patient, the effective field which has the same scatter contribution as the patient is in general smaller than the treatment field. Faw and Glenn (6) have shown that the dose distribution is a function of the field size or the phantom size, whichever is smaller. Therefore, whenever possible, additional phantom materials were placed around the measuring phantom to achieve full scattering

’ Siemens

Mevatron

XX, Iselin. NJ.

TBI using

Fig. 1. (A) Anterior

I8MV X rays ??A. NIROOMAND-RAD

view and (B) side view of patient position

conditions. For the measurement of quantities at 100 cm SSD, a phantom large enough to give 5 cm margin on all four sides of the largest field size was chosen. Central axis dose calibration and the relative depth dose measurements were performed with a Farmer-type chambefiO.6 cm3, with tissue-equivalent plastic walls and a digital electrometer.” The dose calibration was performed under the treatment geometry at 350 cm SSD with a 1 cm-thick mobile perpex screen in place. The validity of inverse square law was tested for this treatment geometry. The product of V%D, where R is the reading of the dosimeter at the distance D from the source, was calculated. Moreover, since the percentage depth dose data is a distance-dependent quantity, its conversion from one distance to another, using the Maynard Conversion Formula ( 19) for a large field size was examined. Note that there are limitations for the use of Maynard Conversion Formula as described in Supplement No. 17 (20). Surface dose, the central axis depth dose in the buildup region (0 to 3 cm), and the exit dose were measured with a parallel-plate ion chamber,* 0.5 cm in diameter. The chamber was placed on the surface of a 20 X 20 X 30 cm3 solid water phantom’ that was carefully designed to

* Nuclear Enterprises America, g Keithley Digital Elecrometer,

Fairfield, NJ, Model 258 I. Model 356 14.

during TBI treatment

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with I8 MV x-ray beam.

house the chamber. Several slabs of solid water with different thicknesses were used for the build-up measurements, The radiation characteristics of this water phantom have been reported by Constantionu et al. (3). Since the radiation characteristics of this phantom are very close to those of water, phantom-to-water corrections. density corrections, and scaling factors were not considered. To ensure that the superficial layers of skin received a dose within 10% of the midline dose, the effect of 1 cm-thick mobile perpex screen on the surface dose was determined by placing the screen at different distances (5 to 40 cm) from the surface. Close to the exit surface the relative dose was measured with respect to full scatter dose for phantom diameters of 8, 10, 15.2, 20.0, 26.0, and 32.0 cm. By summing the entrance-dose and exit dose and comparing its average value with the midline dose for AP/PA treatment, the dose variation for various patient thicknesses was examined. The effect of back scatter from wall to exit surface was also examined for different wall-to-exit surface distances of 10. 20, 30, and 40 cm. For TBI treatments it is important to ensure adequate coverage of the patient with a reasonably flat beam. The

* Nuclear Associate Markus Chamber. + Radiation Measurements. Inc.. Middletown,

WI.

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inherent beam-flattening filter on the linear accelerator is designed to produce optimum beam uniformity for a 30 X 30 cm field at 10 cm depth and 100 cm SSD. This can result in “horns” at shallower depths. Measurements made at 100 cm SSD, 10 cm depth with fully opened diaphragms (40 X 40 cm), show the maximum dose for the central 80% field (32 X 32 cm) is about 1.5% higher than the central axis dose. The +80% dose is defined with respect to the 100% reference dose on the central axis. For TBI purposes, the beam profile was measured at depth of maximum dose and 10 cm depth along the principal axes of the beam in the horizontal and vertical directions. A parallel-plate ion chamber. embedded on a 20 X 20 X 30 cm3 solid water phantom, surrounded by additional phantom materials was moved across the principal axis of the radiation field. The beam profiles were compared with their corresponding beam profiles obtained for a 40 X 40 cm field at 100 cm SSD. The “uniformity index”. a measure of the beam uniformity of a field in a given plane, is defined by the Nordic Association of Clinical Physicists ( 10) as a ratio of the area containing points with dose value exceeding 90% of the reference point to the area containing points with dose value exceeding 50% of the reference point. The reference point, which is the intersection of the central ray axis with a plane perpendicular to the central ray axis at the depth of maximum dose, is normalized to be lOO%l. The 90% and 50% doses are defined with respect to the reference dose. Following these conventions, the uniformity index of the TBI field was calculated from the isodose curves obtained in a plane perpendicular to the central axis at the depth of maximum dose. Verification film.$ kept in paper cassette. was placed between sheets of solid water phantom and exposed perpendicular to the beam axis at TBI treatment geometry. A characteristic curve (optical density versus dose) was developed to establish the relationship between dose and optical density. Since verification films are relatively insensitive, a dose of about 80 cGy was required for a net density of 2.0. All films were chosen from the same batch and were developed with an automatic film processor one after the other. The uniformity index of the TBI field was compared with the uniformity index of its corresponding 40 X 40 cm field at 100 cm SSD. The uncertainty associated with the measurement of each dimension of the isodose curves was determined to be 0.5 mm. This uncertainty was obtained by repeated measurements of the dimensions of the isodose curve and was established by finding the interval within which it was felt that there was 95% confidence that the “actual” dimension lies within +- two standard deviations.

z Kodak X-OMAT V, Eastman Kodak Co. Rochester, NY. BDirect Patient Dose Monitor with 5 channels (DPD-5) as manufactured by Therados, Uppsala, Sweden.

March 199 I, Volume 20. Number 3

Patient dosimetry Following the recommendations of AAPM Task Group 29 ( 1). dose was prescribed to a single point, the midpoint at the level of the xiphoid. The midpoint was described as the intersection of the midplanes between anterior and posterior surfaces and the lateral surfaces at the level of the xiphoid. The dose delivered to the patient at several anatomic locations of interest was monitored and verified during TBI treatment. Attempts were made to determine and to record doses to critical organs. The dose to the liver. with the use of 90% transmission block, was limited to about 12.0 Gy. The dose to midpoint lung, with the 40% transmission blocks and the chest wall electron boost irradiation, was limited to about 7.0 Gy. The dose rate at the prescribed point did not exceed 25 cGy/min. The dose uniformity within the patient was monitored and verified by diode dosimetry.§ The semiconductor detectors are encapsulated in build-up material of stainless steel for high energy photon beams. In each treatment fraction, the dose to the mid-point at the level of xiphoid is determined by monitoring the dose on the patient at this level. If the dose on this channel exceeds the “alarm level” preset value, an audible alarm is triggered. This gives the operator an opportunity to check whether or not the dose values are reasonable for direct detection of errors. Thus in each treatment fraction, only four different locations of interest (two AP points and two corresponding PA points) can be monitored. The dose to these locations are compared relative to that delivered to the xiphoid in each treatment fraction. On a routine basis the head, neck, chest. abdomen, and several points on the lower extremities are monitored. Considering the limits for dose uniformity. the boost dose(s) to lower extremities are calculated. The dose uniformity within the patient was also determined by TLD dosimetry. TLD-100 (LiF) dosimeters calibrated in the accelerator photon beam, by comparison with the ion chamber, have been used in various locations on a huminoid Phantom* which has a maximum width of 40 cm. The TLD results are compared with the diode dosimetry.

RESULTS

AND

DISCUSSION

The central axis depth dose data for 18 MV X ray for 40 X 40 cm field at TBI treatment distance (350 cm SSD) and at standard treatment distance (100 cm SSD) are shown in Figure 2. as well as the result of depth dose data measured at 100 cm SSD and transformed via Maynard formula to the TBI treatment distance. The transformed data via Maynard formula is about l-3% higher than the

* Alderson Rando phantom

TBI using

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I8 MV X rays 0 A. NIROOMAND-RAD

Q”-

---._ ---.___

Z al 40E LX, ;I:

-1

OO

5

IO

15

20

25

30

Depth in Water (cm)

Fig. 2. The central axis percentage depth dose for a 18 MV x-ray beam at 100 cm SSD (- - * -), 350 cm SSD j for a 40 X 40 cm field. (- - -). and transformed data by Maynard Factors (--

measured

data

for most of the distance at 4-25 cm depth.

This result is consistent with the limitations discussed in Supplement No. 17 (20) for the use of Maynard Conver-

sion Formula. Therefore, the measured data at TBI treatment distance were used for patient dose calculation. The validity of inverse square law for the TBI treatment geometry was confirmed, as the product \/RD is constant to within 20.2%. Surface dose and the central axis depth dose in the build-up region for TBI treatment distance and the standard treatment distance are shown in Figure 3. At the TBI treatment distance, the surface dose was significantly

2

6

IO

14

18

22

26

30

Depth in Water (cm) Fig. 3. The central axis build-up dose for a I8 MV x-ray beam at 100 cm SSD without beam spoiler (- - -), 350 cm SSD without and 350 cm SSD with beam spoiler in beam spoiler (-), place ( * - -) for a 40 X 40 cm field.

higher than the surface dose at standard treatment distance. The effect of 1 cm thick mobile perpex screen on the build-up dose at TBI treatment distance for a typical screen-to-phantom distance of 15 cm is also shown in Figure 3. The surface dose and dose in the build-up region increase with the perpex screen in place; however, there is no strong dependence on screen-phantom distances up to 30 cm. For instance, the ratio of surface dose relative to maximum dose was found to be 0.945, 0.950, 0.935 for screen-to-phantom distances of 10, 15, and 30 cm respectively. This ratio was decreased to 0.920 for screento-phantom distance of 40 cm. The dose at exit surface was determined for various phantom thickness, and the effect of backscatter from the wall to the exit surface was minimal. The average value for entrance and exit dose is about 2% to 3% lower than the midline dose for the phantom diameter 8-32 cm. Therefore, in our dosimetric calculations we assume that the predicted and measured values are equal. The beam profiles at depth of maximum dose and 10 cm depth along the principal axis of the beam in the horizontal and vertical directions were obtained for TBI treatment field and its corresponding 40 X 40 cm field at standard treatment distance. Figure 4 shows the beam profile at depth of maximum dose in the vertical direction for a 40 X 40 cm field size at 100 cm SSD and its corresponding field at 350 cm SSD. The uniformity index of the TBI treatment field was obtained using the 90% and 50% area of the isodose curves in a plane perpendicular to the beam axis at a depth of maximum dose. The 90% and 50% isodose curves for a 40 X 40 cm field at TBI treatment distance and at 100 cm SSD are also shown in Figure 5. The result indicates that the uniformity index of TBI treatment field is 0.89 + 0.0 1, which is about 2% lower than that obtained for its corresponding field size at 100 cm SSD. This result

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measured in each treatment fraction as a consistency check, was often within + 1%. The dose to lower extremities, which were measured in the first 2 days of treatment were often within f8% to 5 14% of the average dose given to xiphoid. The boost to lower extremities, which was often given on the third day of treatment, was about 1.O to 2.0 Gy. The boost was delivered to midline of the extremity in one fraction using 6 MV x-ray beam at standard treatment distance of 100 cm SSD. The dose to lower extremities was raised to within +3% to t5% ofthe average dose given to xiphoid. The dose to upper body parts was within +5% of the average dose given to xiphoid. I

OO

5

0

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15

35

52.5

70

SUMMARY

AND

CONCLUSION

- .-

Distance km) from Central Axis

Fig. 4. The beam profile at depth of maximum dose in the vertical direction for a I8 MV x-ray beam for a 40 X 40 cm field at 100 ) and its corresponding field at 350 cm SSD ( . . . ). cm SSD (--

has an important clinical implication. To assure adequate coverage of the TBI patient within 90% isodose curve, all attempts should be made to fit the patient in a light field which is provided by a smaller field setting (say a 38 X 38 cm), and then increase the collimator setting to a 40 X 40 cm. In our treatment set up, since the average gradient between the 90% and 50% isodose lines in a vertical direction was about 1.5 cm at the TBI treatment distance, we decided to use a 38 X 38 cm field size setting for the initial fitting of the patient within the light field. The error involved with these measurements was estimated to be + 1% for a 40 X 40 cm at 100 cm SSD and +2% for its corresponding field at 350 cm TBI treatment distance. The dose uniformity within the patient was determined by monitoring the dose on the patient at various locations with diode. The precision of dose to xiphoid, which was

Fig. 5. The 90% and 50% isodose curves for a 18 MV x-ray beam measured with film in a plane perpendicular to the beam axis at depth of maximum dose for a 40 X 40 cm at 100 cm SSD and it corresponding field at 350 cm SSD.

Since 1985 the Department of Radiation Oncology at the Medical College of Wisconsin has adopted a hyperfractionated regimen for TBI with partial lung and liver blocks. The treatment scheme is to deliver 14 Gy to midline xiphoid in 9 equal fractions in 3 fractions per day on 3 consecutive days while limiting the lung core dose and liver dose to about 7 and 12.0 Gy, respectively. Following the guidelines recommended by AAPM Task Group 29, the physical aspects of a treatment set-up for patients sitting during hyperfractionated total body irradiation are presented. Initially, the TBI treatments were delivered in a standard size treatment room, which necessitated the development of the technique described here. Using a special chair in a standard size treatment room, a set-up technique has been developed to treat patients anteriorly and posteriorly. The patient sits in an upright position with the legs bent backwards so that the entire body is encompassed within a uniform (90% isodose) region of the primary radiation field. This technique, though dictated by the physical limitations of the treatment set-up rather than chosen as optimal, reduces patient movement and provides patient support as well as reproducible patient positioning. The dose to the lower extremities, however, is conveniently monitored and boosted to the prescribed dose. TLD and diode dosimetry, if used carefully, can be a valuable tool in monitoring, verifying and estimating the dose-distribution to various parts of the patient during TBI treatment. Our results indicate that the depth dose data measured at 100 cm SSD and transformed via Maynard Conversion Formula is about l-3% higher than the measured data at TBI distance at 4-25 cm depth. Thus we conclude that the data obtained for standard treatment distance is not applicable at TBI extended distances. The central axis depth dose, surface dose, build-up dose, beam profile, and uniformity index for the TBI condition have been compared with those for the standard distance 100 cm SSD. The average value for entrance and exit dose was about 2% to 3% lower than the mid-line dose for the phantom diameter 8-32 cm. The uniformity index of TBI Field was about 2% lower than that obtained for its corresponding field size at 100 cm SSD. The patient positioning was

TBI using 18 MV X rays 0 A. NIROOMAND-RAD

reproducible using the chair described in the text. In summary we conclude the TBI setup described here has been found practical, reproducible and provides minimal dose

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variation of it_10%. In addition this technique fits into the clinical routine without excessively inconveniencing the patient or the staff.

REFERENCES 1. AAPM Report No. 17: The physical aspects of total and half body photon irradiation. New York: American Institute of Physics: 1986. 2. Baranov, A. E.: Danilove, N. B.; Khrushchev, V. G.; Sukyasyan. G. V.; Guskova, A. K.; Gavrilov, 0. K. Treatment of patients with acute leukemia using large doses of cyclophosphamide, total body irradiation, and transplantation of syngeneic bone marrow (in Russian). Med. Radiol. 11: 25-32; 1982. 3 Constantinou, _ C.; Attix, F. M.; Paliwal. B. R. A solid water phantom material for radiotherapy x-ray and gamma-ray beam calibrations. Med. Phys. 9(3):436-44 I ; 1982. 4. Deeg, H. J.; Rournoy. N.: Sullivan, K. M.. et al. Cataracts after total body irradiation and marrow transplantation: a sparing effect of dose fractionation. Int. J. Radiat. Oncol. Biol. Phys. 10:957-964; 1984. 5. Doughty. D.: Lambert, G. D.: Hirst. A.; Marks, A. M.; Plowman, P. N. Improved total body irradiation dosimetry. Br. J. Radiol. 60:269-278; 1987. 6. Faw. F.; Glenn, D. Dose distribution if the field is larger than the patient. Presented at the Third Meeting of the International Organization of Medical Physics. Gothenberg, Sweden. 1972.

1 I.

12.

13. 14.

15. 16.

17.

I. Glasgow, G. P. The dosimetry of fixed, single source hemibody and total body irradiators. Med. Phys. 9(3):31 i-323; 1982. 8. Lawton. C. A.: Murray, K. J., et al. Technical modifications in hyperfractionated total body irradiation for T-lymphocyte deplete bone marrow transplant (Abstr.). Int. J. Radiat. Oncol. Biol. Phys. lS(Suppl. I):21 1: 1988. 9. Lawton, C. A.; Barber-Derus, S.; Murray, K. J.; Casper, J. T.: Ash, R. C.: Gillin, M. T.; Wilson, J. F. Technical modifications in hyperfractionated total body irradiation for T-lymphocyte deplete bone marrow transplant. Int. J. Radiat. Oncol. Biol. Phys. I7:3 19-322; 1989. 10. Nordic Association of Clinical Physicists. Procedures in external radiation therapy dosimetry with electron and photon

18.

19. 20. 21.

beams with maximum energies between 1 and 50 Mev. Acta Radiol. Oncol. 19(Fasc. 1):55-79; 1980. O’Donoghue, J. A. Fractionated versus low dose rate total body irradiation. Radiological considerations in the selection of regimens. Radiother. Oncol. 7:241-247; 1986. Peters L. J.; Whithers, H. R.: Cundiff. J. H.: Dicke, K. A. Radiobiological considerations in the use of total body irradiation for bone marrow transplantation. Radiol. I3 I: 243-247; 1979. Peters, L. J. Discussion: the radiobiological basis of TBI. Int. J. Radiat. Oncol. Biol. Phys. 6:785-787: 1980. Proceedings of the Workshop of the Radiation Therapy Committee of the Children’s Cancer Study Group, Montreal, Canada. Int. J. Radiat. Oncol. Biol. Phys. 6:743-787; 1980. Quast, U. Total body irradiation-review of treatment techniques in Europe. Radiother. Oncol. 0(2):91-106; 1987. Shank, B.: Hopfan, S.; Kim, J. H., et al. Hyperfractionated total body irradiation for bone marrow transplantation: I. Early results in leukemia patients. Int. J. Radiat. Oncol. Biol. Phys. 7:l 109-I 115: 1981. Shank, B.; Cu, F. C. H.; Dinsmore, R., et al. Hyperfractionated total body irradiation for bone marrow transplantation. Results in seventy leukemia patients with allogeneic transplants. Int. J. Radiat. Oncol. Biol. Phys. 9: 1607- I6 I I: 1983. Simpson, L.; Reid, A.; Hopfan. S.. et al. Hyperfractionated total body irradiation for bone marrow transplantation: II. Physical aspects of the combined electron-photon treatment plan. Int. J. Radiat. Oncol. Biol. Phys. 6:1378; 1980. Supplement No. I 1: Central axis depth dose data for use in radiotherapy. Br. J. Radiol. Appendix B: 1972. Supplement No. 17: Central axis depth dose data for use in radiotherapy. Br. J. Radiol. Appendix B: 1983. Tarbell, N. J.: Amato. D. A.: Down. J. D.; Mauch, P.: Hellman, S. Fractionation and dose rate effects in mice: a model for bone marrow transplantation in man. Int. J. Radiat. Oncol. Biol. Phys. 13:1065-1069; 1987.

Physical aspects of total body irradiation of bone marrow transplant patients using 18 MV x rays.

The physical aspects of a total body irradiation (TBI) treatment are described. Patients seated in a special chair with their legs bent backwards are ...
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