Purpose/Objective(s): Total body irradiation (TBI) is an integral component of many conditioning regimens for bone marrow transplantation in both adult and pediatric populations. There are multiple techniques to deliver TBI much of which have not changed in decades. The goal of this study was to investigate the patterns of care for TBI via an institutional survey, and to understand how technological advances need to be incorporated into TBI techniques.

Materials/Methods: A questionnaire was created to query the patient population (pediatric/adult), dose parameters, treatment technique, and utilization of modern technology (imaging and MLC). This includes beam parameters, patient setup, total dose and fractionation, use of compensators, and other parameters from 101 institutions in the United States. Additionally, 15 CT-based plans at our institution using the lateral technique with 15 MV photon beams were analyzed.

Results: Based on the survey results, 81% percent of institutions utilize an extended SSD ≥ 350 cm and 67.2% utilize photon beams in the 4-6 MV. The dose rate at mid-plane is reported to be from 5-18 cGy/min, with a median of 10-12 cGy/min and maximum dose rate of 36 cGy/min. The total treatment time ranged from 45 min to 2 hrs per fraction. Nearly 1/3 and 2/3 of the institutions use lateral and AP/PA treatment setup, respectively. The use of a compensator to provide uniform dose is used in 68.8% of the facilities. Nearly 20% never use lung blocks and only 28% utilize CT data for planning. Most departments (92.2%) verify treatment dose distribution and variations in dose uniformity recorded through in-vivo dosimetry varied from 2% to 20%. None of the institutions use MLC or portal imaging (EPID) due to the large distances used. The CT-based planning showed maximum and mean dose of 127.96 ± 7.16 and 95.14 ± 2.10 respectively from the prescribed dose which is generally accepted limit of ±10%.

Conclusion: There is wide institutional variation in TBI treatment delivery and techniques. Despite this variation, no institutions are utilizing MLCs and only 28% of institutions surveyed are utilizing CT-based planning. For the most part, very few institutions utilize modern advances in radiation oncology as part of their TBI treatments. Our CT-based plans results supports the need of CT and advanced dose calculation algorithms, however this is possible if there is a paradigm shift in TBI. Collaboration among clinicians, biologists and physicists is needed to allow advanced treatment either in total body or total marrow irradiation with use of cone beam, MLC, and IMRT.

TBI parameters		%	TBI parameters		%
SSD	<350 cm	19.5	Use of CT data	No	72.0
	≥350 cm	80.5		Yes	28.0
Energy	4-6 MV	67.2	Tx Frequency	BID	85.7
	> 10MV	32.8		Other	14.3
Setup Technique	AP/PA	56.4	Tx dose verification (IVD)	Yes	92.2
	Lateral	35.9		No	7.8
	Both	7.7	IVD Tolerance	<10%	32.6
Dose rate	≤ 20cGy/min	77.3		10%	61.0
	>20cGy/min	22.7		>10%	6.4
Compensator	Yes	68.8	Accounting imaging MU	No	61.4
	No	31.2		Yes	38.6
Lung Blocks	Never	19.5	MLC Use	No	100%
	Always	35.1	EPID use	No	100%
	Other	45.4