Impact of contrast-enhanced CT in the dosimetry of SBRT for liver metastases treated with MR-Linac

Radiation Oncology

Table 3 Electrons density (ED) values for regions of interest (ROIs) assessed on plain CT and contrast-enhanced CT (CHCT) and their comparison

ROIs	No. of patients	Ref**	pCT Mean ± SD	CHCT Mean ± SD	pCT vs. CHCT Max Diff (%)	pCT vs. CHCT Mean (%) ± SD	p
Liver-GTV	21	1.05	1.06 ± 0.01	1.09 ± 0.01	3.93	2.42 ± 0.78	<0.001*
Spinal Cord	21	1.04	1.04 ± 0.00	1.04 ± 0.01	0.77	0.31 ± 0.2	<0.001*
Heart	21	1.04	1.03 ± 0.01	1.09 ± 0.01	9.03	6.18 ± 1.27	<0.001*
Great Vessels	21	1.06	1.05 ± 0.00	1.14 ± 0.02	11.48	8.35 ± 1.61	<0.001*
Rib	21	1.44	1.2 ± 0.04	1.21 ± 0.04	4.73	0.5 ± 1.19	0.069
Left Lung^	18	0.26	0.31 ± 0.06	0.34 ± 0.06	21.05	11.73 ± 5.46	<0.001*
Right Lung^	18	0.26	0.29 ± 0.06	0.33 ± 0.06	18.15	12.15 ± 5.41	<0.001*
Tissue	21	1.02	0.95 ± 0.04	0.97 ± 0.04	4.78	2.21 ± 1.41	<0.001*
Esophagus	21	1.04	1.02 ± 0.03	1.03 ± 0.03	3.41	1.52 ± 1.09	<0.001*
Duodenum	21	1.02	1.03 ± 0.02	1.06 ± 0.02	5.47	3.46 ± 1.38	<0.001*
Lumbar	21	1.44	1.17 ± 0.02	1.18 ± 0.02	0.85	0.41 ± 0.23	<0.001*
Small bowel	21	1.02	0.99 ± 0.02	1.01 ± 0.03	3.09	1.67 ± 0.91	<0.001*
KidneyL	21	1.04	1.03 ± 0.01	1.1 ± 0.01	8.40	6.57 ± 0.91	<0.001*
KidneyR	21	1.04	1.03 ± 0.01	1.1 ± 0.01	8.59	6.57 ± 1.13	<0.001*
Stomach	21	1.02	1.02 ± 0.03	1.05 ± 0.02	9.97	2.47 ± 2.06	<0.001*

Note *p < 0.05 indicating significant difference; ** values from reference standards for radiation therapy and radiological protection (ICRU 46, ICRP 110)
^ scans from 3 patients were excluded because the imaging did not cover the entire lung volume, and because of the large difference on the acquisition phases of the pCT and the CHCT scans

ISSN: 1748-717X