Abdominal organ position variation in children during image-guided radiotherapy

Abstract

BackgroundInterfractional organ position variation might differ for abdominal organs and this could have consequences for defining safety margins. Therefore, the purpose of this study is to quantify interfractional position variations of abdominal organs in children in order to investigate possible correlations between abdominal organs and determine whether position variation is location-dependent.MethodsFor 20 children (2.2–17.8 years), we retrospectively analyzed 113 CBCTs acquired during the treatment course, which were registered to the reference CT to assess interfractional position variation of the liver, spleen, kidneys, and both diaphragm domes. Organ position variation was assessed in three orthogonal directions and relative to the bony anatomy. Diaphragm dome position variation was assessed in the cranial-caudal (CC) direction only. We investigated possible correlations between position variations of the organs (Spearman’s correlation test, ρ), and tested if organ position variations in the CC direction are related to the diaphragm dome position variations (linear regression analysis, R2) (both tests: significance level p < 0.05). Differences of variations of systematic (∑) and random errors (σ) between organs were tested (Bonferroni significance level p < 0.004).ResultsIn all directions, correlations between liver and spleen position variations, and between right and left kidney position variations were weak (ρ ≤ 0.43). In the CC direction, the position variations of the right and left diaphragm domes were significantly, and stronger, correlated with position variations of the liver (R2 = 0.55) and spleen (R2 = 0.63), respectively, compared to the right (R2 = 0.00) and left kidney (R2 = 0.25). Differences in ∑ and σ between all organs were small and insignificant.ConclusionsNo (strong) correlations between interfractional position variations of abdominal organs in children were observed. From present results, we concluded that diaphragm dome position variations could be more representative for superiorly located abdominal (liver, spleen) organ position variations than for inferiorly located (kidneys) organ position variations. Differences of systematic and random errors between abdominal organs were small, suggesting that for margin definitions, there was insufficient evidence of a dependence of organ position variation on anatomical location.Electronic supplementary materialThe online version of this article (10.1186/s13014-018-1108-9) contains supplementary material, which is available to authorized users.

Accuracy of abdominal organ motion estimation in radiotherapy using the right hemidiaphragm top as a surrogate during prolonged breath‐holds quantified with MRI

“…Our results also show that variation in DR differences increased with more caudal organ location. This is in agreement with results of Huijskens et al., who found in paediatric cancer patients that position variation of the ipsilateral diaphragm was more representative for position variations of the liver and spleen than for kidney position variations 35 . Additionally, we observed differences in DR within volunteers, that is, between PBHs of individual volunteers.…”

“…This is in agreement with results of Huijskens et al, who found in paediatric cancer patients that position variation of the ipsilateral diaphragm was more representative for position variations of the liver and spleen than for kidney position variations. 35 Additionally, we observed differences in DR within volunteers, that is, between PBHs of individual volunteers. It has been previously reported that respiratory patterns may change during radiation therapy, 36 however the drift of the RHT and all organs is linear throughout the PBH with constant velocity.…”

Advances in radiotherapy technology for pediatric cancer patients and roles of medical physicists: COG and SIOP Europe perspectives

“…Various 4D CT, 4D MRI, and CBCT techniques have been used to measure pediatric tumor and organ motion. [48][49][50][51] As commercial 4D CT was designed primarily for adult patients with lung cancer, the scan parameters and pressure bellows need to be modified for children. Studies have found that the extent of respiration-induced motion is smaller in younger children than in older individuals, but that this motion can approach or exceed 1 cm for the diaphragm, spleen, kidney, and some tumors of adolescents.…”

“…This is particularly relevant when treating pediatric patients with neuroblastoma, HL, hepatoblastoma, Wilms tumor, chest wall sarcoma, or tumors near the diaphragm. Various 4D CT, 4D MRI, and CBCT techniques have been used to measure pediatric tumor and organ motion 48‐51 . As commercial 4D CT was designed primarily for adult patients with lung cancer, the scan parameters and pressure bellows need to be modified for children.…”

Residual positioning errors and uncertainties for pediatric craniospinal irradiation and the impact of image guidance

“…Setup uncertainties have been extensively studied in photon radiotherapy for various treatment sites [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Lately, proton radiotherapy has emerged as a prominent alternative to photon therapy for pediatric CSI and today, both treatment modalities are relevant when studying residual errors and uncertainties.…”