Radiation-induced Liver Injury after 3D-conformal Radiotherapy for Hepatocellular Carcinoma: Quantitative Assessment Using Gd-EOB-DTPA-enhanced MRI

Focal liver reaction (FLR) appears in the hepatobiliary-phase images of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (Gd-EOB-DTPA-enhanced MRI) following radiotherapy (RT). We investigated the threshold dose (TD) for FLR development in 13 patients with hepatocellular carcinoma (HCC) who underwent three-dimensional conformal radiotherapy (3D-CRT) with 45 Gy in 15 fractions. FLR volumes (FLRVs) were calculated based on planning CT images by referring to fused hepatobiliary-phase images. We also calculated the TD and the irradiated volumes (IVs) of the liver parenchyma at a given dose of every 5 Gy (IVdose) based on a dose-volume histogram (DVH). The median TD was 35.2 Gy. The median IV20, IV25, IV30, IV35, IV40, and IV45 values were 371.1, 274.8, 233.4, 188.6, 145.8, and 31.0 ml, respectively. The median FLRV was 144.9 ml. There was a significant difference between the FLRV and IV20, IV25, and IV45 (p<0.05), but no significant differences between the FLRV and IV30, IV35, or IV40. These results suggest that the threshold dose of the FLR is approx. 35 Gy in HCC patients who undergo 3D-CRT in 15 fractions. The percentage of the whole liver volume receiving a dose of more than 30-40 Gy (V30-40) is a potential candidate optimal DVH parameter for this fractionation schedule

カン サイボウ ガン ニ タイスル 3ジゲン ホウシャセン チリョウ ゴ ノ ホウシャセン セイ カン ショウガイ : Gd-EOB-DTPA ゾウエイ MRI デ ノ テイリョウ テキ ヒョウカ

博士(医学)熊本大

Respiratory Gating during Stereotactic Body Radiotherapy for Lung Cancer Reduces Tumor Position Variability

<div><p>Purpose</p><p>We evaluated the effects of respiratory gating on treatment accuracy in lung cancer patients undergoing lung stereotactic body radiotherapy by using electronic portal imaging device (EPID) images.</p><p>Materials and Methods</p><p>Our study population consisted of 30 lung cancer patients treated with stereotactic body radiotherapy (48 Gy/4 fractions/4 to 9 days). Of these, 14 were treated with- (group A) and 16 without gating (group B); typically the patients whose tumors showed three-dimensional respiratory motion ≧5 mm were selected for gating. Tumor respiratory motion was estimated using four-dimensional computed tomography images acquired during treatment simulation. Tumor position variability during all treatment sessions was assessed by measuring the standard deviation (SD) and range of tumor displacement on EPID images. The two groups were compared for tumor respiratory motion and position variability using the Mann-Whitney U test.</p><p>Results</p><p>The median three-dimensional tumor motion during simulation was greater in group A than group B (9 mm, range 3–30 mm vs. 2 mm, range 0–4 mm; p<0.001). In groups A and B the median SD of the tumor position was 1.1 mm and 0.9 mm in the craniocaudal- (p = 0.24) and 0.7 mm and 0.6 mm in the mediolateral direction (p = 0.89), respectively. The median range of the tumor position was 4.0 mm and 3.0 mm in the craniocaudal- (p = 0.21) and 2.0 mm and 1.5 mm in the mediolateral direction (p = 0.20), respectively.</p><p>Conclusions</p><p>Although patients treated with respiratory gating exhibited greater respiratory tumor motion during treatment simulation, tumor position variability in the EPID images was low and comparable to patients treated without gating. This demonstrates the benefit of respiratory gating.</p></div

Three-dimensional tumor respiratory motion during treatment simulation evaluated with four-dimensional CT.

<p>Three-dimensional tumor respiratory motion during treatment simulation evaluated with four-dimensional CT.</p

Variability assessment for each patient.

<p>Variability was assessed by determining the standard deviation (SD) and range of the tumor position during all sessions.</p

Standard deviation (SD) of the tumor position on electronic portal imaging device (EPID) images.

<p>Each point represents a single patient's SD of the tumor position during all treatment sessions. CC  =  craniocaudal; ML  =  mediolateral.</p

Range of the tumor position on electronic portal imaging device (EPID) images.

<p>Each point represents a single patient's range of the tumor position during all treatment sessions. CC  =  craniocaudal; ML  =  mediolateral.</p

Tumor displacement measured with reference to the first EPID image acquired at the first session.

<p>EPID  =  electronic portal imaging device.</p