Target localization of 3D versus 4D cone beam computed tomography in lipiodol-guided stereotactic radiotherapy of hepatocellular carcinomas

Abstract

BackgroundAim of this study was to comparatively evaluate the accuracy of respiration–correlated (4D) and uncorrelated (3D) cone beam computed tomography (CBCT) in localizing lipiodolized hepatocellular carcinomas during stereotactic body radiotherapy (SBRT).Methods4D–CBCT scans of eighteen HCCs were acquired during free–breathing SBRT following trans–arterial chemo–embolization (TACE) with lipiodol. Approximately 1320 x–ray projections per 4D–CBCT were collected and phase–sorted into ten bins. A 4D registration workflow was followed to register the reconstructed time–weighted average CBCT with the planning mid–ventilation (MidV) CT by an initial bone registration of the vertebrae and then tissue registration of the lipiodol. For comparison, projections of each 4D–CBCT were combined to synthesize 3D–CBCT without phase–sorting. Using the lipiodolized tumor, uncertainties of the treatment setup estimated from the absolute and relative lipiodol position to bone were analyzed separately for 4D– and 3D–CBCT.ResultsQualitatively, 3D–CBCT showed better lipiodol contrast than 4D–CBCT primarily because of a tenfold increase of projections used for reconstruction. Motion artifact was observed to subside in 4D–CBCT compared to 3D–CBCT. Group mean, systematic and random errors estimated from 4D– and 3D–CBCT agreed to within 1 mm in the cranio–caudal (CC) and 0.5 mm in the anterior–posterior (AP) and left–right (LR) directions. Systematic and random errors are largest in the CC direction, amounting to 4.7 mm and 3.7 mm from 3D–CBCT and 5.6 mm and 3.8 mm from 4D–CBCT, respectively. Safety margin calculated from 3D–CBCT and 4D–CBCT differed by 2.1, 0.1 and 0.0 mm in the CC, AP, and LR directions.Conclusions3D–CBCT is an adequate alternative to 4D–CBCT when lipoid is used for localizing HCC during free–breathing SBRT. Similar margins are anticipated with 3D– and 4D–CBCT.

Clinical Uses and Short-Term Safety Profile of Ethiodized Poppy Seed Oil Contrast Agent in the Diagnosis and Treatment of Vascular Anomalies and Tumors

“…EPO is also widely used in interventional oncology, such as in transarterial chemoembolization (TACE) or as a radiopaque drug delivery vector [30,31], and can also be used as a fiducial marker for radiation therapy of hepatocellular carcinoma [32]. Lencioni et al reviewed the efficacy and safety data on transarterial chemoembolization (TACE) using lipiodol-based regimens in the treatment of hepatocellular carcinoma (HCC) [33].…”

Analysis of the Amplitude Changes and Baseline Drift of Respiratory Motion during Liver Stereotactic Body Radiation Therapy Based on Intra-Fraction CBCT

“…Chan M reported [9] that there was no signi cant difference between the use of 3 D CBCT and 4 D CBCT in liver radiotherapy. To reduce the CBCT scanning time, we used 3 D CBCT image guidance.…”

“…After 4D CT scanning, using combination of the targets in each respiratory phases (total ten phases) to generate internal target volume (ITV) [7], using the maximum intensity projections (MIP) [8]to delineate ITV or the medium ventilation CT to delineate the target [9] are adopted in clinical practice. The 5 mm uniform PTV margins have achieved widespread use [4].…”

Technological quality requirements for stereotactic radiotherapy

“…For periodically moving targets, stereoscopic X-ray imaging requires short acquisition times. Furthermore, breathing phase information for in-room imaging is required (e.g., breath-hold position for on-board or supplementary in-room imaging, or 4D-CBCT [59,125]). An exception to that is 3D-CBCT under free breathing.…”