Effect of diagnostic cone-beam computed tomography protocols on image quality, patient dose, and lesion detection.

OBJECTIVE: To evaluate the effect of cone-beam computed tomography (CBCT) image acquisition protocols on image quality, lesion detection, delineation, and patient dose. METHODS: 100-patients and a CTDI phantom combined with an electron density phantom were examined using four different CBCT-image acquisition protocols during image-guided transarterial chemoembolization (TACE). Protocol-1 (time: 6s, tube rotation: 360°), protocol-2 (5s, 300°), protocol-3 (4s, 240°) and protocol-4 (3s, 180°) were used. The protocols were first investigated using a phantom. The protocols that were found to be clinically appropriate in terms of image quality and radiation dose were then assessed on patients. A higher radiation dose and/or a poor image quality were inappropriate for the patient imaging. Patient dose (patient-entrance dose and dose-area product), image quality (Hounsfield Unit, noise, signal-to-noise ratio and contrast-to-noise ratio), and lesion delineation (tumor-liver contrast) were assessed and compared using appropriate statistical tests. Lesion detectability, sensitivity, and predictive values were estimated for CBCT-image data using pre-treatment patient magnetic resonance imaging. RESULTS: The estimated patient dose showed no statistical significance (p>0.05) between protocols-2 and -3; the assessed image quality between these protocols manifested insignificant difference (p>0.05). Two other phantom protocols were not considered for patient imaging due to significantly higher dose (protocols-1) and poor image quality (protocol-4). Lesion delineation and detection were insignificant (p>0.05) between protocols-2 and -3. Lesion sensitivities generated were 81-89% (protocol-2) and 81-85% (protocol-3) for different lesion types. CONCLUSION: Data acquisition using protocols-2 and -3 provided good image quality, lesion detection and delineation with acceptable patient dose during CBCT-imaging mainly due to similar frame numbers acquired.

Detectability of hepatic tumors during 3D post-processed ultrafast cone-beam computed tomography.

To evaluate hepatic tumor detection using ultrafast cone-beam computed tomography (UCBCT) cross-sectional and 3D post-processed image datasets. 657 patients were examined using UCBCT during hepatic transarterial chemoembolization (TACE), and data were collected retrospectively from January 2012 to September 2014. Tumor detectability, diagnostic ability, detection accuracy and sensitivity were examined for different hepatic tumors using UCBCT cross-sectional, perfusion blood volume (PBV) and UCBCT-MRI (magnetic resonance imaging) fused image datasets. Appropriate statistical tests were used to compare collected sample data. Fused image data showed the significantly higher (all P < 0.05) diagnostic ability for hepatic tumors compared to UCBCT or PBV image data. The detectability of small hepatic tumors (<5 mm) was significantly reduced (all P < 0.05) using UCBCT cross-sectional images compared to MRI or fused image data; however, PBV improved tumor detectability using a color display. Fused image data produced 100% tumor sensitivity due to the simultaneous availability of MRI and UCBCT information during tumor diagnosis. Fused image data produced excellent hepatic tumor sensitivity, detectability and diagnostic ability compared to other datasets assessed. Fused image data is extremely reliable and useful compared to UCBCT cross-sectional or PBV image datasets to depict hepatic tumors during TACE. Partial anatomical visualization on cross-sectional images was compensated by fused image data during tumor diagnosis.

Dual energy computed tomography thermometry during hepatic microwave ablation in an ex-vivo porcine model.

BACKGROUND: Microwave thermoablation (MTA) is a treatment method used to destroy hepatic tumors. OBJECTIVE: To investigate temperature changes during MTA of ex-vivo porcine liver using dual-energy computed tomography (DECT) imaging. METHODS: Three MTA experiments were performed using ex-vivo porcine liver (15 × 15 × 15 cm(3)) and DECT imaging with 80/Sn140 kVp spectral and 0.5-weighted reconstructions. Images were acquired from basic organ temperature to 100 °C with 10 °C difference during microwave heating and cooling phases. Three fluoro-optic thermometers were used for temperature measurements; two were placed at 1 cm and third one positioned at 2 cm distance from the applicator. Tissue temperature, ablation-region-conspicuity (ARC), ablation-region dimensions and image quality were determined. Regression analysis was performed determining thermal sensitivity during heating and cooling phases. RESULTS: Determined thermal sensitivities during heating phase were: -0.59 Hounsfield Unit/°C (80 kVp), -0.60HU/°C (0.5-weighted) and -0.59HU/°C (140 kVp); furthermore, during cooling: -0.56HU/°C (80 kVp), -0.55HU/°C (0.5-weighted) and -0.55HU/°C (140 kVp). ARC showed significantly higher (all P < 0.05) values for thermometer positions -1 and -2 compared to -3; however, comparison between positions -1 and -2 was insignificant (P > 0.05). Signal-to-noise ratios were higher for 0.5-weighted but ARC values were higher for 80 kVp images. CONCLUSION: Microwave thermal sensitivity on tissue was inversely linear with DECT image datasets. Heating phase showed higher influence of temperature on HU compared to cooling; ARC and ablation-region were increased with increase in temperature.

Ultrafast cone-beam computed tomography: a comparative study of imaging protocols during image-guided therapy procedure.

OBJECTIVE: To evaluate two ultrafast cone-beam CT (UF-CBCT) imaging protocols with different acquisition and injection parameters regarding image quality and required contrast media during image-guided hepatic transarterial chemoembolization (TACE). METHODS: In 80 patients (male: 46, female: 34; mean age: 56.8 years; range: 33-83) UF-CBCT was performed during TACE for intraprocedural guidance. Imaging was performed using two ultrafast CBCT acquisition protocols with different acquisition and injection parameters (imaging protocol 1: acquisition time 2.54 s, and contrast 6 mL with 3 s delay; imaging protocol 2: acquisition time 2.72 s, and contrast 7 mL with 6 s delay). Image evaluation was performed with both qualitative and quantitative methods. Contrast injection volume and dose parameters were compared using values from the literature. RESULTS: Imaging protocol 2 provided significantly better (P < 0.05) image quality than protocol 1 at the cost of slightly higher contrast load and patient dose. Imaging protocol 1 provided good contrast perfusion but it mostly failed to delineate the tumors (P < 0.05). On the contrary, imaging protocol 2 showed excellent enhancement of hepatic parenchyma, tumor, and feeding vessels. CONCLUSION: Tumor delineation, visualization of hepatic parenchyma, and feeding vessels are clearly possible using imaging protocol 2 with ultrafast CBCT imaging. A reduction of required contrast volume and patient dose were achieved due to the ultrafast CBCT imaging.

Cone-beam computed tomography imaging: therapeutic staff dose during chemoembolisation procedure.

Cone-beam computed tomography (CBCT) imaging is an important requirement to perform real-time therapeutic image-guided procedures on patients. The purpose of this study is to estimate the personal-doseequivalent and annual-personal-dose from CBCT imaging during transarterial chemoembolisation (TACE). Therapeutic staff doses (therapeutic and assistant physician) were collected during 200 patient (65 ± 15 years, range: 40­86) CBCT examinations over six months. Absorbed doses were assessed using thermo-luminescent dosimeters during patient hepatic TACE therapy. We estimated personal-dose-equivalent (PDE) and annual-personal-dose (APD) from absorbed dose based oninternational atomic energy agency protocol. APD for therapeutic procedure was calculated (therapeutic physician: 5.6 mSv; assistant physician: 5.08 mSv) based on institutional work load. Regarding PDE, the hands of the staff members received a greater dose compared to other anatomical locations (therapeutic physician: 56 mSv, 72 mSv; assistant physician: 12 mSv, 14 mSv). Annual radiation doses to the eyes and hands of the staff members were lower compared to the prescribed limits by the International Commission on Radiological Protection (ICRP). PDE and APD of both therapeutic staff members were within the recommended ICRP-103 annual limit. Dose to the assistant physician waslower than the dose to the therapeutic physician during imaging. Annual radiation doses to eye-lenses and hands of both staff members were lower than prescribed limits.