Percutaneous ablation of obscure hypovascular liver tumours in challenging locations using arterial CT-portography guidance.

PURPOSE: The purpose of this study was to evaluate the feasibility, safety and efficacy of percutaneous ablation (PA) of obscure hypovascular liver tumors in challenging locations using arterial CT-portography (ACP) guidance. MATERIALS AND METHODS: A total of 26 patients with a total of 28 obscure, hypovascular malignant liver tumors were included. There were 18 men and 6 women with a mean age of 58±14 (SD) years (range: 37-75 years). The tumors had a mean diameter of 14±10 (SD) mm (range: 7-24mm) and were intrahepatic cholangiocarcinoma (4/28; 14%), liver metastases from colon cancer (18/28; 64%), corticosurrenaloma (3/28; 11%) or liver metastases from breast cancer (3/28; 11%). All tumors were in challenging locations including subcapsular (14/28; 50%), liver dome (9/28; 32%) or perihilar (5/28; 18%) locations. A total of 28 PA (12 radiofrequency ablations, 11 microwave ablations and 5 irreversible electroporations) procedures were performed under ACP guidance. RESULTS: A total of 67 needles [mean: 2.5±1.5 (SD); range: 1-5] were inserted under ACP guidance, with a 100% technical success rate for PA. Median total effective dose was 26.5 mSv (IQR: 19.1, 32.2 mSv). Two complications were encountered (pneumothorax; one abscess both with full recovery), yielding a complication rate of 7%. No significant change in mean creatinine clearance was observed (80.5mL/min at baseline and 85.3mL/min at day 7; P=0.8). Post-treatment evaluation of the ablation zone was overestimated on ACP compared with conventional CT examination in 3/28 tumors (11%). After a median follow-up of 20 months (range: 12-35 months), local tumor progression was observed in 2/28 tumours (7%). CONCLUSION: ACP guidance is feasible and allows safe and effective PA of obscure hypo-attenuating liver tumors in challenging locations without damaging the renal function and with acceptable radiation exposure. Post-treatment assessment should be performed using conventional CT or MRI to avoid size overestimation of the ablation zone.

Optically stimulated luminescence (OSL) of carbon-doped aluminum oxide (Al2O3:C) for film dosimetry in radiotherapy.

INTRODUCTION AND PURPOSE: Conventional x-ray films and radiochromic films have inherent challenges for high precision radiotherapy dosimetry. Here we have investigated basic characteristics of optically stimulated luminescence (OSL) of irradiated films containing carbon-doped aluminum oxide (Al2O3:C) for dosimetry in therapeutic photon and electron beams. MATERIALS AND METHODS: The OSL films consist of a polystyrene sheet, with a top layer of a mixture of single crystals of Al2O3:C, ground into a powder, and a polyester base. The total thickness of the films is 0.3 mm. Measurements have been performed in a water equivalent phantom, using 4, 6, 10, and 18 MV photon beams, and 6-22 MeV electron beams. The studies include assessment of the film response (acquired OSL signal/delivered dose) on delivered dose (linearity), dose rate (1-6 Gy/min), beam quality, field size and depth (6 MV, ranges 4 x 4-30 x 30 cm2, dmax-35 cm). Doses have been derived from ionization chamber measurements. OSL films have also been compared with conventional x-ray and GafChromic films for dosimetry outside the high dose area, with a high proportion of low dose scattered photons. In total, 787 OSL films have been irradiated. RESULTS: Overall, the OSL response for electron beams was 3.6% lower than for photon beams. Differences between the various electron beam energies were not significant. The 6 and 18 MV photon beams differed in response by 4%. No response dependencies on dose rate were observed. For the 6 MV beam, the field size and depth dependencies of the OSL response were within +/-2.5%. The observed inter-film response variation for films irradiated with the same dose varied from 1% to 3.2% (1 SD), depending on the measurement day. At a depth of 20 cm, 5 cm outside the 20 x 20 cm2 6 and 18 MV beams, an over response of 17% was observed. In contrast to GafChromic and conventional x-ray films, the response of the Al2O3:C films is linear in the clinically relevant dose range 0-200 cGy. CONCLUSIONS: Measurement of the OSL signal of irradiated films containing Al2O3:C is a promising technique for film dosimetry in radiotherapy with no or small response variations with dose rate, beam quality, field size and depth, and a linear response from 0 to 200 cGy.

Cystic pancreatic lesions: From increased diagnosis rate to new dilemmas.

Cystic pancreatic lesions vary from benign to malignant entities and are increasingly detected on cross-sectional imaging. Knowledge of the imaging appearances of cystic pancreatic lesions may help radiologists in their diagnostic reporting and management. In this review, we discuss the morphologic classification of these lesions based on a diagnostic algorithm as well as the management of these lesions.

Utility of reassessment after neoadjuvant therapy and difficulties in interpretation.

We describe the main tools for MR assessment of the response of rectal cancer tumors after chemotherapy, before surgery. In locally advanced cases of rectal and lower rectal cancer, MR is useful in allowing the treatment strategy to be adjusted, enabling conservative surgery to be performed if the patient responds well. The different types of response (fibrous, desmoplastic and colloid), their appearances and difficulties in MR interpretation are described. We describe the features and performance of MR after neoadjuvant therapy for T and N staging, assessment of circumferential resection margin and diffusion weighted imaging. Quantitative (change in tumor volume) and qualitative (grade of tumor response) MR assessment can distinguish good responders from poor responders.