Breath-hold PET/CT-guided tumour ablation under general anaesthesia: accuracy of tumour image registration and projected ablation zone overlap.

AIM: To assess single-breath-hold combined positron-emission tomography/computed tomography (PET/CT) for accuracy of tumour image registration and projected ablation volume overlap in patients undergoing percutaneous PET/CT-guided tumour-ablation procedures under general anaesthesia. MATERIALS AND METHODS: Eight patients underwent 12 PET/CT-guided tumour-ablation procedures to treat 20 tumours in the lung, liver, or adrenal gland. Using breath-hold PET/CT, the centre of the tumour was marked on each PET and CT acquisition by four readers to assess two- (2D) and three-dimensional (3D) spatial misregistration. Overlap of PET and CT projected ablation volumes were compared using the Dice similarity coefficient (DSC). Interobserver differences were assessed with repeated measure analysis of variance (ANOVA). Technical success and local progression rates were noted. RESULTS: Mean tumour 2D PET/CT misregistrations were 1.02 mm (range 0.01-5.02), 1.89 (0.03-7.85), and 3.05 (0-10) in the x, y, and z planes. Mean 3D misregistration was 4.4 mm (0.36-10.74). Mean projected PET/CT ablation volume DSC was 0.72 (±0.19). No significant interobserver differences in 3D misregistration (p=0.73) or DSC (p=0.54) were observed. Technical success of ablations was 100%; one (5.3%) of 19 tumours progressed. CONCLUSION: Accurate spatial registration of tumours and substantial overlap of projected ablation volumes are achievable when comparing PET and CT acquisitions from single-breath-hold PET/CT. The results suggest that tumours visible only at PET could be accurately targeted and ablated using this technique.

Spine Cryoablation: A Multimodality Image-Guided Approach for Tumors Adjacent to Major Neural Elements.

We report percutaneous cryoablation of spine tumors in 7 consecutive patients (5 men, 2 women [mean age, 47 years; range, 17-68 years]) by using intraprocedural image monitoring of ice ball margins to protect adjacent neural elements. Complete tumor ablation was achieved in all patients without neurologic complication. Pain relief was achieved in 4 of 5 (80%) patients; the patient with persistent pain was later found to have enlarging metastases at other sites.

PET/CT-guided percutaneous liver mass biopsies and ablations: targeting accuracy of a single 20 s breath-hold PET acquisition.

AIM: To determine whether a single 20 s breath-hold positron-emission tomography (PET) acquisition obtained during combined PET/computed tomography (CT)-guided percutaneous liver biopsy or ablation procedures has the potential to target 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG)-avid liver masses as accurately as up to 180 s breath-hold PET acquisitions. MATERIALS AND METHODS: This retrospective study included 10 adult patients with 13 liver masses who underwent FDG PET/CT-guided percutaneous biopsies (n = 5) or ablations (n = 5). PET was acquired as nine sequential 20 s, monitored, same-level breath-hold frames and CT was acquired in one monitored breath-hold. Twenty, 40, 60, and 180 s PET datasets were reconstructed. Two blinded readers marked tumour centres on randomized PET and CT datasets. Three-dimensional spatial localization differences between PET datasets and either 180 s PET or CT were analysed using multiple regression analyses. Statistical tests were two-sided and p < 0.05 was considered significant. RESULTS: Targeting differences between 20 s PET and 180 s PET ranged from 0.7-20.3 mm (mean 5.3 ± 4.4 mm; median 4.3) and were not statistically different from 40 or 60 s PET (p = 0.74 and 0.91, respectively). Targeting differences between 20 s PET and CT ranged from 1.4-36 mm (mean 9.6 ± 7.1 mm; median 8.2 mm) and were not statistically different from 40, 60, or 180 s PET (p = 0.84, 0.77, and 0.35, respectively). CONCLUSION: Single 20 s breath-hold PET acquisitions from PET/CT-guided percutaneous liver procedures have the potential to target FDG-avid liver masses with equivalent accuracy to 180 s summed, breath-hold PET acquisitions and may facilitate strategies that improve image registration and shorten procedure times.

Non-rigid registration of pre-procedural MR images with intra-procedural unenhanced CT images for improved targeting of tumors during liver radiofrequency ablations.

In the United States, unenhanced CT is currently the most common imaging modality used to guide percutaneous biopsy and tumor ablation. The majority of liver tumors such as hepatocellular carcinomas are visible on contrast-enhanced CT or MRI obtained prior to the procedure. Yet, these tumors may not be visible or may have poor margin conspicuity on unenhanced CT images acquired during the procedure. Non-rigid registration has been used to align images accurately, even in the presence of organ motion. However, to date, it has not been used clinically for radiofrequency ablation (RFA), since it requires significant computational infrastructure and often these methods are not sufficient robust. We have already introduced a novel finite element based method (FEM) that is demonstrated to achieve good accuracy and robustness for the problem of brain shift in neurosurgery. In this current study, we adapt it to fuse pre-procedural MRI with intra-procedural CT of liver. We also compare its performance with conventional rigid registration and two non-rigid registration methods: b-spline and demons on 13 retrospective datasets from patients that underwent RFA at our institution. FEM non-rigid registration technique was significantly better than rigid (p < 10-5), non-rigid b-spline (p < 10-4) and demons (p < 10-4) registration techniques. The results of our study indicate that this novel technology may be used to optimize placement of RF applicator during CT-guided ablations.

Noninvasive multidetector computed tomography enterography in patients with small-bowel Crohn's disease: is a 40-second delay better than 70 seconds?

BACKGROUND: Multidetector computed tomography (MDCT) enterography combines neutral enteric contrast with intravenously administered contrast material. The optimal intravenous (IV) contrast material protocol has still not been established. PURPOSE: To determine the optimal delay time to image patients with small-bowel Crohn's disease during MDCT enterography. MATERIAL AND METHODS: After oral administration of 1350 ml of neutral contrast medium, 26 patients with small-bowel Crohn's disease underwent MDCT enterography;scans were obtained 40 s (enteric phase) and 70 s (parenchymal phase) after IV administration of 100 ml of iodinated contrast material. Three radiologists, blinded to clinical and pathological findings, independently and retrospectively evaluated each scan in two separate reading sessions for the presence or absence of CT features of Crohn's disease activity. The interobserver agreement was evaluated, and the efficacy of each phase in detecting active disease in the terminal ileum for each reader was determined. The gold standard was pathology (n=13), endoscopy (n=3), and clinical evaluation (n=10). RESULTS: No statistically significant difference was present between the enteric and the parenchymal phase for each reader in each segment regarding the presence or absence of CT features of Crohn's disease. The interobserver agreement for the presence of five main features of active Crohn's disease in the terminal ileum ranged from poor to excellent.The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for active Crohn's disease in the terminal ileum ranged from 40 to 90%, 88 to 100%, 70 to 94%, 44 to 100%, and 69 to 96%, respectively. There was no statistical difference between the two phases for each reader. CONCLUSION: MDCT enterography in patients with suspected active Crohn's disease can be obtained at either 40 s or 70 s after IV contrast material.