Optimal CT scanning parameters for commonly used tumor ablation applicators.

PURPOSE: CT-beam hardening artifact can make tumor margin visualization and its relationship to the ablation applicator tip challenging. To determine optimal scanning parameters for commonly-used applicators. MATERIALS AND METHODS: Applicators were placed in ex-vivo cow livers with implanted mock tumors, surrounded by bolus gel. Various CT scans were performed at 440mA with 5mm thickness changing kVp, scan time, ASiR, scan type, pitch, and reconstruction algorithm. Four radiologists blindly scored the images for image quality and artifact quantitatively. RESULTS: A significant relationship between probe, kVp level, ASiR level, and reconstruction algorithm was observed concerning both image artifact and image quality (both p=<0.0001). Specifically, there are certain combinations of kVp, ASiR, and reconstruction algorithm that yield better images than other combinations. In particular, one probe performed equivalently or better than any competing probe considered here, regardless of kVp, ASiR, and reconstruction algorithm combination. CONCLUSION: The findings illustrate the overall interaction of the effects of kVp, ASiR, and reconstruction algorithm within and between probes, so that radiologists may easily reference optimal imaging performance for a certain combinations of kVp, ASiR, reconstruction algorithm and probes at their disposal. Optimum combinations for each probe are provided.

Computed Tomography-Guided Tumor Ablation: Analysis and Optimization of Computed Tomography Technique With Various Ablation Devices.

PURPOSE: Ablation device-associated computed tomography beam hardening artifacts can make tumor margin visualization and its relationship to the ablation applicator tip challenging. Determine optimal scanning conditions for currently-used applicators. MATERIALS AND METHODS: Eleven applicators were placed in ex vivo cow livers with implanted mock tumors, surrounded by bolus gel. Various computed tomography scans were performed at 440 mA with 5 mm thickness changing kVp (80, 100, 120, 140), scan time (0.5, 0.7, 1.0, 2.0 seconds), adaptive statistical iterative reconstruction (ASiR) (30, 60, 90), scan type (helical, axial), pitch (0.5, 0.94, 1.37, 1.75), and reconstruction algorithm (soft, standard, lung). Two radiologists blindly scored the images for image quality and artifact quantitatively. RESULTS: Cool-tip single (CTS) RF electrode (Covidien) performed significantly better than all other devices in both perceived image quality and artifact while Boston Scientific 4.0 RF electrode (Boston Scientific) underperformed (all P < 0.001), when not controlling for any other factors. An effect for artifact (P < 0.001) was found for kVp and device: for most conditions, 80 kVp was rated significantly lower than all other levels, whereas 120 and 140 performed significantly better than 100 and 80. No significant effect with ASiR level and device was found for the artifact. There was an effect observed for artifact (P < 0.001) between scan time and probe: for most devices, 0.5 seconds was rated significantly lower than all other scan times, but CTS was resilient-showing no difference from other scan times. Algorithm did not show any significant effects. Taking into account ASiR, kVp, and time, CTS outperformed all other devices. CONCLUSIONS: Higher kVp and scan times reduce device artifacts. It appears that CTS performs the best, even when considering ASiR, kVp, pitch, scan type, and scan time.

Intramural esophageal dissection associated with esophageal perforation.

Intramural esophageal dissection (IED) is a rare clinical entity involving a mucosal injury and creation of a true and false lumen within the esophagus. We report on a case of IED caused by repeated vomiting due to a small bowel obstruction associated with a small amount of pneumomediastinum on CT. IED has traditionally been believed not to be associated with esophageal perforation. Our case adds to the few reported instances where IED has been associated with extraluminal air leakage, the mildest form of esophageal perforation and demonstrates imaging not previously published in the radiology literature. Our case was successfully managed conservatively.

PET-CT of the normal spinal cord in children.

RATIONALE AND OBJECTIVES: The aim of this study was to assess the correlation between age and spinal cord metabolic activity in children using positron emission tomography-computed tomography. MATERIALS AND METHODS: The cohort included 128 children imaged from January 2003 through April 2007, excluding those with spinal disease. Using axial images, the fluorodeoxyglucose activity in the pons and three cervical, three thoracic, and two lumbar spinal cord levels was subjectively graded as minimal, moderate, or intense. From regions of interest at each level, the maximum standardized uptake value was determined. Patients were grouped by age: group 1, <5 years; group 2, > or =5 to <10 years; group 3, > or =10 to <15 years; and group 4, > or =15 to <22 years. Subjective grade and standardized uptake values were compared at each level and for each level between age groups. The alpha level was set at 0.0046 on the basis of Bonferroni's correction for multiple comparisons. RESULTS: There were 16 patients in group 1, 19 in group 2, 33 in group 3, and 60 in group 4. Subjective grades and standardized uptake values were higher in the pons, midcervical, and low thoracic areas than elsewhere in all age groups. Subjective grades significantly increased with age in the cervical and thoracic cord (P < .0005). Standardized uptake values in the pons and all cord levels significantly increased with increasing age (P < or = .0008). CONCLUSIONS: In children, the metabolic activity of the spinal cord increases with age. On positron emission tomography, the cord can appear intensely avid in the midcervical and low thoracic areas.

Fabrication of polymeric replicas of cell surfaces with nanoscale resolution.

We report an approach for fabricating biomimetic surface replicas of cells with nanoscale resolution. Fixed cells serve as a template for a two-stage replica molding process. Cast from the template, the impression replica contains a reproduction of cellular topographical features indented into its surface, and cast from the impression replica, the relief replica contains a copy of these features protruding from its surface. Various polymers and cells can be utilized, and scanning electron microscopy, atomic force microscopy, and white light interferometry analyses confirm the replication of nanoscale features. These replicas are useful for investigating cellular function and for biomimetic tissue engineering.