CT Navigation for Percutaneous Needle Placement: How I Do It.

CT navigation (CTN) has recently been developed to combine many of the advantages of conventional CT and CT-fluoroscopic guidance for needle placement. CTN systems display real-time needle position superimposed on a CT dataset. This is accomplished by placing electromagnetic (EM) or optical transmitters/sensors on the patient and needle, combined with fiducials placed within the scan field to superimpose a known needle location onto a CT dataset. Advantages of CTN include real-time needle tracking using a contemporaneous CT dataset with the patient in the treatment position, reduced radiation to the physician, facilitation of procedures outside the gantry plane, fewer helical scans during needle placement, and needle guidance based on diagnostic-quality CT datasets. Limitations include the display of a virtual (vs actual) needle position, which can be inaccurate if the needle bends, the fiducial moves, or patient movement occurs between scans, and limitations in anatomical regions with a high degree of motion such as the lung bases. This review summarizes recently introduced CTN technologies in comparison to historical methods of CT needle guidance. A "How I do it" section follows, which describes how CT navigation has been integrated into the study center for both routine and challenging procedures, and includes step-by-step explanations, technical tips, and pitfalls.

A General Framework for Monitoring Image Acquisition Workflow in the Radiology Environment: Timeliness for Acute Stroke CT Imaging.

Many facets of an image acquisition workflow leave a digital footprint, making workflow analysis amenable to an informatics-based solution. This paper describes a detailed framework for analyzing workflow and uses acute stroke response timeliness in CT as a practical demonstration. We review methods for accessing the digital footprints resulting from common technologist/device interactions. This overview lays a foundation for obtaining data for workflow analysis. We demonstrate the method by analyzing CT imaging efficiency in the setting of acute stroke. We successfully used digital footprints of CT technologists to analyze their workflow. We presented an overview of other digital footprints including but not limited to contrast administration, patient positioning, billing, reformat creation, and scheduling. A framework for analyzing image acquisition workflow was presented. This framework is transferable to any modality, as the key steps of image acquisition, image reconstruction, image post processing, and image transfer to PACS are common to any imaging modality in diagnostic radiology.

Theoretical breast cancer induction risk from thoracic spine CT in female pediatric trauma patients.

OBJECTIVES: To quantify the radiation dose received during thoracic spine computed tomography (CT) versus plain radiographs as well as the theoretical risk of breast cancer induction in a pediatric trauma population. METHODS: A retrospective evaluation of 179 female pediatric trauma patients who received CT or plain radiographs for clearance of the thoracic spine was performed. Subjects were secondarily grouped as children (0-<12 years) or adolescents (≥12-17.9 years). Radiation doses were calculated by using the ImPACT Patient Dosimetry Calculator. Excess absolute risk (EAR) of induction of breast cancer was determined by multiplying the radiation dose by breast cancer induction rates taken from the National Academy's Biological Effects of Ionizing Radiation Committee's seventh report. RESULTS: The average radiation dose to the breast from a thoracic spine CT was 41.1 (SD 11.4) mSv and 1.8 (SD 0.9) mSv for plain radiographs. The EAR for plain radiographs was 2.7 (95% confidence interval [CI] 2.48-2.85) excess cases of breast cancer per 10 000 studies for female children and 1.4 (95% CI 1.14-1.55) for female adolescents. The breast cancer EAR for thoracic spine CT was significantly higher -79.6 (95% CI 58.6-100.5) and 45.8 (95% CI 42.0-49.6) excess cases per 10 000 scans for female children and adolescents, respectively. There was a substantially higher risk of breast cancer induction for children receiving thoracic spine CT compared with adolescents. CONCLUSIONS: CT clearance of the thoracic spine in the pediatric trauma patient results in a high dose of radiation and an age-dependent increase in theoretical breast cancer induction.

Theoretical increase of thyroid cancer induction from cervical spine multidetector computed tomography in pediatric trauma patients.

BACKGROUND: The trend of increasing cervical spine multidirectional computed tomography (MDCT) imaging of pediatric trauma patients is characteristic of the overall dramatic increase in computed tomography utilization in the United States. The purpose of this study is to compare the amount of radiation a pediatric trauma patient absorbs to the thyroid from plain radiographs and MDCT of the cervical spine and to express risk by calculation of theoretical thyroid cancer induction. METHODS: A retrospective evaluation of pediatric trauma patients admitted from October 1, 2004, to October 31, 2009, was performed at an academic, Level I trauma center. Inclusion criteria were Level I/II trauma patients, cervical spine imaging performed at our institution, and age <18 years. Absorbed thyroid radiation was calculated for patients receiving plain radiographs or MDCT. Thyroid cancer risk was calculated using the 2006 Biological Effects on Ionizing Radiation VII report. RESULTS: Six hundred seventeen patients met inclusion criteria: 224 received cervical spine radiographs and 393 received cervical spine MDCT. The mean thyroid radiation absorbed from radiographs was 0.90 mGy for males and 0.96 mGy for females compared with 63.6 mGy (males) and 64.2 mGy (females) receiving MDCT (p < 0.001). The median excess relative risk of thyroid cancer induction from one cervical spine MDCT in males was 13.0% and females was 25.0%, compared with 0.24% (males) and 0.51% (females) for radiographs (p < 0.001). CONCLUSIONS: The significant difference in radiation that MDCT delivers to the pediatric trauma patient when compared with plain radiographs should temper routine use of computed tomography in pediatric cervical spine clearance algorithms.

Radiographic evaluation of aspirated metallic foil foreign bodies.

OBJECTIVES: Aspirated objects generally represent items accessible to children. When metallic candy wrapper aspiration is questioned, radiographic studies may aid diagnosis. An infant with repeated chest radiographs negative for a metallic foreign body was found to have a multi-layer metallic candy wrapper in the left main bronchus. The purpose of this study was to determine whether conventional and dual-energy radiographic techniques exclude the presence of aspirated metallic foil wrappers. METHODS: Single-layer and multi-layer metallic candy wrappers were radiographically studied with conventional and dual-energy radiographic techniques in 3 tissue models. RESULTS: No single-layer metallic samples were detectable with conventional or dual-energy radiography. The multilayer samples were not detectable at less than 8 layers (pulmonary tissue model) or 16 layers (mediastinal model) by either conventional or dual-energy radiography. CONCLUSIONS: Conventional and dual-energy chest radiographic techniques do not reliably exclude the presence of aspirated metallic foil wrappers.

Multitapered x-ray capillary optics for mammography.

X-ray mammography is currently the primary tool used for breast cancer detection. However, studies have shown that 5%-15% of breast cancers are not visualized mammographically. The long term goal of this project is to improve the x-ray mammographic imaging system using capillary optics. A post-patient capillary optic lens has the potential to increase spatial resolution and eliminate the detection of scattered x rays, thereby improving image contrast and the signal-to-noise ratio (SNR). Several individual and two prototype multitapered optics were studied to determine the feasibility of a full-field multitapered optic. Scatter fraction, contrast, transmission, uniformity, and the modulation transfer function (MTF) were measured for a Mo target tube/computed radiography (CR) imaging system when this prototype was applied. The results were compared with standard grid and airgap techniques. The multitapered optic lens removed 85% of the scattered photons as compared to 66% and 39% for the air gap and grid methods, respectively. This resulted in an improvement of contrast by approximately 80% for the optics, 51% for the air gap, and 30% for grid methods. The single optic lens improved the limiting resolution (5% MTF level) of the CR detector by 78% due to magnification with very little focal spot blurring, while the multitapered prototype improved resolution significantly, but not as much as the single optic. These measurements have shown that it is feasible to create a multitapered optic lens that significantly improves system MTF and virtually eliminates scatter. With continued improvements in fabrication techniques, a full-field multitapered lens will be feasible.