Autonomic Dysreflexia in Patients With Spinal Cord Injury: What the Radiologist Needs to Know.

OBJECTIVE. Autonomic dysreflexia (AD) is a potentially life-threatening condition that occurs in patients with cervical and high thoracic spinal cord injury (SCI). AD is not completely understood and has a high incidence that increases proportional to the level and severity of the SCI. The signs and symptoms can vary, but severe hypertension is a dominant feature and may be fatal. This condition can be precipitated by a wide range of triggers occurring below the level of the injury, several of which are common to both diagnostic and interventional radiology, such as manipulation or distention of the genitourinary or gastrointestinal tract, patient positioning, or the use of certain anesthetic techniques. There is little guidance in the radiology literature specific to risk stratification or the use of premedication in this population. The incidence and pathophysiology of AD are discussed, along with pragmatic tips to aid the radiologist in selecting patients who may require a higher level of care or anesthesiologist involvement, with instructions for the conservative and medical management of acute episodes of AD. CONCLUSION. Awareness of AD is essential for all health care practitioners involved in the care of patients with SCI. A variety of procedures in the radiology department, both diagnostic and interventional, may precipitate AD. Planning, monitoring procedures, knowledge of the relevant pathophysiology and pharmacology, and communication with clinical colleagues are essential to ensure safe practice. Clinicians ordering procedures and radiologists selecting protocols for those procedures should identify at-risk patients before booking a procedure to ensure appropriate supervision and anesthesiology support. Education of radiologists, interventional nursing staff, and technical staff can assist in prevention, early recognition, and successful management of AD.

Contrast-Enhanced Ultrasound of the Liver: Optimizing Technique and Clinical Applications.

OBJECTIVE: The purpose of this article is to review the general principles, technique, and clinical applications of contrast-enhanced ultrasound of the liver. CONCLUSION: Proper technique and optimization of contrast-enhanced ultrasound require a balance between maintaining the integrity of the microbubble contrast agent and preserving the ultrasound signal. Established and emerging applications in the liver include diagnosis of focal lesions, aiding ultrasound-guided intervention, monitoring of therapy, and aiding surgical management.

Approach to the Solitary Liver Lesion: Imaging and When to Biopsy.

The characterization and management of focal liver lesions is a commonly encountered problem in radiology. While the imaging findings will often be diagnostic, in equivocal cases the decision of how to proceed may be challenging. The primary modalities for liver lesion characterization are multiphase contrast-enhanced computed tomography and magnetic resonance imaging. Most lesions have typical imaging features, and when taken in conjunction with patient demographics and biochemistry the diagnosis can usually be made. Ancillary imaging modalities such as contrast-enhanced ultrasound and hepatobiliary specific contrast agents are also useful. Cirrhotic livers present a challenge due to the spectrum of benign, dysplastic, and malignant nodules that can occur. The report should include information necessary for accurate staging, and published standardized reporting guidelines should be taken into consideration. A decision to proceed to biopsy should be made only after multidisciplinary review of the case. If biopsy is required, fine needle aspiration is usually sufficient, though core needle biopsy may be required in certain circumstances.

Towards transcervical ultrasound image guidance for transoral robotic surgery.

PURPOSE: Trans-oral robotic surgery (TORS) using the da Vinci surgical robot is a new minimally-invasive surgery method to treat oropharyngeal tumors, but it is a challenging operation. Augmented reality (AR) based on intra-operative ultrasound (US) has the potential to enhance the visualization of the anatomy and cancerous tumors to provide additional tools for decision-making in surgery. METHODS: We propose a US-guided AR system for TORS, with the transducer placed on the neck for a transcervical view. Firstly, we perform a novel MRI-to-transcervical 3D US registration study, comprising (i) preoperative MRI to preoperative US registration, and (ii) preoperative to intraoperative US registration to account for tissue deformation due to retraction. Secondly, we develop a US-robot calibration method with an optical tracker and demonstrate its use in an AR system that displays anatomy models in the surgeon's console in real-time. RESULTS: Our AR system achieves a projection error from the US to the stereo cameras of 27.14 and 26.03 pixels (image is 540[Formula: see text]960) in a water bath experiment. The average target registration error (TRE) for MRI to 3D US is 8.90 mm for the 3D US transducer and 5.85 mm for freehand 3D US, and the TRE for pre-intra operative US registration is 7.90 mm. CONCLUSION: We demonstrate the feasibility of each component of the first complete pipeline for MRI-US-robot-patient registration for a proof-of-concept transcervical US-guided AR system for TORS. Our results show that trans-cervical 3D US is a promising technique for TORS image guidance.

Three-Dimensional Multi-Frequency Shear Wave Absolute Vibro-Elastography (3D S-WAVE) With a Matrix Array Transducer: Implementation and Preliminary In Vivo Study of the Liver.

Magnetic resonance elastography (MRE) is commonly regarded as the imaging-based gold-standard for liver fibrosis staging, comparable to biopsy. While ultrasound-based elastography methods for liver fibrosis staging have been developed, they are confined to a 1D or a 2D region of interest and to a limited depth. 3D Shear Wave Absolute Vibro-Elastography (S-WAVE) is a steady-state, external excitation, volumetric elastography technique that is similar to MRE, but has the additional advantage of multi-frequency excitation. We present a novel ultrasound matrix array implementation of S-WAVE that takes advantage of 3D imaging. We use a matrix array transducer to sample axial multi-frequency steady-state tissue motion over a volume, using a Color Power Angiography sequence. Tissue motion with the frequency components {40,50,60} and {45,55,65} Hz are acquired over a (90° lateral) × (40° elevational) × (16 cm depth) sector with an acquisition time of 12 seconds. We compute the elasticity map in 3D using local spatial frequency estimation. We characterize this new approach in tissue phantoms against measurements obtained with transient elastography and MRE. Six healthy volunteers and eight patients with chronic liver disease were imaged. Their MRE and S-WAVE volumes were aligned using T1 to B-mode registration for direct comparison in common regions of interest. S-WAVE and MRE results are correlated with R2 = 0.92, while MRE and TE results are correlated with R2 = 0.71. Our findings show that S-WAVE with matrix array has the potential to deliver a similar assessment of liver fibrosis as MRE in a more accessible, inexpensive way, to a broader set of patients.