Understanding and using fluoroscopic dose display information.

Fluoroscopically guided procedures are an area of radiology in which radiation exposure to the patient is highly operator dependent. Modern fluoroscopy machines display a variety of information, including technique factors, field of view, operating geometry, exposure mode, fluoroscopic time, air kerma at the reference point (RAK), and air kerma area-product. However, the presentation of this information is highly vendor specific, and many users are unaware of how to interpret this information and use it to perform a study with the minimum necessary dose. A conceptual framework for understanding the radiation dose readout during a procedure is to compare it to the dashboard of an automobile, where the rate at which radiation is being applied (the RAK rate [mGy/min]) is the dose "speed" and the cumulative amount of radiation applied (cumulative RAK [mGy]) is the dose "odometer." This analogy can be used as a starting point to improve knowledge of these parameters, including how RAK is measured, how RAK correlates with skin dose, and how parameters are displayed differently during fluoroscopy and fluorography. Awareness of these factors is critical to understanding how dose parameters translate to patient risk and the consequences of high-dose studies. With this increased awareness, physicians performing fluoroscopically guided procedures can understand how to use built-in features of the fluoroscopic equipment (pulse rate, beam filtration, and automatic exposure control) and fluoroscopic techniques (procedure planning, patient positioning, proper collimation, and magnification) to reduce patient radiation dose, thereby improving patient safety.

Evaluation of fluoroscopic cases qualifying as potential fluoroscopic sentinel events.

RATIONALE AND OBJECTIVES: To address the risk of radiation injury during interventional procedures, the Joint Commission has defined prolonged fluoroscopy resulting in a cumulative skin dose of 15 Gy or more to a single field as a reviewable sentinel event. The goal of this work is to present a system for identifying potential fluoroscopic sentinel events (FSE) and describing common case characteristics. MATERIALS AND METHODS: Criteria based on fluoroscopic time (FT) > 150 minutes and reference air kerma (RAK) > 6 Gy were used to identify potential sentinel events. Case information including procedure type, number of procedures, and radiation dose parameters was recorded. Peak skin dose (PSD) was calculated by a medical physicist. Values were compared between procedure types and the relationship between FT, RAK, and PSD was evaluated. RESULTS: Between 2008 and 2011, 183 events exceeding the investigation criteria were identified in three interventional categories: cardiology (54%), neuroradiology (31%), and vascular (16%). The average number of procedures/patient was 1.7 ± 0.1, with the majority (59.6%) having undergone only one procedure. Most cases could be identified using the RAK criterion alone (96.7%). Based on the PSD/RAK ratio, a threshold RAK of 7.5 Gy would effectively identify all cases that would exceed 15 Gy in PSD. CONCLUSION: Radiation delivered during interventional cases can place patients at risk of cutaneous radiation injury and potential sentinel events. Using appropriate thresholds to determine which cases require detailed investigation allows efficient utilization of department resources for identifying sentinel events.

A randomized, double-blinded, placebo-controlled pilot trial of anticoagulation in low-risk traumatic brain injury: The Delayed Versus Early Enoxaparin Prophylaxis I (DEEP I) study.

BACKGROUND: Our group has created an algorithm for venous thromboembolism prophylaxis after traumatic brain injury (TBI), which stratifies patients into low, moderate, and high risk for spontaneous injury progression and tailors a prophylaxis regimen to each arm. We present the results of the Delayed Versus Early Enoxaparin Prophylaxis I study, a double-blind, placebo-controlled, randomized pilot trial on the low-risk arm. METHODS: In this two-institution study, patients presenting within 6 hours of injury with prespecified small TBI patterns and stable scans at 24 hours after injury were randomized to receive enoxaparin 30 mg bid or placebo from 24 to 96 hours after injury in a double-blind fashion. An additional computed tomography scan was obtained on all subjects 24 hours after starting treatment (and therefore 48 hours after injury). The primary end point was the radiographic worsening of TBI; secondary end points were venous thromboembolism occurrence and extracranial hemorrhagic complications. RESULTS: A total of 683 consecutive patients with TBI were screened during the 28 center months. The most common exclusions were for injuries larger than the prespecified criteria (n = 199) and preinjury anticoagulant use (n = 138). Sixty-two patients were randomized to enoxaparin (n = 34) or placebo (n = 28). Subclinical, radiographic TBI progression rates on the scans performed 48 hours after injury and 24 hours after start of treatment were 5.9% (95% confidence interval [CI], 0.7-19.7%) for enoxaparin and 3.6% (95% CI, 0.1-18.3%) for placebo, a treatment effect difference of 2.3% (95% CI, -14.42-16.5%). No clinical TBI progressions occurred. One deep vein thrombosis occurred in the placebo arm. CONCLUSION: TBI progression rates after starting enoxaparin in small, stable injuries 24 hours after injury are similar to those of placebo and are subclinical. The next Delayed Versus Early Enoxaparin Prophylaxis studies will assess efficacy of this practice in a powered study on the low-risk arm and a pilot trial of safety of a 72-hour time point in the moderate-risk arm. LEVEL OF EVIDENCE: Therapeutic study, level II.

Myelography: a primer.

Despite recent trends toward evaluation of back and neck pain with magnetic resonance imaging, myelography and postmyelography computed tomography continue to play an important role in the workup of many patients with spinal pathology. We present techniques for the safe and efficient performance of myelography, lumbar, and cervical puncture, which remain important skills to be mastered by radiology residents and fellows.

How will you need me, how will you read me, when I'm 64 (or more!)?: volume computed tomographic scanning and information overload in the emergency department.

Computed tomographic (CT) scanning technology now employs up to 320 detector rows of 0.5-mm width and allows rapid acquisition of isotropic volume datasets over the entire body. Data from a single CT acquisition can be reconstructed into image series that would formerly have required multiple acquisitions. Small isotropic voxels permit scan parameters to be general while reconstruction algorithms remain specific to anatomy. While this results in more efficient operation in the Emergency Department, it necessitates new ways of displaying, interpreting, and archiving the information. Critical decisions include how much of the patient to scan and how to time contrast injections when imaging multiple organs. These choices must be made in light of dose considerations to the patient and the general population of patients. The technical basis of high-density CT scanning is discussed, including detector configurations and reconstruction techniques. Volumetric scanning in the Emergency Department can improve patient care but requires a change of technical habits.

Computed tomography in the diagnosis of occult open-globe injuries.

PURPOSE: To determine the radiographic signs present on computed tomography (CT) most suggestive of occult open-globe injury. DESIGN: Retrospective chart review. PARTICIPANTS: Forty-eight eyes (of 46 patients), 34 of which were found to have an occult open-globe injury on surgical exploration. METHODS: A retrospective chart review of all eyes of patients 18 years or older undergoing surgical exploration to rule out occult open-globe injury after CT examination at Parkland Memorial Hospital between October, 1998, and September, 2003, was conducted. Patients with obvious corneal or corneoscleral lacerations or with uveal prolapse were excluded. The CT films were obtained and independently reviewed by 3 masked observers (2 neuroradiologists and 1 ophthalmologist). MAIN OUTCOME MEASURES: Presence of occult open-globe injury with respect to radiographic globe and orbital findings. RESULTS: The sensitivity of CT for determining occult open-globe injury varied from 56% to 68% between the observers, specificity ranged from 79% to 100%, positive predictive value ranged from 86% to 100%, and negative predictive value ranged from 42% to 50%. Open-globe injuries averaged more CT findings per patient compared with intact globes (P = 0.047). Statistically significant CT findings for occult open-globe injury included any change in globe contour (P = 0.001), obvious volume loss (P = 0.003), an absent or dislocated lens (P = 0.048), vitreous hemorrhage (P = 0.003), and retinal detachment (P = 0.044). Additionally, moderate to severe change in globe contour, obvious volume loss, total vitreous hemorrhage, and absence of lens were seen only in eyes with occult rupture. CONCLUSIONS: Although CT scanning may provide valuable information in patients in whom an occult open-globe injury is suspected, its sensitivity and specificity are inadequate to be relied on fully, and such patients generally should be taken to the operating room for formal surgical evaluation. Significant changes in globe contour or obvious volume loss are strong predictors of globe rupture, and any vitreous hemorrhage should be a concern for occult injury.

Computed tomographic angiography for the diagnosis of blunt cervical vascular injury: is it ready for primetime?

INTRODUCTION: Although the reported sensitivity of computed tomographic angiography (CTA) for the diagnosis of blunt cervical vascular injury (BCVI) has been inadequate, we hypothesized that advances in computed tomographic technology have improved the diagnostic sensitivity of CTA at least to that of invasive catheter angiography (CA). METHODS: Data from all patients at risk for BCVI presenting to a Level I trauma center were collected prospectively. Each patient was evaluated with CTA and these findings were confirmed with standard catheter arteriograms (CA). RESULTS: Over 11 months, 162 patients were at risk for BCVI. In all, 146 patients received both CTA and CA. Forty-six BCVIs were identified among 43 patients. In 45 of 46 cases (98%), the results of CTA and CA were concordant. There was a single false-negative CTA in a patient with a grade I vertebral artery injury (VAI). The remaining 103 patients had normal CTAs confirmed by a normal CA. The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CTA for the diagnosis of BCVI were 97.7%, 100%, 100%, 99.3%, and 99.3%, respectively. CONCLUSIONS: CTA, using a 16-channel detector, can be used to accurately screen at-risk patients for BCVI.

Imaging of acquired cerebral herniations.

The consequences of cerebral herniation are compression of the brain, cranial nerves, and blood vessels that may result in serious neurologic morbidity, coma, and even death. A thorough understanding of the various patterns of cerebral herniation is essential, and it is important to remember that many of these patterns of herniation overlap. CT and MR imaging are effective at establishing the diagnosis of cerebral herniation, which will guide important decisions regarding therapeutic options and prognosis.

Bilateral Memory Dysfunction in Epilepsy Surgery Candidates Detected by the Intracarotid Amobarbital Procedure (Wada Memory Test).

The intracarotid amobarbital procedure (IAP) is widely used in the evaluation of candidates for resective epilepsy surgery, in part to identify patients at risk for postoperative amnesia. Yet there is no widely accepted standardized protocol, and there is a paucity of quantitative data to assess the factors associated with poor IAP performance. This report summarizes our findings on 110 patients with intractable focal epilepsy who underwent IAP testing at our center. Ipsilateral IAP scores for patients with left-sided seizure foci were significantly lower than those for patients with right-sided seizure foci. Falsely and poorly lateralizing scores were also significantly more common in subjects with left-sided seizure onsets. Twenty-four percent of subjects failed the IAP bilaterally, and patients who failed the IAP bilaterally had significantly lower scores on neuropsychologic measures. There was no difference between patients who passed and failed in the location, etiology, duration, or age of onset of epilepsy. We conclude that bilateral memory dysfunction is common in patients with intractable partial epilepsy. Whether memory dysfunction detected by IAP testing as performed at our center is predictive of functionally limiting postoperative amnesia remains to be determined.