Martin L. Gunn

State of the art: technologies for computed tomography dose reduction

The utilization of computed tomography (CT) in the emergency department has grown rapidly in the last decade, driven by strong evidence supporting its effectiveness in the rapid diagnosis of an increasing range of diseases. Concerns have been raised about potential cancer induction caused by the increased use of CT and the high radiation dose associated with some multidetector row CT examinations. Recent research into protocol design and new CT scanner technologies enable high-quality examinations to be performed with a significant reduction in radiation dose. These advances are discussed, with emphasis on their application to emergency radiology.

High-resolution CT findings of bronchiolitis obliterans syndrome after hematopoietic stem cell transplantation.

Purpose To describe the high-resolution computed tomography (CT) findings occurring in bronchiolitis obliterans syndrome (BOS) after hematopoietic stem cell transplantation (HSCT) and to determine the relationship between pulmonary function tests (PFTs) and air trapping detected on expiratory CT. Materials and Methods The high-resolution CT scans of 33 patients who underwent HSCT and subsequently developed BOS were evaluated by 2 observers blinded to PFT results. Scans were ranked for degree of air trapping and scored for findings of bronchial wall thickening, bronchiectasis, and centrilobular opacities. Air-trapping rank was correlated with the degree of airflow obstruction as determined by PFTs. Results The ranking of air trapping correlated significantly with 1-second forced expiratory volume (P=0.001), 1-second forced expiratory volume /forced vital capacity (P<0.001), residual volume (P<0.001), carbon monoxide diffusion capacity (P=0.023), but not forced vital capacity (P=0.14) or total lung capacity (P=0.07). Bronchial wall thickening occurred in 73.0%, predominantly in lower lobes (P=0.007), but was mild. Bronchiectasis occurred in 42.4% and centrilobular opacities in 39.4%. Conclusions In BOS developing after HSCT, air trapping is the principal finding on CT, and its severity correlates with PFTs. Bronchial wall thickening is common, but almost always mild; bronchiectasis and centrilobular opacities occur in less than half of cases and are also mild.

The Obese Emergency Patient: Imaging Challenges and Solutions

The dramatic rise in the prevalence of obesity among children and adults in the United States over the last several decades has brought several new challenges to the delivery of healthcare. The increased utilization of and dependence on imaging for accurate and timely diagnosis has placed the radiology department in a unique position in the provision of care for the obese emergency patient. Radiology practices must be cognizant of the imaging challenges presented by the obese patient and adjust their imaging algorithms accordingly to optimize all types of diagnostic studies. The article systematically reviews common pitfalls and offers methods to improve image quality when using radiography, ultrasonography, and computed tomography to image the obese patient population.

Blunt Abdominal Aortic Injury

BACKGROUND Blunt abdominal aortic injury (BAAI) is a rare injury with less than 200 cases in the current reported world literature, mostly in case report format. We sought to describe the experience of a high-volume trauma center and to provide a contemporary review of the literature to better understand the natural history and management of this injury. METHODS This was a retrospective review of patients with BAAI between 1996 and 2010. Data collected included demographics, mechanism of injury, associated injuries, type of intervention, subsequent imaging, and follow-up. BAAI was classified by the presence of external aortic contour abnormality noted as an intimal tear, large intimal flap, pseudoaneurysm, or free rupture. Abdominal aorta zones of injury were classified by possible surgical approaches as zone I (diaphragmatic hiatus to superior mesenteric artery [SMA]), zone II (includes SMA and renal arteries), and zone III (from the inferior aspect of the renal arteries to the aortic bifurcation). RESULTS We identified 28 individuals (68% male) with BAAI (median age, 28.5; range, 6-61 years). The median injury severity score was 45 (range, 16-75), and 39% were hypotensive at presentation. BAAI presented as intimal tear (21%), large intimal flap (39%), pseudoaneurysm (11%), and free rupture (29%). Zone III was the most common location of injury. Management depended on the location and type of injury: nonoperative (32%), open aortic repair (36%), endovascular repair (21%), and multimodality (10%). Overall mortality was 32%. Most deaths occurred during the initial operative exploration. The mortality rate of free aortic rupture was 100%. Intimal tears resolved or remained stable. Median follow-up was 15.5 months (range, 8 days-7.5 years). Vascular complications due to repair included a thrombosed access femoral artery during an endovascular repair and death of a patient who underwent a hybrid repair. CONCLUSIONS This is the largest BAAI series described in the English literature at one institution. BAAIs range from intimal tears to free rupture, with outcomes and management correlating with type and location of injury. Nonoperative management with blood pressure control using β-blockers coupled with antiplatelet therapy and close follow-up is successful in individuals with intimal tears with minimal thrombus formation because they remain stable or resolve on follow-up. Free rupture remains a devastating injury, with 100% mortality. For all other categories of aortic injury, successful repair correlates with a favorable prognosis.

A text processing pipeline to extract recommendations from radiology reports

Communication of follow-up recommendations when abnormalities are identified on imaging studies is prone to error. The absence of an automated system to identify and track radiology recommendations is an important barrier to ensuring timely follow-up of patients especially with non-acute incidental findings on imaging examinations. In this paper, we present a text processing pipeline to automatically identify clinically important recommendation sentences in radiology reports. Our extraction pipeline is based on natural language processing (NLP) and supervised text classification methods. To develop and test the pipeline, we created a corpus of 800 radiology reports double annotated for recommendation sentences by a radiologist and an internist. We ran several experiments to measure the impact of different feature types and the data imbalance between positive and negative recommendation sentences. Our fully statistical approach achieved the best f-score 0.758 in identifying the critical recommendation sentences in radiology reports.

Interrater agreement in the evaluation of discrepant imaging findings with the Radpeer system

OBJECTIVE The Radpeer system is central to the quality assurance process in many radiology practices. Previous studies have shown poor agreement between physicians in the evaluation of their peers. The purpose of this study was to assess the reliability of the Radpeer scoring system. MATERIALS AND METHODS A sample of 25 discrepant cases was extracted from our quality assurance database. Images were made anonymous; associated reports and identities of interpreting radiologists were removed. Indications for the studies and descriptions of the discrepancies were provided. Twenty-one subspecialist attending radiologists rated the cases using the Radpeer scoring system. Multirater kappa statistics were used to assess interrater agreement, both with the standard scoring system and with dichotomized scores to reflect the practice of further review for cases rated 3 and 4. Subgroup analyses were conducted to assess subspecialist evaluation of cases. RESULTS Interrater agreement was slight to fair compared with that expected by chance. For the group of 21 raters, the kappa values were 0.11 (95% CI, 0.06-0.16) with the standard scoring system and 0.20 (95% CI, 0.13-0.27) with dichotomized scores. There was disagreement about whether a discrepancy had occurred in 20 cases. Subgroup analyses did not reveal significant differences in the degree of interrater agreement. CONCLUSION The identification of discrepant interpretations is valuable for the education of individual radiologists and for larger-scale quality assurance and quality improvement efforts. Our results show that a ratings-based peer review system is unreliable and subjective for the evaluation of discrepant interpretations. Resources should be devoted to developing more robust and objective assessment procedures, particularly those with clear quality improvement goals.

Computed Tomographic and Magnetic Resonance Features of Gynecologic Abnormalities in Women Presenting With Acute or Chronic Abdominal Pain

Advances in technology and improved availability have led to increased use of computed tomography (CT) and magnetic resonance imaging (MRI) to evaluate women presenting to the emergency department or to their primary care provider with abdominal and/or pelvic pain. Computed tomographic examinations are often performed to evaluate the presence of appendicitis or renal stone disease. However, gynecologic abnormalities are frequently identified on these examinations. Although ultrasound remains the primary modality by which complaints specific to the pelvis are evaluated, in many instances, CT and MRI imaging occurs before sonographic evaluation. Historically, because of cost, radiation exposure, and relative ease of use, ultrasound examinations have preceded all other imaging modalities when evaluating pelvic disorders. However, as CT and MRI technology have improved, their use in diagnosing causes of pelvic pain has become equal to that of ultrasound. In some cases, primarily because of historic comfort with sonographic evaluation, gynecologic abnormalities originally diagnosed on CT or MRI may be immediately and unnecessarily reevaluated by ultrasound. For a woman in her reproductive years, the most common adnexal masses are physiological cysts, endometriomas, and cystic teratomas. Although lesions are often asymptomatic and incidentally detected, they can present with pain, and they increase the risk of ovarian torsion. Common causes of chronic pelvic pain in this population include leiomyomata and adenomyosis. In postmenopausal women, ovarian carcinoma, which often does not present clinically until a late stage, has to be included in the differential diagnosis of adnexal masses. If a gynecologic pathology is discovered on CT or MRI, an immediate follow-up ultrasound need not be pursued if the lesion can be characterized as benign, needing immediate surgical intervention, or a variant of normal anatomy. If, on the other hand, findings demonstrate a mass that either is uncharacteristic of a benign lesion, has an indeterminate risk for malignancy, or demonstrates suspicious characteristics for malignancy (such as enhancing mural nodules), further evaluation by serial ultrasound, biochemical marker, and/or CT or MRI is warranted. The purpose of this review is to present a series of commonly encountered gynecologic abnormalities with either CT or MR to make radiologists more familiar with gynecologic pathology on CT and MRI.

Traumatic abdominal aortic injury treated by endovascular stent placement

Traumatic injury of the abdominal aorta is rare and potentially lethal. The authors present the case of a restrained passenger who was involved in a high-speed, head-on motor vehicle accident. On arrival in the emergency department, the patient complained of abdominal pain, was tachycardic and had a large ecchymoses on his right flank and lower abdominal wall. Computed tomography (CT) angiography (CTA) of the abdomen revealed a degloving injury to the abdominal wall, small bowel injury, and a distal abdominal aortic injury with a small amount of retroperitoneal hemorrhage. The patient underwent surgical repair of bowel injuries and the anterior abdominal wall. Because of risk of peritoneal soiling, open repair of the aorta was not attempted. The interventional radiology and vascular surgery services performed an endovascular repair of the aortic injury using a bifurcated endograft.

Assessment of the liver strain among cirrhotic and normal livers using tagged MRI.

To use magnetization tagged magnetic resonance imaging (MRI) (tag‐MRI) to quantify cardiac induced liver strain and compare strain of cirrhotic and normal livers.

Radiation dose to the thyroid gland and breast from multidetector computed tomography of the cervical spine: does bismuth shielding with and without a cervical collar reduce dose?

Purpose: This study aimed to assess the radiation dose reduction that could be achieved using an in-line bismuth shielding over the thyroid gland and breast and to determine the effect of a cervical spine collar on thyroid dose reduction and image noise when performing computed tomography of the cervical spine using automatic tube current modulation. Materials and Methods: An anthropomorphic phantom was scanned using a commercially available 64-channel computed tomographic scanner. A standardized trauma cervical spine protocol was used. Scans were obtained with and without a standard cervical spine immobilization collar and with and without bismuth-impregnated thyroid and breast shields. Thermoluminescent dosimeters were placed over the thyroid gland and breasts for each scan. A paired t test was used to determine whether the skin entry dose differed significantly between the shielded and unshielded thyroid and breast and to determine whether placing the thyroid shield over a cervical immobilization collar resulted in a significant dose reduction. Region of interest of pixel values was used to determine image noise. Results: The average measured skin entry dose for the unshielded thyroid gland was 21.9 mGy (95% confidence interval, 18.9-4.7). With a bismuth shield applied directly over the skin, the dose to the thyroid gland was reduced by 22.5% (P < 0.05). With the bismuth shield applied over the cervical spine collar, the dose reduction to the thyroid was 10.4%, which was not statistically significant (P = 0.16) compared with the dose reduction without the cervical collar. Skin entry dose over the breasts was significant, although they were outside the primary scan range. Without bismuth shielding, the skin entry dose was 1.5 mGy, and with bismuth shielding, the dose was significantly reduced by 36.6% (P < 0.01). Image noise increased most when shielding was used with an immobilization collar. Conclusions: There is a significant dose reduction to the thyroid gland and breasts when a bismuth shield is placed on the skin. The dose saving achieved by placing the shield on the cervical collar is approximately halved compared with placement on the skin, and this did not reach statistical significance, and this was accompanied by an increase on image noise. Bismuth shields should not be used in combination with cervical immobilization collars.