Adaptive and Robust Vessel Quantification in Contrast-Free Ultrafast Ultrasound Microvessel Imaging

The morphological features of vasculature in diseased tissue differ significantly from those in normal tissue. Therefore, vasculature quantification is crucial for disease diagnosis and staging. Ultrasound microvessel imaging (UMI) with ultrafast ultrasound acquisitions has been determined to have potential in clinical applications given its superior sensitivity in blood flow detection. However, the presence of spatial-dependent noise caused by a low imaging signal-to-noise ratio and incoherent clutter artifacts caused by moving hyperechoic scatterers degrades the performance of UMI and the reliability of vascular quantification. To tackle these issues, we proposed an improved UMI technique along with an adaptive vessel segmentation workflow for robust vessel identification and vascular feature quantification. A previously proposed sub-aperture cross-correlation technique and a normalized cross-correlation technique were applied to equalize the spatially dependent noise level and suppress the incoherent clutter artifact. A square operator and non-local means filter were then used to better separate the blood flow signal from residual background noise. On the de-noised ultrasound microvessel image, an automatic and adaptive vessel segmentation method was developed based on the different spatial patterns of blood flow signal and background noise. The proposed workflow was applied to a CIRS phantom, to a Doppler flow phantom and to an inflammatory bowel, kidney and liver, to validate its feasibility. Results revealed that automatic adaptive, and robust vessel identification performance can be achieved using the proposed method without the subjectivity caused by radiologists/operators.

Comparison of emergency department throughput and process times between male and female patients: A retrospective cohort investigation by the Reducing Disparities Increasing Equity in Emergency Medicine Study Group

Introduction

Health equity for all patients is an important characteristic of an effective healthcare system. Bias has the potential to create inequities. In this study, we examine emergency department (ED) throughput and care measures for sex‐based differences, including metrics such as door‐to‐room (DTR) and door‐to‐healthcare practitioner (DTP) times to look for potential signs of systemic bias.

Methods

We conducted an observational cohort study of all adult patients presenting to the ED between July 2015 and June 2017. We collected ED operational, throughput, clinical, and demographic data. Differences in the findings for male and female patients were assessed using Poisson regression and generalized estimating equations (GEEs). A priori, a clinically significant time difference was defined as 10 min.

Results

A total of 106,011 adult visits to the ED were investigated. Female patients had 8‐min longer median length‐of‐stay (LOS) than males (P < 0.01). Females had longer DTR (2‐min median difference, P < 0.01), and longer DTP (5‐min median difference, P < 0.01). Females had longer median door‐to‐over‐the‐counter analgesia time (84 vs. 80, P = 0.58), door‐to‐advanced analgesia (95 vs. 84, P < 0.01), door‐to‐PO (by mouth) ondansetron (70 vs. 62, P = 0.02), and door‐to‐intramuscular/intravenous antiemetic (76 vs. 69, P = 0.02) times compared with males.

Conclusion

Numerous statistically significant differences were identified in throughput and care measures—mostly these differences favored male patients. Few of these comparisons met our criteria for clinical significance.

Lymphatic Mapping Using US Microbubbles before Lymphaticovenous Anastomosis Surgery for Lymphedema

Background Lymphaticovenous anastomosis (LVA) surgery is an effective surgical treatment of secondary lymphedema in the extremities, but indocyanine green (ICG) fluorescent lymphography, the reference standard for imaging target lymphatic vessels, has several limitations. More effective methods are needed for preoperative planning. Purpose To evaluate whether contrast-enhanced US (CEUS) can be used to identify target lymphatic vessels for LVA surgery in patients with secondary upper extremity lymphedema and compare the results with those from ICG fluorescent lymphography. Materials and Methods In this single-center retrospective review, CEUS with intradermal injection of microbubbles was performed in patients before LVA surgery in the upper extremities between October 2019 and September 2021. All patients had secondary upper extremity lymphedema from breast cancer treatment. Technical success rate was defined as lymphatic vessels identified with use of CEUS that led to successful LVAs. Descriptive statistics were used. Results All 11 patients were women (mean age, 56 years ± 8 [SD]). The median number of microbubble injection sites was 11 (range, 8-14). CEUS helped identify lymphatic vessels in all 11 women, including in six women in whom ICG fluorescent lymphography could not be performed or failed to help identify any targets. Thirty-five explorations (median, three per patient; range, two to four) were performed, and 24 LVAs (median, three per patient; range, zero to four) were created. Of the anastomoses, 33% (eight of 24) were mapped with use of both CEUS and ICG fluorescent lymphography, 58% (14 of 24) with CEUS only, and 8% (two of 24) with ICG fluorescent lymphography only. Among the 33 explorations on targets mapped with CEUS, an anastomosis could be made at 22 sites, for a technical success rate of 67%. Seven women had at least one additional LVA created from the use of CEUS. Conclusion Contrast-enhanced US is a promising tool for identifying lymphatic vessels in the upper extremities, especially when indocyanine green fluorescent lymphography fails to depict targets or cannot be used. Published under a CC BY 4.0 license.

The Effectiveness of Identifying Primary Gallbladder Adenocarcinoma Utilizing Contrast-Enhanced Ultrasound: A Case Report

Gallbladder carcinoma is rare and difficult to detect in the early stages of the disease process, due to lack of symptoms. Sonography is typically the first modality of choice for assessing gallbladder pathology due to its high sensitivity, portability, real-time imaging capability, and non-ionizing technique. Conventional gray-scale and color Doppler sonographic imaging may be ambiguous for diagnosing solid tumors, such as gallbladder carcinoma. In this case, gallbladder carcinoma was definitively diagnosed utilizing contrast-enhanced ultrasound, allowing for quick patient treatment options and an optimal surgical outcome.

Three-Dimensional-Printed Liver Model Helps Learners Identify Hepatic Subsegments: A Randomized-Controlled Cross-Over Trial

INTRODUCTION

The purpose of this study was to find out whether 3-dimensional (3D)-printed models improved the learners' ability to identify liver segments.

METHODS

A total of 116 physicians from 3 disciplines were tested in a cross-over trial at baseline and after teaching with 3D models and 2-dimensional (2D) images. Adjusted multilevel-mixed models were used to compare scores at baseline and after 3D and 2D.

RESULTS

Accuracy in identifying hepatic segments was higher with 3D first than 2D (77% vs 69%; P = 0.05) and not significantly improved by a combination of 3D and 2D. Increased confidence in segment identification was highest in trainees after 3D (P = 0.04).

DISCUSSION

3D-printed models facilitate learning hepatic segmental anatomy.

Quantitative Inflammation Assessment for Crohn Disease Using Ultrasensitive Ultrasound Microvessel Imaging: A Pilot Study

OBJECTIVES

Crohn disease (CD) is a chronic inflammation in the digestive tract that affects millions of Americans. Bowel vascularity has important diagnostic information because inflammation is associated with blood flow changes. We recently developed an ultrasensitive ultrasound microvessel imaging (UMI) technique with high vessel sensitivity. This study aimed to evaluate the feasibility of UMI to assist CD detection and staging.

METHODS

Ultrasound microvessel imaging was performed on 76 bowel wall segments from 48 symptomatic patients with CD. Clinically indicated computed tomographic/magnetic resonance enterography was used as the reference standard. The vessel-length ratio (VLR, the number of vessel pixels in the bowel wall segment normalized to the segment length) was derived in both conventional color flow imaging (CFI) and UMI to quantitatively stage disease activity. Receiver operating characteristic curves were then analyzed between different disease groups.

RESULTS

The VLR-CFI and VLR-UMI detected similar correlations between vascularization and disease activity: severe inflammation had a higher VLR than normal/mildly inflamed bowels (P < .05). No significant difference was found between quiescent and mild CD due to the small sample size. The VLR-CFI had more difficulties in distinguishing quiescent versus mild CD compared to the VLR-UMI. After combining the VLR-UMI with thickness, in the receiver operating characteristic curve analysis, the areas under the curves (AUCs) improved to AUC₁ = 0.996 for active versus quiescent CD, AUC₂ = 0.978 for quiescent versus mild CD, and AUC₃ = 0.931 for mild versus severe CD, respectively, compared to those using thickness alone (AUC₁ = 0.968; P = .04; AUC₂ = 0.919; P = .16; AUC₃ = 0.857; P = .01).

CONCLUSIONS

Ultrasound microvessel imaging offers a safe and cost-effective tool for CD diagnosis and staging, which may potentially assist disease activity classification and therapy efficacy evaluation.

Automated Segmentation of Thyroid Nodule, Gland, and Cystic Components From Ultrasound Images Using Deep Learning

Sonographic features associated with margins, shape, size, and volume of thyroid nodules are used to assess their risk of malignancy. Automatically segmenting nodules from normal thyroid gland would enable an automated estimation of these features. A novel multi-output convolutional neural network algorithm with dilated convolutional layers is presented to segment thyroid nodules, cystic components inside the nodules, and normal thyroid gland from clinical ultrasound B-mode scans. A prospective study was conducted, collecting data from 234 patients undergoing a thyroid ultrasound exam before biopsy. The training and validation sets encompassed 188 patients total; the testing set consisted of 48 patients. The algorithm effectively segmented thyroid anatomy into nodules, normal gland, and cystic components. The algorithm achieved a mean Dice coefficient of 0.76, a mean true positive fraction of 0.90, and a mean false positive fraction of 1.61×10-6. The values are on par with a conventional seeded algorithm. The proposed algorithm eliminates the need for a seed in the segmentation process, thus automatically detecting and segmenting the thyroid nodules and cystic components. The detection rate for thyroid nodules and cystic components was 82% and 44%, respectively. The inference time per image, per fold was 107ms. The mean error in volume estimation of thyroid nodules for five select cases was 7.47%. The algorithm can be used for detection, segmentation, size estimation, volume estimation, and generating thyroid maps for thyroid nodules. The algorithm has applications in point of care, mobile health monitoring, improving workflow, reducing localization time, and assisting sonographers with limited expertise.

Racial and Ethnic Disparities in the Utilization of Thrombectomy for Acute Stroke

Background and Purpose- Racial and ethnic disparities in the access to mechanical thrombectomy (MT) for treatment of acute ischemic stroke (AIS) secondary to large vessel occlusion have been previously described. The effect of recent randomized trials validating MT as an effective therapy for AIS secondary to large vessel occlusion on such disparities has not been investigated. Methods- Information on admissions for AIS to endovascular centers occurring between January 2016 and September 2018 was obtained from a national database. The number of patients receiving IV-tPA (intravenous tissue-type plasminogen activator) and MT at each institution was determined, and patient demographics were characterized according to age, sex, race/ethnicity, and insurance status. Comparisons of patients who did and did not undergo MT and between patients of different racial and ethnic backgrounds were performed. Demographic variables independently associated with the utilization of MT were identified using multivariate linear regression analysis. Results- There were 206 853 admissions to 173 endovascular centers during the time period of interest. The overall utilization of MT was 8.4%. The utilization of MT for black/Hispanic patients was lower than that among white/non-Hispanic patients (7.0% versus 9.8%; P<0.001). Black/Hispanic patients were also less likely to receive IV-tPA (16.2% versus 20.5%; P<0.001) and to be admitted to the endovascular center after transfer from a different hospital (20.0% versus 30.1%; P<0.001). On multivariate linear regression analysis, increasing institutional proportions of patients with female sex (β=-0.601; P<0.001), insurance with Medicaid or uninsured status (β=-0.153; P=0.029), and black/Hispanic race/ethnicity (β=-0.062; P=0.046) were independently associated with lower institutional utilization of MT. Conclusions- Despite the mainstream acceptance of MT for the treatment of AIS secondary to large vessel occlusion, racial and ethnic disparities in the utilization of MT persist.

Transvaginal Ultrasound Vibro-elastography for Measuring Uterine Viscoelasticity: A Phantom Study

The purpose of this research was to determine the feasibility of a transvaginal ultrasound vibro-elastography (TUVE) technique for generating and measuring shear wave propagation in the uterus. In TUVE, a 0.1-s harmonic vibration at a low frequency is generated on the abdomen of a subject via a handheld vibrator. A transvaginal ultrasound probe is used to measure the resulting shear wave propagation in the uterus. TUVE was evaluated on a female ultrasound phantom. The shear wave speeds in the region of interest of the uterus of the female ultrasound phantom were measured in the frequency range of 100-300 Hz. The viscoelasticity was analyzed based on the wave speed dispersion with frequency. The measurement of shear wave speed suggests that the uterus of this female ultrasound phantom is much stiffer than the human uterus. This research illustrates the feasibility of TUVE for generating and measuring shear wave propagation in the uterus of a female ultrasound phantom. We will further evaluate TUVE in patients, both normal controls and those with uterine diseases such as adenomyosis.

Racial and economic disparities in the access to treatment of unruptured intracranial aneurysms are persistent problems

Background and purpose

Previous studies have documented disparate access to cerebrovascular neurosurgery for patients of different racial and socioeconomic backgrounds. We further investigated the effect of race and insurance status on access to treatment of unruptured intracranial aneurysms (UIAs) and compared it with data on patients with aneurysmal subarachnoid hemorrhage (aSAH).

Methods

Through the use of a national database, admissions for clipping or coiling of an UIA and for aSAH were identified. Demographic characteristics of patients were characterized according to age, sex, race/ethnicity, and insurance status, and comparisons between patients admitted for treatment of an UIA versus aSAH were performed.

Results

There were 10 545 admissions for clipping or coiling of an UIA and 33 166 admissions for aSAH between October 2014 and July 2018. White/non-Hispanic patients made up a greater proportion of patients presenting for treatment of an UIA than those presenting with aSAH (64.3% vs 48.2%; P<0.001), whereas black/Hispanic patients presented more frequently with aSAH than for treatment of an UIA (29.3% vs 26.1%; P=0.006). On multivariate linear regression analysis, the proportion of patients admitted for management of an UIA relative to those admitted for aSAH increased with the proportion of patients who were women (P<0.001) and decreased with the proportion of patients with a black/Hispanic background (P=0.010) and those insured with Medicaid or without insurance (P=0.003).

Conclusion

For patients with UIAs, racial, ethnic, and socioeconomic backgrounds appear to continue to influence access to treatment.

Differentiation of Benign and Malignant Thyroid Nodules by Using Comb-push Ultrasound Shear Elastography: A Preliminary Two-plane View Study

RATIONALE AND OBJECTIVES

Low specificity of traditional ultrasound in differentiating benign from malignant thyroid nodules leads to a great number of unnecessary (ie, benign) fine-needle aspiration biopsies that causes a significant financial and physical burden to the patients. Ultrasound shear wave elastography is a technology capable of providing additional information related to the stiffness of tissues. In this study, quantitative stiffness values acquired by ultrasound shear wave elastography in two different imaging planes were evaluated for the prediction of malignancy in thyroid nodules. In addition, the association of elasticity measurements with sonographic characteristics of thyroid gland and nodules is presented.

MATERIALS AND METHODS

A total number of 155 patients (106 female and 49 male) (average age 57.48 ± 14.44 years) with 173 thyroid nodules (average size 24.89 ± 15.41 mm, range 5-68 mm) scheduled for fine-needle aspiration biopsy were recruited from March 2015 to May 2017. Comb-push shear elastography imaging was performed at longitudinal and transverse anatomic planes. Mean (E_mean) and maximum (E_max) elasticity values were obtained.

RESULTS

Measurements at longitudinal view were statistically significantly higher than measurements at transverse view. Nodules with calcifications were associated with increased elasticity, and nodules with a vascular component or within an enlarged thyroid gland (goiter) were associated with a lower elasticity value. Receiver operating characteristic curve analysis was performed for E_mean and E_max at each imaging plane and for the average of both planes. Sensitivity of 95.45%, specificity of 86.61%, 0.58 positive predictive value, and 0.99 negative predictive value were achieved by the average of the two planes for each E_mean and E_max parameters, with area under the curve of 92% and 93%, and a cutoff value of 49.09 kPa and 105.61 kPa, respectively.

CONCLUSIONS

The elastic properties of thyroid nodules showed promise to be a good discriminator between malignant and benign nodules (P < .0001). However, probe orientation and internal features such as calcifications, vascular component, and goiter may influence the final elastography measurements. A larger number of malignant nodules need to be studied to further validate our results.

Update on Magnetic Resonance Imaging and Ultrasound Evaluation of Crohn's Disease

Magnetic resonance enterography (MRE) and abdominal ultrasound are integral parts of multimodality assessments for patients with inflammatory bowel disease. Applications include assessing Crohn's disease (CD) extent and severity, differentiating CD from ulcerative colitis, detecting CD complications, evaluating response to therapy, and demonstrating postoperative recurrence. Magnetic resonance imaging protocols are being developed that may reduce or eliminate the need for intravenous contrast agents and better differentiate inflammatory from fibrotic strictures. MRE scoring systems have been created to objectively quantify disease activity and response to therapy. By utilizing advanced sonographic imaging techniques, including ultrasound contrast and Doppler assessments, the role of abdominal ultrasonography in the evaluation and management of CD continues to expand. Abdominal ultrasound may function as a low-cost, point-of care assessment tool, especially in CD restricted to the terminal ileum and ileocolic anastomosis.

A Comparison of the Mental Health and Well-Being of Sexual Minority and Heterosexual First-Year Medical Students: A Report From the Medical Student CHANGE Study

PURPOSE

Research is lacking on psychological distress and disorder among sexual minority medical students (students who identify as nonheterosexual). If left unaddressed, distress may result in academic and professional difficulties and undermine workforce diversity goals. The authors compared depression, anxiety, and self-rated health among sexual minority and heterosexual medical students.

METHOD

This study included 4,673 first-year students who self-reported sexual orientation in the fall 2010 baseline survey of the Medical Student Cognitive Habits and Growth Evaluation Study, a national longitudinal cohort study. The authors used items from published scales to measure depression, anxiety, self-rated health, and social stressors. They conducted bivariate and multivariate analyses to estimate the association between sexual identity and depression, anxiety, and self-rated health.

RESULTS

Of 4,673 students, 232 (5.0%) identified as a sexual minority. Compared with heterosexual students, after adjusting for relevant covariates, sexual minority students had greater risk of depressive symptoms (adjusted relative risk [ARR] = 1.59 [95% confidence interval, 1.24-2.04]), anxiety symptoms (ARR = 1.64 [1.08-2.49]), and low self-rated health (ARR = 1.77 [1.15-2.60]). Sexual minority students were more likely to report social stressors, including harassment (22.7% versus 12.7%, P < .001) and isolation (53.7% versus 42.8%, P = .001). Exposure to social stressors attenuated but did not eliminate the observed associations between minority sexual identity and mental and self-reported health measures.

CONCLUSIONS

First-year sexual minority students experience significantly greater risk of depression, anxiety, and low self-rated health than heterosexual students. Targeted interventions are needed to improve mental health and well-being.

Net-like pattern of calcification on plain soft-tissue radiographs in patients with calciphylaxis

BACKGROUND

Calciphylaxis is a rare, life-threatening syndrome marked by vascular calcification and cutaneous necrosis. The role of radiographic imaging in assisting in diagnosis has not been established.

OBJECTIVE

To investigate the potential role of plain radiographic imaging in the diagnosis of calciphylaxis.

METHODS

We searched for cases of patients at our tertiary referral center with a diagnosis of calciphylaxis between Jan 1, 1996, and Dec 31, 2010. Two control patients receiving dialysis but without calciphylaxis were age- and sex-matched to each study patient. Plain radiographs were obtained from the date closest to diagnosis in patients with calciphylaxis and from matched controls at approximately the same dates. Two radiologists, masked as to cases and controls, read each image together. Size of calcified vessels, pattern and extent of calcifications, presence of net-like or other calcifications, and bone density/mineralization were recorded and analyzed.

RESULTS

Twenty-nine patients with calciphylaxis (mean age, 57 years; 21 [72%] women) were identified. Mean age at diagnosis was 57 years (range, 36-75 years). Compared with those of controls, plain radiographs of patients with calciphylaxis had more vascular calcifications, more small-vessel calcifications, and a netlike pattern of calcifications. A netlike pattern of calcifications had considerable strength of association with calciphylaxis (odds ratio, 9.4) and a specificity of nearly 90%. These findings were preserved even if only one image was used per patient.

LIMITATIONS

This was a retrospective study.

CONCLUSION

A netlike pattern of calcifications on plain radiographs was more common in patients with calciphylaxis and may aid in diagnosis.

Expectant management of uterine incarceration from an anterior uterine myoma: a case report

BACKGROUND

Uterine incarceration is an infrequent complication of pregnancy in the early second trimester. Although imaging can be confirmatory, the diagnosis is made primarily on clinical grounds, and definitive treatment involves manual reduction to restore the proper anatomic position. Except for preexisting uterine retroversion, often this event is idiopathic.

CASE

A 30-year-old primigravida presented at 15 weeks' gestation with uterine incarceration. Manual replacement was unsuccessful. Spontaneous resolution occurred at 20 weeks, followed by uneventful pregnancy. The patient underwent a classical cesarean section at term due to fetal malpresentation.

CONCLUSION

Uterine incarceration may be managed conservatively, with a favorable outcome.

Bexarotene treatment of late-stage mycosis fungoides and Sézary syndrome: Development of extracutaneous lymphoma in 6 patients∗

Bexarotene is a retinoid drug that is approved for the treatment of cutaneous T-cell lymphoma. We report 6 cases in which the initiation of bexarotene therapy for cutaneous T-cell lymphoma was temporally associated with the progression of internal disease despite improvement in cutaneous signs and symptoms. It is possible that bexarotene contributed to this progression. Although bexarotene therapy may alleviate symptoms and signs of cutaneous T-cell lymphoma, careful surveillance of lymph nodes and solid organs during treatment is advised.

Magnetic Properties Experiments on the Mars Exploration Rover Spirit at Gusev Crater

The magnetic properties experiments are designed to help identify the magnetic minerals in the dust and rocks on Mars-and to determine whether liquid water was involved in the formation and alteration of these magnetic minerals. Almost all of the dust particles suspended in the martian atmosphere must contain ferrimagnetic minerals (such as maghemite or magnetite) in an amount of approximately 2% by weight. The most magnetic fraction of the dust appears darker than the average dust. Magnetite was detected in the first two rocks ground by Spirit.

Evaluation of irreversible JPEG compression for a clinical ultrasound practice

A prior ultrasound study indicated that images with low to moderate levels of JPEG and wavelet compression were acceptable for diagnostic purposes. The purpose of this study is to validate this prior finding using the Joint Photographic Experts Group (JPEG) baseline compression algorithm, at a compression ratio of approximately 10:1, on a sufficiently large number of grayscale and color ultrasound images to attain a statistically significant result. The practical goal of this study is to determine if it is feasible for radiologists to use irreversibly compressed images as an integral part of the day to day ultrasound practice (ie, perform primary diagnosis with, and store irreversibly compressed images in the ultrasound PACS archive). In this study, 5 Radiologists were asked to review 300 grayscale and color static ultrasound images selected from 4 major anatomic groups. Each image was compressed and decompressed using the JPEG baseline compression algorithm at a fixed quality factor resulting in an average compression ratio of approximately 9:1. The images were presented in pairs (original and compressed) in a blinded fashion on a PACS workstation in the ultrasound reading areas, and radiologists were asked to pick which image they preferred in terms of diagnostic utility and their degree of certainty (on a scale from 1 to 4). Of the 1499 total readings, 50.17% (95% confidence intervals at 47.6%, and 52.7%) indicated a preference for the original image in the pair, and 49.83% (95% confidence intervals at 47.3%, and 52.0%) indicated a preference for the compressed image. These findings led the authors to conclude that static color and gray-scale ultrasound images compressed with JPEG at approximately 9:1 are statistically indistinguishable from the originals for primary diagnostic purposes. Based on the authors laboratory experience with compression and the results of this and other prior studies, JPEG compression is now being applied to all ultrasound images in the authors' radiology practice before reading. No image quality-related issues have been encountered after 12 months of operation (approximately 48000 examinations).

Clostridium difficile infection: risk factors, medical and surgical management

BACKGROUND

Clostridium difficile has become recognized as a cause of nosocomial infection which may progress to a fulminant disease.

METHODS

Literature review using electronic literature research back to 1966 utilizing Medline and Current Contents. All publications on antibiotic-associated diarrhea, antibiotic-associated colitis, and pseudomembranous colitis as well as C. difficile infection were included. We addressed established and potential risk factors for C. difficile disease such as an impaired immune system and cost benefits of different diagnostic tests. An algorithm is outlined for diagnosis and both medical and surgical management of mild, moderate and severe C. difficile disease.

RESULTS

Diagnosis of C. difficile infection should be suspected in patients with diarrhea, who have received antibiotics within 2 months or whose symptoms started after hospitalization. A stool specimen should be tested for the presence of leukocytes and C. difficile toxins. If this is negative and symptoms persist, stool should be tested with 'rapid' enzyme immunoabsorbent and stool cytotoxin assays, which are the most cost-effective tests. Endoscopy and other imaging studies are reserved for severe and rapidly progressive courses. Oral metronidazole or vancomycin are the antibiotics of choice. Surgery is rarely required for selected patients refractory to medical treatment. The threshold for surgery in severe cases with risk factors including an impaired immune system should be low.

CONCLUSION

C. difficile infection has been recognized with increased frequency as a nosocomial infection. Early diagnosis with immunoassays of the stool and prompt medical therapy have a high cure rate. Metronidazole has supplanted oral vancomycin as the drug of first choice for treating C. difficile infections.

Pheochromocytoma in an incidentally discovered asymptomatic cystic adrenal mass

Cystic adrenal lesions can be either cortical or medullary, and distinguishing between these 2 types of lesions may be important in patient management. Pheochromocytomas, which are adrenal medullary neoplasms, typically manifest with hypertension, headaches, palpitations, tachycardia, sweating, and anxiety symptoms; however, 10% to 17% of patients with pheochromocytomas are asymptomatic. We describe a 67-year-old woman with lifelong headaches and recent persistent cough in whom a left cystic adrenal mass was incidentally discovered by computed tomography of the chest. A moderate increase in normetanephrine and total metanephrine values in two 24-hour urine samples suggested a pheochromocytoma. Computed tomography with use of contrast medium revealed ring enhancement of the cyst wall, a finding consistent with an adrenal medullary tumor. This report demonstrates the importance of repeated 24-hour urine samples to determine the metanephrine values together with contrast-enhanced computed tomography in a patient with nonspecific symptoms.

Fracture interpretation using electronic presentation: a comparison

The purposes of this study were to determine whether (1) fractures are interpreted differently after digitization and electronic presentation; (2) there are differences in accuracy between screen radiographs and electronic presentation; (3) differences in interpretation are a function of monitor resolution; and (4) differences in interpretation between radiographs and electronic images relate to radiological subspecialty. Forty cases with fractures of varying degrees of subtlety and 35 cases without fractures were interpreted. Radiographs were digitized with 2 different systems and displayed on 3 monitors of different spatial resolution. Four radiologists, with varying experience, were asked to decide whether fractures were present, absent, or they were uncertain. Accuracy of interpretation increased with improved electronic image presentation and monitor resolution. The sensitivity, specificity, and accuracy of fracture detection on System A were 63%, 98%, and 78%, respectively. The results were 72%, 98%, and 84% with System B. System C results were 81%, 97%, and 88% with Lumiscan 75, and 82%, 96%, and 88% with Lumiscan 150. Sensitivity, specificity, and accuracy results of the original radiograph interpretation were 89%, 95%, and 92%. Results were significantly different for System A. No significant differences were found for the other systems compared with film radiographs. System A did not have adequate monitors for interpretation of subtle fractures. Systems B and C were capable of displaying even subtle fractures. Our initial results indicate that interpretation with high-quality 1K x 1K monitors is substantially similar to radiograph interpretation.

Arteriovenous fistula of the thyroid gland associated with spontaneous bleeding from a flow-induced aneurysm of the inferior thyroid artery

A case of acute, spontaneous cervical hemorrhage caused by a ruptured aneurysm of the inferior thyroid artery is described. This lesion was accompanied by an arteriovenous fistula within the thyroid gland that caused a flow-induced aneurysm. Diagnosis and treatment were successfully performed by selective angiography with endovascular occlusion and embolization. Both diagnostic and therapeutic management are discussed, and the related literature is reviewed. To our knowledge, this is the first reported case of an aneurysm of a thyroid artery in conjunction with an intraparenchymatous arteriovenous fistula of the thyroid gland.

Magnetic properties experiments on the Mars Pathfinder lander: preliminary results

Many of the particles currently suspended in the martian atmosphere are magnetic, with an average saturation magnetization of about 4 A. m2/kg (amperes times square meters per kilogram). The particles appear to consist of claylike aggregates stained or cemented with ferric oxide (Fe2O3); at least some of the stain and cement is probably maghemite (gamma-Fe2O3). The presence of the gamma phase would imply that Fe2+ ions leached from the bedrock, passing through a state as free Fe2+ ions dissolved in liquid water. These particles could be a freeze-dried precipitate from ground water poured out on the surface. An alternative is that the magnetic particles are titanomagnetite occurring in palagonite and inherited directly from a basaltic precursor.

Overview of the Mars Pathfinder mission and assessment of landing site predictions

Chemical analyses returned by Mars Pathfinder indicate that some rocks may be high in silica, implying differentiated parent materials. Rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past. The moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius. Composite airborne dust particles appear magnetized by freeze-dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle. Remote-sensing data at a scale of generally greater than approximately 1 kilometer and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust-free.