Evaluating the Benefit of Elevated Acoustic Output in Harmonic Motion Estimation in Ultrasonic Shear Wave Elasticity Imaging.

Harmonic imaging techniques have been applied in ultrasonic elasticity imaging to obtain higher-quality tissue motion tracking data. However, harmonic tracking can be signal-to-noise ratio and penetration depth limited during clinical imaging, resulting in decreased yield of successful shear wave speed measurements. A logical approach is to increase the source pressure, but the in situ pressures used in diagnostic ultrasound have been subject to a de facto upper limit based on the Food and Drug Administration guideline for the mechanical index (MI <1.9). A recent American Institute of Ultrasound in Medicine report concluded that an in situ MI up to 4.0 could be warranted without concern for increased risk of cavitation in non-fetal tissues without gas bodies if there were a concurrent clinical benefit. This work evaluates the impact of using an elevated MI in harmonic motion tracking for hepatic shear wave elasticity imaging. The studies indicate that high-MI harmonic tracking increased shear wave speed estimation yield by 27% at a focal depth of 5 cm, with larger yield increase in more difficult-to-image patients. High-MI tracking improved harmonic tracking data quality by increasing the signal-to-noise ratio and decreasing jitter in the tissue motion data. We conclude that there is clinical benefit to use of elevated acoustic output in shear wave tracking, particularly in difficult-to-image patients.

Quantifying Image Quality Improvement Using Elevated Acoustic Output in B-Mode Harmonic Imaging.

Tissue harmonic imaging has been widely used in abdominal imaging because of its significant reduction in acoustic noise compared with fundamental imaging. However, tissue harmonic imaging can be limited by both signal-to-noise ratio and penetration depth during clinical imaging, resulting in decreased diagnostic utility. A logical approach would be to increase the source pressure, but the in situ pressures used in diagnostic ultrasound are subject to a de facto upper limit based on the U.S. Food and Drug Administration guideline for the mechanical index (<1.9). A recent American Institute of Ultrasound in Medicine report concluded that an effective mechanical index ≤4.0 could be warranted without concern for increased risk of cavitation in non-fetal tissues without gas bodies, but would only be justified if there were a concurrent improvement in image quality and diagnostic utility. This work evaluates image quality differences between normal and elevated acoustic output hepatic harmonic imaging using a transmit frequency of 1.8 MHz. The results indicate that harmonic imaging using elevated acoustic output leads to modest improvements (3%-7%) in contrast-to-noise ratio of hypo-echoic hepatic vessels and increases in imaging penetration depth on the order of 4 mm per mechanical index increase of 0.1 for a given focal depth. Difficult-to-image patients who suffer from poor ultrasound image quality exhibited larger improvements than easy-to-image study participants.

Diagnostic performance of MDCT in identifying closed loop small bowel obstruction.

PURPOSE: To assess the diagnostic performance of MDCT in the diagnosis of closed loop small bowel obstruction. MATERIALS AND METHODS: One hundred fifty patients with CT reports including "small bowel obstruction (SBO)" between 1/30/2011 and 12/4/2012 were included (65 men, 85 women, mean age 63 years). CT examinations were independently and blindly reviewed by five radiologists to determine the presence of closed loop obstruction (CL-SBO) and to assess findings of bowel ischemia. Clinical records were reviewed to determine management and operative findings. Using operative findings as a gold standard, reader agreement for the diagnosis of and the CT findings associated with CLO was analyzed using Pearson's correlation (r). Positive predictive value (PPV) and negative predictive value for the diagnosis of CL-SBO and CT signs of bowel ischemia were analyzed. RESULTS: Eighty-eight of 150 patients underwent operative intervention for SBO and 24/88 were considered CL-SBO operatively. Average reader sensitivity and specificity for CL-SBO was 53 % (95 % CI 44-63 %) and 83 % (95 % CI 79-87 %). Reader agreement on CL-SBO was poor to moderate (K = 0.39-0.63). Reader agreement for CT signs of bowel ischemia resulting in a diagnosis of CL-SBO was weak (r = 0.19-0.32). CONCLUSION: The CT diagnosis of CL-SBO is complex and associated imaging findings have variable sensitivity for predicting a closed loop operative diagnosis. CT can be helpful in excluding a closed loop component in patients with SBO.

Safety of an intercostal approach for imaging-guided percutaneous drainage of subdiaphragmatic abscesses.

OBJECTIVE: The objective of our study was to test the hypothesis that an intercostal approach to imaging-guided percutaneous subdiaphragmatic abscess drainage is as safe as a subcostal approach. MATERIALS AND METHODS: A cohort of 258 consecutive patients with one or more subdiaphragmatic abscesses referred for imaging-guided (CT or ultrasound) percutaneous drainage was identified. Demographic characteristics and clinical outcomes were compared between patients who underwent drainage catheter placement via an intercostal approach versus those who underwent drainage catheter placement via a subcostal approach. RESULTS: Percutaneous drainage was performed for 441 abscesses in 258 patients in 409 separate procedures (214 via an intercostal approach, 186 by a subcostal approach, and nine by a combined approach). The total number of pleural complications was significantly higher in the intercostal group (56/214 [26.2%]) than the subcostal group (15/186 [8.1%]; p < 0.001). These complications included a significantly higher pneumothorax rate in the intercostal group than the subcostal group (15/214 [7.0%] vs 0/186 [0%], respectively; p < 0.01) and a higher incidence of new or increased pleural effusions (38/214 [17.8%] vs 14/186 [7.5%]; p < 0.01). The incidence of empyema was low and similar between the two groups (intercostal vs subcostal, 3/214 [1.4%] vs 1/186 [0.5%]; p = 0.63). A few of the complications in the patients who underwent an intercostal-approach drainage were clinically significant. Four of the 15 pneumothoraces required thoracostomy tubes and eight of 38 (21.1%) pleural effusions required thoracentesis, none of which was considered infected. CONCLUSION: An intercostal approach for imaging-guided percutaneous drainage is associated with a higher risk of pleural complications; however, most of these complications are minor and should not preclude use of the intercostal approach.

Can the localization of primary colonic tumors be improved by staging CT without specific bowel preparation compared to optical colonoscopy?

OBJECTIVES: To investigate the ability of staging computed tomography (CT) without bowel preparation to accurately localize colonic tumors compared to optical colonoscopy. METHODS: The local institutional review board approved this retrospective and HIPAA-compliant study. Forty-six patients with colonic adenocarcinoma, preoperative colonoscopy, and staging CT within 60 days of resection were included. Patients underwent contrast enhanced CT imaging without bowel preparation or oral contrast. The colon was divided into four segments with the operative reports used as the standard. Rectal and cecal cancers were excluded. CT scans were reviewed by 5 readers in a segmental binary fashion using a 5-point confidence scale in two sessions blinded and unblinded to the colonoscopy report. RESULTS: At surgery 49 tumors were found in 46 patients. Readers detected 86.1%, 74.3%, and 66.9% of lesions with 92.0%, 94.1%, and 95.4% accuracy for confidence scores of ≥ 3, ≥ 4, and 5. CT interobserver agreement was good (κ=0.82) for the unblinded and moderate (κ=0.60) for the blinded read. Colonoscopic localization was only 78.7% accurate with 2 tumors undiscovered. Colonoscopic accuracy was low in the descending colon (57.1%) and the transverse colon (55.6%). CONCLUSIONS: Preoperative staging CT is more accurate than colonoscopy in the localization of colonic tumors.

Unilateral luteoma of pregnancy mimicking a malignant ovarian mass on magnetic resonance and ultrasound.

Luteoma of pregnancy is a rare, tumorlike ovarian mass that develops during pregnancy and regresses after delivery. Generally, these masses are discovered incidentally during cesarean delivery or tubal ligation. Some of these patients will develop hirsutism or virilization during late pregnancy with or without fetal masculinization due to circulating androgens. The imaging features of this entity have been only rarely reported. An incidentally discovered luteoma of pregnancy in a 23-year-old patient during routine obstetric ultrasound is described and the image features in ultrasound and magnetic resonance (MR) imaging are discussed and compared with other studies. The patient underwent surgery to extract this mass considering the imaging findings were suspicious for neoplasia and the size and location could have potentially caused dystocia. This type of mass can mimic ovarian neoplasia and a correlation with imaging and laboratory findings can avoid an unnecessary surgical procedure during pregnancy.

N/2 ghosting artifacts: elimination at 3.0-T MR cholangiography with SPACE pulse sequence.

This HIPAA-compliant study had institutional review board approval, with waiver of informed consent. The purpose was to test the hypothesis that, compared with a standard magnetic resonance (MR) cholangiography sequence, MR cholangiography with a sampling perfection with application optimized contrasts using different flip angle evolutions (SPACE) sequence reduces ghosting artifacts while maintaining image quality and sufficient contrast-to-noise ratio (CNR) at 3.0 T. The study population consisted of 15 women and 14 men (mean age, 47.2 years +/- 18.1 [standard deviation]) who were consecutively referred for MR cholangiography between November 2004 and November 2005. Acquisition times were lower and N/2 ghosting artifacts were eliminated with SPACE. However, the SPACE sequence yielded images that were visually grainier and had lower CNR. Overall, the readers preferred the appearance of images obtained with the SPACE sequence, most likely because of the elimination of N/2 ghosting artifacts.

Glenoid dysplasia: incidence and association with posterior labral tears as evaluated on MRI.

OBJECTIVE: Glenoid dysplasia is known to predispose affected patients to accelerated degenerative joint disease. We have observed that there is often an association between glenoid dysplasia and posterior labral tears. Our goal was to assess glenoid dysplasia as seen on MRI and to assess its association with posterior labral tears. CONCLUSION: In our study population, we found that moderate to severe glenoid dysplasia is not a rare entity as seen on MRI, with an incidence of 14.3%. Furthermore, we found that there is a statistically significant increase in the incidence of posterior labral tears associated with shoulders with moderate or severe glenoid dysplasia compared with those shoulders with no dysplasia or mild dysplasia as evaluated on MRI. Even when the mild cases were included, the incidence of posterior labral tears was significantly increased versus healthy subjects, indicating that even mild cases of glenoid dysplasia may be clinically relevant.