Influence of visual distractors on detectability of liver nodules on contrast-enhanced spiral computed tomography scans.

RATIONALE AND OBJECTIVES: The authors evaluated the ability of observers to identify simulated nodules placed electronically on normal contrast material-enhanced computed tomography (CT) scans of the liver to assess the effect of nodule size and polarity on detection and localization. METHODS: Seven readers evaluated two sets of CT scans that contained 80 stimuli each. The simulated nodules were either darker or brighter than the contrast-enhanced liver and were 5.6-8.0 mm in diameter. Readers were asked to find the most suspicious-looking nodule on each section and rate the likelihood that the chosen location actually contained a nodule. RESULTS: The fraction of nodules found by each observer was substantially greater for dark nodules than for bright ones (0.679 +/- 0.03 vs 0.345 +/- 0.045, respectively [mean +/- standard error]). This difference was consistent for all nodule sizes. Additional analyses (including receiver operating characteristic curves of conditional responses) suggested that the presence of bright blood vessels distracted the readers and decreased their ability to find bright nodules. CONCLUSION: Normal vascular structures on contrast-enhanced CT scans of the liver impair an observer's ability to detect bright liver nodules.

A contrast agent delivery nomogram for hepatic spiral CT.

PURPOSE: A nomogram for hepatic spiral CT (SCT) was constructed based on randomization of patients into a prospective study using four different injection protocols. Its utility in a separate prospective randomized trial was subsequently evaluated in a new group of patients. METHODS: Thirty-nine patients randomized into four groups underwent SCT (Somatom-Plus S; 24 s exposure, 10 mm collimation, 10 mm/s) using 90 ml Omnipaque 240 (22 g I) at 2.5, 4, 5, or 6 ml/s. Peak and mean aortic and liver enhancement and time to peaks were measured and correlated with patients' age, weight, dose, rate, and contrast agent concentration, and a nomogram was constructed. In the validation experiment, 20 new patients were randomized to nomogram-guided and control groups for contrast dose administration during SCT. All patients underwent SCT (Somatom-Plus S; 32 s exposure, 10 mm collimation, 10 mm/s) using 90 ml Omnipaque 240 or 140 ml Hypaque 60 at 1.5-6 ml/s. Peak and mean aortic and liver enhancement and time to peaks were measured and correlated with patients' age, weight, dose, rate, and contrast agent concentration. Mean and peak aortic and hepatic enhancements were measured and rated by three blinded reviewers. RESULTS: Peak hepatic enhancement occurred 32 s after termination of contrast bolus administration in all groups. Correlation between the predicted and actual enhancement was very good (r = 0.7-0.9). Ninety-eight percent of the nomogram-guided group had optimal timing and utilized 10% less contrast agent than the control group. CONCLUSION: The phenomenon of peak hepatic enhancement occurring 32 s after the termination of contrast bolus regardless of injection rate may be of use in a nomogram for optimal contrast delivery for hepatic SCT.

Small (< or = 3 cm) hyperechoic renal masses: comparison of helical and convention CT for diagnosing angiomyolipoma.

OBJECTIVE: Because hyperechoic renal masses may represent angiomyolipomas or small renal cancers, CT is often used to reveal the fatty component, which allows diagnosis of angiomyolipoma in most cases. Because conventional CT can fail to reveal fat in angiomyolipomas 3 cm or smaller, we conducted a study to determine whether helical CT would improve our detection of fat and allow more of these masses to be diagnosed as angiomyolipomas. SUBJECTS AND METHODS: We used helical and conventional CT to examine 20 masses (5-29 mm in diameter) in 17 patients who had a small hyperechoic mass detected sonographically. Densitometry was performed by three readers and the mean attenuation values were compared. RESULTS: Of the 20 masses, we diagnosed angiomyolipoma in 16 masses using helical CT and in 14 masses using conventional CT. In 11 masses, we found the measured attenuation values to be more negative on helical CT scans than on conventional CT scans. In five masses, we found the opposite to be true. In the remaining four masses, we were unable to diagnose angiomyolipoma. Of the masses that we diagnosed as angiomyolipoma, the mean attenuation value when examined with helical CT (-44 H) was more negative than with conventional CT (-35 H) but not significantly so (p = .058). However, in the subset of patients with masses that were 2 cm or less in diameter (n = 14), the mean attenuation values on helical CT were significantly lower than on conventional CT (-40 H versus -30 H, p < .05). Likewise, for masses with attenuation values that differed by more than 6 H (n = 8), when imaged by the two techniques we again found that mean attenuation values on helical CT were significantly lower (-43 H versus -24 H, p < .05). CONCLUSION: Helical CT revealed angiomyolipoma across all cases as well as conventional CT did. Also, helical CT was more sensitive in revealing fat in masses less than 2 cm in diameter and in masses in which the attenuations of the two CT techniques differed by a significant amount. We preferred helical CT over conventional CT when examining hyperechoic masses for the purpose of diagnosing angiomyolipoma.

Evaluation of nonpalpable solid breast masses with stereotaxic large-needle core biopsy using a dedicated unit.

OBJECTIVE: In our institution for the past 4 years, stereotaxic core breast biopsy using a 14-gauge needle has been offered as an alternative to surgical excision. The purpose of this paper is to describe our protocol, results, and lessons learned from our experience. MATERIALS AND METHODS: From August 1991 to July 1995, 388 stereotaxic needle core biopsies of clinically occult, noncalcified, mammographically detected solid masses were performed. In this group, 103 patients underwent subsequent surgical excision. Another 169 have had follow-up examinations 1 year or more after their biopsies. RESULTS: Of the 61 patients diagnosed with a malignant process on core biopsy, all had confirmation on subsequent surgical excision. Forty-one of the 42 core biopsies that showed a benign process were subsequently confirmed on surgical excision. One patient with atypical ductal hyperplasia on core biopsy had ductal carcinoma in situ on surgical excision. Patients with 169 benign masses on core biopsy have been followed for at least 1 year by mammography. Of these women, 110 have been followed for at least 2 years, and no malignant lesions have been found. CONCLUSION: Stereotaxic large-needle core biopsy appears to be an accurate alternative to surgical excision for evaluating a solid breast mass. However, the mammographic appearance, technical quality of the biopsy, and pathologic findings in each patient must be correlated to ensure the highest possible accuracy when using this technique.

Pseudoangiomatous stromal hyperplasia: mammographic and sonographic appearances.

OBJECTIVE: Pseudoangiomatous stromal hyperplasia is a benign, localized form of stromal overgrowth with a probable hormonal etiology. Our purpose is to describe the mammographic, sonographic, and clinical features of this entity. MATERIALS AND METHODS: A retrospective review of breast imaging studies and demographic information for seven patients identified as having pseudoangiomatous stromal hyperplasia was performed. The patients were chosen from a 1-year period during which 1661 breast biopsies were performed. RESULTS: The patients were 36-61 years old. Six were premenopausal, and the one postmenopausal woman was on hormone replacement therapy. Three patients wee evaluated palpable breast lumps, and four were asymptomatic. All seven women had noncalcified masses that measured 1.1-11 cm and that were visible by mammography. The border characteristics were as follows: three masses were well circumscribed, two were partly circumscribed, and two were indistinct, probably because they were obscured by overlying parenchyma. Sonography was performed for five patients; lesions were visible in four. All four of these lesions were solid and circumscribed. Five of the masses had increased in size since earlier studies, and one palpable mass was found by physical examination to have grown over time. Two patients had a local recurrence of pseudoangiomatous stromal hyperplasia. Surgical excision was performed for three patients, large-core biopsy was performed for three patients, and both surgery and large-core biopsy were performed for one patient. CONCLUSION: Pseudoangiomatous stromal hyperplasia should be included in the differential diagnosis of a circumscribed or partially circumscribed mass, especially in the premenopausal population. These masses often grow over time and can recur locally. Pathologic diagnosis of the lesion may be difficult unless the pathologist is aware of the presence of a mass lesion and appreciates the stromal changes characteristic of such a lesion.

Spiral computed tomography of the liver: contrast agent pharmacokinetics and the potential for improved hepatic enhancement.

RATIONALE AND OBJECTIVES: We conducted a prospective study of 131 patients to evaluate the contrast agent dose-response relationship for liver spiral computed tomography (CT) and to test the hypothesis that spiral CT scanning provides greater enhancement than does dynamic CT scanning. METHODS: Patients were assigned to one of two control groups (dynamic CT) or to one of five experimental groups (spiral CT). Dynamic CT patients received 150 ml and spiral CT patients received either 75, 100, or 150 ml of diatrizoate meglumine. All groups had a monophasic injection rate of 2.5 ml/sec. Hepatic enhancement was compared among experimental and control groups. RESULTS: In the experimental groups, there was a linear dose-response relationship (p < .0001) among the enhancements achieved for the three dosages. The enhancement of the last slice of liver for the spiral CT versus dynamic CT groups receiving 150 ml was significantly greater (p = .002). Peak, first liver slice, and average liver enhancement values were higher with spiral CT scanning, but the difference was not statistically significant (power > .55). CONCLUSION: Using uniphasic injection rates and identical doses of contrast agent, spiral CT scanning has the advantage of improved enhancement of the last part of the liver to be imaged.

Spiral CT of the abdomen: region coverage with a 24-second breath-hold.

A retrospective review of 75 spiral CT examinations of the abdomen was performed to assess: (1) patient's ability to sustain a 24-s breath-hold, and (2) the proportion of targeted regions or organs that were completely imaged at different table feed speeds. Seventy of 72 patients sustained a 24-s breath-hold without motion artifact. Region coverage depended on the prescribed table feed speed and length of exposure. With a fixed exposure time, there was a tradeoff between the volume of tissue that could be imaged and the slice colimation.

Very echogenic amniotic fluid: ultrasonography-amniocentesis correlation.

Very echogenic amniotic fluid has been variably attributed to meconium, blood, or vernix caseosa. However, most previous reports have been case reports, and most cases have not had proof by amniocentesis. In a larger series of patients with proof by amniocentesis, we sought to determine the relative frequency of these substances as causes of very echogenic amniotic fluid. We retrospectively identified obstetric sonograms in which the amniotic fluid was homogeneously filled with innumerable echogenic particles. The cause of the increased echogenicity was determined by fluid appearance at amniocentesis. Of 86 cases identified, immediate proof by amniocentesis was available in 19 patients for whom the gestational age ranged from 32.8 to 39.4 weeks. Vernix was present in 18 (95%) patients and meconium in one (5%) patient. Very echogenic amniotic fluid in the third trimester is most often due to vernix and infrequently due to meconium. This sonographic finding is not a reliable indicator of meconium or blood in amniotic fluid and should not typically alter antenatal management.

Enlarging occult fibroadenomas.

From July 1, 1989, through June 30, 1991, 1,218 preoperative wire-localization breast biopsies were performed at one institution. In this group, 254 (21%) of the abnormalities were fibroadenomas, 26 of which had enlarged or developed in the interval between routine or short-interval follow-up mammography. This interval growth was noted in 21 premenopausal women and in five who were postmenopausal and receiving oral estrogen supplementation.

Computed tomography of angioedema of small bowel due to reaction to radiographic contrast medium.

Although urticaria and facial and peripheral edema are well recognized idiosyncratic reactions to ionic contrast medium, to our knowledge, isolated angioedema of the small bowel has not been reported previously. We present a case of acute onset of small bowel edema and ascites during the infusion of iodiated contrast medium.