Experimental hepatic tumor necrosis. Comparison of spin-echo and pulsed magnetization transfer contrast magnetic resonance imaging.

RATIONALE AND OBJECTIVES: We compared the effectiveness of pulsed magnetization transfer contrast (MTC) magnetic resonance imaging (MRI) and spin-echo MRI in detecting tumor necrosis. METHODS: Adenocarcinoma cells were transplanted in the livers of 12 syngenic BDIX rats. To induce various degrees of tumor necrosis, the rats were randomly assigned to the following groups: 1) control; 2) localized hyperthermia; 3) intralesional cisplatin; and 4) hyperthermia plus intralesional cisplatin. At day 7 after treatment, the rats were imaged using a 1.5-T imager with 1) multiplanar gradient-recalled echo sequence (MPGR) 500/8/20 degrees with and without magnetization transfer contrast (MTC); 2) spin-echo 2500/20,80, and 3) spin-echo 300/20 pulse sequences. The rats were then sacrificed and pathologic specimens were prepared using MR images as guidance. T2 and ratios of signal intensity after saturation to signal intensity before saturation (Ms/Mo ratios) of the necrotic and granulation tissues and viable tumors were determined in 10 rats. RESULTS: Compared with standard MPGR images, MPGR images with MTC provided better contrast between the pathologic tissues and normal liver. However, T2 values were more useful than Ms/Mo ratios in distinguishing necrotic areas from viable tumor. The T2 values of coagulative necrosis and granulation tissue were significantly different from that of viable tumor. No significant difference between the Ms/Mo ratios of the different pathologic tissues and normal liver was found. CONCLUSION: Pulsed magnetization transfer contrast MRI was inferior to spin-echo MRI in distinguishing necrotic from viable tumors in rat livers using the pulse sequences described, and none of the sequences studied was thought to be reliable enough for this purpose.

Intraoperative ultrasonography for localization of recurrent thyroid cancer.

Advances in measurement of thyroglobulin (Tg) and in imaging techniques including high resolution ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET) scan have increased our ability to detect thyroid cancer recurrences at an earlier stage. (1,2) After thyroidectomy, patients are often treated with radioiodine, but the recurrent cancers may not image with radioiodine. In these instances, the only definitive treatment is surgical resection. Reoperative neck surgery can be challenging, especially when trying to find a small cancer nodule within the central neck that contains dense fibrotic scar tissue. Herein we describe the use of intraoperative ultrasonography to identify the location of recurrent thyroid cancer. This technique can aid in tumor localization and may help to avoid complications such as recurrent nerve injury.

Magnetic resonance imaging and hepatic hemodynamics: correlation with metabolic function in liver transplantation candidates.

BACKGROUND: Preoperative assessment of orthotopic liver transplantation candidates requires definition of both the anatomy and metabolic function of the native liver. Current evaluation techniques combine computed tomographic scanning, duplex ultrasonography with blood chemistry analysis, and physical stigmata of end-stage liver disease. Recently, magnetic resonance imaging (MRI) has emerged as an alternative method for delineation of hepatic and portal venous anatomy. In addition, MRI accurately measures hepatic volume and portal venous blood flow. METHODS: To examine the role of MRI-derived indexes of hepatic hemodynamics in the preoperative assessment of liver function, 39 consecutive liver transplantation candidates were studied in a prospective manner. Liver function (aspartate aminotransferase), alanine aminotransferase, alkaline phosphatase, total bilirubin, and albumin levels), hematologic indexes (complete blood cell count, prothrombin time), and Child's classification were determined at the time of evaluation. Axial breath-held multiplanar spoiled-gradient echo MRI measured hepatic volume, whereas a cine phase-contrast sequence perpendicular to the portal vein measured flow. RESULTS: Hepatic index, defined as hepatic mass corrected for body surface area, was found to correlate with prothrombin time (p < 0.04) and platelet count (p < 0.03) by multivariate regression analysis. Portal flow index (PFI), defined as portal flow corrected for hepatic mass), was associated with aspartate aminotransferase (p < 0.02), alanine aminotransferase (p < 0.04), and albumin (p < 0.03) by multivariate regression analysis. In addition, PFI was closely correlated with the patients' functional status as determined by Child's classification system. Increasing values of PFI were associated with declining hepatic functional reserve. Child's class A patients had a mean PFI that was two times less than that of Child's class B patients (0.26 +/- 0.04 versus 0.04 +/- 0.06 ml/min/gm; p < 0.02) and five times less than that of Child's class C patients (0.26 +/- 0.04 versus 1.05 +/- 0.14 ml/min/gm; p < 0.001). Similarly, the mean PFI associated with Child's class B was two times less than that of Child's class C (0.46 +/- 0.06 versus 1.05 +/- 0.14 ml/min/gm; p < 0.01). These data show that MRI-derived indexes of portal hemodynamics and hepatic mass (1) correlate well with biochemical indexes of hepatic dysfunction and (2) serve as anatomic and hemodynamic correlates to Child's functional classification. CONCLUSIONS: We conclude that MRI may serve to noninvasively delineate preoperative hepatic vascular anatomy and metabolic dysfunction in candidates undergoing examination for liver transplantation.

Computed tomography in blunt abdominal trauma.

Emergency abdominal computed tomography (CT) has been performed in more than 200 cases of acute blunt abdominal trauma. Computed tomography was highly sensitive and specific for a wide variety of intraperitoneal and retroperitoneal traumatic lesions. There were no false-positive or false-negative CT interpretations, except for a single case in which residual peritoneal lavage fluid was mistaken for intraperitoneal blood. Computed tomobraphy has major advantages over otherradiologic techniques, including angiography, and may obviate peritoneal lavage and explo4atory laparatomy in some circumstances.

Selective nonoperative management of blunt liver injury using computed tomography.

Computed tomographic (CT) scans are used to evaluate victims of blunt trauma for abdominal injury when reasons for immediate laparotomy are not present. Twenty-four patients whose CT scans showed liver injuries that were small parenchymal lacerations or intrahepatic hematomas were managed without laparotomy. Intra-abdominal blood was absent or estimated to be less than 250 mL in volume. None of the patients were in shock; six patients required transfusions, none for acute abdominal bleeding. None of these patients subsequently required laparotomy or showed hepatobiliary problems at a follow-up examination less than one year later. Five follow-up scans showed varying degrees of resolution. Two patients died of severe head injury, but the liver injury did not contribute to the cause of death. Other patients with more severe blunt liver injury who were treated nonoperatively developed significant complications that required delayed surgery. It seems that patients with limited liver injury diagnosed by CT scan and selected by strictly applied criteria can be managed safely without laparotomy in a setting where rapid evaluation and treatment of any potential complication is available.

Parathyroid localization with high-resolution ultrasound and technetium Tc 99m sestamibi.

HYPOTHESIS: High-resolution ultrasound and technetium Tc 99m sestamibi scanning can be used for preoperative localization of abnormal parathyroid glands in patients with hyperparathyroidism. DESIGN: Ultrasound and sestamibi scanning were performed in patients undergoing neck exploration for hyperparathyroidism. If the 2 scans agreed in identifying a single adenoma, and surgery confirmed the location of a single adenoma and an ipsilateral normal gland, a unilateral exploration was performed. SETTING: University tertiary care center. PATIENTS: Sixty-one consecutive patients undergoing surgery for hyperparathyroidism from September 1, 1994, through September 30, 1997. INTERVENTIONS: High-resolution ultrasound was performed in 59 patients and sestamibi scanning in 58 patients; all patients underwent neck exploration by a single surgeon. MAIN OUTCOME MEASURES: The results of preoperative ultrasound and sestamibi scanning were compared with operative and histological findings. RESULTS: All patients were cured of hypercalcemia. Specificity of ultrasound and sestamibi scanning was 98% and 99%, respectively; however, their sensitivity was only 57% and 54%, respectively. Both imaging modalities had lower sensitivities in the setting of multigland disease. If both imaging studies were considered as a single test, sensitivity for imaging in patients with primary hyperparathyroidism reached 78%. Our localization protocol allowed a unilateral approach in 43% of patients (23 of 53). CONCLUSIONS: These results confirm the value of preoperative localization in patients with hyperparathyroidism. A unilateral approach can be used with a high degree of success in cases when ultrasound and sestamibi scanning agree in the identification of a single adenoma confirmed by surgical exploration with the identification of a normal ipsilateral gland.

Adnexal torsion: color Doppler diagnosis and laparoscopic treatment.

The present case documents normalization of ovarian perfusion after conservative laparoscopic treatment of adnexal torsion. At our institution, Doppler flow assessment in cases of suspected torsion represents an important element of diagnosis and, in this case, allowed for early diagnosis with conservative laparoscopic treatment with documented normalization of ovarian flow postoperatively.

CT with image reformation for noninvasive screening of the carotid bifurcation: early experience.

Twenty-two cervical carotid artery bifurcations were evaluated in 11 patients using a high-resolution computed tomographic (CT) technique with image reformation permitting display of the bifurcation anatomy. Arteriography was also done in eight of the patients, two of whom subsequently underwent carotid endarterectomy. The CT study showed patency of the proximal internal carotid artery in every case and depicted significant stenosis of four vessels. Thrombus within a large ulcer was seen in one vessel on CT, but another shallow ulcer found on angiography was missed. Although the data are limited, this preliminary experience suggests a possible role for this technique in carotid bifurcation screening and indicates further investigation may be worthwhile.

Automated flight path planning for virtual endoscopy.

In this paper, a novel technique for rapid and automatic computation of flight paths for guiding virtual endoscopic exploration of three-dimensional medical images is described. While manually planning flight paths is a tedious and time consuming task, our algorithm is automated and fast. Our method for positioning the virtual camera is based on the medial axis transform but is much more computationally efficient. By iteratively correcting a path toward the medial axis, the necessity of evaluating simple point criteria during morphological thinning is eliminated. The virtual camera is also oriented in a stable viewing direction, avoiding sudden twists and turns. We tested our algorithm on volumetric data sets of eight colons, one aorta and one bronchial tree. The algorithm computed the flight paths in several minutes per volume on an inexpensive workstation with minimal computation time added for multiple paths through branching structures (10%-13% per extra path). The results of our algorithm are smooth, centralized paths that aid in the task of navigation in virtual endoscopic exploration of three-dimensional medical images.

Sonography in acute pancreatitis.

Noninvasive imaging of the pancreas with sonography and computed tomography has proven to be a major diagnostic advance. This article focuses on the unique contribution of sonography in acute pancreatitis, emphasizing patient selection, scanning technique, and newer sonographic observations regarding extrapancreatic spread of acute pancreatitis. The limitations of sonographic imaging in acute pancreatitis are reviewed and compared with computed tomography.

Abdominal imaging in the immunocompromised patient.

Abdominal and gastrointestinal disease may result in clinically important complications in immunocompromised patients. The major types of disease are opportunistic infections and immunodeficiency-associated neoplasms. A multimodality approach is often essential in the diagnosis and staging of these lesions. A combination of bacteriologic culture, endoscopy, barium studies, and cross-sectional imaging of the abdomen with computed tomography and sonography is required to assess the extent of the disease accurately.

Sonography of acute scrotal abnormalities.

Accurate diagnosis in patients with acute scrotal abnormalities remains a challenge to both radiologists and clinicians. Sonography using either small parts scanners or conventional equipment available in almost all departments will continue to play a larger role in aiding the clinical assessment of these patients. As a rapid, noninvasive imagining technique, sonography can reliably answer important clinical questions and guide prompt, early surgical or medical therapy.

CT and ultrasonography of acute renal abnormalities.

Computed tomography and ultrasonography are important in the evaluation of patients with acute renal abnormalities, either as adjuncts or, less commonly, as alternatives to excretory urography. Ultrasonography has become the imaging procedure of choice in evaluation of acute renal failure. Detection of obstructive uropathy by ultrasonography is very accurate, although the potential pitfalls of minimal dilatation obstructive uropathy, false absence of caliectasis in dehydrated patients, and peripelvic cysts simulating hydronephrosis should be considered. Both CT and ultrasonography have improved our ability to define specific causes of intrinsic or extrinsic renal or ureteral obstructing lesions, including tumor, inflammatory masses, and calculi. Renal infections and infarctions also have characteristic appearances on CT and ultrasonography, though ultrasonography is somewhat limited by its inability to reliably demonstrate gas-containing or small abscesses, and its inability to provide functional information about the concentrating capacity of regional areas of the kidney.

Imaging of blunt hepatic trauma.

This article focuses on the clinical role of high resolution computed tomography (CT) in the initial diagnosis and management of hemodynamically stable patients with blunt hepatic trauma. The increased utilization and diagnostic confidence afforded by CT has dramatically changed the surgical approach and need for laparatomy. The most important development has been the growing realization by many trauma surgeons that nonoperative management is often successful in stable patients who have CT evidence of isolated blunt hepatic trauma.

Sonography of appendicitis and diverticulitis.

Graded compression sonography has gained widespread acceptance as a useful technique to evaluate patients with atypical signs and symptoms of appendicitis. When positive, early surgery can be performed prior to perforation. When there is no sonographic evidence of appendicitis, other alternative diagnoses may be established. CT scans and the contrast enema remain the primary imaging modalities to evaluate suspected diverticulitis; however, sonography may be useful in selected patients with an atypical clinical presentation.

Ultrasound evaluation of ectopic pregnancy.

The combined use of a serum radioimmunoassay pregnancy test and high resolution utrasonography allows a more direct approach to be made in the diagnosis of ectopic pregnancy. It is important for ultrasonographers to understand the limitations of the more readily available immunologic pregnancy tests in order to avoid misinterpreting ultrasonograms in the event that a pregnancy test is either falsely positive or falsely negative. Clinical suspicion is mandatory if the early diagnosis of ectopic pregnancy is to be made. The referring physician should take advantage of the highly accurate information resulting from the combined findings of a positive serum HCG and the ultrasonographic images. If the statistics regarding diagnostic delay and tubal rupture are to be improved, these tests should be obtained when a patient is initially evaluated. It is important to recognize that the ultrasonographic interpretation rests primarily upon the uterine findings. A normal viable intrauterine pregnancy essentially excludes the diagnosis of ectopic pregnancy. Other uterine appearances may result from an early intrauterine pregnancy, an abnormal intrauterine gestational event, or, as in approximately 1 per cent of pregnancies, an ectopic gestation. Subsequent evaluation in suspicious cases may require a variety of tests including serial HCG determinations, repeat ultrasound examination, uterine dilatation and curettage, culdocentesis, or laparoscopy. It is impossible to recommend a specific schematic approach for any given patient. In part, the pattern of management depends upon availability of tests, the presence or absence of adnexal or cul-de-sac findings, and, of course, the clinical status of the patient.U

Ultrasound-guided fine-needle aspiration biopsy of thyroid masses.

The purpose of this study was to determine the impact of ultrasound-guided fine-needle aspiration biopsy (USFNA) in the cytological diagnosis of nodular thyroid disease. It remains unclear exactly what role USFNA should play in the cytological diagnosis of nodular thyroid disease. All patients who underwent fine-needle aspiration (FNA) for nodular thyroid disease at Stanford University Medical Center from 1991 to 1996 were included in the study. Histopathologic diagnoses were compared to cytological diagnoses for those patients who underwent surgery. FNA was performed on a total of 497 thyroid nodules. Palpation-guided FNA (pFNA) was performed on 370 nodules, and USFNA was done on 127. The USFNAs were performed for the following reasons: 95 (75%) for nonpalpable or difficult-to-palpate nodules; 14 (11%) for previously failed FNA; and 18 (14%) for incidentally detected nodules. FNA had an unsuccessful biopsy rate of 16% and a sensitivity and specificity of 89% and 69%, respectively. USFNA had an unsuccessful biopsy rate of 7% and a sensitivity and specificity of 100% and 100%, respectively. The cancer yield at surgery for pFNA was 40%, and the cancer yield at surgery for USFNA was 59%. The complementary use of USFNA with pFNA improves the diagnostic approach to nodular thyroid disease. The use of USFNA has increased the cancer yield at surgery and the sensitivity of thyroid biopsy at our institution.

A statistical 3-D pattern processing method for computer-aided detection of polyps in CT colonography.

Adenomatous polyps in the colon are believed to be the precursor to colorectal carcinoma, the second leading cause of cancer deaths in United States. In this paper, we propose a new method for computer-aided detection of polyps in computed tomography (CT) colonography (virtual colonoscopy), a technique in which polyps are imaged along the wall of the air-inflated, cleansed colon with X-ray CT. Initial work with computer aided detection has shown high sensitivity, but at a cost of too many false positives. We present a statistical approach that uses support vector machines to distinguish the differentiating characteristics of polyps and healthy tissue, and uses this information for the classification of the new cases. One of the main contributions of the paper is the new three-dimensional pattern processing approach, called random orthogonal shape sections method, which combines the information from many random images to generate reliable signatures of shape. The input to the proposed system is a collection of volume data from candidate polyps obtained by a high-sensitivity, low-specificity system that we developed previously. The results of our ten-fold cross-validation experiments show that, on the average, the system increases the specificity from 0.19 (0.35) to 0.69 (0.74) at a sensitivity level of 1.0 (0.95).

Pancreatic abscess: impact of computerized tomography on early diagnosis and surgery.

Pancreatic abscess continues to be a lethal complication of acute pancreatitis, with mortality rates of 40 percent in recent surgical series. A major factor contributing to this high mortality has been delay in diagnosis. When combined with diagnostic needle aspiration, computerized tomographic scanning has greatly enhanced the early detection of pancreatic abscesses. In a 4 year period at our institutions, 21 patients with proved pancreatic abscesses were evaluated early in their clinical course by computerized tomography. On follow-up ranging from 7 months to 3 1/2 years, there were only four deaths for a mortality rate of 19 percent. Many of the surviving patients had a long and protracted clinical course (mean length of hospitalization was 56 days) and reoperation for recurrent abscess or gastrointestinal complications was required in eight patients (38 percent). Computerized tomography proved to be of considerable value in localizing the site of de novo or recurrent pancreatic abscess and in detecting postoperative complications. An aggressive approach encompassing early computerized tomographic scanning with diagnostic needle aspiration appears to be a factor in the improved survival rate of these patients.

Radiologic techniques in the treatment of the critically ill trauma patient.

Discussed in this article are portable chest x-ray for imaging abnormalities in pulmonary aeration, pleural disease, and the position of life-support apparatus and abdominal computed tomography and ultrasonography.