Imaging of skeletal muscle function using (18)FDG PET: force production, activation, and metabolism.

The purpose of this study was to determine whether [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used to evaluate muscle force production, create anatomic images of muscle activity, and resolve the distribution of metabolic activity within exercising skeletal muscle. Seventeen subjects performed either elbow flexion, elbow extension, or ankle plantar flexion after intravenous injection of FDG. PET imaging was performed subsequently, and FDG uptake was measured in skeletal muscle for each task. A fivefold increase in resistance during elbow flexion increased FDG uptake in the biceps brachii by a factor of 4. 9. Differences in relative FDG uptake were demonstrated as exercise tasks and loads were varied, permitting differentiation of active muscles. The intramuscular distribution of FDG within exercising biceps brachii varied along the transverse and longitudinal axes of the muscle; coefficients of variation along these axes were 0.39 and 0.23, respectively. These findings suggest FDG PET is capable of characterizing task-specific muscle activity and measuring intramuscular variations of glucose metabolism within exercising skeletal muscle.

Morbidity and mortality following major penetrating liver injuries.

OBJECTIVE: To establish the mortality and morbidity associated with major penetrating liver injuries and to describe the nature and treatment of complications related to these injuries. We postulated that there had been a trend toward less radical initial surgery, as well as an increased utilization of modern imaging techniques in both diagnosing and treating postoperative complications following penetrating liver trauma. DESIGN: A retrospective survey of medical records and radiology files. SETTING: A university trauma center in an urban setting. PATIENTS: Of the 188 patients admitted to our trauma center with penetrating liver trauma between April 1988 and December 1991, 36 had major liver trauma (grades 3 through 5) and are described in this report. MAIN OUTCOME MEASURES: The mortality rate, type of operative treatment, and the nature and treatment of complications for each grade of major liver injury. RESULTS: The mortality rate from major liver injuries was 17%. Surgical techniques employed primarily consisted of the use of hemostatic agents and cautery, simple suturing, direct vessel ligation, and packing. Fifty-two percent of the survivors had major complications related to the liver injury itself, but only two required operative therapy. The remaining patients were successfully treated with interventional radiologic techniques. CONCLUSIONS: The morbidity and mortality following major penetrating liver injuries remain significant. The majority of hepatobiliary complications can be successfully managed without further surgery but require the combined efforts of the surgeon and interventional radiologist.

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.

Magnetic resonance imaging of postpartum pelvic hematomas: early experience in diagnosis and treatment planning.

The purpose of this study was to determine the utility of magnetic resonance imaging (MRI) in detecting and localizing clinically non-apparent postpartum pelvic hematomas, and to describe the therapeutic implications of MRI in these patients. MRI examinations were performed on seven women with pelvic pain and/or fullness following difficult vaginal deliveries. None had clinically evident hematomas, and none were scheduled for surgery. Hematomas in the pelvis were identified with conventional T1-weighted, and conventional and fast spin echo T2-weighted sequences. Intravenous contrast was not used. Pelvic hematomas were identified in contiguity with the vagina, cervix, and bladder, within the broad ligament, and in the presacral space. In two patients, hematomas were confined to the perivaginal and pericervical regions. In three patients, perivaginal hematomas extended between the double layers of the broad ligaments. In one patient, a perivaginal hematoma extended into the perivesical space. In one patient, a hematoma was identified only within the presacral space. Based on MRI as the only contributory imaging study, five patients were treated successfully with invasive means and two patients were managed successfully with conservative means. MRI successfully detects and localizes postpartum hematomas, information that often is unavailable from the clinical examination. This information facilitates decisions regarding the need for intervention and the appropriate type of procedure when intervention is necessary for this potentially life-threatening problem. We advocate the use of MRI to evaluate patients at risk for postpartum hemorrhage following difficult vaginal deliveries.

Unenhanced CT in the evaluation of urinary calculi: application of advanced computer methods.

Recent advances in computer hardware and software technology enable radiologists to examine tissues and structures using three-dimensional figures constructed from the multiple planar images acquired during a spiral CT examination. Three-dimensional CT techniques permit the linear dimensions of renal calculi to be determined along all three coordinate axes with a high degree of accuracy and enable direct volumetric analysis of calculi, yielding information that is not available from any other diagnostic modality. Additionally, three-dimensional techniques can help to identify and localize calculi in patients with suspected urinary colic.

Polyarteritis nodosa mimicking hepatic candidiasis on postcontrast CT.

We report a case in which lesions identical to those typical of hepatic candidal microabscesses were caused by polyarteritis nodosa, the recognition of which was essential to avoid potentially toxic therapy for candidiasis and for prompt initiation of successful therapy for progressing symptomatic arteritis.

Effects of niacin therapy that simulate neoplasia: hepatic steatosis with concurrent hepatic dysfunction.

Niacin, a widely used antihyperlipidemic agent, can produce hepatic steatosis and clinical hepatic abnormalities that together simulate the presentation of hepatobiliary neoplasia. We describe a patient initially suspected of having hepatobiliary neoplasia for whom imaging studies played a pivotal role in reaching the correct diagnosis of niacin-induced hepatotoxicity. Radiologists should become knowledgeable of these niacin-related effects, add niacin effects to the differential diagnosis of hepatic steatosis, and understand the value of correlative imaging in distinguishing these effects from hepatobiliary neoplasia.

Plain film clues to the diagnosis of spinal epidural neoplasm and infection.

Radiographs of 22 normal patients and 35 patients with proven epidural disease were correlated with CT scans to determine the range of normal and abnormal appearances of the osseous surfaces marginating the spinal canal. A subtle but useful plain film clue to early epidural disease was indistinctness of the posterior vertebral body margin, which in at least one case was the solitary radiographic sign of epidural metastasis. The radiographic distinctness of each of the bony margins of the spinal canal varied predictably with spinal level in normal individuals owing to systematic variations in obliquity. Indistinctness of an osseous spinal canal margin, interpreted with knowledge of the range of normal anatomy at the appropriate level, may provide the earliest plain film clue to the presence of spinal epidural disease.

AIDS risk and risk reduction in the radiology department.

As the AIDS epidemic progresses, concern about the risk of occupational transmission of the causative organism, human immunodeficiency virus (HIV), is increasing. In this article, we summarize the risk of occupational acquisition of HIV in the health care setting and specify protocol and equipment that can reduce this risk in the radiology department. Accidental needle-stick injury is the most common form of exposure to infected blood, which is the only body fluid implicated to date in the occupational transmission of HIV. Prospective cohort studies demonstrate a 0.3-0.4% risk of infection for each needle-stick event. The most important instruction to health care workers that can reduce this risk is the following: Do not recap needles. Other risk-reduction measures include the adoption of universal precautions against transmission of infectious disease; sharp-instrument precautions; the use of protective garb to prevent skin and mucous membrane contamination when blood or bloody body fluid may splash; the availability of stable, puncture-resistant disposal containers for sharp instruments; the exclusion of breakable glass syringes; and the accessibility of resuscitation equipment in all rooms in order to avoid direct mouth-to-mouth contact. These and other measures discussed here are designed to prevent exposure of skin or mucous membrane to blood. If exposure does occur, the contaminated area should be washed immediately. A multicenter research protocol to evaluate the effectiveness of zidovudine (AZT) therapy in preventing seroconversion after exposure to HIV-contaminated blood recommends AZT therapy after massive exposure (e.g., injection of measurable quantities of blood) and endorses it for serious parenteral exposure (e.g., deep needle sticks).

Flow quantification using low-spatial-resolution and low-velocity-resolution velocity images.

In this report, a flow-quantification method using Fourier velocity encoding (FVE) with limited spatial and velocity resolution is presented. The total flow rate in a vessel corresponds to the first moment of the velocity histogram of spins in the vessel, whereas the spin density of flowing spins is the normalization constant. Because the measured histogram using FVE is distorted by RF saturation effects, the RF saturation effects are first estimated and then accurately compensated by acquiring five velocity-encoded images. The spatial resolution in each image can be relatively low because all stationary spins vanish in the resultant flow map. In a phantom study, the errors in measured flow rates were within +/-10% even when the pixel size was greater than the vessel size. This method was also successfully applied to measure flow in the femoral artery. In general, this method constitutes a basis for analyzing multiple velocity-encoded images and is particularly useful for quantifying slow flow or flow in small vessels. Magn Reson Med 42:682-690, 1999.

Accuracy of detection and measurement of renal calculi: in vitro comparison of three-dimensional spiral CT, radiography, and nephrotomography.

PURPOSE: To compare accuracy of three-dimensional (3D) spiral computed tomography (CT) performed without administration of contrast material with that of radiography and linear nephrotomography in detection and measurement of renal calculi. MATERIALS AND METHODS: Fifty renal calculi within an abdominal phantom were imaged with 3D spiral CT, radiography, and linear nephrotomography. Spiral CT data were analyzed with workstation-based 3D imaging software, with a thresholding procedure based on the maximally attenuating voxel within each calculus during measurement. Measurement accuracy and detection rates were compared according to modality. Conventional and magnification-corrected measurements from radiography and linear nephrotomography were included. RESULTS: Spiral CT depicted calculi and allowed determination of the collective two-dimensional and 3D linear measurements statistically significantly more accurately than the other techniques; the mean linear measurement errors along individual axes did not exceed 3.6%. With 3D spiral CT, calculus volumes were determined with a mean error of -4.8%. CONCLUSION: 3D spiral CT enabled highly accurate determination of the volumes and all three linear dimensions of renal calculi. In addition, 3D spiral CT depicted calculi more sensitively than traditional techniques and provided new information and improved accuracy in the evaluation of nephrolithiasis.

Detection of active intraabdominal arterial hemorrhage: value of dynamic contrast-enhanced CT.

Contrast-enhanced dynamic CT was used prospectively to diagnose and locate the site of active arterial intraabdominal hemorrhage in 18 patients. Active arterial extravasation was confirmed by angiography in five patients and by immediate surgery in nine. Two patients not undergoing surgery or angiography required multiple blood transfusions to correct rapidly falling hematocrit due to a coagulopathy. One patient died of hypovolemic shock, and autopsy confirmed a large acute retroperitoneal hematoma. Another patient with a splenic laceration and massive hemoperitoneum on CT had no active bleeding at the time of surgery, which was delayed 1 hr from the time of the CT. All patients were clinically thought to be hemodynamically stable and had systolic blood pressures greater than 110 mm Hg at the time of CT. In seven patients, hypotension developed either during (two patients) or immediately after (five patients) CT scanning, necessitating either immediate surgery or angiographic embolization. Contrast-enhanced dynamic CT is valuable in the diagnosis and localization of active arterial intraabdominal hemorrhage. Identification of the anatomic site of this potentially life-threatening hemorrhage is critical in determining whether immediate laparotomy or angiographic embolization is the preferred method of treatment.

Dual-phase helical CT of locally invasive pancreatic adenocarcinoma.

Dual-phase helical CT permits imaging of the pancreas and the peripancreatic structures in the arterial dominant and portal venous phases of enhancement, providing information crucial in the assessment of the local extent of pancreatic adenocarcinoma. This essay reviews the dual-phase helical CT findings of local extension that preclude potentially curative surgery, including vascular involvement, ligamentous or mesenteric invasion, extension of the tumor to involve the stomach or duodenum, and invasion of adjacent solid organs.

Power versus color Doppler sonography of the normal cystic artery: implications for patients with acute cholecystitis.

OBJECTIVE: The purposes of this investigation were to compare prospectively the pattern and extent of cystic artery flow revealed by power Doppler sonography and color Doppler sonography in patients with normal gallbladders and to analyze the potential implications of these findings for power Doppler sonography in diagnosing acute cholecystitis. SUBJECTS AND METHODS: The cystic arteries of 142 patients (79 women and 63 men) with normal gallbladders were imaged with both power Doppler sonography and color Doppler sonography using 5-MHz transducers and settings optimized to reveal low-volume flow. The presence or absence of cystic artery flow and the anatomic extent of its visualization were recorded for each patient. RESULTS: Power Doppler sonography revealed flow in 73% of patients with normal gallbladders compared with 53% revealed by color Doppler sonography. Cystic artery flow within the distal fundal quartile was revealed by power Doppler sonography in 20% of patients and flow spanning greater than 50% of the anterior gallbladder wall was revealed by power Doppler sonography in 17% of patients. These findings differed from those of color Doppler sonography at a highly significant level (p < .0001, chi-square test). CONCLUSIONS: Power Doppler sonography is significantly more sensitive than color Doppler sonography for revealing cystic artery flow in patients with normal gallbladders. The flow patterns in patients with normal gallbladders obtained with power Doppler sonography overlap flow patterns previously reported as fairly specific criteria for diagnosing acute cholecystitis using color Doppler sonography, namely, flow within the distal fundal quartile and flow spanning greater than 50% of the anterior gallbladder wall. Accordingly, these color Doppler sonography criteria are not applicable to the diagnosis of acute cholecystitis with power Doppler sonography. Different power Doppler sonography criteria are necessary for the diagnosis of acute cholecystitis.

Improved 2D time-of-flight angiography using a radial-line k-space acquisition.

For flow imaging applications, radial-line k-space acquisition methods offer advantages over conventional 2DFT methods. Specifically, radial-line acquisition methods mitigate artifacts resulting from pulsatile flow while offering a potential reduction in scan times. In this paper, radial-line and 2DFT acquisitions are compared in a two-dimensional time-of-flight angiography sequence. The twisting radial-line (TwiRL) trajectory, a variant of 2D projection reconstruction, is used to represent the family of radial-line trajectories. In both phantom and in vivo studies, the TwiRL images demonstrate improved vessel depiction including a more uniform signal intensity and better delineation of the vasculature in comparison with images obtained via the 2DFT method.

Liver tumors: utility of characterization at dual-frequency US.

PURPOSE: To evaluate the potential utility of a technique for analysis of ultrasonographic (US) images obtained at two center frequencies in a phantom model and in a clinical study of liver tumors. MATERIALS AND METHODS: A US phantom was built that contained target regions with polystyrene scatterers both smaller and larger than scatterers in the background material. High- and low-frequency US images of target regions were obtained, and changes in the contrast-to-noise ratio (CNR) of the targets relative to the background were determined. In a clinical evaluation, 12 hemangiomas, 13 liver metastases, one adenoma, and two hepatomas were evaluated in a similar manner, and the results were correlated with the histologic findings in resected lesions. RESULTS: For targets containing scatterers smaller than those in the background, there was an increase in CNR of higher frequency images. The converse was true for target regions having scatterers larger than those in the background. Liver metastases generally showed an increase in CNR of higher frequency images, whereas hemangiomas generally showed somewhat decreased CNR of higher frequency images, differing significantly from metastases (P < .01-.001). CONCLUSION: Changes in CNRs of relatively high- and low-frequency US images may give useful information on the frequency dependence of backscattering, which is descriptive of the histologic findings in lesions and which is not evident with conventional US images.

The injection technique for repositioning central venous catheters: technical note.

Malpositioned central venous catheters must be repositioned in order to avoid damage caused by concentrated or irritating infusates. Floppy catheters may be repositioned rapidly with a brisk injection of fluid. The ease of this technique, with its anticipated low risk of infection, makes it an attractive alternative to manipulation using guidewires.

Urinary bladder pseudolesions on contrast-enhanced helical CT: frequency and clinical implications.

OBJECTIVE: The goals of this study were to define the distinguishing characteristics and frequency of urinary bladder pseudolesions that are produced as opacified urine enters the bladder during contrast-enhanced helical CT of the abdomen and to evaluate the usefulness of delayed imaging in differentiating pseudolesions from true lesions. SUBJECTS AND METHODS: Contrast-enhanced routine CT scans of 184 patients were obtained prospectively. For each patient, we also obtained 5-min delayed images of the bladder. The images were evaluated for apparent focal thickening or polypoid lesions involving the bladder wall, findings that may represent bladder neoplasia, without knowledge of the indications for the scan, the patient's clinical history, or the patient's diagnosis. Apparent lesions that were visible on routine images and entirely absent on delayed images were considered to be pseudolesions. RESULTS: Apparent lesions were identified on 20 (10.9%+/-4.5% [limits of the 95% confidence interval]) of the routine CT scans. Using delayed images, the 21 apparent lesions in these 20 patients were resolved as 13 pseudolesions and eight true lesions. Pseudolesions were present in 6.5%+/-3.6% of patients. CONCLUSION: Pseudolesions of the bladder that are indistinguishable from true lesions pose a significant clinical problem in routine contrast-enhanced helical CT of the abdomen. Delayed imaging of the bladder is useful in distinguishing pseudolesions from true lesions.

Catheter tract hemorrhage during percutaneous biliary intervention: management with use of a retained transhepatic guide wire.

PURPOSE: The authors present their experience in managing freely flowing hemorrhage from immature catheter tracts in patients undergoing biliary drainage. PATIENTS AND METHODS: Transhepatic guide wires were maintained securely whenever catheters were removed from the liver. Six patients among 71 hemorrhaged profusely when drains were manipulated within 4 days of initial catheterization. Management was attempted with use of the transhepatic guide wires. RESULTS: Maneuvers performed over the retained guide wire controlled bleeding in all six patients. Reintubation constituted definitive therapy in five patients. A biliary-portal venous fistula in the remaining patient was treated with thrombin. The retained guide wire proved necessary in all cases. CONCLUSION: Hemorrhage from immature catheter tracts can be managed, often definitively, with maneuvers performed over a retained transhepatic guide wire. Accordingly, a secure transhepatic guide wire is essential prior to removal of hepatic catheters and should remain in place until the absence of bleeding is established. These maneuvers may become increasingly important as courses of biliary catheterization become shorter.