Scan length optimization for pulmonary embolism at CT angiography: analysis based on the three-dimensional spatial distribution of 370 emboli in 100 patients.

AIM: To determine the size and three-dimensional spatial distribution of pulmonary emboli (PE) at computed tomography angiography (CTA) to optimize the scan length. MATERIALS AND METHODS: Two experienced radiologists jointly reviewed 100 consecutive, positive PE CTA studies performed in the Emergency Department (53 women; age 61±17 years). All studies were conducted on a 16-detector row CT machine. In each case, the number of emboli was counted and the proximal and distal spatial coordinates of each embolus documented. Coordinates of the main pulmonary artery bifurcation (MPAb) and carina were recorded. For normalization, the thoracic cavity height (H)-from inlet to lowest hemidiaphragm-was measured. The minimal scan lengths for (a) capturing all emboli and (b) rendering a positive diagnosis were determined. RESULTS: Three hundred and seventy (370) emboli were detected. The average number of PE per patient was 3.7 (maximum 12, minimum 1). Their average length was 2.7 cm. Nine patients had saddle emboli (9%), and 71% of emboli were at or below the MPAb. An 18 cm (0.90×H) scan length, centred 4 cm (0.18×H) below the carina, captures all PE in this dataset while reducing z-axis coverage by 29% (34% for normalized data). Moreover, a 14.2 cm (0.78×H) scan length appropriately centred captures at least one embolus in all patients while reducing coverage by 44% (43%). Decreasing scan length to the lesser of 14.2 cm and 0.78×H per patient reduces coverage by 47%. CONCLUSION: Scan length at CTA for PE can be reduced by up to 47% while preserving diagnostic accuracy for PE detection.

Fibrin sheath stripping versus catheter exchange for the treatment of failed tunneled hemodialysis catheters: randomized clinical trial.

PURPOSE: To compare the effectiveness of two treatments for tunneled hemodialysis catheter malfunction: percutaneous fibrin sheath stripping (PFSS) and over-the-wire catheter exchange (EX). MATERIALS AND METHODS: Adult patients with poorly functioning tunneled hemodialysis catheters (flow rates < 200 mL/min) were randomly assigned to receive either PFSS or EX. Over the course of 20 months, 30 patients (37 encounters) referred to a single institution met the inclusion criteria and consented to participate. PFSS employed transcatheter snares via femoral vein puncture, whereas EX was performed over a guide wire with use of fluoroscopic guidance. Patients were followed up to determine the duration of continued adequate hemodialysis via manipulated catheters for up to 4 months (primary outcome measure). RESULTS: Overall technical success rate was 97%. Mean catheter patency for the PFSS group was 24.5 +/- 29.3 days, and 52.2 +/- 43 days for the EX group (P < .0001). After EX, patency rates at 1, 2, 3, and 4 months were 71%, 33%, 27%, and 27%, compared to 31%, 16%, 7%, and 0% after PFSS (P = .04, logrank test). Exchanged catheters were significantly more likely to be patent for as long as 4 months (23% versus 0%; P < .05, chi2 test). CONCLUSIONS: Malfunctioning tunneled hemodialysis catheters treated by means of EX are significantly more likely to remain patent for up to 4 months than are those treated by means of PFSS. According to the results of this trial, PFSS should not be performed as a routine therapy for catheter malfunction.

Embolotherapy of large pulmonary arteriovenous malformations: long-term results.

BACKGROUND: The purpose of this study was to document the long-term results of transcatheter embolotherapy of large pulmonary arteriovenous malformations (PAVMs). METHODS: From a data base of 221 consecutive patients with PAVMs treated by embolotherapy between 1978 and 1995, 45 patients with 52 PAVMs, supplied by feeding arteries 8 mm in diameter or larger, were selected for a retrospective investigation. RESULTS: Of 45 patients with 52 large PAVMs, 38 patients (84%) with 44 PAVMs (85%) were cured by the first embolotherapy (mean follow-up, 4.7 years). Acute periprocedural complications included self-limited pleurisy (31%), angina secondary to air embolus (2%), and paradoxical embolization of a device during deployment (4%). None of these events led to short- or long-term sequelae. Seven patients (16%) had persistence of the PAVM attributable to either recanalization (n = 4) or interim accessory artery growth (n = 3). Two of these patients presented with ischemic stroke several years after the initial treatment. Persistent PAVMs (n = 8) were retreated successfully by a second procedure (n = 7), or a third procedure (n = 1) (mean follow-up, 5.9 and 5.3 years, respectively). CONCLUSIONS: Embolotherapy of large PAVMs results in permanent occlusion in an overwhelming majority of patients. Continued patency due to recanalization or accessory artery growth is easily detected and treated.

Cost-effectiveness of stereotactic core needle biopsy: analysis by means of mammographic findings.

PURPOSE: To determine the cost savings of stereotactic core needle biopsy over open surgical biopsy in patient subgroups defined according to mammographic findings. MATERIALS AND METHODS: From July 1992 through February 1995, stereotactic core needle biopsy was performed in 356 women with 405 nonpalpable breast lesions (254 were masses and 151 were calcification). Lesions were classified according to mammographic finding, size, and level of suspicion. Two hundred three lesions were classified as indeterminate, 166 as suspicious, and 36 as highly suspicious. Medicare reimbursements for 1995 were used to determine costs and cost savings. RESULTS: Overall cost savings for stereotactic core biopsy over open surgical biopsy was $741 per case. Average cost savings per case was $807 for masses and $630 for calcifications. The greatest savings occurred in the cases of indeterminate masses, with an average of $856 saved per case. The least savings occurred in the cases of highly suspicious calcifications, with $446 saved per case. CONCLUSION: Cost savings of stereotactic core needle biopsy vary in subgroups of patients defined according to mammographic findings. Over-all savings will depend on the distribution of patients among these groups. In this series, cost savings were realized with stereotactic core biopsy over open surgical biopsy for all mammographic subgroups.

Replacement of accidentally removed tunneled venous catheters through existing subcutaneous tracts.

PURPOSE: The authors describe their experience with reinsertion of accidentally removed tunneled venous catheters using existing subcutaneous tracts. MATERIALS AND METHODS: Replacement of 13 dislodged tunneled venous catheters was attempted a median of 12 hours (range, 3 hours to 5 days) after accidental removal. The catheters were needed for hemodialysis (n = 11), plasmapheresis (n = 1), or antibiotic therapy (n = 1). The tunnel exit was probed in the same fashion as for a dislodged nephrostomy tube, and new catheters were reinserted once a guide wire was advanced into the central veins. The medical record was reviewed to determine materials used and occurrence of complications, if any. RESULTS: Replacement was successful in 12 of 13 patients. The remaining patient had a new catheter placed through a fresh puncture during the same visit. There were no infections associated with re-use of existing tunnels. In five patients, after probing the tract with a guide wire, new catheters were simply advanced into the desired position. Seven other successes required additional manipulations with use of dilators and peel-away sheaths. CONCLUSIONS: Tunneled catheters that "fall out" can be readily replace even when reinsertion is attempted up to 5 days later. This represents an important contribution that radiologists can offer in the management of venous access cases.

Context bias. A problem in diagnostic radiology.

OBJECTIVE: To determine whether radiologists' interpretations of images are biased by their context and by prevalence of disease in other recently observed cases. METHODS: A test set of 24 right pulmonary arteriograms with a 33% prevalence of pulmonary emboli (PE) was assembled and embedded in 2 larger groups of films. Group A contained 16 additional arteriograms, all showing PE involving the right lung, so that total prevalence was 60%. Group B contained 16 additional arteriograms without PE so that total prevalence was 20%. Six radiologists were randomly assigned to see either group first and then "cross over" to review the other group after a hiatus of at least 8 weeks. The direction of changes in a 5-point rating scale for the 2 readings of each film in the test set was compared with the sign test; mean sensitivity, specificity, and areas under receiver operating characteristic (ROC) curves were compared with the paired t test. RESULTS: In the context of group A's higher disease prevalence, radiologists shifted more of their diagnoses toward higher suspicion than expected by chance (P=.03, sign test). In group A, mean sensitivity for diagnosing PE was significantly higher (75% vs 60%; P=.04), and area under the ROC curve was significantly larger (0.88 vs 0.82; P=.02). CONCLUSIONS: Radiologists' diagnoses are significantly influenced by the context of interpretation, even when spectrum and verification bias are avoided. This "context bias" effect is unique to the evaluation of subjectively interpreted tests, and illustrates the difficulty of obtaining unbiased estimates of diagnostic accuracy for both new and existing technologies.

Renal artery pseudoaneurysm after blunt abdominal trauma: case report and literature review.

Renal vascular injuries such as transection, thrombosis, dissection, and arteriovenous fistula formation are unusual but well-recognized consequences of blunt abdominal trauma. We discuss a rare case of renal artery pseudoaneurysm presenting 6 weeks after blunt abdominal trauma that was successfully treated with selective embolization.

The case for better research standards in peripheral thrombolysis: poor quality of randomized trials during the past decade.

RATIONALE AND OBJECTIVES: We assessed how well published randomized controlled trials (RCTs) of peripheral thrombolysis have been designed and how they adjusted for patient characteristics that may influence responses to therapy. METHODS: RCT studies published between 1984 and 1994 were reviewed to determine whether they included nine crucial elements: sample size calculations, description of unenrolled eligible participants, homogeneous samples, balanced experimental groups, equal potency therapies, equal follow-up of outcomes, appropriate statistical inference, multivariable or subgroup analyses, and anonymous review of subjective endpoints. RESULTS: The nine RCTs complied with a median of three of nine standards (range = 2-6). Each report exhibited serious flaws that may affect generalizability and external validity. None adequately adjusted for sample heterogeneity or sought to identify characteristics that may affect responses to therapy. CONCLUSION: Failure to address prognostic or confounding variables restricts the utility of peripheral thrombolysis RCTs and helps explain why contentious debates about this therapy persist. A model for future thrombolysis trials is proposed.

Complications of peripheral arteriography: a new system to identify patients at increased risk.

PURPOSE: The most quoted literature on arteriographic complications is based on self-reports collected during the mid 1970s. We sought to determine whether those results remain valid despite changes in arteriographic practice and whether patient subgroups at increased risk could be identified. METHODS: Five hundred forty-nine consecutive patients were examined after arteriography and twice over 72 hours. Patients were telephoned at least 2 weeks later to identify delayed complications. The sample was divided into two groups to allow independent validation of suspected prognostic factors. RESULTS: The rate of major complications was 2.9% (16/549), but varied from 0.7% to 9.1% among three strata of relative risk. Rates were highest in patients studied for suspected aortic dissection, mesenteric ischemia, gastrointestinal bleeding, or symptomatic carotid artery stenosis and lowest in patients with trauma or aneurysmal disease. Patients studied for claudication or limb-threatening ischemia had intermediate risk (2.0%). Within these strata, congestive heart failure and furosemide use were the only variables independently associated with a significantly increased complication rate. CONCLUSIONS: Previous reports have overestimated the risk of arteriography for trauma or aneurysm but substantially underestimate the risk for patients with other common conditions. Such stratified complication rates are essential to understand relative costs and benefits of arteriography and other vascular imaging modalities in specific clinical situations.

Treatment of ureteral obstructions with the Wallstent endoprosthesis: preliminary results.

PURPOSE: To evaluate the efficacy of the Wallstent endoprosthesis in the treatment of ureteral strictures. PATIENTS AND METHODS: Wallstents with diameters of 10 mm were placed across five malignant and six benign ureteral strictures in eight patients. All patients were believed to have poor surgical options, and their strictures were being maintained with catheter drainage. Ten lesions involved ureteroenteric anastomoses, and one malignancy involved the midureter. RESULTS: Three stents (two patients) across malignant disease remained patent until the time of patient death (3-5 months); the remaining two stents (one patient) became occluded within 1 month. Only one of six stents placed for benign disease remained patent at 11 months. All occlusions in benign strictures resulted from ingrowth of hyperplastic urothelium and granulation tissue. Complete obstruction was usually present only focally within the stent. The malignant occlusions were caused by tumor ingrowth and granulation tissue. No major complications were directly related to the stents, but two infections occurred. CONCLUSION: Wallstent endoprostheses are ineffective in providing long-term relief in patients with benign ureteroenteric strictures. Further evaluation of their role in malignant strictures is needed.

Retrieval of intravascular foreign bodies: experience in 32 cases.

OBJECTIVE: Recent reports suggest that both the nature of intravascular foreign bodies and the tools available to retrieve them have changed substantially in the past decade. We reviewed our recent experience with percutaneous retrieval of intravascular foreign bodies to determine the efficacy and safety of the procedure using currently available devices. MATERIALS AND METHODS: Between 1990 and 1994, we attempted retrieval of 35 intravascular foreign bodies in 32 patients. Twelve patients (38%), including all five with intraarterial foreign bodies, were treated for complications of transcatheter interventional procedures that resulted in embolization of seven coils, four intravascular stents, an inferior vena cava filter, and a valvuloplasty balloon fragment. From procedure records, we reviewed the types of retrieval devices and methods used; the medical record was studied to determine the occurrence and treatment of any procedure-related complications. RESULTS: Retrieval was successful in 31 (97%) of 32 patients. All five intraarterial and 29 of 30 IV objects were removed. Nitinol goose-neck snares were used in 28 of 32 cases, but more than one retrieval system was required in eight cases (25%), often using grasping forceps, tip-deflecting wires, or stone baskets to move the foreign body into a more favorable position for snaring. In the single failure, the tip of a largely extravascular catheter fragment lay in a venous valve and could not be snared in a patient who refused surgery. Two of five patients with arterial foreign bodies suffered occlusive arterial spasm, reversible with local administration of nitroglycerine. Two large objects were repositioned to the femoral vein and removed by surgical cutdown. No other procedural complications occurred, and none of the patients required additional compression, transfusion, or surgical intervention. CONCLUSION: We conclude that use of preformed nitinol goose-neck snares facilitates retrieval of intravascular foreign bodies in most cases, although interventional radiologists must be familiar with a variety of techniques to deal with the expanding spectrum of foreign bodies currently encountered.

Peripheral vascular occlusive disease: accuracy and reliability of time-of-flight MR angiography.

PURPOSE: To determine the accuracy and reliability of magnetic resonance (MR) angiography for identification of stenosis and patent distal vessels in patients with peripheral vascular disease. MATERIALS AND METHODS: Two-dimensional time-of-flight MR angiography and conventional arteriography were performed in 22 patients. Four blinded radiologists independently graded multiple anatomic segments. RESULTS: MR angiography allowed detection of more patent vessel segments than did conventional arteriography. For detection of significant stenosis (> 75%), MR angiography had 43%-67% sensitivity and 74%-89% specificity. Discrepancies in detection of significant stenosis occurred in 39 segments for the most accurate reviewer; 27 of these discrepancies were avoidable. CONCLUSION: For detection of significant stenosis, MR angiography has low to moderate sensitivity and specificity; however, observer variability appears to be a major contributing factor to the discrepancies. Greater reviewer experience or techniques for improving reliability may improve the accuracy of MR angiography in peripheral vascular disease.

Clinical results of transvenous systemic embolotherapy with a neuroradiologic detachable balloon.

PURPOSE: To evaluate the efficacy of transvenous systemic embolotherapy with a neuroradiologic detachable balloon. MATERIALS AND METHODS: As part of a clinical trial, a detachable silicone balloon was used to occlude pulmonary arteriovenous malformations (PAVMs) in 35 patients and varicocele in 14 patients. In patients with PAVM, the indications for embolotherapy were prophylaxis against paradoxic embolization (n = 35) and dyspnea, fatigue, or both (n = 26); in patients with varicocele, they were pain or a discomforting lesion (n = 8) or infertility (n = 6). RESULTS: Balloon embolotherapy was successful in 79 (98%) of the 81 lesions in which it was attempted; 29 (37%) of these 79 balloons were used in conjunction with coils. Ninety-six (97%) of 99 balloons were successfully placed; the three technical failures had no substantial clinical sequelae, and in all three, occlusion was eventually achieved with either detachable balloons or coils. Of six late deflations, five occurred in balloons placed adjacent to coils; only one, which occurred between 1 day and 21 days after placement, resulted in recanalization. CONCLUSION: Transvenous embolization with this detachable balloon was relatively simple and provided cross-sectional occlusion of PAVMs and varicocele.

Extension of saphenous thrombophlebitis into the femoral vein: demonstration by color flow compression sonography.

Five cases are presented in which compression and color flow sonography were used to diagnose extension of superficial saphenous thrombophlebitis into the deep system at the saphenofemoral junction. In one case thrombus originated in the calf, demonstrating an unusual mode of propagation into the deep venous system above the knee. Color Doppler imaging is especially helpful in diagnosing this complication of superficial thrombophlebitis.

Variance of the position of the cerebellar tonsils with age: preliminary report.

The position of the cerebellar tonsils relative to the foramen magnum was measured with sagittal magnetic resonance (MR) images in 221 patients aged 5 months to 89 years who were considered not to have disorders that would affect tonsillar position. All patients were grouped according to age. All measurements of the tonsils were obtained directly from the video console. Statistically significant (P less than .05) differences in tonsillar position were found between the 1st and 9th decades (P less than .001) and the 3rd and 9th decades (P less than .003) of life. An obvious trend existed: tonsillar ascent with increasing age. Therefore, the authors believe that a single reference standard that indicates the normal distance of the cerebellar tonsils from the foramen magnum is inappropriate unless age is considered. They suggest that the following distances below the foramen magnum (more than 2 standard deviations out of the normal range) be used as criteria for ectopia of the cerebellar tonsils: 1st decade of life, 6 mm; 2nd and 3rd decades, 5 mm; 4th to 8th decades, 4 mm; and 9th decade, 3 mm.

Transfemoral venous catheterization through inferior vena caval filters: results in seven cases.

Use of the transfemoral route for venous catheterization has been considered contraindicated in patients with inferior vena caval (IVC) filters. The transjugular route has been used instead in such patients when subsequent diagnostic or therapeutic procedures are required. Many radiologists, however, are more accustomed to the transfemoral approach, and may not find the transjugular route a desirable alternative. We describe seven patients with previously placed IVC filters in whom the transfemoral route was used to perform pulmonary arteriography (five patients) or to place additional IVC filters (two patients). After venographic confirmation of caval patency, filters were catheterized under fluoroscopic control and the procedures were performed. All procedures were technically successful; no complications occurred. We believe the transfemoral route to be a safe and feasible approach for performing venous procedures in selected patients with IVC filters, obviating the less familiar and potentially more hazardous transjugular approach.

Ewing's sarcoma. Radiographic pattern of healing and bony complications in patients with long-term survival.

The radiographic appearance of Ewing's sarcoma was studied retrospectively in 22 patients who survived 5 years or longer after diagnosis and treatment. Expected changes from treatment, including regression of the extraosseous soft tissue mass, periostitis, and reconstitution of the cortex, occurred in all patients. Local recurrence occurred in one patient 10 years after complete remission whereas secondary osteosarcoma occurred more than 5 years after complete remission in two other cases. Both recurrent and secondary tumors presented as new lytic foci at the site of the original primary lesion. Lytic changes from radiation (radiation osteitis) may develop more than 2 years after treatment and in this sample; such findings were widely distributed in the radiation port. The authors conclude that bone remodeling and postradiation changes occur slowly over 2 years after treatment, and that any localized lysis at the primary site is suspicious for recurrence or secondary neoplasm. Knowledge of the expected changes and patterns of local recurrence and secondary neoplasms helps one to detect any significant change in its early phase.

Differentiation between hemangiomas and metastases of the liver with ultrafast MR imaging: preliminary results with T2 calculations.

We studied the efficacy of T2 measurements at high field strength in distinguishing between liver hemangiomas and hepatic metastases when an ultrafast (single-excitation) MR imaging technique is used. Fourteen patients with known liver tumors were imaged in a 2.0-T prototype ultrafast MR scanner with a spin-echo (infinite TR and TE of 30-340 msec) pulse sequence. Each image was obtained with a total data acquisition time of 20 msec. T2 calculations for hepatic metastases (n = 6) showed a mean of 79.3 +/- 13.5 msec, whereas hemangiomas (n = 8) showed a T2 of 139.8 +/- 18.8 msec (p less than .0001). T2 values of lesions had a smaller relative standard deviation than previously reported, and the range of T2 values of hemangiomas (119-181 msec) and metastases (68-103 msec) did not overlap. Our preliminary results suggest that T2 calculations with ultrafast MR imaging may be useful for differentiating hemangiomas from metastases. We hypothesize that T2 values obtained from ultrafast MR images are more reliable than those obtained from conventional MR images, primarily because of the elimination of T1 information and effects of motion on image signal intensity.

Epiphyseal marrow in infancy: MR imaging.

Hypointense epiphyseal marrow on T1-weighted magnetic resonance images often suggests disease. To determine whether hypointense marrow sometimes represents normal red marrow in a recently ossified epiphyseal center, the authors studied 38 infants without known marrow disease. Patients with hypointense epiphyseal marrow on T1-weighted images were younger (3.9 months +/- 3.2) than those with hyperintense marrow (9.6 months +/- 3.9) (P less than .001). T1-weighted imaging and histologic correlation were also performed in animals. The signal was hypointense and the marrow was red in the epiphyseal centers of all newborn animals, while all 6-week-old animals had hyperintense signal and yellow marrow. The authors conclude that hypointense marrow on T1-weighted images represents normal red marrow in a recently formed ossification center in newborn rabbits and lambs, and the same is probably true in humans. Epiphyseal marrow becomes hyperintense within a few months of development of the secondary center of ossification.

Overall body fat and regional fat distribution in young women: quantification with MR imaging.

Overall body fat and its distribution in different regions are important predispositions to known aberrations in lipid and glucose metabolism. The accuracy of MR imaging in estimating overall body fatness and regional fat distribution at individual landmarks was determined by comparing it with well-accepted measures by deuterium-oxide (D2O) dilution and bioimpedance analysis. Fourteen normal young women (athletes and control subjects) were studied. A total of 308 axial, T1-weighted, spin-echo MR images over a specific region in the trunk (21-24 scans per subject) were obtained. Morphometric computer image analysis was performed to determine the subcutaneous, internal, and total fat volumes in each image. The data were analyzed in two ways: data from all slices were summed to assess overall body fatness, and six anatomic landmarks were chosen for regional comparisons. MR-determined estimates of overall body fatness strongly correlated with total body fat measures by D2O dilution in both total fat (r = .91) and subcutaneous fat (r = .92) determinations. Athletes in both the low- and high-intensity training phases had significantly lower values of MR-determined total body fatness than did control subjects. Parallel to total body fatness, athletes had significantly lower MR-determined ratios of total fat/total volume in four of six individual landmarks compared with control subjects. Our experience suggests that MR is an accurate method to quantify overall body fatness, when compared with D2O dilution and bioimpedance analysis. MR could also discriminate regional components of subcutaneous and internal body fat at individual landmarks.