[Diagnostic accuracy of contrast-enhanced 64-row MSCT coronary angiography in patients with severe coronary calcification in the clinical routine]

PURPOSE

Our aim was to evaluate the diagnostic accuracy of contrast-enhanced 64-MSCT coronary angiography (MSCT-CA) in patients with severe coronary calcification.

MATERIALS AND METHODS

110 patients with an Agatston score > 400 were included in this retrospective analysis. Each patient underwent both conventional coronary angiography and MSCT-CA. No patient was excluded from the study because of coronary artery bypass grafting or coronary stenting. The results of MSCT-CA were compared with those of conventional coronary angiography and the diagnostic accuracy for detecting a hemodynamically significant stenosis was determined for coronary segments, vessels and patients.

RESULTS

The average Agatston score for the study population was 1368 ± 1105. At least one significant stenosis was detected in 97 patients (88%) during conventional coronary angiography defining the gold standard. The sensitivity, specificity, positive and negative predictive values of MSCT-CA for detecting a significant stenosis were 54%, 83%, 52% and 85% for coronary segments (n = 1384), 80%, 70%, 74% and 77% for coronary vessels (n = 440), and 100%, 31%, 92% and 100% for patients (n = 110), respectively. No significant correlation could be observed between the degree of coronary calcification and the number of misclassified coronary segments.

CONCLUSION

Artifacts caused by severe coronary calcification decrease the diagnostic accuracy of MSCT-CA. Performing MSCT-CA in patients with an Agatston score > 400 with the drawbacks of contrast media application and radiation exposure should be critically questioned and this decision should be made on an individual basis.

Multislice CT-image-guided endoscopic sinus surgery using an electromagnetic tracking system

Our objective was to assess the practicability and accuracy of a computer-assisted multislice CT-guided frameless electromagnetic tracking for endoscopic sinus surgery. Eighty-two patients with various paranasal sinus diseases were evaluated. Prior to surgery, axial multislice spiral-CT scans with 2.5-mm collimation, 0.8-mm reconstruction increment, and a pitch of 3 were acquired. After Ethernet transfer of the CT data set to the guidance system, coronal and sagittal images were reconstructed. For intraoperative navigation the Insta Trak System (Visualization Technology, Boston, Mass.) was used. Navigational procedures are described in detail in the paper. Accuracy was assessed by means of visual landmarks which could be clearly identified endoscopically as well as on CT images. A second parameter for accuracy was calculated by the system itself as the root mean square (RMS). The system was able to display the position of the aspirating tip relative to anatomical structures with an average accuracy of 0.70 +/- 0.40 mm. Root mean square values showed a mean value of 0.40 +/- 0.20 mm. During surgical procedures the Insta Trak System provides the surgeon with additional image-based information to the endoscopic view. The device accuracy is high and the system proves to be practicable and efficient in ENT surgery.

Cystic adventitial degeneration of the popliteal artery-the diagnostic value of duplex sonography

Cystical adventitial degeneration of the popliteal artery is a disorder which is difficult to diagnose, due to the similarity of the symptoms of people presenting with peripheral arterial occlusive disease (PAOD) or popliteal entrapment syndrome. The only thing that differs from patients suffering from PAOD is the lack of typical risk factors for arteriosclerosis. Typical diagnostic procedures like conventional angiography or magnetic resonance Imaging angiography can be negative, too and therefore misleading. The only which is crucial in the diagnosis of cystic adventitial degeneration of the popliteal artery is to know the morphological background of this disorder, namely that it is a cyst of the adventitia of the artery which leads to a dynamic exercise-dependent flow inhibition. We present a 57-year old white male who had a week's history of intermittent claudication in his left calf. He was lacking of typical risk factors for arteriosclerosis and on first examination all pulses in both lower extremities were palpable and Doppler index on both legs was >1. Only duplexsonography revealed a cystic formation impressing the left popliteal artery in the hight of the rift in the popliteal joint.

Peripheral primitive neuroectodermal tumour of the kidney: CT findings

Peripheral primitive neuroectodermal tumour in the kidney is a rare entity with high malignant potential. The distinctive demographic, clinical and radiological findings, as described in the present case, should suggest this aggressive tumour in the differential diagnosis of renal neoplasms in adolescents.

Small-bowel disease: comparison of MR enteroclysis images with conventional enteroclysis and surgical findings

PURPOSE

To investigate if magnetic resonance (MR) enteroclysis can be performed routinely and to compare MR enteroclysis findings with those of conventional enteroclysis or surgery.

MATERIALS AND METHODS

MR enteroclysis was prospectively performed in 30 patients with symptoms of inflammatory bowel disease or small-bowel obstruction (SBO). A methylcellulose-water solution was used to distend the small bowel. To monitor dynamic changes in the small bowel, a single-shot fast spin-echo T2-weighted sequence was applied. For morphologic assessment, breath-hold T2-weighted fast spin-echo and coronal T1-weighted gradient-recalled-echo MR images were obtained without and with gadolinium enhancement. Image quality and degree of small-bowel distention were graded. MR imaging findings and degree of SBO were compared with findings at conventional enteroclysis (n = 25) or surgery (n = 5).

RESULTS

MR enteroclysis was well tolerated and provided adequate image quality and sufficient small-bowel distention. SBO grade based on MR enteroclysis images (n = 10) was identical to that based on conventional enteroclysis images (n = 6) or surgical findings (n = 4). There was exact agreement between MR enteroclysis and retrospective findings in all five patients who underwent surgery, and MR findings were identical to those at enteroclysis in 18 patients, superior in six patients, and inferior in one patient.

CONCLUSION

MR enteroclysis can be performed routinely with adequate image quality and sufficient small-bowel distention. The functional information provided by MR enteroclysis is identical to that provided at conventional enteroclysis.

Osteomyelitis of the spine and abscess formation in the left thigh after stent-graft implantation in the superficial femoral artery

PURPOSE

To present a rare case of abscess formation around a covered stent in the superficial femoral artery.

METHODS AND RESULTS

Two weeks after balloon dilation of a left superficial femoral artery (SFA) occlusion, during which a Hemobahn covered stent had been placed to treat dissection, a 77-year-old nondiabetic male developed intolerable pain and swelling of his left thigh. An abscess had formed around the stent, which was patent; intravenous antibiotic therapy quelled the symptoms, and the patient discontinued his oral antibiotic regimen weeks after discharge. General septicemia ensued. Acute lower limb ischemia and excruciating back pain prompted readmission. The SFA stent-graft occlusion required femoropopliteal bypass; the abscess and spondylodiskitis that had developed in the T12 and L1 vertebrae responded to intravenous antibiotics. The patient is without signs of infection at 6 months.

CONCLUSIONS

Local and systemic infections associated with intraluminal prostheses are rare, and prophylactic antibiotic therapy is not commonly employed. Balloon- or device-induced arterial injury may expose the arterial wall to bacterial colonization, suggesting that patients receiving lengthy stents or experiencing arterial injury during angioplasty should receive antibiotics as a precautionary measure.

Contrast-enhanced MR imaging of two superparamagnetic RES-contrast agents: functional assessment of experimental radiation-induced liver injury

The purpose of this study was to compare liver contrast-enhancing characteristics of two superparamagnetic reticuloendothelial system (RES)-directed agents with different particle sizes, polycrystalline iron oxide nanocompounds (PION) and carboxydextran-coated maghemite (DDM128N/389, later referred to as DDM128), in an experimental model of focal radiation-induced hepatitis. PION, for the small particle size (31 nm), and DDM128, for the large particle size (59 nm), RES-directed agents were compared for liver enhancement after radiation-induced liver injury. A single x-irradiation exposure varying from 10 to 60 Gy was delivered to one side of the liver. T2-weighted spinecho magnetic resonance imaging was performed 3 days after x-irradiation at 30 minutes post-contrast. Using the RES-directed PION, the normal, non-irradiated portion of the liver decreased in signal intensity with a maximum negative enhancement of -66%, while the irradiated portion of the liver decreased in signal intensity by -24% (60 Gy). The signal intensity decline of irradiated liver tissue using PION was dose dependent, but was found at all radiation dose levels (10-60 Gy). The difference in signal intensity between irradiated (-63%) and non-irradiated (-82%) portions was also statistically different using DDM128 at 60 Gy. However, lower irradiation doses (10 and 30 Gy) failed to produce a statistically significantly different enhancement in the irradiated and non-irradiated portion of the liver. Sensitivity of liver enhancement with RES-directed agents is size dependent. The smaller particle (PION) is more sensitive for detection of radiation-induced hepatitis than the larger particle (DDM128). The relative insensitivity of DDM128 enhancement for diffuse liver injury will be clinically advantageous for detecting focal lesions in the presence of diffuse hepatic injury.

Renal masses--evaluation by amplitude coded colour Doppler sonography and multiphasic contrast-enhanced CT

OBJECTIVE

To assess the efficacy of amplitude coded colour Doppler US (aCDS) in the evaluation of renal masses as shown by multiphasic contrast-enhanced CT.

MATERIAL AND METHODS

Eighty patients (155 kidneys) with suspicion of renal masses underwent aCDS and spiral CT. The findings were classified into normal kidneys, kidneys with tumours, kidneys with cysts, and those with "other findings" (i.e. bleeding, calcifications, inflammation, parenchymal hypertrophy). The aCDS findings were compared to CT results and to histological findings or clinical, laboratory and follow-up data.

RESULTS

Eighteen renal cell carcinomas and 8 other tumours were found; 78 kidneys had cysts, 12 polycystic kidneys and 10 fibrotic kidneys were detected, 20 kidneys showed other findings. Diagnostic aCDS data were obtained in 129 kidneys (83.2%) showing pathology with an accuracy of 94%. CT adequately showed pathology in all patients with some diagnostic uncertainty in the evaluation of complicated cysts.

CONCLUSION

Though contrast-enhanced multiphasic spiral CT is the method of choice for evaluating renal masses, US including aCDS can provide valuable information, particularly in differentiating vascularized from non-vascularized lesions and in the evaluation of complicated renal cysts.

[Evaluation of renal vascularization using amplitude-coded Doppler ultrasound]

PURPOSE

To evaluate the benefit of "Colour Doppler Energy" (CDE) or "Power Doppler" applications in healthy kidneys and in renal disease including paediatric assessment.

PATIENTS AND METHOD

Ten healthy volunteers (range: neonate to adults) were studied using conventional colour Doppler sonography (CDS) and CDE in order to evaluate the visibility of intrarenal vasculature. In addition, ten children and ten adults with known renal disease were evaluated. The findings were compared to clinical, scintigraphic and biopsy results.

RESULTS

CDE showed far better visualisation of intrarenal vasculature than CDS. CDE demonstrated focal and diffuse reduced cortical perfusion with an overall accuracy of 95% and a sensitivity of 88%. In 7 healthy volunteers cortical vasculature was visualised throughout the kidney. In 3 infants incomplete visualisation was obtained because of motion artifacts. In the diseased kidneys, CDE findings correlated well with clinical findings, scintigraphy results and biopsy findings.

CONCLUSION

CDE can be successfully applied to adults and infants demonstrating renal vasculature in healthy kidneys and in kidneys with focally or diffusely altered perfusion.

Postoperative radiotherapy in radically resected non-small cell lung cancer

PURPOSE

To evaluate the value of adjuvant postoperative external-beam radiation (EBR) in patients with radically resected non-small cell lung cancer (NSCLC) pT1-3 pN0-2 compared to patients with resected NSCLC without adjuvant EBR.

MATERIALS AND METHODS

In 155 patients (121 male, 34 female; mean age, 59 years) 105 lobectomies, 12 bilobectomies, and 38 pneumonectomies with radical lymph node dissection of the contralateral [corrected] side were performed. Postoperative staging was done according to the TNM system and was as follows: pT1 (n=38), pT2 (n=89), pT3 (n=28); pN0 (n=39), pN1 (n=67) and pN2 (n=49). Histopathologic study revealed 68 squamous cell carcinomas, 53 adenocarcinomas, 21 large cell carcinomas, 6 adenosquamous cell carcinomas, and 7 bronchioloalveolar cell carcinomas. All patients were randomly assigned into two treatment groups: 72 patients with no further treatment (control group), and 83 patients (EBR group) with adjuvant postoperative EBR of the bronchial stump and mediastinum (50 to 56 Gy, 8 or 23 MV photons, 2 Gy/d, 5 d/wk) beginning 4 to 6 weeks after surgery.

RESULTS

The overall 5-year survival rate (median observation time, 43 months) of all patients was 24.1% (EBR group, 29.7%; control group, 20.4%; p>0.05, not significant). The relative risk of the EBR group was 0.85 with a two-sided confidence interval of 0.66 to 1.09. The overall 5-year recurrence-free survival was 20.6% (EBR, 27.1%; control group, 15.6%; p=0.07). The relative risk of the EBR group was 0.80 with a confidence interval of 0.63 to 1.01. The rate of local recurrences at the bronchial stump and/or mediastinum was significantly smaller in the EBR group (n=5) than in the control group (n=17) (p<0.01). Multivariate analysis (chi2 test) demonstrated an independent influence of postoperative EBR on the incidence of local recurrences. The incidence of distant metastases was slightly but not significantly higher in patients without EBR (38 patients) compared to those who had EBR (32 patients).

CONCLUSION

High-dose postoperative EBR to the mediastinum significantly reduces the risk of local recurrence at the bronchial stump and/or mediastinum. Age, sex, histologic subtype, tumor size, surgical approach, or extent of lymph node involvement had no prognostic value--only postoperative EBR had an independent influence on the risk of local recurrence. The effect of postoperative EBR was on the verge of significance with respect to recurrence-free survival and showed the same tendency in overall survival, however with an attenuated relative risk.

Percutaneous cholangioscopy in obstructed biliary metal stents

PURPOSE

To reevaluate the reasons for the occlusion of self-expanding biliary metal stents, on the basis of cholangioscopic findings.

METHODS

Percutaneous transhepatic cholangioscopy (PTCS) was performed in 15 patients with obstructed biliary Wallstents. The reason for stent insertion was a malignant obstruction in 14 patients; 1 had a benign biliary stricture. Conventional noncovered stents had been inserted in 12 patients; in 3 cases a polyurethanecovered prototype Wallstent had been used. Stent occlusions occurred after 1-55 months. PTCS was performed with a 2.3-mm endoscope through an 11 Fr sheath. Biopsies were taken via the working channel of the endoscope.

RESULTS

In all patients with noncovered stents the inner surface of the stent was highly irregular with seaweed-like protrusions (biopsy-proven granulation tissue). Stent incorporation varied from absent (n = 1) to subtotal (n = 8), but was always incomplete, no matter how long the stent had been in place. Tumor ingrowth was histologically proven in 2 patients. One patient had a large occluding concrement at the proximal end of the stent. In patients with covered stents, the inner surface appeared more regular; however, viable granulation tissue was found inside two stents and tumor ingrowth in one of them.

CONCLUSION

PTCS showed that incorporation of the stent is virtually always incomplete. The factors contributing most to stent occlusion are the buildup of granulation tissue, bile sludge, and tumor overgrowth. Stone formation and tumor ingrowth can also be important, although less common causes of occlusion. A polyurethane stent covering could not prevent tumor ingrowth in one patient and the buildup of viable granulation tissue inside the stent in two further patients; mean stent patency in the three patients with such a stent was 3 months.

Quantification of the extent of area at risk with fast contrast-enhanced magnetic resonance imaging in experimental coronary artery stenosis

Fast magnetic resonance (MR) imaging techniques have the capability of demonstrating regions of ischemia caused by stenosis. The size of the potentially ischemic area determines the importance of the stenosis. The purpose of this study was to determine the relative values of relaxivity-enhancing and magnetic-susceptibility MR contrast media in detecting and sizing the area at risk in dogs. Eight dogs were subjected to critical left circumflex coronary artery (LCX) stenosis. Sixty sequential inversion-recovery- and driven-equilibrium-prepared fast gradient recalled echo images were acquired during bolus administration of 0.03 mmol/kg gadodiamide or 0.4 mmol/kg sprodiamide in basal and vasodilated (dipyridamole-stress) states. The size of the area at risk was measured and compared with that measured post mortem. In the basal state, gadodiamide and sprodiamide equivalently altered the signal intensities of nonischemic myocardium and the territory of stenosed coronary artery. Dipyridamole produced a significant increase in left anterior descending coronary artery flow with a decrease in LCX flow. The hypoperfused region was observed as a low-and high-signal intensity region after administration of gadodiamide and sprodiamide, respectively. The size of the hypoperfused region was slightly smaller with gadodiamide (37.4% +/- 2.8%) and sprodiamide (34.0% +/- 2.2%) than the true area at risk measured post mortem (41.8% +/- 2.2%; p < 0.05). Dipyridamole perfusion MR imaging with relaxivity or susceptibility contrast media is a noninvasive method to identify and quantify the area at risk in the territory of a stenotic coronary artery. Changes in myocardial signal intensity on fast gradient recalled echo images reflect the augmentation of flow and volume induced with dipyridamole and are consistent with the "steal phenomenon."

Cerebral schistosomiasis: MR and CT appearance

After returning from Africa, a 54-year-old man began to have episodes of headache and nausea, then a cerebral convulsion. Clinical and laboratory findings and response to chemotherapy indicated the diagnosis of cerebral schistosomiasis. Three lesions were seen on CT and MR studies: two appeared to be subacute intracerebral hematomas, one in the right parietal lobe and one in the frontal lobe; the third lesion, in the cortex of the left occipital lobe, appeared to be a cyst. These lesions could represent small granulomatous tissue reactions with secondary hemorrhages.

Acute hemodynamic effects of recently developed monomer and dimer magnetic resonance imaging contrast media: a comparative study

RATIONALE AND OBJECTIVES

We evaluated and compared the acute cardiovascular effects of equiosmolar doses of recently developed nonionic monomer and macrocyclic dimer magnetic resonance (MR) imaging contrast media with the clinically available ionic and nonionic MR contrast media.

METHODS

Normotensive adult Sprague-Dawley rats were divided into six groups of seven rats per group. Group 1 received the nonionic monomer Gd-CMPA-BMPA (500 mmol/l solution); group 2 received the nonionic dimer Gd(2)2(O)DO3A (500 mmol/l solution); group 3 also received Gd(2)2(O)DO3A but at a higher concentration (1,000 mmol/l solution); group 4 received gadopentetate dimeglumine (500 mmol/l solution); and group 5 received gadodiamide (500 mmol/l solution). Each rat received a rapid (1-2 sec) bolus intravenous injection of 0.1, 0.25, and 0.5 mmol/kg of each contrast agent. Group 6 was used to test the peak effects of quiosmolar glucose solutions (500, 1,000, and 2,000 mOsm/kg water). Data were acquired at baseline, 20 sec (peak effect) after injection, and 1, 3, 5, and 10 min after injection. Peripheral (systolic, diastolic, and mean) pressure, central venous pressure, left ventricular (LV) pressure (peak systolic and end diastolic) pressure, first derivative of left ventricular pressure (+/-dP/dt), rate pressure product, and heart rate were measured.

RESULTS

Bolus administration (0.1, 0.25, and 0.5 mmol/kg) of Gd-CMPA-BMPA and gadodiamide (500 mmol/l) had no significant effects on the monitored cardiovascular parameters. Bolus injection of 0.25 and 0.5 mmol/kg Gd(2)2(O)DO3A (500 and 1,000 mmol/l) and gadopentetate dimeglumine (500 mmol/l) caused transient cardiovascular depression, including decreased peripheral blood pressure, LV systolic pressure, peak positive and negative dP/dt, and rate pressure product, but an increased LV end diastolic pressure. These cardiovascular effects were slightly less profound than those produced by gadopentetate dimeglumine.

CONCLUSION

Gd-CMPA-BMPA and gadodiamide have no adverse cardiovascular effects. Gd(2)2(O)DO3A and gadopentetate dimeglumine cause vasodilation and reduced cardiac performance. Therefore, presuming similar effects, if Gd(2)2(O)DO3A and gadopentetate dimeglumine are to be used at high doses for the MR quantification of blood volume or as a bolus for perfusion study, appropriate consideration should be given to possible adverse physiologic changes.

Differentiation of delayed kidney graft function with gadolinium-DTPA-enhanced magnetic resonance imaging and Doppler ultrasound

RATIONALE AND OBJECTIVES

The authors differentiate acute tubular necrosis from transplant rejection in patients with delayed kidney graft function using gadolinium (Gd)-DTPA enhanced magnetic resonance (MR) imaging.

METHODS

Twenty-four patients after renal transplantation (10 with normal graft function, 14 with delayed graft function) underwent conventional and Doppler sonography and MR imaging examination after bolus application of Gd-DTPA. Within a time period of 512 seconds, 39 single-slice MR images were obtained. Measurements of signal intensity in three regions of interests (cortex, medulla, renal pelvis) resulted in a graphic description of the dynamics of the contrast enhancement. The time between the start of the scan and the peaks of the curves was measured.

RESULTS

In patients with normal graft function the curves reached the peaks between 39 and 55 seconds (cortex), 44 and 61 seconds (medulla), and between 161 and 318 seconds (renal pelvis). Six patients with acute tubular necrosis showed normal values for the curves 1 and 2 but markedly prolonged time for curve 3 (between 420 and 512 seconds). In all patients with histologically proven transplant rejection, the peaks of all curves were not reached before the ends of the scans.

CONCLUSION

The authors' preliminary results suggest that MR imaging seems to be a sensitive, noninvasive diagnostic tool to differentiate acute tubular necrosis from transplant rejection in the critical early postoperative period.

Ultrasonography, CT and MRI of retropharyngeal ganglioneuroma: a very rare neoplasm in adults

Ganglioneuroma, a rare benign tumour, very occasionally presents in adult life. We report a case with the additional unusual feature of a retropharyngeal location.

Contrast enhancement in experimental radiation-induced liver injury: comparison of hepatocellular and reticuloendothelial particulate contrast agents

We compared the liver enhancement of two superparamagnetic agents, polycrystalline iron oxide nanoparticles (PION) and PION coated with asialofetuin (ASF), in an experimental model of focal radiation-induced hepatitis. PION, a reticuloendothelial system-directed agent, and PION-ASF, a hepatocellular-directed agent, were compared for time-dependent liver enhancement in an experimental model of radiation-induced liver injury. Using the reticuloendothelial system (RES)-directed PION, the normal, nonirradiated portion of the liver decreased in signal intensity (SI) with a mean negative enhancement of -66% +/- 4, whereas the irradiated portion (60 Gy, 3 days before imaging) of the liver decreased in SI by -24% +/- 2, significantly less (P <.05). SI changes in irradiated liver tissue using PION were dose-dependent, being more pronounced with lower radiation exposure. The difference in SI changes induced by PION-ASF between irradiated and nonirradiated liver was not statistically different, but SI decreased with a mean negative enhancement of -80% +/- 2. The RES-directed PION is more sensitive for the detection of radiation-induced hepatitis than is the hepatocyte-directed PION-ASF. The insensitivity of PION-ASF enhancement for diffuse liver injury may be clinically advantageous for detecting focal lesions in the presence of diffuse hepatic injury.

Assessment of hemodynamic effects of angiotensin-converting enzyme inhibitor therapy in chronic aortic regurgitation by using velocity-encoded cine magnetic resonance imaging

Long-term treatment with angiotensin-converting enzyme (ACE) inhibitors has beneficial effects in patients with chronic aortic regurgitation by reducing left ventricular volumes and regurgitant fraction. Velocity-encoded cine magnetic resonance imaging can directly measure antegrade (forward stroke volume) and retrograde blood flow (regurgitant volume) in the ascending aorta. Velocity-encoded cine magnetic resonance imaging was used in 9 patients with moderate to severe aortic regurgitation (regurgitant fraction 49% +/- 17%) to measure regurgitant fraction, regurgitant volume, and forward stroke volume at baseline and 3 months after therapy with enalapril (mean dose 29 +/- 13 mg). Ten additional patients with aortic regurgitation without any drug therapy served as a control group. In the treatment group, systolic blood pressure slightly decreased from 132 +/- 20 mm Hg to 121 +/- 14 mm Hg (p = not significant), whereas diastolic blood pressure and heart rate (beats per minute) remained unchanged. Regurgitant fraction decreased in 6 patients (responders) from 49% +/- 19% to 39% +/- 20% (percentage change 24% +/- 14%, p = 0.002) and was unchanged in 3 patients (nonresponder, 49% +/- 19% vs 51% +/- 16%; p = not significant). In the responder group, forward stroke volume increased from 128 +/- 32 ml to 148 +/- 57 ml, whereas regurgitant volume remained unchanged (67 +/- 40 ml vs 65 +/- 51 ml). At baseline, the responder group had a significant higher total vascular resistance than the nonresponder group (998 +/- 538 dyne.sec.cm-5 vs 625 +/- 214 dyne.sec.cm-5; p < 0.05). With enalapril treatment, total vascular resistance in the responder group tended to decrease (891 +/- 576 dyne.sec.cm-5), but slightly increased in the nonresponder group (679 +/- 276 dyne.sec.cm-5). The control group showed no changes in regurgitant fraction, regurgitant volume, forward stroke volume, and total vascular resistance at follow-up.

Strength, elasticity, and plasticity of expandable metal stents: in vitro studies with three types of stress

PURPOSE

Five types of expandable metal stents (Palmaz, Strecker, Gianturco, Cragg, and Wallstent) were subjected to standardized tests to obtain objective, comparable data of their mechanical characteristics.

MATERIALS AND METHODS

The stents were subjected to area loads, point loads, and circular loads; the resistance of the stents to a continually increasing deformation was measured. Elasticity and deformation characteristics of the stents were also noted. Another experiment simulated the situation of the stent in an implanted state. The stents were covered with a thin self-adhesive foil to simulate optimal wall contact by limiting the mobility of the mesh struts.

RESULTS

For all types of stress, the Palmaz stent showed the highest resistance but was completely inelastic. The Strecker stent and the Wallstent showed higher resistance when coated in foil (simulating good wall contact). The Gianturco stent showed the lowest resistances but was completely elastic. A point load on a Wallstent caused concentric constriction over a longer distance.

CONCLUSIONS

Palmaz stents are appropriate for insertion into highly resistant obstructions. Strecker stents and Wallstents require good wall contact to achieve adequate strength. Because of their unique deformation characteristics, Wallstents may not function well if implanted into eccentric stenoses of tough consistency. The Gianturco stent showed the lowest resistances.

Relationship between heart rate threshold, lactate turn point and myocardial function

We examined the relationship between heart rate threshold (HRT), lactate turn point (LTP) and myocardial function expressed as left ventricular ejection fraction (LVEF) determined by radionuclide ventriculography. Two groups of subjects (G I: N = 8; G II: N = 7) with and without a deflection of heart rate performance curve (HRPC) underwent sitting cycle ergometry. HRT (G I), aerobic threshold (AeT; G I, G II), and LTP (G I, G II) were determined by means of linear regression break point analysis. Also, a break point in LVEF performance curve (LVEFBP) was obtained. Power output at HRT and at LTP was not significantly different between G I and G II (272.5 +/- 38.7 W; 294.3 +/- 20.6 W). Power output at LVEFBP (G I: 182.6 +/- 31.7 W; G II: 211.8 +/- 21.5 W) was not significantly different to power output at LTP (G I: 194.2 +/- 32.7 W; G II: 215.2 +/- 24.4 W) and HRT (G I: 193.0 +/- 38.2 W). Significant differences (p < 0.05) could only be found between G I and G II for heart rate (HR) at LTP (G I: 163.5 +/- 5.8 b.min-1; G II: 154.4 +/- 6.7 b.min-1) and LVEF at the end of the load (LVEFend) (G I: 77.9 +/- 2.9%; G II: 71.3 +/- 7.0%). The drop of LVEF at LVEFBP was significantly related to LTP in all cases. The present data suggest that the noninvasive determination of anaerobic threshold by means of heart rate curve analysis is not always possible due to different response of myocardial function and heart rate to graded cycle ergometer exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

The sphenoid sinus during childhood: establishment of normal developmental standards by MRI

To obtain baseline standards of normal age-related development of the sphenoid sinus during childhood magnetic resonance images of the sphenoid sinus in 401 patients less than 15 years old were reviewed. T1-weighted sagittal and T2-weighted axial scans were evaluated for bone marrow conversion, development of pneumatization, spatial enlargement and septation of the sphenoid sinus. The sphenoid sinus had a uniformly low signal intensity (red bone marrow) on T1-weighted images in all children less than 4 months old. Signal intensity changes from hypo- to hyperintense (bone marrow conversion) started at age of 4 months. Onset of pneumatization was observed in 12% of the patients at age 13-15 months. By age 43-48 months, 85% of the patients showed pneumatization of the anterior part of the sphenoid bone. Pneumatization was complete in all patients older than 10 years. Enlargement of the sinus showed a characteristic profile in each dimension. Median septation was observed irregularly with age, with a maximum of 77%. Septum variants were noticed between 4.5% and 20%. The recognition of this phenomenon may serve as a reference for evaluating normal and abnormal development of the sphenoid sinus and may be of great value for diagnostic and therapeutic management of pathologic conditions of the child's sphenoid sinus and its surrounds.

Magnetic resonance assessment of age-related development of the sphenoid sinus

Magnetic resonance images of the sphenoid sinus in 401 patients under 15 years old were reviewed to establish normal age-related standards. T1-weighted sagittal and T2-weighted axial scans were evaluated for bone marrow conversion, development of pneumatization, spatial enlargement and septation of the sphenoid sinus. The sphenoid sinus had a uniformly low signal intensity (red bone marrow) on T1-weighted images in all children less than 4 months old. Signal intensity changes from hypointense to hyperintense (bone marrow conversion) started at the age of 4 months. Onset of pneumatization was observed in 12% of the patients at age 13-15 months. By age 43-48 months, 85% of the patients showed pneumatization of the anterior part of the sphenoid bone. Pneumatization was complete in all patients older than 10 years. Enlargement of the sinus showed a characteristic profile in each dimension. Median septation was observed irregularly with age, with a maximum of 77%. Septum variants were noticed between 4.5% and 20%. Because paediatric sinus disease is a challenging problem in children, these results may be useful as baseline standards of normal age-related development of the sphenoid sinus during childhood.

Malignant ureteral obstruction: preliminary results of treatment with metallic self-expandable stents

Self-expandable metal stents 7 mm in diameter were percutaneously implanted into 13 ureters in 10 patients with malignant ureteral obstruction not amenable to double-J stent placement. In nine ureters, one stent was placed, and in four ureters, two overlapping stents were placed. Primary reconstitution of ureteral patency was achieved in all ureters. After 1-2 weeks, four ureters showed a urothelial reaction encroaching on the lumen of the ureter, and a double-J stent was placed coaxially. One ureter was occluded by urothelial hyperplasia 4 weeks after stent placement, and a double-J stent was therefore placed. One ureter was occluded 8 months after stent placement by distal tumor overgrowth. The other ureters showed no signs of obstruction during a follow-up of 3-14 (average, 5.8) months. Peristalsis was preserved at both ends of the stent in all ureters. The use of this stent alone or in combination with a double-J stent alleviated upper urinary tract obstruction and avoided external drainage in all patients.