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Biomedical subjects

R Coulden

Publications and source records attributed to R Coulden.

18 recordsLinked to original sources
PubMed2004

Myocardial first-pass perfusion magnetic resonance imaging: a multicenter dose-ranging study.

BACKGROUND: MRI can identify patients with obstructive coronary artery disease by imaging the left ventricular myocardium during a first-pass contrast bolus in the presence and absence of pharmacologically induced myocardial hyperemia. The purpose of this multicenter dose-ranging study was to determine the minimally efficacious dose of gadopentetate dimeglumine injection (Magnevist Injection; Berlex Laboratories) for detecting obstructive coronary artery disease. METHOD AND RESULTS: A total of 99 patients scheduled for coronary artery catheterization as part of their clinical evaluation were enrolled in this study. Patients were randomized to 1 of 3 doses of gadopentate dimeglumine: 0.05, 0.10, or 0.15 mmol/kg. First-pass perfusion imaging was performed during hyperemia (induced by a 4-minute infusion of adenosine at a rate of 140 microg x kg(-1) x min(-1)) and then again in the absence of adenosine with otherwise identical imaging parameters and the same contrast dose. Perfusion defects were evaluated subjectively by 4 blinded reviewers. Receiver-operating curve analysis showed that the areas under the receiver-operating curve were 0.90, 0.72, and 0.83 for the low-, medium-, and high-contrast doses, respectively, compared with quantitative coronary angiography (diameter stenosis > or =70%). For the low-dose group, mean sensitivity was 93+/-0%, mean specificity was 75+/-7%, and mean accuracy was 85+/-3%. CONCLUSIONS: First-pass perfusion MRI is a safe and accurate test for identifying patients with obstructive coronary artery disease. A low dose of 0.05 mmol/kg gadopentetate dimeglumine is at least as efficacious as higher doses.

Adenosine↗
PubMed2004

Detection of coronary artery disease by magnetic resonance myocardial perfusion imaging with various contrast medium doses: first European multi-centre experience.

AIMS: Magnetic resonance (MR) first-pass myocardial perfusion imaging during hyperaemia detects coronary artery stenoses in humans with test sensitivity depending on contrast medium (CM)-induced signal change in myocardium. In this prospective multi-centre study, the effect of CM dose on myocardial signal change and on diagnostic performance was evaluated using a stress-only approach. METHODS AND RESULTS: Ninety-four patients with known or suspected coronary artery disease (CAD) were randomised to 0.05,0.10, or 0.15 mmol/kg body weight of an extravascular CM (Gd-DTPA) and X-ray coronary angiography was performed within 30 days prior/after the MR examination. A multi-slice MR technique with identical hardware and software in all centres was used during hyperaemia (adenosine 0.14 mg/kg/min) to monitor myocardial CM wash-in kinetics and data were analysed semi-automatically in a core laboratory. Protocol violations resulted in 80 complete studies with CAD (defined as > or =1 vessel with diameter stenosis > or =50% on quantitative coronary angiography) present in 19/29, 13/24, and 20/27 patients for doses 1, 2, and 3, respectively. In normal myocardium, the upslope increased with CM dose (overall-p<0.0001, ANOVA). For CAD detection the area under the receiver operator characteristics curve for subendocardial data (3 slices with quality score<4 representing 86% of cases) was 0.91+/-0.07 and 0.86+/-0.08 for doses 2 and 3, respectively, and was lower for dose 1 (0.53+/-0.13, p<0.01 and p<0.02 vs. doses 2 and 3, respectively). Corresponding sensitivities/specificities (95% confidence intervals) for pooled doses 2/3 were 93% (77-99%; ns vs. dose 1) and 75% (48-92%;p<0.05 vs. dose 1), respectively. CONCLUSIONS: With increasing doses of CM, a higher signal response in the myocardium was achieved and consequently this stress-only protocol, with CM doses of 0.10-0.15 mmol/kg combined with a semi-automatic analysis, yielded a high diagnostic performance for the detection of CAD.

Analysis of Variance↗
PubMed2000

Role of computed tomographic scanning of the thorax prior to bronchoscopy in the investigation of suspected lung cancer.

BACKGROUND: Fibreoptic bronchoscopy (FOB) is the usual initial investigation of choice in patients with suspected endobronchial carcinoma, but it is often non-diagnostic. Once a positive diagnosis has been made, many patients undergo staging by computed tomographic (CT) scanning to assess the extent of the disease and its suitability for radical treatment. To determine whether initial CT scanning before FOB is a cost effective way of reducing subsequent unnecessary or unhelpful invasive diagnostic procedures, a study was undertaken in 171 patients with suspected endobronchial carcinoma. METHODS: A randomised two group study was performed with all patients undergoing an initial CT staging scan. In group A the CT scans were reviewed before FOB, allowing cancellation or a change to an alternative invasive procedure if considered appropriate. In group B all patients proceeded to FOB with the bronchoscopist blinded to the result of the CT scan until after the procedure. RESULTS: In group A six of 90 patients (7%) required no further investigations as the CT scan was either normal, consistent with benign disease, or consistent with widespread metastatic disease. Of the remainder, bronchoscopy was diagnostic in 50 of 68 (73%) in group A compared with 44 of 81 (54%) in group B (p = 0.015). Overall, a positive diagnosis was made after a single invasive investigation in 64 of 84 patients (76%) in group A compared with only 45 of 81 patients (55%) in group B (p = 0.005). Only seven of 90 patients (8%) in group A required more than one invasive investigation compared with 15 of 81 patients (18.5%) in group B. In patients with malignancy, bronchoscopy was more likely to be diagnostic in group A (50 of 56 patients (89%)) than in group B (44 of 62 (71%); p = 0. 012), and the diagnosis was more frequently made on the initial invasive investigation (group A, 63 of 70 (90%); group B, 44 of 62 (71%); p = 0.004). Because of the lower number of invasive procedures performed in group A than in group B, the cost of performing CT scans before FOB in all patients in group A would have equated to a projected cost of performing CT scans in 60% of patients after FOB in group B. CONCLUSIONS: Performing initial CT thoracic scans before bronchoscopy in patients with suspected endobronchial malignancy is a cost effective way of improving diagnostic yield from invasive diagnostic procedures and occasionally may obviate the need for any further investigation.

Adult↗
PubMed1999

Valvular heart disease.

Congenital and acquired valvular disease remains a frequent cause of morbidity and mortality. It presents a diagnostic challenge in all age groups, and often occurs in conjunction with other types of heart disease. Traditional chest radiography provides the earliest opportunity for radiologic diagnosis, hence the need for skill and knowledge in interpreting the radiographic findings. Echocardiography with color flow Doppler measurements is frequently the next modality applied. CT and MR imaging can simultaneously display cardiovascular morphology with greater spatial resolution than ultrasound, and at the same time provide quantitative assessment of cardiac function. The role of diagnostic imaging is therefore crucial, both for primary diagnosis and in the management of valvular heart disease. Furthermore, it is fundamental in evaluating the results of all forms of interventional therapy.

Echocardiography, Doppler, Color↗
PubMed1998

Improving surgical resection rate in lung cancer.

BACKGROUND: Surgical resection is the recognised treatment of choice for patients with stage I or II non-small cell lung cancer (NSCLC). In the UK surgical resection rates have remained far lower (< 10%) than those achieved in Europe and the USA (> 20%), despite the recent introduction of fast access investigation units. It remains unclear therefore why UK surgical resection rates lag so far behind those of other countries. METHODS: A new quick access two stop investigation service was established at Papworth in November 1995 to investigate all patients presenting to any of three surrounding health districts with suspected lung cancer. Once staging was complete, all patients with confirmed lung cancer were reviewed by a multidisciplinary team which included an oncologist and a thoracic surgeon. Time from presentation to definitive treatment and surgical resection rates were reviewed. RESULTS: Two hundred and nine (76%) of a total of 275 consecutive patients investigated had confirmed lung cancer (28 small cell, 181 non-small cell). Of the remainder, eight patients (2%) had metastatic disease, four (1%) had other thoracic malignancy (thymoma, mesothelioma), four patients (1%) had benign thoracic tumours, and 50 (18%) had other non-malignant diseases. Of the 181 patients with non-small cell primary lung cancer, 47 (25%) underwent successful surgical resection, of whom 59% had stage I and 21% stage II disease. The failed thoracotomy rate was 11%. Median time from presentation at the peripheral clinic to surgical resection was 5 weeks (range 1-13). CONCLUSION: Quick access investigation, high histological confirmation rates, routine CT scanning, and review of every patient with confirmed lung cancer by a thoracic surgeon led to a substantial increase in the successful surgical resection rate. These results support the growing concern that many patients with operable tumours are being denied the chance of curative surgery in our present system.

Aged↗
PubMed1998

CT measurement of main pulmonary artery diameter.

The aim of this study was to determine the upper limit of the normal main pulmonary artery diameter using a modern CT system. This was measured at the level of the pulmonary artery bifurcation in 100 normal subjects using unenhanced contiguous 10 mm CT slices viewed at fixed mediastinal window settings (400/20). These normal subjects were then compared with similar unenhanced 10 mm images from 12 patients with proven pulmonary arterial hypertension (mean pulmonary artery pressure > 20 mmHg). The main pulmonary artery diameter in normal subjects was 2.72 cm (SD = 0.3). Main pulmonary artery diameter in patients with pulmonary arterial hypertension was significantly greater (p < 0.01) at 3.47 cm (SD = 0.33). A pulmonary artery diameter of 3.32 cm (main pulmonary artery diameter + 2 SD) had a 58% sensitivity and 95% specificity for the presence of pulmonary arterial hypertension. It is concluded that, using unenhanced axial 10 mm CT sections, the upper limit of normal main pulmonary artery diameter is 3.32 cm. Pulmonary arterial hypertension should be considered in patients with values above this level.

Adolescent↗
PubMed1997

Splenic blood flow: evaluation with computed tomography.

RATIONALE AND OBJECTIVES: To study splenic perfusion with use of computed tomography (CT). METHODS: Twenty-six control patients without splenoportal disease, six with cirrhosis, and seven with other splenic disease were examined with electron-beam CT. Twenty-five milliliters of iohexol (300 mg of iodine per milliliter) was given intravenously at 10 mL/sec followed by a saline bolus. Multiple single-level axial sections were acquired 8-90 seconds after injection. Perfusion was calculated by dividing maximal splenic enhancement by the area under the circulation-corrected aortic time-enhancement curve. Subjective assessments of enhancement heterogeneity were made, and regional perfusion was calculated in 10 patients with heterogeneous enhancement. Total splenic volume and blood flow were computed in 21 patients. RESULTS: Mean perfusion (controls: 1.29 mL/min/mL, miscellaneous group: 1.07 mL/min/mL) was close to predictions. There was a trend toward lower perfusion in cirrhotic patients (0.87 mL/min/mL), but the difference was not statistically significant. Total splenic blood was increased in patients with cirrhosis (P < .01). Marked perfusion heterogeneity was observed in 41% of spleens, but by 2 minutes splenic enhancement was uniform. CONCLUSION: CT shows promise in the study of splenic blood flow.

Evaluation Studies as Topic↗
PubMed1996

Surgical angioplasty of the left main coronary artery: follow-up with magnetic resonance imaging.

BACKGROUND: Ostial stenosis of the left main coronary artery is a serious condition with a dismal prognosis. The treatment is surgical, with the two viable options being coronary artery bypass grafting and surgical angioplasty of the left main coronary artery. METHODS: We describe the use of surgical angioplasty to treat 3 patients (2 women and 1 man) with left main ostial stenosis using the posterior approach. Patency of the angioplasty was demonstrated subsequently with magnetic resonance imaging. RESULTS: All 3 patients were free of angina 12, 18, and 24 months after operation. Magnetic resonance imaging scans in all 3 patients demonstrated the widely patent left main coronary artery. CONCLUSIONS: Surgical angioplasty is an effective alternative to coronary artery bypass grafting in patients with left main ostial stenosis. Magnetic resonance imaging is an excellent noninvasive method for monitoring the patency of the left main coronary artery.

Adult↗
PubMed1993

Ultrasonic backscatter system for automated on-line endocardial boundary detection: evaluation by ultrafast computed tomography.

OBJECTIVES: The purpose of this study was to evaluate the accuracy of the recently developed echocardiographic on-line endocardial border detection system using ultrafast computed tomography, an independent and proved tomographic imaging modality. BACKGROUND: The automated system for on-line endocardial border detection identifies the blood-tissue interface by acoustic quantification of the ultrasonic backscatter signal. METHODS: Eighteen subjects were screened by conventional echocardiography and acoustic quantification. Ten of these, with high quality echocardiographic images, were also examined by ultrafast computed tomography. Comparable image planes at the midpapillary level were analyzed. Measurements of left ventricular cavity area were compared at end-diastole and end-systole and time course analyses of cavity area during the cardiac cycle were performed. RESULTS: There was good correlation between values for left ventricular end-diastolic area (r = 0.99), end-systolic area (r = 0.93) and fractional area change (r = 0.91) using the two methods. The on-line backscatter system underestimated end-diastolic area (p < 0.001), but the negative bias was small (-1.6 cm2) and the 95% confidence intervals were narrow (-3.6 cm2 to +0.4 cm2). In contrast, the backscatter system overestimated end-systolic area (p < 0.02); the positive bias for this variable was also small (+2.6 cm2) but the confidence intervals were relatively wide (+7.9 to -2.8 cm2). The negative bias of backscatter values for cavity area was fairly constant during diastole and early systole (range -5% to -10%), but during the second half of systole, backscatter values increased progressively relative to computed tomographic values. Real time values for fractional area change measured by the backscatter system were 13% smaller than those determined by ultrafast computed tomography (p < 0.001), with wide confidence intervals (+3% to -30%). Absolute peak rates of area change during systole and diastole were lower by 39% (p < 0.001) and 41% (p < 0.01), respectively, using the on-line ultrasonic backscatter system. Time course analyses revealed the errors to be consistent with cardiac cycle-dependent alterations in gain sensitivity of the ultrasonic backscatter system. CONCLUSIONS: The ultrasonic backscatter system is associated with cyclic cavity area measurement errors that need to be addressed if its early promise for on-line assessment of ventricular function is to be fulfilled. Incorporation of an electrocardiographically triggered time-varying gain control may improve accuracy for on-line analysis of ventricular performance.

Echocardiography↗
PubMed1993

Contrast bolus dynamic computed tomography for the measurement of solid organ perfusion.

RATIONALE AND OBJECTIVES: The authors have investigated the aortic responses to various intravenous bolus injections of nonionic and ionic contrast media and have presented data illustrating the potential of ultrafast computed tomography (CT) to quantify perfusion in the kidney, liver, and spleen. METHODS: Bolus Dynamics Study: Performed in 3 healthy dogs (weight: 35 kg to 36 kg). In 2 dogs, 15 mL of the nonionic agent iohexol and the ionic agent sodium-meglumine diatrizoate were injected at 5, 10 and 20 mL/sec via a venous catheter placed in the superior vena cava; the order of injection was alternated between the 2 dogs. In the third dog, 25 mL of iohexol 300 mg I/mL was compared with diatrizoate 370 mg I/mL with injection rates of 10 and 20 mL/sec. Computed tomography scanning at the level of the midabdominal aorta was performed using an ultrafast CT scanner. Time-density curves were drawn for regions of interest over the aorta, and gamma-variate fits performed. Perfusion Studies: Dynamic perfusion scans of the upper abdomen were performed in more than 50 patients. A dose of 25 mL of iohexol 300 mg I/mL was injected at 10 mL/sec via an intravenous cannula in the antecubital fossa, followed immediately by 25 mL of saline, at the same rate. Scanning was performed at a single level using an ultrafast CT scanner. Regions of interest were drawn and gamma-variate fits were applied to the vascular time-density curves. RESULTS: Bolus Dynamics: Excellent curve fits for aortic time-density curves were obtained. A 10-mL/sec versus a 5-mL/sec bolus produced an 8% higher peak density. Nonionic contrast increased the peak density by a mean of 6%, increased the area under the corrected time-density curve by a mean of 22%, and lengthened the increase time by a mean of 21%. Perfusion Studies: Values obtained were reproducible and correlated well with values predicted from inert gas washout techniques. CONCLUSIONS: Changes in the CT number in a region after an intravenous injection of contrast medium may be used to calculate blood flow per unit volume of tissue. Ultrafast CT offers sufficient data points for accurate calculation. The quality of the aortic bolus is of great importance. Nonionic media offer several important advantages: hemodynamic perturbation is minimized, and they are better tolerated at the high injection rates needed. Low-osmolality nonionic agents produce "better" curves than conventional high-osmolality ionic agents, all other factors being equal. The resulting data are relevant to intravenous digital subtraction angiography and indirect portography as well as to perfusion measurement. The technique of quantitative dynamic CT is theoretically applicable to any cross-sectional modality, notably magnetic resonance.

Animals↗
PubMed1993

Noninvasive imaging for the diagnosis and management of myocardial ischemia.

The past 10 years has seen a revolution in noninvasive cardiac imaging. UFCT and MRI can demonstrate cardiac anatomy in exquisite detail and have become our most accurate methods of measuring ventricular function. PET and MRS are giving insights into myocardial metabolism that were previously impossible in vivo. UFCT and MRI have also made progress in imaging the coronary arteries and bypass grafts. Although neither technique is in a position to rival coronary arteriography, the first steps have been made. Accurate quantification of coronary calcium is possible with UFCT and promises to be our most valuable noninvasive tool in the diagnosis and management of patients with asymptomatic disease. Myocardial perfusion has been assessed with 201TL imaging for years, but new radiopharmaceutical agents and advances in UFCT and contrast-enhanced MRI are likely to bring great improvements. Table 2 lists the current modalities and outlines their main advantages and disadvantages. Despite all this progress, there has been little change in clinical practice. Invasive procedures, i.e., cardiac catheterization or transesophageal echocardiography, are still being performed even when equivalent information can be obtained noninvasively. While limited availability may explain the scant use of PET and UFCT for cardiac imaging, in those centers where it is available, interest is still muted. The need to foster multidisciplinary interaction is real. If the benefits of this revolution are to be passed on to patients, there needs to be a greater willingness among physicians from different specialties to collaborate and to be more tolerant than has occurred in many centers to date. This will not only improve patient care but it will also provide an appropriate evaluation of new technologies. All are critical if we are to solve the continuing problems of ischemic heart disease.

Contrast Media↗
PubMed1992

Duplex Doppler ultrasound for the detection of vascular occlusion following liver transplantation in children.

Sixty-three children and adolescent patients who received 78 consecutive orthotopic liver transplants and had serial duplex ultrasound monitoring were retrospectively reviewed for episodes of occlusion of the hepatic artery or portal vein. There were 13 documented episodes of complete occlusion of the main hepatic artery or a major branch, of which nine were diagnosed by the absence of flow during duplex ultrasound examination. Four occlusions were not detected, two affected hepatic artery branches, one an accessory hepatic artery, and one the main hepatic artery. The overall sensitivity of the method was 69% and specificity 100%. Six portal vein occlusions were documented in five patients and all six were successfully diagnosed on ultrasound examination, giving a sensitivity and specificity of 100%. Three of the patients had simultaneous occlusions of both vessels. In the early post-operative period duplex Doppler ultrasound examination has proved an effective non-invasive method for the detection of vascular occlusion, but is not yet sensitive enough to replace angiography fully for the detection of hepatic artery occlusion, particularly when this occurs distal to the main hepatic artery.

Adolescent↗
PubMed1992

Magnetic resonance imaging and ultrafast computed tomography in cardiac tomography.

Cardiac magnetic resonance imaging and ultrafast computed tomography have been available for several years. While both modalities have become established research tools, neither has gained much acceptance in everyday clinical practice. Continued development has made both techniques easier to use and far more versatile. For patients to benefit from these improvements, it is important that clinicians become more familiar with the current state of the art.

Contrast Media↗
PubMedDate not supplied

Liver perfusion studied with ultrafast CT.

OBJECTIVE: Our goal was to quantify absolute hepatic arterial and portal venous perfusion noninvasively in patients with and without liver disease using ultrafast CT. MATERIALS AND METHODS: A single slice through the porta hepatis was repeatedly scanned after bolus injection of 25 ml of iohexol 300 mg I/ml, followed by a 25 ml saline "chaser" intravenously at 10 ml/s. Thirty-nine controls, 7 cirrhotic patients, and 5 patients with known metastases on the slice plane were studied; hepatic arterial perfusion was determined in 41 patients and portal venous perfusion in 24. Time-attenuation curves from regions of interest drawn over the liver, spleen, aorta, and portal vein were analysed. Hepatic arterial perfusion was calculated by dividing the peak gradient of the liver time-attenuation curve prior to the time of peak splenic attenuation by the peak aortic CT number increase. Splenic perfusion was calculated by dividing the peak gradient of the splenic time-attenuation curve by the peak aortic CT number increase. Portal perfusion was derived by scaling the splenic time-attenuation curve by the ratio of hepatic arterial/splenic perfusion. This scaled curve was subtracted from the liver time-attenuation curve to give a portal curve. The peak up-slope of this curve was divided by the peak rise in splenic or portal vein density. RESULTS: Hepatic arterial perfusion averaged 0.19 ml/min/ml (n = 31) in controls and was raised in cirrhosis to 0.25 ml/min/ml (n = 6) and metastases 0.43 ml/min/ml (n = 4). Portal venous perfusion was 0.93 ml/min/ml (n = 19) in controls and 0.43 ml/min/ml (n = 4) in cirrhosis. Reproducibility has been confirmed. CONCLUSION: Dynamic ultrafast CT shows potential in quantifying arterial and portal hepatic perfusion. The technique may be adaptable to dynamic bolus MRI.

Female↗
PubMedDate not supplied

Aortic motion: a potential pitfall in CT imaging of dissection in the ascending aorta.

OBJECTIVE: Artefacts complicate the diagnosis of thoracic aortic dissection by CT. Aortic compliance and cardiac motion may be responsible but the precise cause of these artefacts remains unclear. MATERIALS AND METHODS: Fifty consecutive clinical thoracic CT examinations performed on a Siemens Somatom Plus scanner (8 mm slice thickness, 1 s scan time) were reviewed (mean patient age 56 years). For each examination, the presence, position, and displacement of motion artefact from the aortic wall were noted at three ascending aortic levels. Cine ultrafast CT on 10 volunteers (mean age 49 years) was used to assess aortic motion for the same three levels (8 mm slice thickness, 50 ms scan time). Digital subtraction of consecutive cine CT allowed the position of the aortic wall throughout the cardiac cycle to be tracked. RESULTS: Curvilinear motion artefacts were seen in the ascending aorta in 17 conventional CT scans, occurring left anterior and right posterior in all but one and maximally at the aortic root (mean amplitude 3.5 mm). Ultrafast CT, however, showed no motion artefact and no significant change in aortic area with systole. Aortic motion in the sagittal-oblique plane at the ascending aorta was confirmed. CONCLUSION: Motion artefacts simulating ascending aortic dissection occur frequently on conventional CT. Their position is predictable and is related to systolic aortic motion from the left anterior to the right posterior position.

Aortic Dissection↗