Peter Theissen

Comparison of Low-Dose Dobutamine–Gradient-Echo Magnetic Resonance Imaging and Positron Emission Tomography With [18F]Fluorodeoxyglucose in Patients With Chronic Coronary Artery Disease A Functional and Morphological Approach to the Detection of Residual Myocardial Viability

BACKGROUND There have been conflicting reports of whether substantial myocardial thinning alone as an indirect sign of myocardial scarring is sufficient evidence to exclude the presence of viable myocardium in patients with previous myocardial infarction and persisting regional left ventricular akinesia. Demonstration of a dobutamine-induced contraction reserve in postischemic viable but akinetic myocardium may serve as a direct indicator of myocardial viability. In the present study, end-diastolic wall thickness at rest and dobutamine-induced systolic wall thickening assessed by magnetic resonance imaging (MRI) were compared with corresponding [18F]fluorodeoxyglucose uptake as assessed by positron emission tomography (FDG-PET). METHODS AND RESULTS Thirty-five patients with myocardial infarction (infarct age, > 4 months) and regional akinesia or dyskinesia assessed by left ventriculography underwent rest and dobutamine MRI studies (10 micrograms dobutamine.min-1.kg-1) and FDG-PET followed by segmental analyses of end-diastolic wall thickness, systolic wall thickening, and FDG uptake in corresponding short-axis tomograms. Two definitions of viability, as assessed by MRI, of a segment akinetic at baseline were used: (1) end-diastolic wall thickness of > or = 5.5 mm (the mean minus 2.5 SD of a healthy control group [n = 21]) and (2) evidence of dobutamine-induced systolic wall thickening > or = 1 mm. Segments were graded as viable by FDG-PET if FDG uptake was > or = 50% of the maximum uptake in a region with normal wall motion as assessed by left ventriculography. Preserved end-diastolic wall thickness in akinetic regions was found in 17 of 35 (48%) patients at rest, and functional recovery within the infarct region was found in 19 of 35 (54%) patients during dobutamine infusion. Viability of the infarct region was indicated by FDG-PET in 23 of 35 patients (66%), yielding a diagnostic agreement between FDG uptake and myocardial morphology in 29 of 35 (83%) and between dobutamine-induced contraction reserve and FDG-PET in 31 of 35 (89%). Of 2200 segments, 482 (22%) were akinetic at rest. Of these akinetic segments, 234 (48%) had preserved end-diastolic wall thickness, 251 (52%) had a dobutamine-induced contraction reserve, and 299 (62%) were graded as viable by FDG-PET. Correlations of FDG uptake with end-diastolic wall thickness at rest (r = .48) and with dobutamine-induced wall thickening (r = .42) were similar. Comparison of segmental MRI and FDG-PET gradings indicated that dobutamine-induced wall thickening was a better predictor of residual metabolic activity (sensitivity, 81%; specificity, 95%; positive predictive accuracy, 96% than was end-diastolic wall thickness (sensitivity, 72%; specificity, 89%; positive predictive accuracy, 91%). However, grading a segment as viable if at least one of both MRI parameters fulfilled viability criteria improved the sensitivity (88%) of MRI for FDG-PET-assessed metabolic activity without a major decrease in specificity (87%) or positive predictive accuracy (92%). CONCLUSIONS Viable myocardium is characterized by preserved end-diastolic wall thickness and a dobutamine-inducible contraction reserve. Both parameters should be taken into account to maximize the sensitivity of MRI in the detection of regions with signs of viability on FDG-PET images.

Dobutamine Magnetic Resonance Imaging Predicts Contractile Recovery of Chronically Dysfunctional Myocardium After Successful Revascularization

OBJECTIVES This study sought to evaluate whether myocardial viability, as assessed by magnetic resonance imaging (MRI), reliably predicts postrevascularization left ventricular (LV) recovery. BACKGROUND Compared with positron emission tomographic findings, MRI has proved to be a reliable technique for the identification of residual myocardial viability. However, the predictive accuracy of MRI-assessed preserved end-diastolic wall thickness (DWT) and dobutamine-induced systolic wall thickening (SWT) for LV functional recovery has not yet been evaluated. METHODS Rest and low dose dobutamine MRI was performed in 43 patients with a chronic infarct (> or =4 months since ischemic event) and LV dysfunction who had undergone revascularization of the infarct-related vessel. On the basis of segmental evaluation of corresponding short-axis tomograms, infarct regions were graded viable by MRI if 1) DWT was > or =5.5 mm, and 2) dobutamine-induced SWT was > or =2 mm in > or =50% of dysfunctional segments related to the infarct region. Functional recovery was defined as SWT > or =2 mm in > or =50% of infarct-related segments at rest 4 to 6 months after successful revascularization. RESULTS Recovery of regional SWT could be observed in 27 (63%) of 43 patients. Comparison MRI grading before and after revascularization indicated that dobutamine-induced SWT was a better predictor of LV functional recovery (sensitivity 89%, specificity 94%) than was preserved DWT (sensitivity 92%, specificity 56%). Segments that remained akinetic after revascularization had significantly lower DWT (6.0+/-3.1 mm [n = 219] vs. 9.8+/-2.6 mm [n = 188], p < 0.001) than those with improved SWT. Left ventricular ejection fraction increased significantly in patients with dobutamine-induced SWT than in those with no contractile reserve (14+/-9% vs. 3+/-9%, p < 0.0002), and the magnitude of this increase was correlated with the number of dobutamine-responsive segments per infarct region (r = 0.68, p < 0.0001). CONCLUSIONS Quantitative assessment of dobutamine-induced SWT in chronic infarcts by MRI is a highly accurate predictor of LV functional recovery, and the presence of significantly reduced DWT reliably indicates irreversible myocardial damage. Therefore, dobutamine stress testing for the assessment of myocardial viability can be restricted to patients with preserved DWT.

Fluorine-18 fluorodeoxyglucose positron emission tomography and iodine-131 whole-body scintigraphy in the follow-up of differentiated thyroid cancer

Abstract.Metastases of differentiated thyroid cancer may show different uptake patterns for fluorine-18 fluorodeoxyglucose and [131I]NaI. FDG positron emission tomography (PET), iodine-131 whole-body scintigraphy (131I WBS) and magnetic resonance imaging were performed in 58 unselected patients, and spiral computed tomography (CT) of the lung in 25 patients. Thirty-eight patients presented with papillary carcinomas, 15 patients with follicular carcinomas and five patients with variants of follicular carcinoma. Primary tumour stage (pT) was pT1 in 3, pT2 in 19, pT3 in 11 and pT4 in 25 cases. For the detection of metastases, FDG PET was found to have a sensitivity of 50%, 131I WBS a sensitivity of 61%, and the two methods combined a sensitivity of 86%. When FDG PET was limited to patients with elevated thyroglobulin (Tg) levels and negative 131I WBS, the sensitivity of this algorithm was 82%. Of the 21 patients with lymph node metastases, seven presented with FDG uptake but no iodine uptake. In four of them, a second FDG hot spot appeared in a lymph node metastasis of normal size. Five of the seven patients underwent surgery. None of the eight patients with pulmonary metastases smaller than 1 cm exhibited FDG uptake, while five of them had iodine uptake. All had positive results on spiral CT. In conclusion, FDG PET cannot be substituted for 131I WBS. If the Tg level is elevated and 131I WBS is negative, FDG PET can be used to detect lymph node metastases and complements anatomical imaging. A spiral CT of the lung is useful to exclude pulmonary metastases before planning a dissection of iodine-negative lymph node metastases.

Cost-effectiveness of FDG-PET for the management of potentially operable non-small cell lung cancer: priority for a PET-based strategy after nodal-negative CT results

Abstract. Decision analysis is used here to establish the most cost-effective strategy for management of potentially operable non-small cell lung cancers (NSCLCs). The strategies compared were conventional staging (strategy A), dedicated systems of positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) in patients with normal-sized (strategy B) or in patients with enlarged mediastinal lymph nodes (part of strategy C), and FDG-PET followed by exclusion from surgical procedures when both computed tomography (CT) and PET were positive for mediastinal lymph nodes (strategy D) or when PET alone was positive (strategy E). Based on published data, the sensitivity and specificity of FDG-PET were estimated at 0.74 and 0.96 for detecting metastasis in normal-sized mediastinal lymph nodes, and at 0.95 and 0.76 when these lymph nodes were enlarged. The calculated probability of up-staging to M1 by using PET was 0.05. The costs quoted correspond to the cost reimbursed in 1999 by the public health provider in Germany. The incremental cost-effectiveness ratio (ICER) of strategy B was much more favourable (143 EUR/LYS; LYS = life year saved) than the ICER of strategy C (36,667 EUR/LYS). In strategy B, the use of PET did not raise the overall costs because the costs of PET were almost balanced by a better selection of patients for beneficial cancer resection. The exclusion from biopsy confirmation in strategies D and E led to cost savings that did not justify the expected reduction in life expectancy. In sensitivity analyses, the ICERs of strategy B were robust to the pretest likelihood of N2/N3, to penalized test parameters of PET and to reimbursement of PET. However, the ICER of strategy B would be raised to 28,000 EUR/LYS through use of thoracic PET without whole-body scanning. To conclude, the implementation of whole-body PET with a full ring of detectors in the preoperative staging of patients with NSCLC and normal-sized lymph nodes is clearly cost-effective. However, patients with nodal-positive PET results should not be excluded from biopsy.

Feasibility of high-dose dipyridamole-magnetic resonance imaging for detection of coronary artery disease and comparison with coronary angiography

To assess the feasibility, safety and usefulness of gradient-echo magnetic resonance imaging (MRI) combined with pharmacologic stress testing for the detection of coronary artery disease, 23 patients without previous myocardial infarction but with significant stenosis (greater than 70% diameter stenosis) of greater than or equal to 1 major coronary artery were selected for dipyridamole-MRI stress testing. Each patient underwent MRI at rest, and high-dose dipyridamole-MRI (0.75 mg/kg over 10 minutes) of corresponding basal and midventricular short-axis tomograms. Additionally, these patients performed symptom-limited exercise stress tests. All short-axis tomograms were evaluated on a standardized segmental basis by grading each segment as normal, hypokinetic, akinetic or dyskinetic. Dipyridamole-MRI was considered pathologic if segmental wall motion deteriorated by greater than or equal to 1 grade after dipyridamole. For comparison with coronary angiography, segmental wall motion gradings were related to the respective coronary artery territories in the short-axis plane. Pathologic dipyridamole-MRI was obtained in 18 of 23 (78%) patients. For 1- and 2-vessel diseases, sensitivity was 69 and 90%, respectively. Exercise stress tests were pathologic in 14 of 23 (66%) patients. For 1- and 2-vessel diseases, sensitivity of exercise stress test was 58% (7 of 12 patients) and 77% (7 of 9), respectively. Sensitivity/specificity of dipyridamole-MRI for the localization of the stenosed coronary artery was 78/100% for left anterior descending, 73/100% for left circumflex, and 88/87% for right coronary artery stenoses. It is concluded that dipyridamole-MRI is a feasible nonexercise-dependent test for detection and localization of functionally significant coronary artery disease.

Chronic myocardial infarction: Assessment of morphology, function, and perfusion by gradient echo magnetic resonance imaging and 99mTc-methoxyisobutyl-isonitrile SPECT

To assess the ability of magnetic resonance imaging (MRI) to identify the anatomic and functional abnormalities associated with completely scarred myocardium, 20 patients with chronic transmural myocardial infarction confirmed by electrocardiography and cineventriculography were examined by gradient echo MRI. Myocardial perfusion at rest was assessed in corresponding transverse sections using 99mTc-methoxyisobutyl-isonitrile single-photon emission computed tomography (MIBI-SPECT). MRI scar was defined as diastolic wall thickness (DWT) 2.5 SD below corresponding normal values or systolic wall thickening (delta WT) less than or equal to 1 mm. For MIBI-SPECT images, scar was defined as a MIBI uptake less than 2.5 SD below normal values. By MIBI-SPECT, 152 segments contained normal tissue and 88 contained scarred myocardium. In 226 of 240 (94%) segments, MRI gradings by DWT and MIBI-SPECT gradings were identical. DWT by MRI was higher in normal than in scarred MIBI-SPECT segments (10 +/- 1 versus 4 +/- 2 mm, p less than 0.001). In 230 of 240 (96%) segments, MRI gradings by delta WT and MIBI-SPECT gradings were identical. Segments graded normal by MIBI-SPECT showed higher delta WT by MRI than scar segments (5 +/- 1 versus 0.3 +/- 1 mm, p less than 0.001). MIBI-SPECT perfusion defect size and regions with reduced DWT on MRI tomograms correlated well (r = 0.85). This study indicates that myocardial regions fulfilling electrocardiographic and ventriculographic criteria for transmural myocardial scar are clearly depicted by regional diastolic wall thinning and delta WT less than or equal to 1 mm on gradient echo MR images.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Systemic Steroid Treatment in Chronic Polypoid Rhinosinusitis Evaluated with Magnetic Resonance Imaging

BACKGROUND: The aim of this prospective study was to evaluate the efficacy of a combined (local and systemic) steroid therapy on the extent of chronic polypoid rhinosinusitis and patient symptoms. METHODS AND PATIENTS: Subjects of this study were 20 patients with severe chronic polypoid rhinosinusitis with total or subtotal narrowing of the all sinuses. A nasal budesonide spray (2 × 0.1 mg/day) and an oral fluocortolone medication with a daily reduction during a 12-day period (total dose: 560 mg = group 1) and a 20-day period (total dose: 715 mg = group 2), respectively, were administered. Before and after the steroid treatment we evaluated the extent of the sinusitis with MRI and patient symptoms with symptom-related questionnaires. RESULTS: A significant reduction (>30%) of the chronic polypoid rhinosinusitis was observed in 50% of MRI findings. The steroid effect on polypoid masses was heterogeneous in different anatomic areas (maxillary sinus 40%, anterior ethmoid 19%, posterior ethmoid 33%, sphenoidal sinus 61%, frontal sinus 46%). Most sinusitis-related symptoms were distinctly diminished in most patients (80%). No major side effects were observed. CONCLUSIONS: A combined short-term steroid therapy is highly effective in chronic polypoid rhinosinusitis, reducing the mucosal inflammation mainly in the large sinuses and reducing the incidence of symptoms significantly. However, this therapy was insufficient in the anterior ethmoid and cannot replace the current surgical treatment concept of the osteomeatal complex in CPR. The indication for such a short-term steroid therapy is the preoperative treatment. It facilitates functional endoscopic sinus surgery by reducing the extent of surgical procedures, the time, and thereby the risks of sinus surgery. (Otolaryngol Head Neck Surg 1999;120:517-23.)

Depth of olfactory sulcus and olfactory function.

The aim of this study was to identify whether the depth of the olfactory sulcus relates to olfactory function in healthy subjects. Forty-four healthy, male volunteers (age range 22-45 years, mean age 28.3 years) were included in this study. Olfactory function was measured for phenyl ethyl alcohol odor thresholds, odor discrimination, and odor identification. Magnetic resonance imaging of the olfactory sulcus was performed immediately following olfactometry. Based on previous investigations the depth of the olfactory sulcus was measured in the plane of the posterior tangent through the eyeballs. Olfactory function correlated significantly with left-sided depth of the olfactory sulcus (r(44)=0.33, P=0.03); no such correlation was seen for the right side. In addition, olfactory sulcus depth was found to be significantly deeper on the right compared to the left side (t=5.61, P<0.001). The present results suggest that there is small, but significant relation between morphological brain structures and measures of olfactory function. Further, lateralization of olfactory sulcus depth may correlate to functional lateralization in the olfactory system. Thus, it may be carefully speculated that sensory input in the olfactory system results in cortical growth in the area of the olfactory sulcus, at least at some developmental stage.

Stress functional MRI: Detection of ischemic heart disease and myocardial viability

Breath‐hold gradient‐echo magnetic resonance imaging (MRI) in conjunction with pharmacologic dobutamine stress has become a practical tool to investigate patients with chest pain. The presence of high‐grade coronary artery stenoses can be detected more accurately than with stress echocardiography. The main diagnostic advantage of MRI is in patients with suboptimal echocardiographic image quality. Depiction of left ventricular anatomy and function at rest and during low‐dose dobutamine stress is also clinically useful for evaluating patients with severely impaired left ventricular function for the presence of residual myocardial viability. Recovery of regional and global left ventricular function can be accurately predicted by stress functional MRI. J. Magn. Reson Imaging 1999;10:667–675, 1999.

Assessment of residual viability in patients with myocardial infarction using magnetic resonance techniques

Magnetic resonance techniques have only recently been employed to assess residual myocardial viability after myocardial infarction. Three approaches have been described to achieve this purpose: First, the use of signal intensity changes on spin-echo images with and without the application of contrast media to define irreversible injury to the myocardium in acute and subacute infarcts; second, measurement of metabolite concentrations within the infarct area using magnetic resonance spectroscopy, and third, quantitation of myocardial thickness and systolic wall thickening in chronic infarcts. This paper reviews the pertinent literature and compares MR techniques with other imaging techniques used in the diagnosis of myocardial viability.