Automated comparison of dual-photon absorptiometric studies of the lumbar spine.

An automated image comparison procedure was developed to optimize the precision of bone mineral density measurements by dual-photon absorptiometry. Changed acquisition conditions cause differences between two images to be compared. Alignment of one image with respect to the other is performed by a transformation that involves a rotation, a horizontal or vertical shift, and a correction for the soft tissue level. The best possible transformation is found in a stepwise search, guided by initial estimations of its parameters. After optimum transformation of one image, the region of interest of the other image is applied to both of them. Duplicate measurements of 9 patients and 15 normal subjects were performed; automated analysis yielded improved precision with respect to manual analysis. The coefficient of variation (CV) was also computed. The CV for automated analysis was 2.00% for patients and 1.04% for normal subjects compared to 3.55 and 1.93%, respectively, for manual analysis. For phantoms, the precision was 2.67% for manual analysis and 0.49% for automated analysis.

Cerebral blood flow during migraine attacks without aura and effect of sumatriptan.

OBJECTIVE: To study regional cerebral blood flow (rCBF) during migraine attacks without aura and after treatment with sumatriptan. DESIGN AND INTERVENTION: We performed three technetium Tc99m hexemethyl-propyleneamineoxime single photon emission computed tomography scanning procedures in patients with migraine who participated in a double-blind, placebo-controlled, randomized clinical trial (1) outside an attack, (2) during an attack, and (3) after treatment of the attack with 6 mg of subcutaneous sumatriptan. SETTING: University hospital. PATIENTS: We studied 20 patients with migraine without aura, 15 of whom were evaluated under all three conditions and five of whom were evaluated under only two conditions. OUTCOME MEASURES: The single photon emission computed tomographic images were evaluated semiquantitatively with regard to (1) the degree of asymmetry of the rCBF between the headache side and the nonheadache side and (2) the ratio of the rCBF in regions of interest to the rCBF in two reference areas (cerebellum or frontal cortex). RESULTS: We found no significant rCBF asymmetries outside or during the attack or after treatment with sumatriptan, and there were no significant changes of the rCBF ratios during the attack (compared with outside the attack) or after treatment of the attack (compared with during the attack). CONCLUSION: Migraine attacks without aura and treatment of the attacks with 6 mg of subcutaneous sumatriptan are not associated with detectable focal changes of the rCBF.

Optimization of follow-up measurements of bone mass.

In bone densitometry, the precision of the instrument, the number of measurements and the time-points of the measurements are important criteria for monitoring bone mass changes. The most appropriate follow-up procedure can be determined by numerical comparison of various combinations of these three criteria. This can be done by computing the confidence interval of changes in bone mass. We developed a model to estimate the length of a confidence interval for the observed changes in individual patients. With specific instrument precision, a specified number of measurements and, assuming a linear rate of bone mass changes, the best estimate of the actual changes in bone mass is obtained by measurements at the end of an observation period. With the current precision of bone densitometers, follow-up of patients with yearly duplicate measurements is recommended. A shorter scan time interval offers no additional information unless very rapid bone loss is expected.

Limited precision of lumbar spine dual-photon absorptiometry by variations in the soft-tissue background.

The estimation error due to variations in soft-tissue baseline in lumbar bone mineral content (BMC) measured by dual-photon absorptiometry (DPA) was calculated with a new method of automatic baseline subtraction. In water phantom measurements, the s.d. of the soft-tissue (ST) baseline matched closely (r = 0.98) to the random error, calculated using 44 keV and 100 keV count rates and the directly determined baseline variations. In 21 volunteers and in 70 patients with osteoporosis, the ST variations were larger than the expected random error, revealing a source of error related to the inhomogeneity of soft tissue. The estimation error in BMC caused by ST variations was 0.7% in healthy subjects (mean BMC 40.5 gHA) and 1.5% in patients (mean BMC = 26.4 gHA). These results indicate that ST-related errors are an important limit to the precision of lumbar DPA measurements.

Delineating elliptical objects with an application to cardiac scintigrams.

To delineate the myocardium in planar thallium-201 scintigrams of the left ventricle, a method, based on the Hough transformation, is presented. The method maps feature points (X, Y, Y')-where Y' reflects the direction of the tangent in edge point (X,Y)-into the two-dimensional space of the axis lengths of the ellipse. Within this space, a probability density function (pdf) can be estimated. When the center of the ellipse or its orientation are unknown, the 2-D pdf of the lengths of the axes is extended to a 5-D pdf of all parameters of the ellipse (lengths of the axes, coordinates of the center, and the orientation). It is shown that the variance of the edge-point-based estimates of the axis lengths increases when the location error of the center of the supposed ellipse or its orientation error increases. The likelihood of the estimates is expected to decrease with increasing variance. Therefore, local search algorithms can be applied to find the maximum likelihood estimate of the parameters of the ellipse. Curves describing the convergency of the algorithm are presented, as well as an example of the application of the algorithm to real scintigrams. The method is able to detect contours even if they are only partly visualized, as in thallium scintigrams of the myocardium of patients with ischemic heart disease. As long as the number of parameters describing the contour is relatively low, such an algorithm is also suitable for application to differently curved contours.

Assessment of acute myocardial infarction by nuclear imaging techniques.

In recent years, nuclear cardiology techniques have been successfully applied in patients with acute myocardial infarction. These scintigraphic measurements have provided important diagnostic, therapeutic, and prognostic information based on the extent of myocardial damage and the functional reserve of the left ventricle. In particular, in the thrombolytic era, myocardial perfusion imaging and radionuclide angiography have been shown to be valuable methods for studying the effects of reperfusion on the extent of myocardial damage. Nuclear magnetic resonance imaging, preferably with contrast enhancement, is one of the newly developed nuclear imaging techniques that have probably the greatest potential in accurately delineating myocardial infarct size and in evaluating left ventricular function. Radionuclide procedures, on the other hand, employ more biologically oriented tracers and are therefore capable of monitoring biochemical changes in the course of acute myocardial infarction.

Scintigraphic evidence of asymptomatic impaired left ventricular function in type I diabetics.

Asymptomatic myocardial disease has been described in relation to longstanding insulin-dependent diabetes mellitus. To detect myocardiopathy in a selected group of 14 patients (aged 21-38 years, duration of diabetes 10-20 years) with insulin-dependent diabetes, we have performed equilibrium gated nuclear angiography with Fourier filtered analysis. These patients had no clinical or echocardiographic signs of cardiac disease. We examined six patients with severe proliferative retinopathy, and eight patients with no signs of retinopathy at fluorescence angiography. The global ejection fraction was within normal limits in all cases. Fourier analysis of scintigraphic data, however, revealed wall motion abnormalities (abnormal amplitude and phase shift) of the left ventricle in all 14 patients, particularly in the anterior and/or septal region. No correlation was found between the degree of wall motion disturbances and prevailing blood glucose or HbA1 concentrations or the presence of retinopathy or autonomic neuropathy. It is concluded that equilibrium gated nuclear angiography in combination with Fourier filtered analysis is a sensitive method of detecting myocardial abnormalities in patients suffering from insulin-dependent diabetes mellitus without cardiac symptoms.

Markers of bone turnover in Gaucher disease: modeling the evolution of bone disease.

CONTEXT: Gaucher disease (GD) is a lysosomal storage disorder characterized by abundant presence of macrophages. Bone complications and low bone density are believed to arise from enhanced bone resorption mediated through macrophage-derived factors. OBJECTIVE: The objective of the study was to investigate the relationship between bone turnover and bone complications in GD. DESIGN: This was a retrospective cohort study and review of the literature. PATIENTS: Forty adult type I GD patients were included in the study. OUTCOME MEASURES: Levels of the bone-resorption marker, type 1 collagen C-terminal telopeptide, and two bone-formation markers, N-terminal propeptide of type 1 procollagen and osteocalcin, were investigated in relation to clinical bone disease, measures of overall disease severity, and imaging data representing bone marrow infiltration. RESULTS: Osteocalcin was decreased in 50% of our patients (median 0.35 nmol/liter, normal 0.4-4.0), indicating a decrease of bone formation. Type 1 collagen C-terminal telopeptide and N-terminal propeptide of type 1 procollagen were within the normal range for most patients. Osteocalcin concentration was negatively correlated to measures of overall disease severity and positively correlated with imaging data (correlation coefficient 0.423; P = 0.025), suggesting a relation with disease severity. A review of the literature revealed variable outcomes on bone resorption markers but more consistent abnormalities in bone formation markers. Two of three reports conclude that bone-formation parameters increase in response to enzyme therapy, but none describes an effect on bone-resorption markers. CONCLUSIONS: In contrast to earlier hypotheses, we propose that in GD patients, primarily a decrease in bone formation causes an imbalance in bone remodeling.

Aspects of performance assessment of whole body imaging systems.

Regular quality control is one of the cornerstones of nuclear medicine and a prerequisite for adequate diagnostic imaging. Many papers have been published on quality control of planar and tomographic imaging systems. Up to now, however, only minor attention has been given to the assessment of the performance of whole body imaging systems. In this paper we present a comprehensive set of test procedures including acceptance testing and regular quality control. It is not our purpose to present a thorough analysis of the methods and results. The selection of the tests is discussed and the tests are described; some results are presented. In addition action thresholds are proposed. The quality control tests can be applied to systems with either a moving detector or a moving imaging table, and to both detectors with a large field of view and detectors with a small field of view. The tests presented in this paper do not require special phantoms or sources other than those used for quality control of stationary gamma cameras. They can be applied for acceptance testing and for performance testing in a regular quality assurance programme.

The clinical value of 18F-FDG detection with a dual-head coincidence camera: a review.

Positron emission tomography (PET) has evolved into a technique that can accurately determine the distribution of positron-emitting radionuclides. The addition of a coincidence detection mode to a standard dual-head detector system has resulted in the option of single-photon and annihilation coincidence detection. This new device for imaging fluorine-18 2-fluoro-2-deoxy-D-glucose (18F-FDG) accumulation in neoplasms became commercially available in 1994. Besides conventional low-energy imaging in the collimated single-photon mode, it offers a relatively inexpensive opportunity to perform uncollimated PET by switching to the coincidence acquisition mode. This review summarises the clinical value of 18F-FDG detection with a dual-head coincidence camera in oncology. The results are compared with the overall results obtained using dedicated PET scanners. With respect to head and neck tumours, 18F-FDG coincidence mode gamma camera imaging (CGI) yields results that are in agreement with those obtained with dedicated PET scanners. With regard to other malignancies, such as lung cancer, lymphoma and brain tumours, data in the literature are too scarce to draw any definite conclusions. In general, the results of 18F-FDG CGI in tumours >15 mm seem to be comparable to those obtained with dedicated PET scanners, whereas in tumours <15 mm, the relative sensitivity of 18F-FDG CGI is approximately 80%. Using attenuation correction, the diagnostic yield of 18F-FDG CGI may increase. However, further clinical investigation is required to definitely establish its value in staging primary disease, therapy monitoring and assessment of tumour recurrence in clinical oncology.

A breathing lung phantom for 81mKr lung ventilation studies its use in dosimetry and quality control.

The construction of a breathing lung phantom that can be used to measure the amount of radioactive gas in the lungs as well as to determine the absorbed dose is described. For a lung ventilation study that consists of 6 views of 300 kcnts each, an effective dose equivalent of 50 microSv was calculated. The phantom is also suitable for comparison of different generator systems.

Comparison of four commercially available 81Rb-81mKr generators: quality testing using a breathing lung phantom.

Four commercially available 81Rb-81mKr generators, including their elution systems, were compared. Considerable differences in useful output between the various generators were found. When a standardized elution system was used, the differences became much less. Differences in the tubing and inaccuracy of the flow meters were found to be the major causes of the original differences. The user should be aware of a loss of output that may occur when the generator is eluted with dry air.

Automatic assignment of elliptical ROIs: first results in planar scintigrams of the left ventricle.

Several algorithms for quantitative analysis of 201Tl scintigrams require operator assigned elliptical regions. Therefore these algorithms are hampered by inter- and intra-observer errors. In this paper we present a robust algorithm to determine automatically contours with elliptical shapes. The algorithm is based on the Hough transformation and can determine the parameters describing an ellipse even in low signal-to-noise ratio images and when the contour is only partially visualized such as in non-perfused regions of the left ventricular myocardium. As long as the number of parameters to describe the shape of the contour is not too large, the same kind of algorithm can also be used for differently shaped contours, and for 3D elliptical contours as in SPECT.

The reproducibility of single photon absorptiometry in a clinical setting.

The reproducibility of single photon absorptiometry (SPA) results for detection of changes in bone mineral content (BMC) was evaluated in a clinical setting. During a period of 18 months with 4 different sources, the calibration scans of an aluminium standard had a variation of less than 1% unless the activity of the 125I source was low. The calibration procedure was performed weekly and this was sufficient to correct for drift of the system. The short term reproducibility in patients was assessed with 119 duplicate measurements made in direct succession. The best reproducibility (CV = 1.35%) was found for fat corrected BMC results expressed in g/cm, obtained at the site proximal to the 8 mm space between the radius and ulna. Analysis of all SPA scans made during 1 year (487 scans) showed a failure of the automatic procedure to detect the space of 8 mm between the forearm bones in 19 scans (3.9%). A space adjacent to the ulnar styloid was taken as the site for the first scan in these examinations. This problem may be recognized and corrected relatively easy. A significant correlation was found between BMC of the lower arm and BMC of the lumbar spine assessed with dual photon absorptiometry. However, the error of estimation of proximal BMC (SEE = 20.0%) and distal BMC (SEE = 19.4%) made these measurements of little value to predict BMC at the lumbar spine in individuals. The short term reproducibility in patients combined with the long term stability of the equipment in our clinical setting showed that SPA is a reliable technique to assess changes in bone mass at the lower arm of 4% between 2 measurements with a confidence level of 95%.

Dual photon absorptiometry for bone mineral measurements using a gamma camera.

A gamma camera was equipped with a special collimator and arm assembly for bone mineral measurements with dual photon absorptiometry (DPA). The system was evaluated in vitro and in vivo and compared both with a rectilinear DPA and a dual energy X-ray (DEXA) system. All 3 systems showed a linear response in measurements of 4 vials, containing different amounts of hydroxyapatite. Phantom measurements with the gamma camera system showed a precision of 1.6% to 2.8%. Results obtained in 8 healthy volunteers with rectilinear and gamma camera systems were well correlated (R2 = 0.78). With the photon beam directed from posterior to anterior, the separation of vertebrae was easy with the gamma camera system. We conclude that bone mineral measurements can be made with a gamma camera for assessment of fracture risk and in the decision process whether a patient needs treatment or not. For follow-up, the precision of DPA with a gamma camera is inadequate.

The diagnostic value of immediate post-exercise left ventricular ejection fraction (LVEF).

The diagnostic value of immediate post-exercise left ventricular ejection fraction (LVEF) was assessed in 161 patients at rest, during maximal exercise, and immediately post-exercise by radionuclide angiography. Fifteen patients had a second examination, giving a total of 176 radionuclide examinations. Additionally, the correlation between post-exercise LVEF and physical validity was investigated. Sixty-one patients (35%) with a recent myocardial infarction (less than 4 weeks), 66 patients (37%) with an old myocardial infarction (greater than 4 weeks), and 21 patients (12%) with valvular lesions were studied. Twenty-eight patients (16%) with an abdominal aneurysm were considered as controls based on history and a normal resting and exercise electrocardiogram (ECG). LVEF and a cumulative regional wall motion (RWM) score for three regions were obtained. LVEF post-exercise was significantly increased compared to LVEF at maximal exercise in all four diagnostic groups. Absolute LVEF values were significantly dependent on the level of exercise. We conclude that immediate post-exercise LVEF should not be used for separating patients with and without coronary artery disease.

Improvement of left ventricular function in silent ischemia following myocardial infarction, after administration of diltiazem.

In a group of 72 patients with acute myocardial infarction who underwent a maximal symptom-limited predischarge exercise test in conjunction with radionuclide angiography, 25 (35%) showed greater than 1 mm asymptomatic ST-T-segment depression during exercise. All 25 patients underwent repeated exercise radionuclide angiography 2 days later, 2 h after oral intake of 120 mg diltiazem. Double product was not significantly different before and after diltiazem both at rest and during exercise. Maximal ST-T-segment depression after diltiazem was reduced from 2.4 +/- 0.9 mm to 0.8 +/- 0.6 mm (p less than 0.01). Left ventricular ejection fraction (LVEF) at rest was (before diltiazem) 52.1 +/- 8.9% and (after diltiazem) 55.1 +/- 12.3% (NS). During exercise, LVEF improved after diltiazem from 42.8 +/- 12.1% to 49.1 +/- 10.8% (p less than 0.05). Regional wall motion score (1 = normal, 2 = hypokinetic, 3 = akinetic, 4 = dyskinetic) at rest before diltiazem was 9.9 +/- 2.3 and, after diltiazem, was 9.0 +/- 1.9 (NS). During exercise, regional wall motion score improved after diltiazem from 5.9 +/- 1.3 to 4.2 +/- 1.2 (p less than 0.02). We conclude that diltiazem has acute beneficial effects on asymptomatic ST-T-segment depression and on global and regional left ventricular function in post-infarction patients with silent ischemia.

The acute effects of intravenous nisoldipine on left ventricular function within 24 h after acute myocardial infarction.

Nisoldipine is a calcium antagonist with potent coronary vasodilating effects in patients with chronic stable angina pectoris. We studied the acute effects of nisoldipine in six patients within 24 h (mean 14 +/- 4 h) after the onset of myocardial infarction. Nisoldipine was administered as a 4.5 micrograms kg-1 intravenous bolus over 3 min followed by intravenous infusion of 0.2 microgram kg-1 min-1 during 60 min. Radionuclide angiography, cardiac output and intra-arterial blood pressure measurements were performed before and during nisoldipine. Left ventricular ejection fraction increased from 48.3 +/- 10.3% to 55.3 +/- 11.8% (P = 0.034) during nisoldipine infusion. Regional wall motion score changed during nisoldipine infusion from 3.3 +/- 2.5 to 1.8 +/- 2.6 (P = 0.027). Cardiac output increased from 5.5 +/- 1.0 to 7.3 +/- 1.3 l min-1 (P = 0.0001). Heart rate increased from 78 +/- 12 to 88 +/- 11 beats.min-1 (P = 0.004). Mean arterial blood pressure decreased from 91.7 +/- 20.2 to 78.7 +/- 13.1 mmHg (P = 0.038). The rate-pressure product did not change significantly during nisoldipine infusion. It is concluded that nisoldipine improves global and regional left ventricular function in patients with acute myocardial infarction within the first 24 h. Our findings suggest that this effect is achieved without increasing myocardial oxygen demand.

Aspects of fetal thyroid dose following iodine-131 administration during early stages of pregnancy in patients suffering from benign thyroid disorders.

Detrimental effects on the thyroid of the developing fetus as a result of iodine-131 treatment for thyrotoxicosis of the mother in the first trimester of pregnancy are discussed. Dose estimations under typical clinical circumstances yield a fetal thyroid dose of 100- 450 Sv. This dose may increase considerably if the blood concentration of (131)I in the mother remains high. Under such circumstances there may be fetal thyroid dysfunction, which can lead to severe abnormalities.