Right ventricular ejection fraction: comparison of technetium-99m first pass technique and ECG-gated steady state krypton-81m angiocardiography

Right ventricular ejection fraction (RVEF) calculated from ECG-gated steady-state 81mKr angiocardiography and from 99mTc first-pass studies were compared in 30 patients using a digital, single crystal, gamma-camera. Despite the two entirely different approaches RVEF values obtained by the two methods were comparable (r = 0.97): the mean absolute difference between the two techniques was 2.5% +/- 1.5% and the largest observed absolute difference was 5%. In the absence of an accepted reference method for measuring RVEF, this close correlation provides indirect validation of both techniques. The choice of method will therefore depend on several factors, including radiotracer availability, the characteristics of the gamma-camera and the protocol of clinical investigation.     

Automated determination of the right ventricular ejection fraction by digital processing of 81mKr scintigrams

A method is presented for the automated determination of the right ventricular ejection fraction (RVEF) by digital image processing of scintigrams obtained by intravenous infusion of Krypton 81m (^81mKr) dissolved in a glucose solution. End-diastolic and end-systolic sum pictures were computed by the addition of approximately 30–40 frames selected from the time-activity curve of a preliminary, manually drawn, right ventricular region of interest. After processing these two images with an adaptive Wiener filter, the right ventricular contour was determined by a recently developed algorithm using morphological and functional criteria. The RVEF was calculated for a series of 51 patients from the counts in the detected right ventricular regions in the end-diastolic and end-systolic sum images. In 16 patients without evidence of cardiopulmonary disease, the mean RVEF was 50±6.1%. RVEF was significantly reduced in 18 patients with obstructive pulmonary disease (42±6.5%) and in 17 patients with congestive cardiomyopathy (36±7.1%). The correlation coefficient between two determinations of the RVEF was r=0.94. Through digital image processing, the determination of the RVEF by radioimage processing, the determination of the RVEF by radioventriculography with ^81mKr showed high reliability and reproducibility.     

Dynamic isotopic phlebography using soluble krypton-81m

Intravenous peripheral injection of krypton-81m in an isotonic solution permits venous scintigraphy of the lower limbs to be carried out. An anatomic definition of the obstructions and the collateral pathways is therefore easily displayed from the popliteal vein to the vena cava. The physical characteristics of the radionuclide permit iterative or sustained perfusions without accumulation of an excessive background noise and the method is used to obtain scintigraphic images in changing physiological conditions. Analysis of the dynamic data permits venous stasis to be assessed in terms of regional radioactivity at a steady state and transit rate. Various physiological and pathological conditions are analyzed by this method.     

The use of a computer in ventilation-perfusion scintigraphy with Tc-99m macroaggregates and Kr-81m,to obtain a physiological model

In this article we describe a computer program to demonstrate ventilation-perfusion relationships in the lungs, using ^99mTc-MAA and ^81mKr, with the patients sitting upright, the normal physiological situation. The ventilation and perfusion scans are performed simultaneously with both gamma camera and computer adjusted for dual isotope mode. Steady state images are acquired in frontal, dorsal, and left and right posterior oblique positions. Additionally, in the dorsal and frontal projections, a sequence of 12 washout images (5 s) is registered, after closing the Krypton supply. After normalization and further computer processing, the following parameters are calculated in the frontal and dorsal projections, in the whole lung and in four horizontal subregions: washout values, ventilation-perfusion ratios, left to right ratios of ventilation and perfusion, and left to right ratios of the everage pixel values for ventilation and perfusion. Results in a group of eight healthy volunteers are described and discussed.     

81mKr equilibrium radionuclide ventriculography for the assessment of right heart function

Right heart^81mKr equilibrium radionuclide ventriculography was used to derive right ventricular ejection fraction (RVEF) in 12 healthy male volunteers. Anatomical lung subtraction using^99mTc-MAA perfusion scintigraphy was compared with conventional background correction and the effect of imaging projection on the techniques of image analysis evaluated. Both intra and inter observer variability were reduced by anatomical lung subtraction when compared to conventional background correction. In the right anterior oblique (RAO) projection, background corrected RVEF was lower than lung subtracted RVEF - 0.544 ±0.05 and 0.612±0.08 (mean ± SD) (P<0.02). Lung subtracted RVEF in the anterior projection was lower than that with background correction (P<0.05) and lower than lung subtracted RVEF in the RAO projection (P < 0.001). We conclude that optimal separation of right heart structures is achieved in the RAO projection and that reproducibility of the analytical technique is improved by anatomical lung subtraction.     

Evaluation of global and regional left ventricular function using technetium-99m sestamibi ECG-gated single-photon emission tomography

We evaluated a method for the assessment of left ventricular (LV) function with technetium-99m sestamibi ECG-gated single-photon emission tomography (GSPET). GSPET was performed at rest in 21 patients. Images were reconstructed to obtain end-diastolic (ED) and end-systolic (ES) images. Endocardial and epicardial edges of the left ventricle for the ED and ES images were defined using the gradient images and the algorithm developed. LV wall thickness was measured for the mid-ventricular slices of ED and ES images at 10° intervals. The systolic thickening (ST) and the LV ejection fraction [LVEF(GSPECT)] could be determined. These values were compared with the LV ejection fraction (LVEF) estimated using the gated blood pool method. There was a linear correlation between LVEF and ST (r=0.79), and LVEF and LVEF(GSPET) (r=0.87). Histograms of LV thicknesses were generated. Agreement for evaluation of regional wall motion between the method using histograms of LV thicknesses and the gated blood pool study was 92.8% (kappa=0.75). It is concluded that with an appropriate method for LV edge detection, GSPET with ^99mTc-labelled perfusion agents is of use for simultaneous evaluation of myocardial perfusion and assessment of LV function. Received 1 December 1997 and in revised form 26 January 1998     

Comparison of post-stress ejection fraction and relative left ventricular volumes by automatic analysis of gated myocardial perfusion single-photon emission computed tomography acquired in the supine and prone positions

Background  We have previously described an automatic method for measuring left ventricular ejection fraction (LVEF) for myocardial perfusion single-photon emission computed tomography (SPECT). The repeatability of this method has not been previously described. Methods and Results  This study compares LVEF and relative end-systolic and end-diastolic volumes assessed from myocardial perfusion SPECT by our automatic method in 180 consecutive patients undergoing gated myocardial perfusion SPECT with injection of ^99mTc-labeled sestamibi in whom the acquisitions were performed sequentially in supine and prone positions. The algorithm operated completely automatically in the prone and supine positions in 178 of the 180 patients. Very high correlations were observed for LVEF (r=0.93), relative left ventricular end-systolic volume (r=0.98), and relative left ventricular end-diastolic volume (r=0.97). The mean paired absolute difference between LVEFs in the prone and supine position was 3.8±3.2, for left ventricular end-systolic volume was 4.9±4.8 ml, and for left ventricular end-diastolic volume was 7.4±6.7 ml. When patients were classified by the extent and severity of stress perfusion defect, there was no significant difference in repeatability for the measurements in any category. Conclusions  Our algorithm for automatic quantification of LVEF and relative end-systolic and end-diastolic volumes from gated ^99mTc sestamibi myocardial perfusion SPECT is repeatable. When performed in the prone position, values of ejection fractions and ventricular volumes are essentially identical to those obtained in the supine position.     

Blood pool ventriculography with a new technetium-labelled complex (99mTc-DEPIC) : a clinical evaluation

A new, single bolus method of in vivo blood pool imaging using a technetium Tc99m phosphine isocyanide complex (DEPIC) which binds to pre-albumin was evaluated in volunteers (n=4) and patients (n=20). DEPIC was assessed for its safety and possible drug interactions. Its duration of action and quality of ventriculography were compared with imaging using standard in vivo red cell labelling (PYP) during two 3-h scanning periods 1 week apart. DEPIC had a mean plasma halflife of 3.3 h. The count rate over the left ventricle was initially 42% higher with DEPIC than with PYP. However, removal of DEPIC by the liver resulted in equivalent count rates by 1 h, and by 3 h PYP count rates were 22% higher than DEPIC. Immediately post injection mean (SD) difference in the left ventricular ejection fraction between the two methods was 2.4% (7.7%). Satisfactory DEPIC scans were obtained up to 2 h post injection, but by 3 h there was a mean difference of 13% (11.3%). DEPIC was found to be a safe alternative to red all labelling for blood pool angiography, suitable for routine work. The single bolus methodology and high initial count rates offer improved efficiency and a capability for truly emergency scanning.     

Kinetics of Tc-99m hexakis t-butyl isonitrile in normal and ischemic canine myocardium

Hexakis ^99mTc-tertiary butyl isonitrile (^99mTc-TBI) was studied as a cardiac perfusion imaging agent in nine dogs with partial occlusion of the LAD. Thirty min after applying the stenosis, ^99mTc-TBI was injected into the right atrium (RA) in five dogs and left atrium (LA) in four dogs. Normal and ischemic zone regional myocardial ^99mTc-TBI activites were monitored continuously for 4 h. Dogs with LA injections had minimal and equivalent 4 h fractional clearance from the normal and ischemic zones. Dogs with RA injections had minimal, but significantly lower 4 h fractional ^99mTc clearances in the ischemic zone (0.08±0.08) compared to the normal zone (0.16±0.07, P<0.05). The delayed ischemic zone clearance is probably due to the high initial lung uptake observed after RA injection. Despite the differences in clearance, this minimal amount of redistribution could not be detected on gamma camera images. The minimal myocardial washout and redistribution, and the 140 keV gamma make ^99mTc-TBI a promising cardiac perfusion imaging agent.Dr. Okada is an Established Investigator of the American Heart Association     

Identification of factors affecting technetium 99m leucocyte labelling by phagocytic engulfment and evelopment of an optimal technique

Human autologous leucocytes can be simply and reproducibly labelled by phagocytic engulfment of technetium 99m stannous colloid with high leucocyte-labelling efficiency (LLE), similar human biodistribution to indium-111-oxine labelled leucocytes and good cell viability. A mean particle size of 2.1 ms is optimal for phagocytosis and the most important parameter in maintaining reproducibly high neutrophil uptake. It is more critical than hitherto appreciated. When such variables as type of colloid, purity of starting materials, speed of mixer rotation when preparing colloid and labelling leucocytes, heparin concentration, freshness of colloid preparation, type of sterilising membrane filter used and incubation time of cells with colloid are rigidly controlled, consistent labelling efficiencies in excess of 90% can be obtained with neutrophil predominance. The lyophilised kit tested produced suboptimal results.     

Clinical evaluation of technetium-99m infecton for the localisation of bacterial infection

The aim of the study was to distinguish infection from inflammation in patients with suspected infection using technetium-99m Infecton. Ninety-nine patients (102 studies) referred for infection evaluation underwent imaging with 400 MBq^99mTc-Infecton at 1 and 4 h. Most patients had appropriate microbiological tests and about half (56) had radiolabelled white cell scans as well. No adverse effects were noted in any patient. The clinical efficacy of^99mTc-Infecton depended in part on whether imaging was undertaken during intibiotic therapy for infection or not. In consultation with the microbiologist, 5–14 days of appropriate and successful antibiotic therapy was considered adequate to classify some results as true-negatives. The figures for sensitivity and specificity of^99mTc-Infecton for active or unsuccessfully treated infection were 83% and 91% respectively. It is concluded that^99mTc-Infecton imaging contributed to the differential diagnosis of inflammation. It is being used as the first imaging modality when bacterial infection is suspected.     

Accuracy of a new method for semi-quantitative assessment of right ventricular ejection fraction by cardiovascular magnetic resonance: Right ventricular fractional diameter changes

Objective

Longitudinal shortening is traditionally considered the predominant part of global right ventricular (RV) systolic function. Less attention has been paid to transverse contraction. The aim of this study was to evaluate RV transverse motion by cardiovascular magnetic resonance (CMR) in a large cohort of patients and to assess its relationship with RV ejection fraction (RVEF).

Study design

We retrospectively analyzed the CMR scans of 300 patients referred to our center in 2010. RVEF was determined from short axis sequences using the volumetric method. Transverse parameters called RV fractional diameter changes were calculated after measuring RV diastolic and systolic diameters at basal and mid-level in short axis view (respectively FBDC and FMDC). We also measured the tricuspid annular plane systolic excursion (TAPSE) as a longitudinal reference.

Results

Our population was divided into 2 groups according to RVEF. 250 patients had a preserved RVEF (>40%) and 50 had a RV dysfunction (RVEF ≤40%). Transverse and longitudinal motions were significantly reduced in the group with RV dysfunction (p < .0001). After ROC analysis, areas under the curve for FBDC, FMDC and TAPSE, were respectively 0.79, 0.82 and 0.72, with the highest specificity and sensitivity respectively of 88% and 68% for FMDC (threshold at 20%) for predicting RV dysfunction. FMDC had an excellent negative predictive value of 93%.

Conclusion

RV fractional diameter changes, especially at the mid-level, appear to be accurate for semi-quantitative assessment of RV function by CMR. A cut-off of 20% for FMDC differentiates patients with a low (EF ≤ 40%) or a preserved RVEF.     

Osteoid osteoma simulating osteomyelitis: Differentiation with Tc-99m HIG scintigraphy

We present a case of osteoid osteoma with a history of mild pain, local swelling and point tenderness on the right lower leg. The diagnosis of osteoid osteoma was difficult due to the atypical clinical history and misleading radiological and bone scan findings. When it is difficult to differentiate an osteoid osteoma from osteomyelitis using CT, MRI or bone scan; HIG scintigraphy can be used to exclude an infection.     

99mTc-labelling of leucocytes with 99mTc-DPO: a complex developed for myocardial imaging

The lipophilic ^99mTc-DPO complex, developed as a myocardial imaging radiopharmaceutical, was used to label leucocytes. After an incubation of 0.1 ml ^99mTc-DPO (8 g DMPE*2HCl) with mixed leucocytes in plasma, the labelling efficiency was over 70%. During incubation in 5 ml plasma, a loss of activity was found between 20% (1 h) and 35% (3 h) caused by elution. Disturbances of cell viability could not be found with the help of the chemiluminescence test. The in vivo recovery was determined in three dogs and was 45%–50% (0.5 h), 30%–36% (1 h), and 18%–24% (3 h). Autologous ^99mTc-DPO-leucocytes were used on seven patients with suspected osteomyelitis, there were four true negative and three true positive results. The target/nontarget ratio determined by ROI in the positive cases was 1.8 to 2.5 at 3 h after injection.     

The scintigraphic evaluation of myocardial infarction and regional ventricular performance using technetium-99m hexakis (t-butylisonitrile) technetium (I) (TBI): A new myocardial imaging agent

Technetium-99m hexakis (t-butylisonitrile) technetium (I) (^99mTc-TBI) is a new myocardial perfusion imaging agent. To determine its potential in the evaluation of myocardial infarction, 15 patients with suspected or confirmed acute infarction were studied by bedside imaging in the coronary care unit. Good-quality planar scintigrams in multiple projections were obtained in 13 patients. Gated perfusion studies were performed in 14 patients, and for comparison 13 of these were restudied 24–72 h later by standard gated equilibrium blood pool radionuclide ventriculography. Conventional and planar scintigraphic criteria for myocardial infarction (acute or old) agreed in 12 (92%) patients (k=0.81, p<0.05). All the infarctions detected by scintigraphy were associated with electrocardiographic Q-waves. Localization of infarction by the electrocardiogram and scintigraphy exhibited moderate agreement (k=0.49, p<0.1). Regional wall motion analysis by standard radionuclide ventriculography and gated ^99mTc-TBI scintigraphy were in complete agreement for 25 (64%) of 39 left ventricular segments (k=0.35, p<0.05). However, in 7 other segments, associated with areas of infarction, regional wall motion abnormalities were noted only on gated ^99mTc-TBI scintigraphy. Therefore, ^99mTc-TBI scintigraphy can readily provide data on regional myocardial perfusion and wall motion, permitting detection and localization of areas of myocardial infarction. The superior imaging properties, ready availability and low cost of ^99mTc point to the considerable potential value of ^99mTc-TBI in assessing patients with suspected or confirmed myocardial infarction.This work was done during the tenure of a British-American Research Fellowship of the American Heart Association and the British Heart Foundation, with Dr. S. Campbell the recipient     

The effect of chemotherapy on the uptake of technetium-99m sestamibi in breast cancer

Technetium-99m sestamibi scintimammography has been used primarily in the diagnosis of breast cancer. It has also been suggested that this technique could be used to monitor response to chemotherapy and possibly to predict those patients in whom no response can be expected. An initial study was performed in nine patients with primary breast cancer. All patients underwent prone lateral and anterior^99mTc-sestamibi imaging at diagnosis and 4–7 months later, after they had received cytotoxic chemotherapy. The uptake of^99mTc-sestamibi in the breast was compared with that in normal surrounding breast tissue and this ratio was expressed as the target to background ratio. In all patients treated there was a reduction in uptake of^99mTc-sestamibi after treatment, such that whilst all the tumours could be seen before treatment, only three were visible following chemotherapy. There was a significant fall in the mean target to background ratio of the patients undergoing chemotherapy: the tumour to background ratio was 2.48 before chemotherapy and 1.40 after treatment (P<0.001, paired Student'st test). This fall in tumour activity was observed both in those patients in whom a clinical response was seen and in the two patients in whom the tumour enlarged despite chemotherapy. It appears that the reduced uptake of^99mTc-sestamibi seen after chemotherapy may be a non-specific change and therefore may not be predictive of the clinical response to treatment.     

Mismatch between99mTc-DTPA aerosol and81mKr lung ventilation scintigraphy: a pitfall of radionuclide imaging

Pulmonary ventilation and perfusion scintigraphies were performed using^99mTc-MAA,^81mKr, and^99mTc-DTPA aerosol in a patient with asthma. Lung perfusion scintigraphy and^99mTc-DTPA aerosol scintigraphy showed multiple matching defects, however,^81mKr ventilation scintigraphy showed mismatch with lung perfusion scintigraphy. A pitfall of this examination was discussed.     

A micro-autoradiographical study of the localization of 99mTc(Sn)-MDP and 99mTc-MDP in undecalcified bone sections

The localization of ^99mTc(Sn)-MDP in bone tissue was compared with ^99mTc-MDP by means of microautoradiography of undecalcified bone sections. Sections of good histological quality were obtained by a rapid embedding method in methylmethacrylate. No differences were found in the localization of these radiopharmaceuticals in fetal rat calvariae after incubation in vitro or in rat femora after administration in vivo. In the incubation experiment, hydrolyzed ^99mTc was formed. The uptake was high in areas of new bone formation. No uptake was seen in cells or in resorbing areas. In compact bone ^99mTc(Sn)-MDP was predominantly taken up in the vicinity of blood vessels.     

Abnormal uptake of technetium-99m hexakis-2-methoxyisobutylisonitrile in a primary cardiac lymphoma

Abnormally high uptake of technetium-99m hexakis-2-methoxyisobutylisonitrile (^99mTc-SESTAMIBI) in the right ventricle and in the septum was observed in a 47-year-old woman initially presenting with dysarthria and left hemiparesis. Endomyocardial biopsy demonstrated a high-grade malignant non-Hodgkin's lymphoma. Complete remission was achieved by combined cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) chemotherapy and radiotherapy of the heart and mediastinum. The post-remission single photon emission tomography (SPET) ^99mTc-SESTAMIBI study showed a homogeneous distribution pattern, in agreement with echocardiography computed tomography and magnetic resonance imaging. Increased uptake of ^99mTc-SESTAMIBI, a myocardial perfusion agent, has been observed in some benign and malignant tumours. It may prove to be useful in the diagnosis and follow-up of malignancies. Offprint requests to: G. Medolago     

Detection of anomalous systemic venous return and intraatrial baffle leakage by radionuclide angiocardiography

The case presented here is a 27-year-old patient who was born with common atrium and left superior vena cava (LSVC). Construction of interatrial septum and intraatrial baffle with pericardium was performed 16 years ago. Radionuclide angiocardiography (RAC) showed that a substantial amount of blood flow from the LSVC was directed to the inferior vena cava through the hemiazygos vein (HAV). It also detected a baffle leak and a left to right shunt at the atrial level. Subsequent RAC after reoperation initially showed insignificant flow through the atrial baffle, major flow through the HAV, and no shunt. Repeat RAC one year after surgery showed increased flow through the baffle and diminished flow through the HAV, without a satisfying explanation. This case illustrates the value of RAC in detecting various types of cardiovascular abnormality and subtle hemodynamic changes.