Blood Pool Imaging Research Articles

A new subtraction method for obtaining myocardial perfusion images with oxygen-15 water and positron emission tomography.

The myocardial positron emission tomograms which are obtained during the perfusion phase following bolus injection of O-15 water (H2(15)O) intravenously require subtraction of the blood pool activity overlaid upon the myocardium. Subtraction has been carried out using the blood pool images obtained in the same position following single inhalation of O-15 labeled carbon monoxide gas (C15O). However, because a difference in activity exists between the left ventricular (LV) cavity and the right ventricular (RV) cavity, simple subtraction of the LV cavity activity using C15O blood pool images induced significant over-subtraction in the right-side heart including the interventricular septum and RV wall. We developed a new method, "two-component subtraction," in which the C15O blood pool images were decomposed into the right-side and left-side components using the early phase images of the H2(15)O dynamics under the assumption that the whole activity of that phase was distributed in the right-side heart homogeneously. Thus we subtracted the blood pool spillover from RV and LV separately. This method provided myocardial perfusion images of high quality which were well correlated with N-13 ammonia images.

Noninvasive Evaluation of Angina Pectoris

There is a sturdy body of evidence that exercise radionuclide studies are both more sensitive and more specific than the exercise ECG in the diagnosis of suspected coronary disease. The two major radionuclide diagnostic-prognostic techniques used for coronaiy disease—perfusion imaging of myocardial blood flow and cardiac blood-pool imaging—are reviewed.

Cardiac nuclear medicine

In this paper, the principal applications of nuclear medicine to studies of the heart are described. First, gated cardiac blood pool imaging is discussed, then thallium-201 myocardial imaging, myocardial infarct scintigraphy with 99mTc pyrophosphate, and evaluation of intracardiac shunts. In gated cardiac blood pool imaging, the patient's red blood cells are labeled with 99mTc. Images of the cardiac blood pool are then obtained in multiple projections and displayed in an endless-loop cine display. Quantitative indices of cardiac function are readily obtained, and a variety of functional images can be generated. Blood pool imaging may also be performed with use of a first-pass technique that yields similar information. Applications of blood pool imaging are discussed. The theory and techniques of planar and tomographic thallium-201 myocardial imaging are described, together with their application in the diagnosis of coronary artery disease. The prognostic value of thallium imaging is also examined. Myocardial infarct imaging with 99mTc pyrophosphate is described, and clinical indications are reviewed. Left-to-right cardiac shunts can be evaluated by following the first transit of a bolus of radiopharmaceutical through the lungs. Right-to-left shunts may be evaluated by injection of 99mTc macroaggregated albumin.

Acute left ventricular dysfunction during unsuccessful weaning from mechanical ventilation.

The authors studied the hemodynamic effects of rapidly weaning from mechanical ventilation (MV) 15 patients with severe chronic obstructive pulmonary disease (COPD) and cardiovascular disease who were recovering from acute cardiopulmonary decompensation. In each patient, 10 min of spontaneous ventilation (SV) with supplemental oxygen resulted in reducing the mean esophageal pressure (X +/- SD, + 5 +/- 3 to -2 +/- 2.5 mmHg, P less than .01) and increasing cardiac index (CI) 3.2 +/- 0.9 to 4.3 +/- 1.3 1/min/M2, P less than .001), systemic blood pressure (BP 77 +/- 12 to 90 +/- 11 mmHg, P less than .001), heart rate (HR 97 +/- 12 to 112 +/- 16 beats/min, P less than .001), and, most importantly, transmural pulmonary artery occlusion pressure markedly increased (PAOPtm 8 +/- 5 to 25 +/- 13 mmHg, P less than .001), mandating a reinstitution of MV. In four patients with left ventricular (LV) catheters, the PAOP correlated with the LV end-diastolic pressure during both MV and SV. Gated blood pool imaging showed SV increased the LV end-diastolic volume index (65 +/- 24 to 83 +/- 32/M2, P less than .002) with LV ejection fraction unchanged. Patients were treated for a mean of 10 days with diuretics, resulting in a reduction of blood volume (4.55 +/- 0.9 1 to 3.56 +/- 0.55 1) and body weight (-5 kg, P less than .001). Subsequently, nine of the 15 patients were weaned successfully from mechanical ventilation with unchanged PAOP.

Prolonged PR interval associated with an abnormal frontal plane QRS axis as an electrocardiographic criterion of left ventricular function

The aim of this study was to investigate whether, in patients who had had one or more myocardial infarctions, the electrocardiographic appearances of prolonged PR interval associated with an abnormal frontal plane QRS axis are correlated with the value of left ventricular ejection fraction. Seventy-three consecutive patients all of whom had had at least one myocardial infarction, were divided into 3 groups: Group A, 22 patients having on their electrocardiogram a prolonged PR interval and an abnormal frontal plane QRS axis; Group B, 15 patients having an abnormal QRS axis as a solitary conduction disturbance; and Group C, 36 patients without conduction abnormalities. The ejection fraction, determined in all patients by gated blood pool imaging, was found to be 30% ± 8 (mean ± 1 SD) in Group A, 53% ± 21 in Group B, and 52% ± 14 in Group C ( P < 0.001). An ejection fraction of less than 40% was found in 91% of patients in Group A, in 33.33% in Group B, and in 8.33% in Group C ( P < 0.01). Multiple segment ventricular wall contraction abnormalities were found in 50, 6.66, and 11.11%, respectively ( P < 0.001). It can be presumed, therefore, that in patients after one or more myocardial infarctions, this association of conduction abnormalities signifies a severe impairment of ventricular contractility and may identify a subgroup with a high prevalence of severely depressed ejection fraction.

THREE PHASE BONE SCAN (TPBS) FOLLOWING POROUS COATED HIP ARTHROPLASTY (PCHA)

Twenty-five uncomplicated PCHA in 21 patients were prospectively studied with serial TPBS at approximately 7 days, and 3, 6, 12, 18, and 24 months (mos) postoperatively. The medial (MS), distal (DS), and lateral (LS) segments of the tip were evaluated for intensity of uptake on flow, blood pool, and bone images (grade O = background, 1+ < iliac crest, 2+ = iliac crest, 3+ > iliac crest). The flow and blood pool reference was contralateral iliac vein. On flow 135/136 scans had grade O activity. On blood pool 131/136 scans had grade O activity. Of the extensive bone scan data, which will be presented, several patterns were identified: 1. The MS had stable or decreasing activity from 3 to 24 mos in (23/25) PCHA; 2. No patient had MS activity of 3+ from 12 to 24 mos; 3. The MS was always less than or equal to LS from 3 to 24 mos; 4. The LS had increasing activity during at least one interval in (12/25) PCHA; 5. The LS was 2+ or 3+ at 24 mos in 8/25 PCHA; 6. Activity “migrated” from MS to DS to LS in 7/25 PCHA; 7. No dominant pattern was noted in the DS. In conclusion, this study presents the spectrum of findings at the prosthetic tip on TPBS in uncomplicated PCHA. Based on these findings the following recommendations are made: If (1) increased activity is present on flow or blood pool, (2) the MS increases in activity during 3–24 mos, (3) the MS has 3+ activity during 12–24 mos, or (4) the MS is > LS, then one should evaluate further for complications. Increasing activity in LS or LS activity of 3+ does not necessarily imply a complication.

The role of ischemia and ventricular asynergy in the genesis of exercise‐induced ST elevation

Sixty-five patients with ST elevation were retrospectively studied in order to evaluate the clinical significance and underlying mechanisms of ST-segment elevation during exercise. Of these, 50 patients had previous myocardial infarction (Group I) and 15 patients did not (Group II). Exercise thallium-201 imaging was performed on 30 patients, resting gated blood pool imaging was performed on 33 patients, and 23 underwent cardiac catheterization for clinical indications. When the two groups were compared, patients in Group I had more frequent multivessel disease (9/13 vs. 3/10, p less than 0.05), anterior infarctions (33/50 vs. 4/10, p less than 0.02), while Group II patients had more frequent single-vessel disease (7/10 vs. 4/13, p less than 0.05). For Group I patients, the most common reason for termination of exercise was fatigue and/or dyspnea (35/50 vs. 0/15, p less than 0.05), with an irreversible defect noted in both stress and delayed views on thallium imaging (20/24 vs. 1/6, p less than 0.05). In Group II, the most common reason for termination was angina (15/15 vs. 2/50, p less than 0.001), with reversible thallium defects noted more frequently (4/6 vs. 3/24, p less than 0.01). Thus, we conclude that in patients with Q waves, left ventricular dysfunction rather than ischemia is the mechanism for ST elevation. In these patients angina is rare, but fatigue, dyspnea, multivessel disease, and fixed thallium defects are common. In patients with non-Q-wave exertional ST elevation, ischemia is the rule, manifested by frequent chest pain and reversible thallium defects.

Left ventricular characteristics during exercise in patients after Fontan's operation for tricuspid atresia.

Left ventricular function during supine bicycle exercise was studied using multigated blood pool imaging in ten patients with tricuspid atresia after Fontan's operation and in 13 children and adults (control group). The mean age of the patients was 16 years and the mean interval between operation and study was 5 years. The peak work loads that the patients could perform were similar to those in the control group. Work loads and heart rates during radionuclide study in the operated group were also similar to those in the control group. The left ventricular ejection fraction at rest and during exercise in the operated group was less than in the control group, although the net increase during exercise was similar in the two groups. During exercise, left ventricular end-diastolic volume decreased significantly in the operated group. In the control group, this variable did not change significantly. Left ventricular stroke volume increased during exercise in the control group but it did not change significantly in the operated group. These data indicate that in patients after Fontan's operation, left ventricular performance remains low during exercise, which is in part due to diminished left ventricular preload reserve, and this in turn may be caused by reduced reserve of right heart output.

こう筋前縁部に発生した静脈性血管腫の１例

A case of venous hemangioma in the premasseteric region of a 22-year-old man was reported. The chief complaint was a painless swelling in his right premasseteric region. His general condition was good. A thumb-tip-sized, elastic soft tumor, which fluctuated in size, was found at the premasseteric region. The first impression was hemangioma. CT-scan and ultrasonography revealed a soft tissue mass with several cystic spaces. Together with the findings of RI-angiography and blood pool imaging, a hemangioma was diagnosed. Under general anesthesia, the tumor was removed surgically by intra-oral approach. Histologically, it was diagnosed as a venous hemangioma.

｀９９ｍ´Ｔｃ標識ジエチレントリアミン五酢酸‐ヒト血清アルブミン（ＤＴＰＡ‐ＨＳＡ）による左室機能測定

A newly developed blood pool agent 99mTc-DTPA-HSA (Japan Mediphysics, Inc.) was used for ECG gated blood pool scintigraphy. The radiopharmaceutical remained in the blood pool with disappearance half time of 420 min in a healthy subject. The gated blood pool study in the same subject clearly demonstrated contracting left ventricle and right ventricle both with planar and SPECT images. Three healthy volunteers and 14 patients were included in the study, in that gated blood pool images were successfully obtained. The left ventricular ejection fraction (LVEF) calculated by the analysis of LV volume curves correlated well with those obtained by echocardiography (US). In 11 patients with implanted pacemaker for complete atrioventricular block and sick sinus syndrome changes of LVEF were evaluated in relation to pacing rates. The mean LVEF at pacing rate of 60/min was 58.5%, which decreased to 54.4% at 100/min pacing rate. However, changes of LVEF in individual patient did not show same pattern. We conclude that 99mTc-DTPA-HSA is a convenient blood pool scanning agent which does not require time consuming labeling preparations. Stable labeling and slow blood clearance allows its use for repeat measurements of LVEF in different conditions in a patient such as with pacemaker.

Serial assessment of left ventricular function following coronary bypass surgery by radionuclide angiocardiography.

The serial change in left ventricular function was investigated by radionuclide angiocardiography in 25 patients undergoing coronary artery bypass grafting (CABG). Multiple gated equilibrium blood pool imaging was performed at rest before, and at 1, 2 and 4 weeks after the operation and also during exercise on a supine bicycle ergometer before and 4 weeks after surgery. Global ejection fraction at rest was unchanged after CABG while peak ejection rate increased significantly at 1 and 2 weeks (p less than 0.01 and p less than 0.05 respectively) after the operation. Peak filling rate at rest was generally unchanged after surgery but peak filling rate during the first third of diastole at rest decreased significantly at 1 and 2 weeks (p less than 0.01 and p less than 0.05). After CABG, the increases in ejection fraction and peak ejection rate with exercise were significantly greater than those values measured before surgery. The increases, due to exercise, in peak filling rate and peak filling rate during the first third of diastole were unchanged after the operation. Radionuclide angiocardiography affords a safe, noninvasive, and highly reproducible procedure for serially assessing ventricular function in patients undergoing CABG. Our study revealed early diastolic dysfunction within 2 weeks of surgery and that CABG abolished abnormalities in left ventricular function induced by exercise.

A new approach to image subtraction in immunoscintigraphy: preliminary results.

Recently proposed image comparison software is applied to immunoscintigraphy. The software performs geometric and gray level registration of two images and generates an image of the statistically significant differences. It permits the comparison of scintigraphic images recorded at different times. It is used to subtract 113mIn and 111Inphytate colloid liver scans and early (blood pool) images from 131I or 111In-monoclonal Ab images and to compare Ab images recorded at different times. Using the procedures made possible by this software, only images recorded using the same radionuclide or using radionuclides of about the same energy are compared. Anti CEA, 19-9 and OC 125 F(ab)2 fragments labeled with 131I or 111In are used in 32 patients with 47 demonstrated recurrences or metastases of colorectal or ovarian cancers. The overall sensitivities of the unprocessed and processed images are 25/47 and 41/47 respectively. The improvement in sensitivity is particularly high in the liver when In labelled Ab are used. This technique improves the contrast of the images, but the interpretation must take into account the components of the non target activity (kidney, bone marrow, colon...) which are not removed by the image subtraction method.

Abnormalities of the hands during the blood-pool phase of skeletal scintigraphy

A 12-year-old boy with renal adenocarcinoma presented for follow-up metastatic evaluation by skeletal scintigraphy. After nephrectomy, he had been treated with doxorubicin, dactinomycin, vincristine, and cyclophosphamide. He had been staged preoperatively and at one year postoperatively by bone scintigraphy; both previous studies were unremarkable. Incidental triplephase images of the hands were obtained subsequent to injection on the dorsum of the left hand, prompted by a futile search for accessible veins of both upper extremities (Fig 1). There are four possible explanations of the abnormal finding depicted in Fig 1. Three of the four considerations are: adherence of the radiopharmaceutical to chemically traumatized venous endothelium, secondary to chemotherapy; adherence of the radiopharmaceutical to mechanically traumatized venous endothelium, secondary to a recent indwelling venous catheter; or thrombophlebitis, secondary to one of the first two possibilities. Intravenous administration of doxorubicin, dactinomycin, and vincristine, the three chemotherapeutic agents which had been used to treat this patient, can be complicated by soft-tissue inflammatory reactions. 1'2 However, the patient had received none of these medicines for the past year. The patient had had no indwelling catheter for the past year and had no current symptoms or signs of thrombophlebitis. Hence, the probability that the abnormal finding could be attributable to an artifact from a catheter is unlikely. Having eliminated the first two possible explanations, the third explanation is likewise discounted. Because of the patient's generalized weakness, imaging began 15 seconds after the patient was injected while he was seated in a wheelchair with subsequent placing of hands on camera surface. An arterial-phase image was acquired, that initially and incidentally recorded the venous phase, which demonstrated gradual clearance by the basilic vein and slower clearance by the cephalic vein via the dorsal rete (Fig 2). The literature is replete with articles reporting blood-pool images of the hands subsequent to arterial-phase imaging. We are unaware of any reports of direct evaluation of venous drainage of the hands, which would of course require venipuncture of the hand. The recording of venous clearance in our patient was mere happenstance and provided an initially vexing blood-pool image. In the osseous-phase image in this patient, the venipuncture artifact persisted, but the curvilinear abnormality was no longer demonstrated. We conclude that the blood-pool image (Fig 1) represents normal venous clearance in the unfamiliar setting of hand injection. First-pass and osseous-phase imaging of various skeletal sites has been widely used in resolving a variety of clinical questions. However, image acquisition during the blood-pool phase was not widely employed until it was reported within the context of triple-phase scintigraphy, popularized recently in the differentiation of cellulitis from underlying osteomyelitis. Because osteomyelitis of the hands and wrists is infrequent in contrast to its more frequent suspicion involving the lower extremities and pelvis, few reports of blood-pool imaging of the hands have been generated. However, a wide variety of lesions of the hands, particularly neurovascular instability, have been reported, as reflected in the following gamut.

Digitizing and signal averaging of left ventricular pressure signals using a dedicated radionuclide imaging system.

A method for obtaining left ventricular (LV) volume curves, synchronized with average LV pressure (LVP) curves for calculation of LV contractility, is described. Multiple gated blood pool imaging was performed to calculate average LV volume curves. Simultaneously with this acquisition, LVPs and aortic pressures were measured by indwelling catheters and recorded on an FM tape recorder. These signals were fed to the computer as image information and averaged and processed by the software developed for this purpose. Pressure resolution of the calibrated images was 4 mmHg/pixel when provision was made for a maximum pressure of 200 mmHg. A good correlation (r = 0.99) was obtained between the calculated peak LVPs and mean peak LVPs read from the chart recorder. The regression equation was: digitized peak LVP = 1.04 x chart recording--5.11 mmHg and the standard error of the estimate was 2.9 mmHg. Similar results were obtained with the aortic pressure (AP) measurements (digitized AP = 0.94 x chart recording + 6.37 mmHg, the standard error of the estimate was 3.8 mmHg). The digitized data also allowed the construction of pressure-volume loops for interpretation of ventricular contractility.

Abnormalities of the hands during the arterial phase of skeletal scientigraphy

A 37-year-old woman presented for the evaluation of reflex sympathetic dystrophy syndrome (RSDS). Seven years prior to the current study, her right hand was accidentally caught in a large industrial machine. Most of the skin of her right hand and wrist had been avulsed, and three ipsilateral fingers were fractured. After left antecubital injection, a rapid sequence arterial flow study was obtained (Fig 1). A static blood-pool image was acquired 1 to 2

Comparison of intravenous dipyridamole thallium cardiac imaging with exercise radionuclide angiography

Sixty-eight patients underwent dipyridamole thallium imaging and exercise blood pool imaging in order to determine the functional significance of various dipyridamole thallium imaging redistribution patterns. Serial thallium images and blood pool regional wall motion were interpreted by three independent observers. Rest and exercise left ventricular ejection fractions were calculated by two observers and were averaged. Transient thallium defects were associated with normal rest and exercise left ventricular ejection fraction and regional wall motion. Mild persistent thallium defects were associated with normal ejection fraction and regional wall motion at rest, with a deterioration in both with exercise. Severe persistent thallium defects were associated with reduced ejection fraction and regional wall motion at rest, but no further deterioration with exercise. These data support the following postulates: Transient dipyridamole thallium defects are due to mild coronary artery stenoses that cause no detectable functional consequence during levels of exercise achieved in this study. Mild persistent defects are due to more severe stenoses that do cause a functional reduction in wall motion during exercise. Although appearing qualitatively persistent, these defects probably represent very slow thallium redistribution and ischemia rather than scar. Finally, severe persistent defects probably represent myocardial scar.

Abdominal SPECT imaging

Over the past several years, abdominal single photon emission computed tomography (SPECT) imaging has evolved from a research tool to an important clinical imaging modality that is helpful in the diagnostic assessment of a wide variety of disorders involving the abdominal viscera. Although liver-spleen imaging is the most popular of the abdominal SPECT procedures, blood pool imaging is becoming much more widely utilized for the evaluation of cavernous hemangiomas of the liver as well as other vascular abnormalities in the abdomen. Adjunctive indium leukocyte and gallium SPECT studies are also proving to be of value in the assessment of a variety of infectious and neoplastic diseases. As more experience is acquired in this area, SPECT should become the primary imaging modality for both gallium and indium white blood cells in many institutions. Renal SPECT, on the other hand, has only recently been used as a clinical imaging modality for the assessment of such parameters as renal depth and volume. The exact role of renal SPECT as a clinical tool is, therefore, yet to be determined.

Evaluation of myocardial perfusion and function by single photon emission computed tomography

Although planar radionuclide techniques provide accurate, noninvasive measurements of myocardial perfusion and function that are of proven clinical value in the evaluation of the cardiac patient, they are limited by poor object contrast and superimposition of surrounding structures. Due to incomplete angular sampling and significant longitudinal distortion, limited angle tomography did not solve these problems. Single photon emission computed tomography (SPECT) can acquire scintillation information over very small angles of rotation and, thus, improve both object contrast and delineation of overlying or adjacent structures without distortion. The early SPECT systems were cumbersome, dependent on individual user developed software, and had extremely long acquisition and processing time. Improved camera design, new software algorithms, and the use of array processors have simplified and standardized quality control, decreased processing time, and minimized the number of user interventions. New image display formats and quantitative methods of analysis have made interpretation less cumbersome, more reliable and highly reproducible. Cardiac SPECT has been used with thallium-201 and gated blood pool imaging in both research and clinical applications and shown an improvement over planar methods of acquisition.

Atrial kinetics and left ventricular diastolic filling in the healthy elderly

A delay of left ventricular isovolumic relaxation and decrease in myocardial compliance may result in a decline of measured early filling rates in elderly subjects. Previous studies of diastolic function, however, have not excluded coronary artery disease or addressed the contribution of atrial contraction to diastole. The present study evaluated radionuclide-derived diastolic variables in 13 healthy elderly volunteers aged 75 +/- 6 years without symptoms or risk factors for coronary disease who had normal findings on the stress electrocardiogram, stress gated blood pool imaging and two-dimensional echocardiogram. Results were compared with those of a group of 10 healthy young volunteers aged 26 +/- 5 years. High count, 32 frame, double-buffered gated blood pool acquisitions were obtained at rest in the left anterior oblique view with an RR interval variation less than 5%. Left ventricular time-activity curves were analyzed and flow-volume loops for each group were constructed. In the healthy elderly: peak early diastolic filling rate is decreased, time of peak early filling and time to first third of diastolic filling are delayed, and peak late left ventricular filling rate and percent of atrial filling volume are augmented, suggesting an adaptive response of the atria to diminished left ventricular compliance.

Inotropic effect of enoximone in patients with severe heart failure: Demonstration by left ventricular end-systolic pressure-volume analysis

Left ventricular end-systolic pressure-volume analysis was employed to assess the inotropic effect of the phosphodiesterase inhibitor enoximone (formerly MDL-17,043) in nine patients with severe heart failure (New York Heart Association class IV symptoms, mean ejection fraction = 0.22). Left ventricular pressure-volume loops were constructed using high fidelity left ventricular pressure measured with micromanometer-tipped catheters and simultaneous left ventricular volume obtained by gated blood pool imaging. Afterload was reduced with the vasodilator nitroprusside to generate the baseline left ventricular end-systolic pressure-volume relation, a relatively load-independent measure of contractile function. The intravenous administration of enoximone (mean dose 75 mg) shifted the end-systolic pressure-volume point upward and leftward from the baseline pressure-volume relation in eight of the nine patients, demonstrating a positive inotropic effect of this agent. The maximal rate of left ventricular pressure development (peak positive dP/dt) increased from 1,030 +/- 142 to 1,381 +/- 219 mm Hg/s (p less than 0.01) on enoximone despite a significant decrease in preload (as assessed by left ventricular end-diastolic pressure and volume) and a small, insignificant decrease in mean arterial pressure. Two patients developed angina after enoximone administration; both patients had coronary artery disease and experienced a greater than 30% increase in heart rate-systolic blood pressure product. Thus, enoximone has a significant inotropic effect in patients with severe heart failure. Like other inotropic drugs, it has the potential to increase myocardial oxygen demand and thereby precipitate ischemia.