Cerebral hemodynamics in patients with chronic obstructive carotid disease by rCBF, rCBV, and rCBV/rCBF ratio using SPECT.

To evaluate cerebral hemodynamics, 21 patients with chronic occlusion or severe stenosis of the internal carotid or middle cerebral artery with normal or only lacunar infarction on x-ray CT were studied using single photon emission computed tomography (SPECT). We measured rCBV with 99mTc erythrocytes after rCBF with 133Xe, and calculated rCBV/rCBF. rCBF and rCBV of the 25 affected hemispheres were classified as (a) patients with normal rCBF [type I (n = 7) and type II (n = 3)]; (b) patients with decreased rCBF [type III (n = 6) and type IV (n = 9)]. These two groups then could be subdivided according to findings of rCBV, normal, and increased blood volumes. rCBV/rCBF increased as the cerebral perfusion pressure dropped from type I to type III. In type IV, other situations but cerebral autoregulation could be assumed. rCBV/rCBF signifies vascular mean transit time. Type III (high rCBV/rCBF) assumed as the increased OEF, misery perfusion as reported in PET. We propose rCBF, rCBV and rCBV/rCBF using SPECT can be an index for cerebral circulatory reserve.

Quantitative measurement of regional cerebral blood flow using N-isopropyl-(iodine-123)p-iodoamphetamine and single-photon emission computed tomography.

We have developed a quantitative method of measuring regional cerebral blood flow (rCBF) by using N-isopropyl-(iodine-123)p-iodoamphetamine and single-photon emission computed tomography (SPECT). Twenty-five dynamic SPECT images (24 sec/scan) were collected immediately after tracer injection using a ring-type SPECT system and the accumulation curve (C(t)) was obtained. The time-activity curve corresponding to the arterial blood activity curve was used as B(t). The latter curve was calculated from the lung time-activity curve monitored during scanning and corrected by the actual activity obtained by one-point blood sampling 5 min after tracer injection. The octanol extraction ratio during scanning was considered to be constant and taken as the value measured 5 min after tracer injection (E). The uptake constant (K) per pixel was calculated by the least squares fitting method as the slope of the linear relationship in which C(t)/E x B(t) was plotted against E x integral of t(o)B(tau)d tau/E x B(t). Functional maps of rCBF values were obtained on a 64 x 64 matrix by calculating the uptake constant per pixel and the cross calibration factor (CF) between the SPECT system and a well counter (rCBF = K.CF x 100).

Normal perfusion pressure breakthrough syndrome in giant arteriovenous malformations.

The treatment of large, high-flow cerebral arteriovenous malformations is one of the most difficult operations which neurosurgeons encounter because of the complex surgery and the post-operative effects on the brain. We have evaluated 10 patients with large, high-flow AVMs who underwent surgical resection. Patients were investigated with contrast-enhanced computed tomography and magnetic resonance imaging, 1231-IMP single photon emission computed tomography (SPECT) studies of cerebral flow and cerebral vasodilatory function, intraoperative Laser Doppler flowmetry (4 or 10 patients), and conventional angiography. The volume of the arteriovenous malformation nidi ranged from 32.8 to 210.5 cc. SPECT imaging performed on the first post-operative day showed marked hyperperfusion in the brain tissue surrounding the resected nidus, and these regions were normal on images on the 7th post-operative day. Laser Doppler flowmetry showed sudden, and marked increase in CBF immediately following placement of temporary clips on the main feeding artery. Angiograms done on 7-14 days following surgery showed a stagnating artery, fragile vessel, and a prolonged circulation time. Our results indicate that pre- and post-operative SPECT study, especially a dynamic SPECT study done on the first post-operative day, was the most useful examination for ascertaining the post-operative normal perfusion pressure breakthrough.

Evaluation of regional cerebral blood flow changes on perifocal brain tissue SPECT before and after removal of arteriovenous malformations.

In fifteen cases of arteriovenous malformation (AVM), serial examinations of regional cerebral blood flow (rCBF) using single photon emission computed tomography (SPECT) and N-isopropyl-(123I)p-iodoamphetamine were performed. On SPECT images, the nidus was visualized as a focal rCBF defect in all cases preoperatively and seven of these cases had abnormal decreased perfusion areas in the tissues adjacent to the nidus. In five cases, the postoperative SPECT images on the day after surgery revealed an abnormal increased perfusion area adjacent to the nidus and in one case the increased perfusion was accompanied by a massive intracerebral haemorrhage detected by brain computed tomography (CT). In seven cases, postoperative SPECT images showed widespread abnormal decreased perfusion areas in the surrounding tissues and brain CT revealed either intracerebral haemorrhage or significant cerebral oedema. In the other three cases, no remarkable rCBF changes were found in comparison with the pre-operative study. There was a tendency for the preoperative abnormal decreased perfusion area adjacent to the nidus to correlate with the postoperative hyperperfusion and for the postoperative abnormal decreased perfusion area to reflect brain damage.

Quantitative measurement of regional cerebral blood flow with I-123 IMP SPECT: a correction of the microsphere model by global extraction between artery and internal jugular vein.

Quantitative measurements of regional cerebral blood flow with N-isopropyl-(Iodine 123)p-iodoamphetamine (I-123 IMP) as a microsphere model were performed in forty cases. The regional cerebral blood flow values obtained with I-123 IMP were slightly underestimated compared with those of Xe-133 inhalation methods (y = 0.90x-2.1, r = 0.85, p less than 0.01). After correction by global extraction (87%) between the artery and internal jugular vein, which was measured in four patients by means of a catheter technique, the underestimation of the values obtained with I-123 IMP was improved (y = 1.0x-2.4, r = 0.85, p less than 0.01). Several problems in the accurate quantitative measurement of regional cerebral blood flow with I-123 IMP are discussed.

Minor changes in regional cerebral blood flow revealed by the early distribution of I-123 IMP in brain.

To evaluate the early distribution of I-123 IMP in the brain, 10 dynamic images were obtained in the first 10 minutes after injection using a ring-type SPECT system with a high-sensitivity collimator. In cases of chronic carotid occlusion without brain CT abnormalities, areas of low perfusion were more clearly demonstrated in dynamic images than in static images obtained beginning 20 minutes after injection and continuing for 15 minutes using a high-resolution collimator. In cases of hyperperfusion following infarct or surgery, there was a difference between dynamic and static images in the visualization of hyperemic lesions. The distribution of I-123 IMP in the brain changes gradually, even in the early period after injection, and evaluation of early accumulation is useful for the detection of minor changes in regional cerebral blood flow.

Improvement in Fourier analysis of gated blood-pool studies using single photon emission computed tomography: methodology and clinical feasibility.

We have developed a new method for obtaining reconstructed left ventricular (LV) planar images acquired from multidirectional views using gated blood-pool single photon emission computed tomography (SPECT), and have applied Fourier analysis to these planar images. In this paper, we describe the methodology of our new technique and discuss its feasibility for the detection of LV wall motion abnormalities (WMA) in patients with coronary artery disease (CAD). Sagittal long-axis, horizontal long-axis and short-axis sections of the LV were generated from the reconstructed transaxial tomograms. Sections covering only the LV at the same phase of the cardiac cycle were added to reconstruct planar images. Fourier analysis was then performed to construct phase and amplitude images. In 42 patients with significant WMA, a comparative study concerning the detection of WMA was performed between conventional and SPECT methods. The SPECT method had greater sensitivity in all segments of the LV, with no significant loss in specificity. In particular, the sensitivity of the SPECT method was significantly greater than that of the conventional method for inferior and posterior WMA (91% vs 57%; and 76% vs 35%, respectively). The method described here shows greater clinical effectiveness for the detection of LV WMA in patients with CAD.

[A successful treatment of spontaneous carotid cavernous fistula causing hemorrhagic infarction treated by detachable balloon].

A rare case of hemorrhagic infarction associated with carotid-cavernous fistula is reported. The patient was a 74-year-old female. CT scan showed hemorrhagic infarction of the left superior temporal gyrus, irregular vascular enhancement of the bilateral front-temporal lobe, and dilatation of the cavernous sinus. Left carotid angiogram revealed a high-flow left-sided CCF, cross filling to the right cavernous sinus, and intracavernous aneurysm. Bilateral front-temporal cortical veins were visualized early in the arterial phase. In this case, there was a direct shunt between the internal carotid artery and the cavernous sinus, and venous hypertension. Therefore urgent treatment using detachable balloon catheters was performed. Postoperative digital subtraction angiography revealed the disappearance of CCF. In conclusion, in CCF with cortical venous drainage there is a high possibility of developing hemorrhagic infarction. Only immediate detachable balloon occlusion can improve the outcome in elderly patients.

[Evaluation of cerebral hemodynamics by 123I-IMP in cerebral AVMs before and after operation by using SPECT].

To evaluate cerebral hemodynamics by N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) preoperative and postoperative (after 1 day, and after 7-10 days) regional cerebral blood flow scan, 6 arteriovenous malformations (AVMs) which performed total removal operations were studied by using a ring type SPECT "HEADTOME". We performed the dynamic scan just after the intravenous injection of 222 MBq (6 mCi) of 123I-IMP, then the static scan 20 minutes after the intravenous injection. In preoperative dynamic scans of all cases, only the first frame image showed the increased activity on the nidus probably because of the blood pool. Preoperative static scans of all cases showed the remarkable decreased activity on the nidus, and decreased activity surrounding the nidus probably because of the peripheral steal phenomenon. In postoperative scan of the next day, 4 out of 6 cases showed the transient decreased peripheral steal, particularly 2 out of those 4 cases showed the transient hyperperfusion probably because of the normal perfusion pressure breakthrough (NPPB). And, 2 out of 6 cases showed transient peripheral low perfusion on much larger area than those of the preoperative scans probably because of the focal brain damages and edemas. We conclude that 123I-IMP SPECT on AVM is very useful to decide the indication of the removal operation, and to estimate the postoperative risk, and to evaluate the preoperative and postoperative cerebral hemodynamic changes in the peripheral area of AVM.

[SPECT measurement of cerebral hemodynamics in transient ischemic attack patients--evaluation of pathogenesis and detection of misery perfusion].

To evaluate the cerebral hemodynamics and the pathogenesis by regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV), 42 transient ischemic attack (TIA) patients and 9 normal volunteers were studied using SPECT. We classified these patients into Group A (n = 23: no occlusion or stenosis of the internal carotid or middle cerebral artery; non large vessel disease) and Group B (n = 19: chronic occlusion or severe stenosis of the internal carotid or middle cerebral artery; large vessel disease). We obtained rCBF with 133Xe inhalation and rCBV with 99mTc-red blood cells. Of 9 normal volunteers aged 43-70 yr (mean age 59.8 +/- 8.3 yr), the mean rCBF was 45.8 +/- 5.1 (ml/100 g brain/min), the mean rCBV was 4.0 +/- 0.4 (ml/100 g brain). The examination was done by comparing the values of the affected hemispheres of Group A and Group B patients with the mean rCBF and the mean rCBV of normal volunteers. Eleven out of Group A patients and 15 out of Group B patients showed decreased rCBF. But of those patients, no patients of Group A showed increased rCBV and 6 out of 19 Group B patients showed increased rCBV. Thromboembolic mechanism which is of Group A patients and Group B patients without increased rCBV, and hemodynamic mechanism which is of Group B patients with increased rCBV were considered as the main cause of TIA. Decreased rCBF and increased rCBV in Group B patients can be assumed as the misery perfusion as reported in PET studies.(ABSTRACT TRUNCATED AT 250 WORDS)

[The influence of the time activity variation on dynamic SPECT images in camera based SPECT].

Image quality of dynamic single photon emission computed tomography (SPECT) using a rotating gamma camera is dependent on the time activity variation of the tracer such as accumulation and excretion in the object's organ. Especially at the early time after injection of radionuclide, artifacts may occur strongly in the SPECT images. Simulated and experimental projection data of line sources and Jaszczak phantom were altered by sequentially weighting the projections with a function that varied linearly with time. With a variation of object activity given by linearly decaying functions, the main effect observed on the SPECT images obtained from simulated line sources was an elliptical deformation on the object. If the changing rate (R (t + 1)-R(t))/R(t) x 100 remained within 20% during acquisition, this deformation of SPECT images of line sources was not noticeable visually and resolution (FWHM) of line sources scarcely was degraded. In renal dynamic SPECT study using 99mTc-DTPA, the image quality of the first scan (30 sec) was considerably degraded. However, the changing rates after the third scan were less than 20% on the mean of 10 kidneys and the image quality was not noticeable visually.

[The administered activity of radionuclides in nuclear medicine--rational reduction of medical radiation exposure].

A survey of 104 hospitals was conducted to determine the administered activity of radionuclides. Eighty-five hospitals responded, and reported a total of 119,614 examinations in one year. The examinations included: bone scintigraphy, 26.4%; Thallium-201 (201Tl) myocardial scintigraphy, 15.5%; Gallium-67 (67Ga) scintigraphy, 13.3%; N-isopropyl-p-[123I]iodoamphetamine (IMP) brain perfusion scintigraphy, 7.0%. The administered activity was corrected by body weight only for children at more than 80% of the responding hospitals. The number of hospitals that reported over-administration of radionuclide varied according to the type of scintigraphy performed: bone, 76%; inflammatory (67Ga), 93%; myocardial (201Tl), 89.2%; brain (IMP), 8.5%. The administered activity of IMP was closer to the upper limits specified in the Recommendations on Standardization of Radionuclide Imaging by the Japan Radioisotope Association (1987), because IMP is very expensive and is supplied as single vials. The highest average effective dose was for myocardial scintigraphy, the second-highest for inflammatory scintigraphy, and the third-highest for bone scintigraphy. In 201Tl and 67Ga scintigraphy, the entire contents of the vial may be administered two days before the expiration date, because the ratio of (true patient administered activity) to (declared patient administered activity) is similar to the ratio of (radioactivity on the day of supply) to (radioactivity on the day of expiration). The factors that influence administered activity are throughput, price of the radionuclide, and whether the radionuclide is sold as a single vial. In order to decrease the effective dose, it is necessary to establish a close cooperation between medical personnel, the makers of radiopharmaceuticals, and manufacturers of gammacameras.

[Evaluation of the clinical usefulness of super dynamic 99mTc-HM-PAO SPECT in ischemic cerebrovascular disease--detection of hypo- and hyperperfusion area].

The purpose of this study is to assess the clinical usefulness of super dynamic SPECT of 99mTc-HM-PAO. Six patients with unilateral occlusion of middle cerebral artery (MCA) or internal carotid artery (ICA) in the chronic phase, and 5 patients with subacute cerebral infarction were studied. We used a ring-type SPECT "HEADTOME." Two types of collimator were used: a high sensitivity (HS) collimator for super dynamic scan and a high resolution (HR) collimator for static scan. First, the intravenous constant infusion of 99mTc-HM-PAO (925-1480 MBq) for 1 minute was started. After 30 seconds from the beginning of the injection, we performed the 12 seconds/frame super dynamic SPECT for 2 minutes. Then, the static SPECT for 10 minutes was done. For semiquantitative analyses, differential percentage of regional activity between affected and non-affected hemispheres was calculated in the 6th frame image of super dynamic SPECT and static SPECT image. In all 6 patients with unilateral occlusion of MCA and ICA, super dynamic SPECT images showed the better contrast of low perfusion areas in comparison with the static SPECT images. In 5 patients with subacute cerebral infarction who showed focal hyperactivities on static SPECT, focal hyperactivities (hyperperfusion or hyperemia) were displayed in 3 cases, whereas, focal hypo- or isoactivities (hypo- or isoperfusion) were shown in 2 cases on super dynamic SPECT. However, all patients with subacute cerebral infarction showed hyperfixation on static SPECT as compared with super dynamic SPECT. Although the image quality on super dynamic SPECT is not as high as that on static SPECT, cerebral hemodynamics would be detected with less backdiffusion of 99mTc-HM-PAO from the brain to blood, and with less accumulation of hydrophilic components in subacute infarct region. In conclusion, super dynamic SPECT in early distribution of 99mTc-HM-PAO using dedicated SPECT device might be helpful to detect cerebral perfusion close to true cerebral blood flow distribution.

[Evaluation of the system performance and clinical images of the single photon emission computed tomography for head using ring arranged detector].

To evaluate the system performance, several preoperational fundamental tests of single photon emission computed tomography (SPECT) were carried out. Spatial resolutions (FWHM) measured with the point-spread functions of a 99mTc line source were 12.5 mm with a high resolution (HR) collimator and 17.2 mm with a high sensitivity (HS) collimator respectively. Slice thicknesses (FWHM) obtained from the profile curves of slice images were 17.5 mm (HR) and 29.0 mm (HS) at the center of rotation. System sensitivities were 5.4 kcps/slice (HR) and 27.8 kcps/slice (HS). Uniformities calculated from the SPECT images of a pool phantom were 4.7% (HR) and 2.7% (HS) at the condition of 3,000 kcounts to be acquired. SPECT images of the HEADTOME SET-031 were considered very useful to diagnose the cerebrovascular disease.