Influence of technetium-99m-hexamethylpropylene amine oxime injection time on single-photon emission tomography perfusion changes in epilepsy

By digitally computing perfusion changes from ictal or postictal (peri-ictal) injections referenced to those acquired interictally, an enhanced method for localizing the epileptogenic area is reported. Computer-based image processing methods for quantifying regional percent change in the brain are applied to a group of 19 epilepsy patients after the injection of technetium-99m hexamethylpropylene amine oxime (HMPAO) and after acquiring single-photon emission tomography (SPET) data. Each patient’s region of epileptogenesis was independently localized through pathology and/or successful surgery. The positive and negative quantitative perfusion changes were plotted as a function of the time of the ^99mTc-HMPAO ictal injection. This time scale was normalized relative to the seizure duration and is referenced to the time of seizure termination. Eight patients, injected ictally, demonstrated perfusion increases of 25%–100% in the area of known epileptogenesis. Five patients, injected immediately after seizure cessation, demonstrated excessive perfusion decreases of 30%–92% associated with the region of seizure onset. Six patients, injected well after seizure termination, demonstrated hypoperfusion changes less than 30% at the epileptogenic area. Observations on perfusion changes calculated from ^99mTc-HMPAO SPET scans, as a function of normalized time, support a progression from ictal hyper- to excessive hypo-, then finally to persistent interictal hypoperfusion. By applying this perfusion pattern model and by noting the time of injection for peri-ictal images, an improved method for localizing the epileptogenic area is demonstrated. Received 27 June and in revised form 7 September 1998     

“Luxury perfusion” with99mTc-HMPAO and123I-IMP SPECT imaging during the subacute phase of stroke

To compare the merits of¹²³I-isopropyl-iodoam-phetamine (¹²³I-IMP) and^99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with¹²³I-IMP and^99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal^99mTc-HMPAO SPECT and abnormal¹²³I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on^99mTc-HMPAO in areas corresponding to defects on the¹²³I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination,^99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on¹²³I-IMP. Crossed cerebellar diaschisis was found in 7 patients with^99mTc-HMPAO and was absent for both¹²³I-IMP and^99mTc-HMPAO in 3. We suggest that SPECT with⁹⁹mTc-HMPAO could show transient hyperemia not demonstrated by¹²³I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with^99mTc-HMPAO than with¹²³I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.     

Required time delay from <Superscript>99m</Superscript>Tc-HMPAO injection to SPECT data acquisition: healthy subjects and patients with rCBF pattern

Purpose  Functional brain ^99mTc-HMPAO single-photon emission computed tomography (SPECT) is a useful diagnostic tool for assessment of regional cerebral blood flow, particularly in dementia, cerebrovascular disease and epilepsy. Currently, the European and American Association of Nuclear Medicine Procedure Guidelines for Brain Perfusion SPET using ^99mTc-labeled Radiopharmaceuticals recommend a time delay of 90 min between injection of ^99mTc-HMPAO and data acquisition. This time delay is difficult to comply within the daily routine and present a problem, particularly with the elderly or demented patients. This study investigates in patients with perfusion deficits and in healthy subjects if the quality of the SPECT image is affected by lowering the time delay between ^99mTc-HMPAO injection and data acquisition to 30 or 60 min. Methods  Thirty-seven healthy subjects (17 females; mean age 65; range 42–84 years) with normal cerebral blood flow distribution and 31 patients (17 females; mean age 67; range 38–84) with reduced rCBF distribution were included. Images were obtained with a three-headed Philips IRIX SPECT scanner with high-resolution collimators. The healthy subjects were scanned 30, 60 and 90 min after ^99mTc-HMPAO injection, and the patients were scanned 30 and 90 or 60 and 90 min after ^99mTc-HMPAO injection. For evaluation of differences between the images obtained at various time points after injection, two different methods were used. The z-map method was used to subtract images from each other prior to visual inspection. In addition, principal component analysis was used as a quantitative analysis of the similarity of the images. Results  Visual inspection of the subtracted images (30 or 60 versus 90 min) revealed that there was no spatial bias. Quantitatively, the average proportion of the total variance explained by the first principal component was 99.5% (range 98.9–99.6) for the healthy subjects and 99.4% (range 98.5–99.8) for the patients. Conclusion  The time delay from injection of ^99mTc-HMPAO to the start of the SPECT data acquisition can be reduced from 90 to 30 min without any significant impact on the quality of the acquired image.     

Brain SPECT imaging in temporal lobe epilepsy

Summary Temporal lobe epilepsy is diagnosed by clinical symptoms and signs and by localization of an epileptogenic focus. A brain SPECT study of two patients with temporal lobe epilepsy, using^99mTc-HMPAO, was used to demonstrate a perfusion abnormality in the temporal lobe, while brain CT and MRI were non-contributory. The electroencephalogram, though abnormal, did not localize the diseased area. The potential role of the SPECT study in diagnosis and localization of temporal lobe epilepsy is discussed.     

Benzodiazepine receptors and cerebral blood flow in partial epilepsy

It was the aim of this study to compare benzodiazepine (Bz) receptor binding and cerebral perfusion in patients with partial epilepsy. Single photon emission tomography (SPET) studies with the flow-marker technetium 99m hexamethylpropylene amine oxine (^99mTc-HMPAO) and with the¹²³I-labelled Bz-receptor ligand Ro 16-0154 (¹²³I-Iomazenil) were performed in 12 patients with partial epilepsy, all with normal magnetic resonance imaging (MRI) and computed tomography (CT) scans. The SPET studies with¹²³I-Iomazenil were carried out 5 min and 2 h after injection. At 2 h the distribution of activity was very similar to the expected distribution of Bz-receptors in the human brain, known from positron emission tomography (PET) work and post-mortem studies. Early images showed a significantly higher tracer accumulation in the area of the basal ganglia, cerebellum, and naso-pharyngeal space. This finding is caused by non-specific binding and the contribution of the tracer in the blood pool in this phase. Also after 2 h p.i. of¹²³I-Iomazenil, 9 of the 12 patients showed a focal decrease of of Bz-receptor binding. Ten patients had focal flow abnormalities with^99mTc-HMPAO SPET. In 8 subjects impairment of flow was seen in sites of reduced¹²³I-Iomazenil uptake.¹²³I-Io-mazenil is suitable for Bz-receptor mapping. In this series of patients, Bz-receptor mapping with SPET seems to offer no advantage over^99mTc-HMPAO in the detection of epileptic foci. Offprint requests to: P. Bartenstein     

A quantitative approach to technetium-99m ethyl cysteinate dimer: a comparison with technetium-99m hexamethylpropylene amine oxime

To develop non-invasive regional cerebral blood flow (rCBF) measurements using technetium-99m ethyl cysteinate dimer (^99mTc-ECD) and single-photon emission tomography (SPET), the same graphical analysis as was described in our previous reports using technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO) was applied to time-activity data for the aortic arch and brain hemispheres after intravenous injection of^99mTc-ECD. Hemispherical brain perfusion indices (BPI) for^99mTc-ECD showed a highly significant correlation (n = 22,r = 0.935,P = 0.0001) with those for^99mTc-HMPAO in 11 patients who underwent both tracer studies. Using both linear regression line equations between^99mTc-ECD BPI and^99mTc-HMPAO BPI and between^99mTc-HMPAO BPI and mean cerebral blood flow (CBF) values obtained from a xenon-133 inhalation SPET method in a previous study,^99mTc-ECD BPI was converted to¹³³Xe CBF values (y = 2.60x + 19.8). Then raw SPET images of^99mTc-ECD were converted to rCBF maps using Lassen's correction algorithm. In this algorithm, the correction factor a was fixed to 1.5, 2.6 and infinite. In the comparison of rCBF values for^99mTc-ECD SPET with those for^99mTc-HMPAO SPET in 396 regions of interest in the aforementioned 11 patients, the fixed correction factor of 2.6 gave nearly the same rCBF values for^99mTc-ECD (50.1 ± 16.9 ml/100 g/min, mean ± SD) as for^99mTc-HMPAO (49.9 ± 17.3 ml/100 g/min). In conclusion, the same non-invasive method as has been used in^99mTc-HMPAO studies is applicable to a^99mTc-ECD study for the measurement of rCBF without any blood sampling.     

Brain single-photon emission tomography with technetium-99m hexamethylpropylene amine oxime in adolescents with initial-stage schizophrenia

The objective of this study was to search for regional cerebral blood flow (rCBF) abnormalities in adolescents with initial-stage schizophrenia by means of brain single-photon emission tomography (SPET) using technetium-99m hexamethylpropylene amine oxime (HMPAO). SPET studies were performed on a homogeneous sample of 15 carefully selected adolescents with a recent diagnosis of schizophrenia, and without previous electroconvulsive or antipsychotic drug treatment. Computed tomography (CT) and electro-encephalographic (EEG) studies were performed in all patients. Qualitative and semiquantitative analysis of^99mTc-HMPAO SPET studies showed an impaired rCBF in 12 patients (80%). The most common pattern was a decreased uptake of^99mTc-HMPAO in the frontal lobes, usually in the left hemisphere. Conventional and quantitative EEG was positive in 12 (80%) and 15 (100%) patients, respectively. CT findings were positive in two patients (13%). There was a high level of concordance between SPET and EEG results and between SPET and clinical features (P>0.05). This study suggests that previously untreated patients in the first stages of schizophrenia present functional abnormalities that are revealed by brain SPET.     

Postoperative assessment of cerebral blood flow in subarachnoid haemorrhage by means of99mTc-HMPAO tomography

Regional hypoperfusion is a very frequent complication of subarachnoid haemorrhage (SAH), being related to vasospasm in the majority of cases. Twenty-six patients who were admitted for SAH underwent follow-up with technetium-99m hexamethylpropylene amine oxime single photon emission tomography (SPECT) 3 and 8 days after surgery. Fifteen patients of these had one more examination 15 days after surgery. The degree of hypoperfusion was quantified using an index of asymmetry which allow the comparison of two symmetrical regions of interest (ROIs) on the transaxial slice which presented the greatest perfusion defect. Comparison of CT data, transcranial Doppler data and clinical signs with the perfusion as quantified by^99mTc-HMPAO SPECT indicates that a difference in counts of less than 10% between the two symmetrical ROIs is of no diagnostic value. Follow-up of the brain perfusion clearly shows that the most pronounced hypoperfusion was observed just after surgery, with progressive normalization at 8 and 15 days after surgery.^99mTc-HMPAO SPECT performed 8 days after surgery allows prediction of the clinical outcome. For these reasons,^99mTc-HMPAO SPECT, which is the only method for follow-up of cerebral perfusion in routine clinical practice, should be the first examination to be performed after surgery in patients with SAH.     

In vivo metabolism and kinetics of99mTc-HMPAO

The cerebral distribution of^99mTc-labeled d, l, hexamethyl-propylene-amine-oxime (^99mTc-HMPAO) as a function of rCBF and time was examined in rats and in man. The results of this study confirm that^99mTc-HMPAO is distributed in brain in proportion to rCBF. However, the rapid systemic breakdown of the tracer in blood results in considerable difficulties in the assessment of the arterial concentration of the parent compound; incomplete extraction of^99mTc-HMPAO from blood to brain and significant efflux from brain represent further limitations in the use of this tracer for quantification of rCFB. Despite these limitations^99mTc-HMPAO is of potential interest for a qualitative assessment of rCBF in specific clinical conditions.     

Video/EEG,SPECT和MRI对部分性癫痫定位诊断作用及临床意义探讨

目的：探讨录像脑电图检测（Ｖｉｄｅｏ／ＥＥＣ）,ＳＰＥＣＴ和ＭＲＩ３种方法对部分性癫痫的无创性定位和病因诊断的作用及临床意义。材料与方法：对５２例部分性癫痫患者分别进行Ｖｉｄｅｏ／ＥＥＧ,＾９９ｍＴｃ－ＨＭＰＡＯ－ＳＰＥＣＴ脑血流显像,＾１２３Ｉ－Ｉｏｍａｚｅｎｉｌ ＳＰＥＣＴ脑受体显像和全脑ＭＲＩ检查。根据Ｖｉｄｅｏ／ＥＥＧ记录的癫痫发作类型,ＳＰＥＣＴ显示的ｒＣＢＦ和ＢＺＤ的分布以及ＭＲＩ显示     

Tumour-like thallium-201 accumulation in brain infarcts,an unexpected finding on single-photon emission tomography

Thallium-201 brain single-photon emission tomography (²⁰¹Tl-SPET) is widely used to detect viable tumour tissue with increased metabolic activity. When reperfusion takes place early in cerebrovascular lesions of embolic origin, the presence of tissue areas with increased regional blood flow and preserved metabolic activity can also be assumed. In the present study our purpose was to investigate whether or not foci of ²⁰¹Tl accumulation occur in reperfused areas with sustained morphological integrity indicated by computed tomography (CT) scans not showing hypodensity in the acute or subacute period.In 16 stroke patients with possible cortical embolic infarction, dual ²⁰¹Tl and technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO) SPET was performed in both the acute and the subacute period. ^99mTc-HMPAO SPET was performed to detect reperfusion. Follow-up CT scans from the same period were also available. In five cases ^99mTc-HMPAO SPET ruled out reperfusion and ²⁰¹Tl SPET was also negative. In four cases ^99mTc-HMPAO studies indicated reperfusion early in the acute phase (24–72 h), and comparative CT, without showing hypodensity in the acute or subacute period, also favoured the possibility of sustained metabolic activity. In these cases ²⁰¹Tl SPET was negative in both the acute and the subacute period. In seven cases CT already showed necrosis in ^99mTc-HMPAO hypoperfused areas in the acute period, with negative results on corresponding ²⁰¹Tl SPET. Later reperfusion occurred in the subacute period (8–14 days) as indicated by ^99mTc-HMPAO SPET, at which time an unexpected focal accumulation of ²⁰¹Tl was detected. We cannot give any explanation for the findings, but further studies might clarify the matter and improve our knowledge of the precise mechanism of ²⁰¹Tl uptake under different conditions. Until then the phenomenon should be borne in mind as a possible pitfall when assessing tissue viability.     

Visualization of pressure-dependent luxury perfusion in a patient with subacute cerebral infarction

Luxury perfusion characterized by depressed metabolism compared with CBF might be changed by decreasing cerebral perfusion pressure during the sitting position. A 77-yr-old man with subacute cerebral infarction was studied with brain X-ray computed tomography (CT), raise-up test with^99mTc-d,1-hexamethylpropyleneamine oxime (HMPAO) brain single photon emission tomography (SPECT) and positron emission tomography (PET). Brain X-ray CT revealed a low-density area in the left middle cerebral artery (MCA) anterior area. Raise-up^99mTc-HMPAO brain SPECT revealed decreased uptake in the left MCA anterior area in the sitting position and subsequent supine^99mTc-HMPAO brain SPECT revealed hot accumulation there. PET study in the supine position demonstrated some differences between CBF and the cerebral metabolic rate for oxygen in the left MCA anterior area, indicating luxury perfusion. CBF in the area of luxury perfusion might be decreased during the sitting or standing position and increased during the supine position by dysautoregulation of the cerebral vessels in the luxury perfusion during the subacute infarct.     

Regional cerebral blood flow distributions in normal volunteers: dynamic susceptibility contrast MRI compared with 99mTc-HMPAO SPECT

PURPOSE: Relative regional cerebral blood flow (rCBF) at rest was measured in 44 volunteers using both dynamic susceptibility contrast (DSC) MRI and (99m)Tc-HMPAO SPECT on the same day. METHOD: In MRI, a Gd-DTPA-BMA contrast agent bolus (0.3 mmol/kg body wt) was monitored with a simultaneous dual FLASH pulse sequence (time resolution 1.5 s). MRI-based rCBF images were calculated by singular value decomposition-based deconvolution of the measured tissue concentration-time curve with an arterial input function from a small artery within the imaging slice. In the SPECT investigation, 900 MBq of (99m)Tc-HMPAO was injected intravenously. Relative rCBF in gray matter in the thalamus and in frontal white matter was determined. RESULTS: The ratio of relative rCBF in gray matter to relative rCBF in white matter was 2.21 +/- 0.57 using MRI and 2.24 +/- 0.54 using SPECT (mean +/- SD). CONCLUSION: Relative rCBF maps from DSC MRI and (99m)Tc-HMPAO SPECT showed good agreement, and the MRI-based rCBF ratio correlated with the corresponding SPECT-based ratio (r = 0.79, p < 0.0000006).     

An evaluation of99mTc-HMPAO uptake in cerebral gliomas —a comparison with X-ray CT

Nineteen patients with biopsy-proven cerebral gliomas were studied with^99mTc-HMPAO single photon emission tomography (SPELT) imaging and X-ray computed tomography (CT). The uptake of^99mTc-HMPAO was correlated with tumour size and morphology as shown by X-ray CT, and overall patient survival. It appears that uptake of^99mTc-HMPAO is associated with larger, ill-defined tumours and was an adverse factor in patient survival. In those tumours with normal or increased uptake,^99mTc-HMPAO imaging is useful in distinguishing the tumour margin from surrounding oedema.     

Regional cerebral blood flow in patients with sickle cell disease: study with single photon emission computed tomography

Objective Neurological complications have been reported in patients with sickle-cell disease (SCD) using positron emission tomography (PET), magnetic resonance imaging (MRI), and computed tomography (CT), but not with single photon emission computed tomography (SPECT). The objective of this study was to investigate brain perfusion in the patients with SCD using SPECT after technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO), was administered and compare the findings with those of demography, physical examination, MRI and hematological profile. Methods The study involved 21 patients (12 males, 9 females, age at study 8–45 years) who were known to be having SCD for a duration of at least 5 years. The patients were not in acute crisis and had normal neurological assessments with no known history of stroke or transient ischemic episode or previous abnormal CT or MRI brain scan, and were right-handed. The brain SPECT was performed after intravenous injection of 740 MBq (20 mCi) ^99mTc-HMPAO in adults or an appropriate dose in pediatric patients. The scans were visually interpreted by two nuclear medicine physicians and a decision was reached by consensus. An MRI done 3 months later was interpreted by a radiologist. The demographic data and hematological profile were obtained from the medical records of the patients. Results Of the 21 patients, 7 (age 11–22 years) had brain perfusion deficit mostly in the frontal lobe either alone or in combination with temporal and/or parietal lobe. The MRI was abnormal in 2 patients. The brain perfusion deficit was not associated with the demographic data of the patients or hematological profiles. Conclusions The findings show that SPECT was useful in detecting brain perfusion deficit in SCD patients, and such an early detection may be clinically useful in the subsequent follow-up of such patients, since it is known that cerebral perfusion deficit can lead to silent infarct and/or overt stroke, and affect cognitive skills.     

Regional cerebral blood flow single-photon emission tomography with 99mTc-HMPAO and the acetazolamide test in the evaluation of vascular and Alzheimer’s dementia

The diagnostic potential of technetium-99m hexamethylpropylene amine oxime (HMPAO) following systemic administration of the cerebral vasodilator acetazolamide (acetazolamide test) was evaluated by regional cerebral blood flow (rCBF) single-photon emission tomography (SPET) in patients with Alzheimer’s disease (AD) or vascular dementia (VD). An initial, high-resolution SPET study was performed with ^99mTc-HMPAO, and after 2 days the patients were re-evaluated with ^99mTc-HMPAO following systemic administration of acetazolamide. Reconstructed SPET slices were evaluated visually and semiquantitatively by a semi-automatic rCBF map method. When ^99mTc-HMPAO alone was used, bilateral hypoperfusion was found in the temporal and/or parietal regions in 33% (6/18) of the VD patients and in 70% (23/33) of the AD patients. The corresponding data obtained by quantitative evaluation were 41% (7/17) and 71% (15/21), respectively. The vascular reserve capacity, as determined with the acetazolamide test, was preserved visually in 22% (4/18) and quantitatively in 29% (5/17) of the VD patients, but in 73% (24/33) and 76% (16/21) of the AD patients. The differences in the perfusion patterns between the VD and AD patients were statistically significant (P<0.01, Fischer’s exact test). Of the VD patients with hypoperfusion (bilateral temporal and/or parietal), 4/6 (67%, visual evaluation) and 4/7 (57%, quantitative evaluation) had a decreased vascular reserve capacity as determined with the acetazolamide test. In the AD group of patients the corresponding results were 3/23 (13%) and 4/15 (27%). It is concluded that the acetazolamide test is promising in rCBF SPET to differentiate VD from AD. Received 1 August and in revised form 30 October 1998     

脑SPECT显像在癫痫中的应用

目的：本文主要研究脑ＳＰＥＣＴ在癫痫应用中的作用和地位。材料和方法：对８１例癫痫患者进行了１０２次发作间期脑ＳＰＥＣＴ血流灌注显像，并与ＥＥＧ、脑ＣＴ、ＭＲＩ比较。结果：８１例ＳＰＥＣＴ检查中６６例显示异常，检出率８１．４％（６６／８１），ＥＥＧ、ＭＲＩ、ＣＴ阳性率分别为８２．９８％（３９／４７）、３８．２４％（１３／３４）、４５．９５％（１７／３７）。结论：ＳＰＥＣＴ显像在癫痫诊断和定位方面与ＥＥＧ、ＭＲＩ、ＣＴ相比具有优势，且有助于癫痫病灶局部血流变化与临床症状、疗效及其他影响因素之间关系的研究。     

RCBF-quantification with 99mTc-HMPAO-SPECT: Theory and first results

The activity concentrations of ^99mTc-HMPAO in brain after intravenous injection were evaluated in 25 patients using SPECT. With additional first pass studies of heart and brain with the short lived isotope ^195mAu, the cardiac output and the mean cerebral transit times of the patients were measured a short time before the HMPAO injection. The time dependence of ^99mTc-HMPAO activity in the brain was registered during the first 5 min after injection over both hemispheres. Using a simplified three compartment model it was possible to calculate the mean retention fraction of HMPAO in brain from the time activity curves. It could be shown that the regional cerebral blood flow in ml/min per 100 g can be calculated from the activity concentration of HMPAO in the brain, the cardiac output and the retention fraction. In 15 of the 25 cases the rCBF was measured using the planar ¹³³Xe inhalation method as a reference. We found a significant correlation between the mean hemisphere CBF from our method and the mean hemisphere grey matter CBF from the Xenon method with a correlation coefficient of 0.73.     

Comparison of simultaneous 99mTc-HMPAO and 111In oxine labelled white cell scans in the assessment of inflammatory bowel disease

Forty-seven patients, 29 with chronic inflammatory bowel disease (1131) and 18 with presumed irritable bowel syndrome, including one with uncomplicated diverticular disease, were studied with simultaneous technetium-99m hexamethylpropylene amine oxime and indium-111 oxine labelled leucocyte scans performed at 1, 3 and 24 h. Twenty-seven patients with IBD had active disease as judged by clinical and laboratory criteria and all of these had positive scans with both agents. No false positive studies were obtained. The 1-h ^99mTc-HMPAO WBC scans showed the same distribution to disease as the 3-h ¹¹¹-In WBC scans, with no difference in intensity (P < 0.92); they showed more extensive disease (P < 0.02) and more intense uptake (P < 0.001) than did the 1-h ¹¹¹-In scans. The 3-h ^99mTc-HMPAO WBC scans showed more extensive disease (P < 0.002), with greater intensity (P < 0.0005), than did the 3-h ¹¹¹In WBC scans. Physiological bowel activity on 3-h ^99mTc-HMPAO WBC scans was present in 12 patients but was faint and did not interfere with assessment of disease extent and activity. It is concluded that in terms of isotope availability, radiation dosimetry and image quality, ^99mTc-HMPAO is the agent of choice in detecting active IBD, with localization of disease possible at 1-h after re-injection and optimal resolution and definition of disease extent at 3 h. A negative scan reliably excludes active disease. Correspondence to: R.A. Allan     

Influence of SPECT attenuation correction on the quantification of hibernating myocardium as derived from combined myocardial perfusion SPECT and 18F-FDG PET

Background

To evaluate the influence of SPECT attenuation correction on the quantification of hibernating myocardium derived from perfusion SPECT and ¹⁸F-FDG PET.

Methods and Results

20 patients underwent rest ^99mTc-tetrofosmin perfusion SPECT/CT and ¹⁸F-FDG PET/CT. Perfusion images were reconstructed without attenuation correction (NC), with attenuation correction based on the CT from the SPECT/CT (AC_SPECT), and with attenuation correction based on the CT from the PET/CT (AC_PET). Another 56 patients had rest ^99mTc-tetrofosmin perfusion SPECT and ¹⁸F-FDG PET/CT. Perfusion images were reconstructed as NC and AC_PET. The amounts of hibernating myocardium and scar were quantified with QPS^® and corresponding AC and NC normative databases. In both cohorts, perfusion in the inferior wall was higher in the AC scans than without AC. Global and regional values for total perfusion deficit (TPD), hibernation and scar areas did not differ between NC, AC_SPECT, and AC_PET scans. In a retrospective evaluation with 7% cut-off of hibernating myocardium as a condition for revascularization, the therapeutic approach would have been altered in 5 of 56 patients, if the AC_PET approach had been used.

Conclusions

AC of SPECT perfusion scans with an attenuation map derived from PET/CT scans is feasible. If AC is unavailable, perfusion scans should be compared to NC normative databases for assessing TPD, hibernation, and mismatch. It should be taken into account that in approximately 10% of the patients, a therapeutic recommendation based on published thresholds for hibernating myocardium would be altered if NC scans were used as compared to AC scans.