Comparative study of regional cerebral blood flow images by SPECT using xenon-133, iodine-123 IMP, and technetium-99m HM-PAO

Regional cerebral blood flow (rCBF) was measured by single photon emission computed tomography (SPECT) using 133Xe, N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) and [99mTc] hexamethylpropyleneamine oxime ([99mTc]HM-PAO) in 24 patients with cerebrovascular diseases. The greatest advantage of 133Xe SPECT was to be able to provide absolute rCBF values without arterial sampling. However, its image quality was very poor. Iodine-123 IMP SPECT provided rCBF images of higher quality and it had good correlation to 133Xe SPECT. Iodine-123 IMP SPECT provided the best images to detect mild ischemic lesions. It could detect obstructive or stenotic changes of large cerebral arteries very well except for a moderate stenosis of internal carotid artery. Technetium-99m HM-PAO SPECT also provided very good rCBF images and it had good correlation to 133Xe SPECT. However, the count-density ratios for the ischemic lesions to the contralateral presumed normal areas of [99mTc] HM-PAO SPECT were significantly higher than those of [123I]IMP SPECT.     

Pathology results in [18F]fluorodeoxyglucose positron emission tomography of the thyroid gland

The aim of this retrospective study was to evaluate pathologically increased uptake of [18F]fluorodeoxyglucose (18F-FDG) in positron emission tomography (PET) results of the thyroid gland. Results of 18F-FDG PET and [99mTc]pertechnetate scintigraphy of the thyroid gland are shown, compared to each other and discussed. In a retrospective study 16 patients underwent whole-body 18F-FDG PET and [99mTc]pertechnetate scintigraphy of the thyroid gland within 3 weeks. In addition, an examination of the thyroid gland by using ultrasound and laboratory tests was carried out. The 18F-FDG PET studies were carried out on a dedicated whole-ring PET scanner. Eight patients had a pathological FDG uptake in the thyroid and a cold nodule in [99mTc]pertechnetate scintigraphy of the thyroid gland (in 7/8 cases histology showed malignancy). Five patients had an inhomogeneous FDG uptake in the thyroid gland and were suspected of thyroiditis in 18F-FDG PET (in 3/5 cases thyroiditis was confirmed). Three patients had an especially low FDG uptake compared to normal physiological FDG uptake (no malignancy). Results from studies using 18F-FDG represent a growing body of evidence showing the differentiation between malignant and benign disease: we saw many pathological results in the thyroid gland. High uptake of 18F-FDG in the thyroid gland suggests possible malignancy. Thyroiditis can only be suspected based upon the results of 18F-FDG PET. We conclude that 18F-FDG PET has a potential clinical impact for detecting possible malignant lesions of the thyroid gland, but further studies, in which a higher number of patients are evaluated, are necessary.     

Radiolabelled 5'-iodo-2'-deoxyuridine: a promising alternative to [18F]-2-fluoro-2-deoxy-D-glucose for PET studies of early response to anticancer treatment

We investigated the potential of radiolabelled 5-iodo-2'-deoxyuridine (IUdR) as a pharmacodynamic probe for use with positron emission tomography (PET) in studies of early proliferative response to anticancer treatment. Using the hormone-responsive rat mammary carcinoma OES.HR1, we used a multiple radiotracer method to examine treatment-induced changes in 24 h tumour retention of [131I]IUdR, uptake of [3H]2-deoxy-D-glucose ([3H]DG) together with [99mTc]hexylmethylpropylene amineoxine ([99mTc]HMPAO) uptake as a measure of blood flow. Radiotracer data were compared with macroscopic changes in tumour growth, and cell proliferation as determined by DNA histogram flow cytometry. From 4 days after tumour growth arrest induced by oestrogen ablation, a sustained fall in tumour cell proliferation was demonstrated, which was associated with reduced tumour uptake of each tracer. Whereas reduced levels of tumour [3H]DG could be accounted for by changes in blood flow, this was not the case for [131I]IUdR, which was found to be closely related to percentage S-phase cells within tumour (r = 0.73, p < 0.002). It was also estimated that residual levels of radioiodide may contribute significantly, to the low levels of retained radioactivity associated with responding tumours at 24 h following IUdR administration, suggesting that metabolite correction methods should be implemented as part of IUdR PET imaging protocols. We conclude that [124I]IUdR is a promising alternative to [18F]fluorodeoxyglucose ([18F]FDG) for the early assessment by PET of tumour response to treatments directed at targets associated with cell proliferation.     

Estimation of myocardial perfusion and viability using simultaneous 99mTc-tetrofosmin--FDG collimated SPECT.

This study was designed to elucidate the usefulness of crosstalk correction for dual-isotope simultaneous acquisition (DISA) with 99mTc-tetrofosmin and FDG in estimating myocardial perfusion and viability. METHODS: Eighteen patients with coronary artery disease were studied. First, SPECT was performed with a low-energy high-resolution collimator after a single injection of 99mTc-tetrofosmin (single 99mTc-tetrofosmin). Second, PET and DISA with an ultra-high-energy collimator were performed after glucose loading and an injection of FDG. DISA was designed to operate with simultaneous 3-channel acquisition, and weighted scatter correction of crosstalk from the 18F photopeak to the 99mTc photopeak was performed by modification of an existing dual-window technique. The FDG SPECT images were compared with the images obtained by PET. Both crosstalk-corrected and uncorrected 99mTc-tetrofosmin images were generated and compared with the single 99mTc-tetrofosmin images. RESULTS: Regional percentage uptake of FDG agreed well between DISA and PET. However, regional percentage uptake of 99mTc-tetrofosmin was generally higher on the uncorrected 99mTc-tetrofosmin images than on the single 99mTc-tetrofosmin images, especially in areas of low flow (percentage count of 99mTc-tetrofosmin > or = 50%). The crosstalk correction contributed to improving the agreement between regional percentage uptakes and significantly improved the detectability of myocardial perfusion-metabolism mismatching. CONCLUSION: With 3-channel acquisition and weighted-scatter correction of crosstalk from the 18F photopeak to the 99mTc photopeak, DISA with 99mTc-tetrofosmin and FDG is feasible for assessing regional myocardial perfusion and viability.     

Low efficacy of 18F-FDG PET for detection of uveal malignant melanoma compared with 123I-IMP SPECT.

Earlier investigations showed that N-isopropyl-p-123I-iodoamphetamine SPECT (123I-IMP SPECT) is useful for the diagnosis of uveal malignant melanoma, whereas the feasibility and usefulness of 18F-FDG PET in uveal malignant melanoma have not yet been established. We compared the usefulness of 123I-IMP SPECT and 18F-FDG PET for the detection of uveal malignant melanoma on the same subjects. METHODS: Nineteen patients (10 men, 9 women) with suspected uveal malignant melanoma were examined by 123I-IMP SPECT. Thirteen of them were also examined by 18F-FDG PET. 123I-IMP SPECT was performed at 15 min or at 3 and 24 h after intravenous administration of 123I-IMP. RESULTS: In 12 of 19 study patients, 123I-IMP SPECT obtained at 24 h after intravenous administration of 123I-IMP delineated an area of increased uptake in the site corresponding to the ocular tumor. All of the ocular tumors in the 12 123I-IMP SPECT-positive patients were confirmed histopathologically and clinically to be uveal malignant melanoma. The other 7 123I-IMP-SPECT-negative patients have been monitored under the diagnosis of choroidal nevus, choroidal hemangioma, hyperplasia of the pigment epithelium of the retina, or idiopathic inflammatory lesions without any complications. In a total of 13 patients examined by 18F-FDG PET, 9 of whom were 123I-IMP SPECT positive and 4 were negative, only 1 patient showed abnormal uptake of 18F-FDG PET in the site corresponding to the ocular tumor. Therefore, 8 of 9 patients with uveal malignant melanoma showed false-negative results in 18F-FDG PET. The 18F-FDG PET-positive patient with uveal malignant melanoma had the largest tumor mass with a short diameter of 12 mm, a long diameter of 17 mm, and a height of 7 mm. In the other 8 18F-FDG PET-negative patients, the tumors had a dimension of 11 x 13 x 7 mm or less. CONCLUSION: 123I-IMP SPECT is a sensitive and accurate method for the detection of uveal malignant melanoma, whereas the efficacy of 18F-FDG PET for this purpose is low because of a high incidence of false-negative results. 123I-IMP SPECT is far more superior in comparison with 18F-FDG PET in detecting uveal malignant melanoma.     

SPECT imaging of para-axial neurofibromatosis with technetium-99m DTPA

Single photon emission computed tomography (SPECT) was used to study uptake of technetium-99m diethylenetriaminepentaacetic acid ([99mTc]DTPA) by para-axial neurofibromas in 13 patients. SPECT imaging led to better resolution of uptake in nine instances and detection of 12 lesions unsuspected on planar imaging (PI). Two false-positive instances and one false-negative instance of uptake are described. The planning of the surgical approach and placement of graft material for spinal fusion was assisted by SPECT in two patients. One patient with disability secondary to recurring abdominal pain had detection of the causative lesion by SPECT and subsequent relief of her symptoms following excision of the tumor. SPECT imaging of soft-tissue tumors of neurofibromatosis appears to have potential use in preplanning surgery on structural or cosmetic lesions, in the detection of occult lesions, and the monitoring of patients with neurofibromatosis at regular intervals.     

Dynamic SPECT with technetium-99m HM-PAO in meningiomas--a comparison with iodine-123 IMP

Technetium-99m hexamethylpropyleneamine oxime ([99mTc]HM-PAO) has recently been introduced as an alternative to N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) for measurement of regional cerebral blood flow. This study compares dynamic SPECT studies using the two tracers in seven patients with meningiomas. Regions of interest were placed over the lesion and contralateral homologous presumed normal area. The counting-rate ratio for the lesion to the contralateral homologous area (L/N ratio) was then calculated in the first image. L/N ratios of [99mTc]HM-PAO single photon emission computed tomography (SPECT) were lower than those of [123I])IMP SPECT, particularly in hypervascular meningiomas. Furthermore, time-activity curves showed that the washout of [99mTc]HM-PAO in the tumors was very slow or incomplete, preventing an accurate assessment of vascularity of meningiomas with [99mTc]HM-PAO, as is generally possible with [123I]IMP.     

Digital image fusion of CT and PET data sets--clinical value in abdominal/pelvic malignancies

PURPOSE: We investigated the clinical relevance of digital image fusion of CT and 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) positron emission tomography (PET) studies in patients with suspected abdominal and/or pelvic metastasis. METHOD: Nineteen patients with suspected residual/recurrent malignancies underwent CT and [18F]FDG PET studies of the abdomen and/or pelvis. The data sets of both modalities were fused on a digital workstation by automatic adaptation of the pixel size and the slice thickness. Different body positions were corrected by semiautomatic adaptation of the body axes. The fused images were reconstructed in sagittal, coronal, and axial planes. RESULTS: Good spatial correlation between both modalities was achieved in all patients. Image fusion improved the spatial allocation of pathologically increased [18F]FDG uptake in 7 of 35 lesions (20%). CONCLUSION: This work suggests that digital image fusion of CT and [18F]FDG PET data sets improves the anatomical localization of foci with increased [18F]FDG enhancement of the retroperitoneum and the abdominal/pelvic wall, respectively.     

Uptake of 99mTc labelled (Fab')2 fragments of monoclonal antibody 225.28S by a benign ocular naevus

Malignant melanoma is one of the most common primary intraocular neoplasms. Recently, 99mTc radiolabelled (Fab')2 fragments of monoclonal antibody 225.28S raised against cutaneous melanomas have been used for imaging uveal melanomas. We report here a case where uptake of radiolabelled antibody was observed in a choroidal melanoma of the right eye and a benign choroidal naevus of the left.     

Positron emission tomography with [<Superscript>18</Superscript>F]FDOPA and [<Superscript>18</Superscript>F]FDG in the imaging of small cell lung carcinoma: preliminary results

Small cell lung carcinomas (SCLC) express neuroendocrine markers, and dihydroxyphenylalanine (DOPA) is known to accumulate in neuroendocrine tumours. This study was performed with the aim of evaluating the uptake of 3,4-dihydroxy-6-¹⁸F-fluoro-phenylalanine ([¹⁸F]FDOPA) by SCLC, based on comparison with the results of fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography (PET) and standard imaging procedures. [¹⁸F]FDG PET and [¹⁸F]FDOPA PET were performed on four patients with newly diagnosed SCLC. There was agreement between the results of [¹⁸F]FDOPA PET and [¹⁸F]FDG PET in four tumoural sites out of 11, whereas [¹⁸F]FDG PET and standard imaging procedures were in full agreement. A semi-quantitative analysis based on standardised uptake values (SUVs) was performed in order to compare [¹⁸F]FDG and [¹⁸F]FDOPA tumour uptake. The median [¹⁸F]FDG SUV_max was 5.9 (with a 95% confidence interval from 4.4 to 9.2), while the median [¹⁸F]FDOPA SUV_max was 1.9 (with a 95% confidence interval from 1.6 to 3.8). The difference between [¹⁸F]FDG SUV_max and [¹⁸F]FDOPA SUV_max was significant (P<0.01). [¹⁸F]FDOPA PET appeared less sensitive than [¹⁸F]FDG PET and standard imaging procedures in the staging of SCLC. No clear relation between [¹⁸F]FDOPA uptake and positivity of neuroendocrine markers on immunohistochemistry emerged from these preliminary results; however, since [¹⁸F]FDOPA uptake may reflect better differentiation of the tumour, and possibly a better prognosis, this point warrants clarification in a larger study.     

The value of fluorine-18 fluorodeoxyglucose PET in patients with medullary thyroid cancer

The early detection of metastases from medullary thyroid cancer (MTC) is important because the only curative therapy consists in surgical removal of all tumour tissue. There is no single sensitive diagnostic imaging modality for the localization of all metastases in patients with MTC. Therefore, in many cases several imaging modalities (e.g. ultrasonography, magnetic resonance imaging, computerized tomography and scintigraphy using pentavalent technetium-99m dimercaptosuccinic acid, thallium-201 chloride, indium-111 pentetreotide, anti-CEA antibodies or metaiodobenzylguanidine) must be performed consecutively in patients with elevated calcitonin levels until the tumour is localized. In this prospective study, we investigated the value of fluorine-18 fluorodeoxyglucose positron emission tomography ([18F]FDG PET) in the follow-up of patients with MTC. [18F]FDG PET examinations of the neck and the chest were performed in 20 patients with elevated calcitonin levels or sonographic abnormalities in the neck. Positive [18F]FDG findings were validated by histology, computerized tomography or selective venous catheterization. [18F]FDG PET detected tumour in 13/17 patients (nine cases were validated by histology, four by computerized tomography). Five patients showed completely negative PET scans (of these cases, one was true-negative and four false-negative). One patient with [18F]FDG accumulation in pulmonary lesions from silicosis and one patient with a neck lesion that was not subjected to histological validation had to be excluded. Considering all validated localizations, [18F]FDG PET detected 12/14 tumour manifestations in the neck, 6/7 mediastinal metastases, 2/2 pulmonary metastases and 2/2 bone metastases. In two patients with elevated calcitonin levels, no diagnostic modality was able to localize a tumour. The sensitivity of [18F]FDG PET in the follow-up of MTC was 76% (95% confidence interval 53%-94%); this is encouraging. [18F]FDG PET promises to be a valuable diagnostic method, especially for the detection of lymph node metastases, surgical resection of which can result in complete remission.     

Radiographic and neuro-SPECT imaging in an immature third ventricle teratoma: case report.

We report a case of an immature teratoma of the third ventricle, which was preoperatively thought to be a choroid plexus papilloma. The diagnosis was made by biopsy since the radiographic (CT, MRI), angiographic and scintigraphic findings ([99mTc]pertechnetate, 99mTc-DTPA, 99mTc-HMPAO brain SPECT) were nonspecific. Disruption of the blood-brain barrier is the mechanism for radionuclidic and contrast tumoral uptake and is demonstrated by marked contrast enhancement on CT and focal concentration on [99mTc]pertechnetate and 99mTc-DTPA images. No suppression of [99mTc]pertechnetate tumor uptake was observed following the administration of potassium perchlorate. Increased concentration of tumor protein is suggested by the increased signal on the T1-weighted magnetic resonance images and high [99mTc]pertechnetate uptake. The tumor's detection on the 99mTc-HMPAO brain SPECT was due to its intraventricular location. A number of potential mechanisms for brain tumor localization of 99mTc-HMPAO are discussed.     

Biodistribution,pharmacokinetics and PET Imaging of [18F]FMISO, [18F]FDG and [18F]FAc in a sarcoma- and inflammation-bearing mouse model

2-Deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG), [¹⁸F]fluoroacetate ([¹⁸F]FAc) and [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO) were all considered to be positron emission tomography (PET) probes for tumor diagnosis, though based on different rationale of tissue uptake. This study compared the biodistribution, pharmacokinetics and imaging of these three tracers in a sarcoma- and inflammation-bearing mouse model.MethodsC3H mice were inoculated with 2×10⁵ KHT sarcoma cells in the right thigh on Day 0. Turpentine oil (0.1 ml) was injected in the left thigh on Day 11 to induce inflammatory lesion. Biodistribution, pharmacokinetics and microPET imaging of [¹⁸F]FMISO, [¹⁸F]FDG and [¹⁸F]FAc were performed on Day 14 after tumor inoculation.ResultsThe inflammatory lesions were clearly visualized by [¹⁸F]FDG/microPET and autoradiography at 3 days after turpentine oil injection. The tumor-to-muscle and inflammatory lesion-to-muscle ratios derived from microPET imaging were 6.79 and 1.48 for [¹⁸F]FMISO, 8.12 and 4.69 for [¹⁸F]FDG and 3.72 and 3.19 for [¹⁸F]FAc at 4 h post injection, respectively. Among these, the tumor-to-inflammation ratio was the highest (4.57) for [¹⁸F]FMISO compared with that of [¹⁸F]FDG (1.73) and [¹⁸F]FAc (1.17), whereas [¹⁸F]FAc has the highest bioavailability (area under concentration of radiotracer vs. time curve, 116.2 h×percentage of injected dose per gram of tissue).ConclusionsMicroPET images and biodistribution studies showed that the accumulation of [¹⁸F]FMISO in the tumor is significantly higher than that in inflammatory lesion at 4 h post injection. [¹⁸F]FDG and [¹⁸F]FAc delineated both tumor and inflammatory lesions. Our results demonstrated the potential of [¹⁸F]FMISO/PET in distinguishing tumor from inflammatory lesion.     

Efficiency of 18F-FDG and 99mTc-depreotide SPECT in the diagnosis of malignancy of solitary pulmonary nodules

Purpose The purpose of the study was to compare ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and ^99mTc-depreotide single-photon emission computed tomography (SPECT) in the diagnosis of malignancy of solitary pulmonary nodules (SPNs).Methods Twenty-eight patients without any history of cancer and presenting an SPN (0.8–3 cm in size) underwent FDG PET and depreotide SPECT. Depreotide SPECT and FDG PET were performed on a double-head gamma camera and a dedicated PET scanner respectively. Twenty-five out of 28 lesions were removed by thoracotomy or assessed by biopsy (n=1) and histologically examined. A strategy of serial CT scanning was adopted in the three remaining patients.Results Histological findings revealed 18 malignant nodules and seven benign lesions. Stability over a 2-year period indicated a benign process in the remaining three cases. Both techniques yielded true positive results in 15 of the 18 cancers. FDG PET identified two additional adenocarcinomas not detected by depreotide SPECT. A carcinoid tumour not visualised on FDG PET was identified by depreotide SPECT. Seven of the ten benign lesions did not reveal tracer uptake on either depreotide SPECT or FDG PET. Both techniques showed false positive results for the same two lesions. One more false positive was seen on FDG PET. FDG PET and depreotide SPECT had a sensitivity of 94.4% and 88.9% respectively; this difference was not significant. In our experience, depreotide SPECT and FDG PET are equally sensitive (92.3%) for large (>1.5 cm) and equally specific (85.7%) for small (up to 1.5 cm) SPNs suspicious for malignancy.Conclusion This study showed ¹⁸F-FDG PET to be more sensitive than ^99mTc-depreotide SPECT in the diagnosis of malignancy of SPNs. However, the combination of both techniques may provide additional accuracy.     

The value of fluorine-18 fluorodeoxyglucose positron emission tomography in patients with medullary thyroid cancer

The early detection of metastases from medullary thyroid cancer (MTC) is important because the only curative therapy consists in surgical removal of all tumour tissue. There is no single sensitive diagnostic imaging modality for the localization of all metastases in patients with MTC. Therefore, in many cases several imaging modalities (e.g. ultrasonography, magnetic resonance imaging, computerized tomography and scintigraphy using pentavalent technetium-99m dimercaptosuccinic acid, thallium-201 chloride, indium-111 pentetreotide, anti-CEA antibodies or metaiodobenzylguanidine) must be performed consecutively in patients with elevated calcitonin levels until the tumour is localized. In this prospective study, we investigated the value of fluorine-18 fluorodeoxyglucose positron emission tomography ([¹⁸F]FDG PET) in the follow-up of patients with MTC. [¹⁸F]FDG PET examinations of the neck and the chest were performed in 20 patients with elevated calcitonin levels or sonographic abnormalities in the neck. Positive [¹⁸F]FDG findings were validated by histology, computerized tomography or selective venous catheterization. [¹⁸F]FDG PET detected tumour in 13/17 patients (nine cases were validated by histology, four by computerized tomography). Five patients showed completely negative PET scans (of these cases, one was true-negative and four false-negative). One patient with [¹⁸F]FDG accumulation in pulmonary lesions from silicosis and one patient with a neck lesion that was not subjected to histological validation had to be excluded. Considering all validated localizations, [¹⁸F]FDG PET detected 12/14 tumour manifestations in the neck, 6/7 mediastinal metastases, 2/2 pulmonary metastases and 2/2 bone metastases. In two patients with elevated calcitonin levels, no diagnostic modality was able to localize a tumour. The sensitivity of [¹⁸F]FDG PET in the follow-up of MTC was 76% (95% confidence interval 53%–94%); this is encouraging. [¹⁸F]FDG PET promises to be a valuable diagnostic method, especially for the detection of lymph node metastases, surgical resection of which can result in complete remission. Received 16 September 1999 and in revised form 19 January 2000     

New color imaging of [99mTc]-pyrophosphate and [201Tl]-chloride dual isotope single photon emission computed tomography in acute myocarditis

[99mTc]-pyrophosphate (PYP) and [201Tl]-chloride dual isotope single photon emission computed tomography (SPECT) is now available to detect the site and extent of acute myocardial infarction. In inflammatory myocardial disease, [99mTc]PYP makes hot image on damaged area. We performed dual isotope SPECT of [99mTc]PYP and [201Tl]Cl in two patients with acute myocarditis and severe rhythm disturbance to evaluate the severity of inflammation. Myocardial damage was estimated by [201Tl] perfusion coloring blue and myocardial inflammation was estimated by [99mTc]PYP uptake coloring red. The overlap display of both images made it clear to detect spatial extent of myocardial inflammation. Using this technique, we expect to estimate the severity of myocarditis and to make a decision of therapeutic plan.     

Biodistribution, dosimetry, and clinical evaluation of technetium-99m ethyl cysteinate dimer in normal subjects and in patients with chronic cerebral infarction

Technetium-99m ethyl cysteinate dimer (ECD) has high initial cerebral uptake with slow clearance in nonhuman primates suggesting ideal characteristics for single photon emission computer tomography (SPECT) imaging. We evaluated the biodistribution, dosimetry and scintigraphic pattern of [99mTc]ECD in normal subjects and the accuracy of SPECT imaging in patients with chronic cerebral infarction. Sixteen normal subjects were injected with approximately 10 mCi of [99mTc]ECD. Anterior and posterior single-pass whole-body images were obtained at multiple times after injection. Blood clearance of the radiotracer was rapid, falling to 10.0 +/- 6.6% and 4.9 +/- 1.1% of the injected dose at 2 and 60 min, respectively. Brain uptake was 6.4 +/- 2.1% of the injected dose 5 min after injection. The critical organ was the urinary bladder. Technetium-99m ECD SPECT was performed with a rotating gamma camera in ten of the 16 normal subjects and 34 patients with clinical and CT evidence of chronic stroke. Thirty-three of the thirty-four patients had focal [99mTc]ECD abnormalities on SPECT (97.1%) based on visual inspection of the SPECT images. In summary, we obtained high quality SPECT images as a result of the optimal physical and biologic characteristics of the tracer. Technetium-99m ECD SPECT shows promise for the evaluation of patients with stroke.     

~（99m）Tc－MIBISPECT检测梗塞区存活心肌（与~（18）F－FDGPET结果比较）

评价９９ｍＴｃ-甲氧基异丁基异腈（ＭＩＢＩ）ＳＰＥＣＴ定量分析在心肌梗塞（ＭＩ）区存活心肌判断中的准确性，及视觉判断９９ｍＴｃ-ＭＩＢＩＳＰＥＣＴ结果在缺血与坏死心肌鉴别中的局限性．方法：３４例ＭＩ患者进行了９９ｍＴｃ-ＭＩＢＩＳＰＥＣＴ心肌灌注显像及１８Ｆ标记的脱氧葡萄糖（ＦＤＧ）ＰＥＴ显像．结果：当局部心肌９９ｍＴｃ-ＭＩＢＩ放射性小于左室心肌峰计数的４０％，存活心肌存在的可能性仅为２４％左右；相反，当局部９９ｍＴｃ-ＭＩＢＩ放射性大于左室心肌峰计数的４０％，则９０％以上的心肌节段均为存活心肌．故视觉判断不可逆性缺损明显低估存活心肌．约５９％的不可逆性缺损节段在ＰＥＴ显像中有明确１８Ｆ-ＦＤＧ摄取，提示为存活心肌．结论：９９ｍＴｃ-ＭＩＢＩＳＰＥＣＴ定量分析能明显提高存活心肌的定位诊断，慎重判断及定义心肌灌注显像中的不可逆性缺损区，重视定量分析的研究及应用对ＭＩ区存活与坏死心肌的鉴别诊断有重要价值．     

Initial experience with technetium-99m HM-PAO brain SPECT

Technetium-99m hexamethylpropyleneamineoxime ([99mTc]HM-PAO) brain single photon emission computed tomography (SPECT) was performed with a dual head rotating scintillation camera. Normal tracer distribution and side/side differences of counting rates were obtained in 11 healthy volunteers. Almost stable gray/white matter ratios were found (1.97-2.1) in one normal subject during 2 hr after tracer administration. Eighty-three investigated patients had the following diagnoses (in parentheses is percent of positive findings in each group): cerebral vascular disease 18 (94.4%), epilepsy 23 (82.6%), extrapyramidal disorders 8 (100%), dementia 12 (100%), headache 11 (63.6%), psychiatric disorders 11 (27.3%). In addition, SPECT was performed in 28 male volunteers during motor or visual imagery tasks and a significant increase (p = 0.035) of relative tracer deposition was observed in the left inferior occipital region during visual imagery when compared with motor imagery. The results indicate that [99mTc]HM-PAO SPECT is valuable for demonstrating pathologic and physiologic changes of the brain.     

NanoPET imaging of [18F]fluoromisonidazole uptake in experimental mouse tumours

Purpose The purpose of this study was to assess the potential and utility of ultra-high-resolution hypoxia imaging in various murine tumour models using the established hypoxia PET tracer [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO).Methods [¹⁸F]FMISO PET imaging was performed with the dedicated small-animal PET scanner NanoPET (Oxford Positron Systems) and ten different human tumour xenografts in nude mice as well as B16 melanoma tumours in syngeneic Balb/c mice. For comparison, [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) PET scans were also performed in the mice bearing human tumour xenografts.Results In 10 out of 11 experimental tumour models, [¹⁸F]FMISO PET imaging allowed clear-cut visualisation of the tumours. Inter- and intratumoural heterogeneity of tracer uptake was evident. In addition to average TMRR (tumour-to-muscle retention ratio including all voxels in a volume of interest (VOI)), the parameters TMRR_75% and TMRR₅ (tumour-to-muscle retention ratio including voxels of 75% or more of the maximum radioactivity in a VOI and the five hottest pixels, respectively) also served as measures for quantifying the heterogeneous [¹⁸F]FMISO uptake in the tumours. The variability observed in [¹⁸F]FMISO uptake was related neither to tumour size nor to the injected mass of the radiotracer. The pattern of normoxic and hypoxic regions within the human tumour xenografts, however, correlated with glucose metabolism as revealed by comparison of [¹⁸F]FDG and [¹⁸F]FMISO images.Conclusion This study demonstrates the feasibility and utility of [¹⁸F]FMISO for imaging murine tumour models using NanoPET.