Imaging discordance between hepatic angiography versus Tc-99m-MAA SPECT/CT: a case series,technical discussion and clinical implications

During pre-therapy evaluation for yttrium-90 (Y-90) radioembolization, it is uncommon to find severe imaging discordance between hepatic angiography versus technetium-99m-macroaggregated albumin (Tc-99m-MAA) single photon emission computed tomography with integrated low-dose CT (SPECT/CT). The reasons for severe imaging discordance are unclear, and literature is scarce. We describe 3 patients with severe imaging discordance, whereby tumor angiographic contrast hypervascularity was markedly mismatched to the corresponding Tc-99m-MAA SPECT/CT, and its clinical impact. The incidence of severe imaging discordance at our institution was 4% (3 of 74 cases). We postulate that imaging discordance could be due to a combination of 3 factors: (1) different injection rates between soluble contrast molecules versus Tc-99m-MAA; (2) different arterial flow hemodynamics between soluble contrast molecules versus Tc-99m-MAA; (3) eccentric release position of Tc-99m-MAA due to microcatheter tip location, inadvertently selecting non-target microparticle trajectories. Tc-99m-MAA SPECT/CT more accurately represents hepatic microparticle biodistribution than soluble contrast hepatic angiography and should be a key criterion in patient selection for Y-90 radioembolization. Tc-99m-MAA SPECT/CT provides more information than planar scintigraphy to guide radiation planning and clinical decision making. Severe imaging discordance at pre-therapy evaluation is ominous and should be followed up by changes to the final vascular approach during Y-90 radioembolization.     

Computed tomography hepatic arteriography has a hepatic falciform artery detection rate that is much higher than that of digital subtraction angiography and 99mTc-MAA SPECT/CT: Implications for planning 90Y radioembolization?

Purpose

To compare the hepatic falciform artery (HFA) detection rates of digital subtraction angiography (DSA), computed tomography hepatic arteriography (CTHA) and 99mTc-macroaggregated albumin (99mTc-MAA) single photon emission computed tomography with integrated CT (SPECT/CT) and to correlate HFA patency with complication rates of yttrium-90 (90Y) radioembolization.

Material and methods

From August 2008 to November 2010, 79 patients (range 23–83 years, mean 62.3 years; 67 male) underwent pre-treatment DSA, CTHA and 99mTc-MAA scintigraphy (planar/SPECT/CT) to assess suitability for radioembolization with 90Y resin microspheres. Thirty-seven patients were excluded from the study, because CTHA was performed with a catheter position that did not result in opacification of the liver parenchyma adjacent to the falciform ligament. DSA, CTHA and 99mTc-MAA SPECT/CT images and medical records were retrospectively reviewed.

Results

A patent HFA was detected in 22 of 42 patients (52.3%). The HFA detection rates of DSA, CTHA and 99mTc-MAA SPECT/CT were 11.9%, 52.3% and 13.3%, respectively (p < 0.0001). An origin from the segment 4 artery was seen in 51.7% of HFAs. Prophylactic HFA coil-embolization prior to 90Y microspheres infusion was performed in 2 patients. Of the patients who underwent radioembolization with a patent HFA, none developed supra-umbilical radiation dermatitis. One patient experienced epigastric pain attributed to post-embolization syndrome and was managed conservatively.

Conclusion

The HFA detection rate of CTHA is superior to that of DSA and 99mTc-MAA SPECT/CT. Complications related to non-target radiation of the HFA vascular territory rarely occur, even in patients undergoing radioembolization with a patent HFA.     

The relationship between the percentage of lung shunting on Tc-99m macroaggregated albumin (Tc-99m MAA) scan and the grade of hepatocellular carcinoma vascularity

Background

Hepatocellular carcinoma (HCC) stands for the majority of primary liver malignancy. HCC has variable grade of vascularity according to the histological tumor grade and underlying liver damage. Yttrium-90 radioembolization is a promising catheter-based hepatic intra-arterial therapy for HCC that necessitates proper planning. Technetium-99m macroaggregated albumin (Tc-99m MAA), a simulation of the treatment, is used to identify the shunting of microspheres to the lungs or gastrointestinal tract.

Objective

To evaluate the relationship between the percentage of lung shunting on Tc-99m MAA scan performed in treatment planning of Yttrium-90 (Y-90) microsphere selective internal radiation therapy (SIRT) for HCC and the grade of tumor vascularity shown on digital subtraction hepatic angiography.

Materials and methods

This study was conducted on 19 patients diagnosed to have HCC, based on typical computed tomography (CT) criteria and/or elevated alpha-fetoprotein (AFP) ?200 ng/ml, and planned for Y-90 therapy. They were injected by Tc-99m MAA into the hepatic arterial territory with prior digital subtraction angiography. Tc-99m MAA scan was reviewed for extrahepatic shunting within the abdomen. Additionally, the hepatopulmonary shunt (HPS) fraction or the lung shunting (LS) percentage was calculated and further evaluated in relation to the grade of tumor vascularity shown on digital subtraction hepatic angiography.

Results

There was no extrahepatic accumulation of Tc-99m MAA related to umbilical, gastroduodenal or splenic shunting. The LS percentage assorted among patients and ranged between 0.8% and 42.9% with a median of 5.5%. LS more than 20% occurred in only 1 patient. Subsequent therapy plan was changed accordingly in 5% of patients. The more vascular the lesion was, the higher lung shunting percentage was detected.

Conclusion

Tc-99m MAA scan is fundamental prior to Y-90 microsphere SIRT as it minimizes the risk of post-radioembolization complications, hence, enhancing the safety of Y-90 microsphere subsequent administration. Moreover, the percentage of lung shunting varies considerably among patients with HCC relying on the grade of tumor vascularity.     

Anterior abdominal wall uptake in intrahepatic arterial brachytherapy with yttrium-90 sir spheres for hepatic malignancy

Patients with primary or secondary liver cancer who are not suitable for surgical resection may be treated with selective internal radiation therapy with yttrium-90. This may cause down staging of the tumor to a resectable size in some patients, and in these and other patients may prolong survival. It delivers a high dose of radiation therapy directly to the tumor, thus minimizing exposure to liver sensitive to radiation. Prior scanning with Tc-99m macroaggregated albumin is performed to assess lung shunting and potential extrahepatic deposition, which can cause significant clinical sequelae. Two patients with hepatic malignancy are presented who demonstrated extrahepatic deposition of Tc-99m macroaggregated albumin in the anterior abdominal wall. This is thought to be related to a patent hepatic falciform ligament artery.     

Hepatic falciform artery. Angiographic findings in 25 patients

Purpose: To determine the frequency of hepatic falciform artery (HFA) occurrence on celiac or hepatic angiograms and elucidate the anatomy and clinical importance.Material and Methods: Among 1,250 patients who underwent celiac or hepatic arteriography, we encountered 25 patients (2%) with a HFA. Prospectively, CT hepatic falciform arteriography (CTHA) was performed in 4 patients. Indigocarmine dye was injected into the HFA in 6 patients to evaluate whether the abdominal skin was stained. Embolization of the HFA before chemoembolization for hepatocellular carcinoma was performed in 4 patients to prevent abdominal wall injury.Results: Among 25 patients, the HFA arose as a terminal branch of the middle hepatic artery in 14 patients (56%) and of the left hepatic artery in 11 patients (44%). The vessel was single in 18 patients (72%) and double in 7 patients (28%). Two vessels ran side by side along the hepatic falciform ligament. On CTHA, the HFA ran within the hepatic falciform ligament and the branches were connected with the liver around the hepatic falciform ligament. After indigocarmine dye injection, the stain of abdominal skin was recognized in all 6 patients. No abdominal wall injury occurred in any of the 4 patients who were subjected to hepatic chemoembolization.Conclusion: HFA is an extrahepatic pathway which runs to the abdominal wall. Before chemoembolization of the middle or left hepatic artery for hepatic malignancy, the HFA should be recognized.     

Ventilation/perfusion lung scintigraphy: what is still needed? A review considering technetium-99m-labeled macro-aggregates of albumin

Lung perfusion scintigraphy (LPS) with technetium-99m-labeled macro-aggregates of albumin (Tc-99m-MAA) is well established in the diagnostic of pulmonary embolism (PE). In the last decade, it was shown that single-photon emission computer tomography (SPECT) acquisition of LPS overcame static scintigraphy. Furthermore, there are rare indications for LPS, such as preoperative quantification of regional lung function prior to lung resection or transplantation, optimization of lung cancer radiation therapy, quantification of right-left shunt, planning of intra-arterial chemotherapy, and several rare indications in pediatrics. Moreover, LPS with Tc-99m-MAA is a safe method with low radiation exposure. PE can also be diagnosed by spiral computer tomography (CT), ultrasound, magnetic resonance angiography, or pulmonary angiography (PA, former gold standard). The present review considers all these methods, especially spiral CT, and compares them with LPS with respect to sensitivity and specificity and gives an overview of established and newer publications. It shows that LPS with Tc-99m-MAA represents a diagnostic method of continuing value for PE. In comparison with spiral CT and/or PA, LPS is not to be defeated as mentioned also by the most actual Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II reports. This applies in particular to chronic or recurring embolisms, whereas currently spiral CT may be of greater value for major or life-threatening embolisms. At present, LPS cannot be replaced by other methods in some applications, such as pediatrics or in the quantification of regional pulmonary function in a preoperative context or prior to radiation therapy. LPS still has a place in the diagnostics of PE and is irreplaceable in several rare indications as described earlier.     

Nontumorous Perfusion Abnormalities of Liver Parenchyma Adjacent to the Falciform Ligament As Revealed by Angiographic Helical Ct and Angiography

Purpose: To investigate nontumorous abnormalities in the liver around the falciform ligament as revealed by arteriography and helical CT arterial portography (CTAP) and helical CT during hepatic arteriography (CTHA).Material and Methods: One hundred and seventeen patients simultaneously underwent hepatic arteriography and CTAP and CTHA of the common hepatic artery. The number, size, and shape of nontumorous defects of portal perfusion in the liver adjacent to the falciform ligament on CTAP as well as the nontumorous contrast enhancement in the same area on CTHA were determined. In 1 case, in which nontumorous enhancement was observed on CTHA, selective arteriography from the gastric arteries was performed.Results: On CTAP a nontumorous area of decreased portal perfusion of the liver around the falciform ligament was detected in 18 (15.4%) of the 117 patients, while nontumorous enhancement on CTHA was seen in 7 (6.0%). In 4 patients, both of these nontumorous abnormalities were observed. In the patient undergoing selective gastric arteriography, nonportal venous inflow to the liver in the direction to the liver adjacent to the falciform ligament was seen.Conclusion: One cause of nontumorous vascular abnormalities adjacent to the falciform ligament as shown on angiographic helical CT is aberrant gastric venous inflow to this region.     

Focal fatty change of the liver adjacent to the falciform ligament: CT and sonographic findings in five surgically confirmed cases

Five cases of surgically confirmed focal fatty infiltration of the liver were detected by CT and sonography. In all five cases, the abnormality was located at the anterolateral edge of the medial segment of the liver. It was seen as a small area of low attenuation adjacent to the falciform ligament on CT and as an echogenic area next to the ligamentum teres on sonography. Dynamic CT performed during infusion of contrast medium via the superior mesenteric artery (arterial portography) showed portal blood flow within the lesion and was useful for excluding the presence of a hepatic tumor. Focal fatty infiltration of the liver adjacent to the falciform ligament constitutes a diagnostic pitfall on CT and sonography.     

Hepatic falciform artery: anatomy, angiographic appearance, and clinical significance

Three patients developed supraumbilical skin rashes during hepatic artery infusion chemotherapy by a surgically placed perfusion catheter and drug-infusion pump. In one patient, hepatic arterial scintigraphy with technetium-99m macroaggregated serum albumin showed increased uptake corresponding to the rash, and a hepatic arteriogram showed a dilated falciform branch of the left hepatic artery. Surgical ligation of the falciform artery permitted further treatment without recurrent rash. Based on a review of 100 celiac arteriograms, the incidence of the falciform artery on angiographic studies is approximately 2%. The angiographic appearance of this artery is presented, and its potential clinical significance in hepatic artery perfusion chemotherapy is discussed.     

镰状韧带旁肝假性病灶的影像表现及其原因分析

目的分析镰状韧带旁肝假性病灶(简称镰旁肝假病灶)的影像学征象及形成原理.方法 收集CT检查发现镰旁肝假病灶的患者40例(A型23例,B型17例),复习相关资料并结合2例活检、6例随访、5例MRI的结果,回顾性分析其CT平扫、增强密度的变化及其形成原理和机制.结果 25例镰旁肝假病灶动脉期呈低密度,13例呈等密度,2例呈稍高密度;40例镰旁肝假病灶门静脉期CT值均低于周围肝实质;27例镰旁肝假病灶延迟期呈低或略低密度,13例A型镰旁肝假病灶延迟扫描为等密度.2例A型镰旁肝假病灶MRI任何序列均呈等信号,反相位未观察到信号变化;3例B型镰旁肝假病灶反相位信号减低或稍减低.6例CT追踪随访2例A型镰旁肝假病灶无变化,4例B型镰旁肝假病灶缩小或消失;其中1例B型镰旁肝假病灶1月后MRI复查更变淡、缩小.结论 镰旁肝假病灶A型可由特殊血供引起,B型可由局灶脂肪浸润引起,其发生部位特殊,在CT、MRI上有特征性影像学表现,一般可明确诊断.     

SPECT/CT zum initialen Staging und Therapiemonitoring in der Onkologie

CLINICAL/METHODICAL ISSUE: Hybrid imaging of function and morphology has gained significant importance for lesion detection and treatment monitoring in oncology. In patients with differentiated thyroid carcinoma (DTC) a planar whole body scan is carried out after radioiodine therapy (RIT) for staging. However, due to limited spatial resolution the diagnostic accuracy of this scintigraphy method is impaired. Radioembolization utilizing (90)Yttrium loaded micro-spheres by selective internal radiotherapy (SIRT) allows a minor invasive therapy of primary and secondary liver tumors. In order to avoid side effects of the micro-spheres caused by an outflow into intestines, stomach or lungs, imaging the arteries supplying the liver has to be performed by means of technetium-99m macroaggregated albumin ((99m)Tc-MAA) and scintigraphy. The limited morphological information supplied by scintigraphy is again a challenge in treatment monitoring. STANDARD RADIOLOGICAL/NUCLEAR MEDICAL METHODS: (131)Iodine whole body scanning is used for staging in patients with DTC 3-4 days after ablation. Monitoring of the tumor marker thyroglobulin and selective radioiodine whole body scans are available for patients with a high risk profile in the further follow-up with imaging of the arteries supplying the liver by means of (99m)Tc-MAA scintigraphy in preparation of SIRT. METHODICAL INNOVATIONS: Single photon emission computed tomography/computed tomography (SPECT/CT) of the neck and thorax with a therapeutic activity of radioiodine for staging after ablation. Techniques include imaging of arteries supplying the liver by means of (99m)Tc-MAA SPECT/CT before SIRT and evaluation and quantification of the uptake of liver tumors, especially in comparison to the uptake of liver parenchyma by means of SPECT/CT. PERFORMANCE: Due to the integration of combined functional and morphological information SPECT/CT can be used to characterize the morphology and iodine uptake of lesions more accurately, resulting in optimized staging in patients with DTC in comparison to whole body iodine scans and SPECT/CT provides more accurate imaging of the arterial supply of the liver and of potential outflows of micro-spheres into other organs. SPECT/CT allows evaluation and quantification of the uptake of liver tumors. ACHIEVEMENTS: Improved postablative staging in patients with differentiated thyroid cancer by SPECT/CT in comparison to radioiodine whole body scans can be achieved. Improved planning and monitoring of SIRT therapies utilizing SPECT/CT leads to optimized therapeutic doses within liver lesions. PRACTICAL RECOMMENDATIONS: Integration of SPECT/CT into the clinical standard for postablative staging in patients with DTC is recommended as well as utilization of SPECT/CT during the planning process, for dose calculation and treatment monitoring of SIRT therapies.     

Potential false positive Tc-99m sestamibi parathyroid study due to uptake in brown adipose tissue

We report on a 55-year-old woman with suspected primary hyperparathyroidism who underwent dual phase Tc-99m sestamibi parathyroid imaging. Symmetric, patchy activity in the neck and shoulders was localized to low attenuation areas on integrated SPECT/CT and attributed to uptake in brown adipose tissue (BAT). Focal uptake in the anterior thorax on SPECT images, which potentially may have been misinterpreted as ectopic parathyroid tissue, was demonstrated on SPECT/CT as uptake in BAT. Recognition of this pattern on parathyroid SPECT/CT scintigraphy may avoid false positive reports. Our case provides further evidence that in addition to F-18 FDG, I-123 MIBG, and Tc-99m tetrofosmin, Tc-99m sestamibi may also accumulate in BAT.     

Comparison of Two Different Segmentation Methods on Planar Lung Perfusion Scan with Reference to Quantitative Value on SPECT/CT

Purpose

Until now, there was no single standardized regional segmentation method of planar lung perfusion scan. We compared planar scan based two segmentation methods, which are frequently used in the Society of Nuclear Medicine, with reference to the lung perfusion single photon emission computed tomography (SPECT)/computed tomography (CT) derived values in lung cancer patients.

Methods

Fifty-five lung cancer patients (male:female, 37:18; age, 67.8?±?10.7 years) were evaluated. The patients underwent planar scan and SPECT/CT after injection of technetium-99 m macroaggregated albumin (Tc-99 m-MAA). The % uptake and predicted postoperative percentage forced expiratory volume in 1 s (ppoFEV1%) derived from both posterior oblique (PO) and anterior posterior (AP) methods were compared with SPECT/CT derived parameters. Concordance analysis, paired comparison, reproducibility analysis and spearman correlation analysis were conducted.

Results

The % uptake derived from PO method showed higher concordance with SPECT/CT derived % uptake in every lobe compared to AP method. Both methods showed significantly different lobar distribution of % uptake compared to SPECT/CT. For the target region, ppoFEV1% measured from PO method showed higher concordance with SPECT/CT, but lower reproducibility compared to AP method. Preliminary data revealed that every method significantly correlated with actual postoperative FEV1%, with SPECT/CT showing the best correlation.

Conclusion

The PO method derived values showed better concordance with SPECT/CT compared to the AP method. Both PO and AP methods showed significantly different lobar distribution compared to SPECT/CT. In clinical practice such difference according to different methods and lobes should be considered for more accurate postoperative lung function prediction.

     

Usefulness of Bremsstrahlung Images after Intra-arterial Y-90 Resin Microphere Radioembolization for Hepatic Tumors

Purpose

Y-90 resin microsphere radioembolization is used to treat inoperable hepatic tumors. After injection of Y-90 resin microsphere, the only method to visualize the distribution of Y-90 is the scintigraphic imaging of bremsstrahlung radiation. The purpose of this study was to evaluate the characteristics and usefulness of bremsstrahlung imaging in Y-90 resin microsphere treatment.

Methods

Twenty patients (22 administrations) underwent intra-arterial Y-90 resin microsphere treatment. For pre-treatment planning, images of Tc-99m albumin macroaggregate (MAA) arterial injection and hepatic contrast angiography were obtained. Post-treatment bremsstrahlung images were taken and compared with pre-treatment images. The extrahepatic activity was evaluated on bremsstrahlung images. To correlate the size and vascularity of the tumors with tumor visualization on bremsstrahlung images, the individual tumors were grouped according to visualization on each image and compared with one another by size and tumor-to-normal ratio.

Results

All post-therapeutic bremsstrahlung images showed similar contours of the liver with pre-treatment angiography. No extrahepatic activity was seen in all cases. The visualized tumors on bremsstrahlung images were significantly larger than the non-visualized tumors. Tumor-to-normal ratios of the visualized tumors on bremsstrahlung images were significantly higher than those of the non-visualized tumors.

Conclusions

Bremsstrahlung images after intra-arterial Y-90 resin microsphere treatment are useful in evaluating the intrahepatic distribution of radioisotope and detecting possible extrahepatic activity.     

Compare FDG-PET and Tc-99m tetrofosmin SPECT to detect metastatic thyroid carcinoma

RATIONALE AND OBJECTIVES: The effectiveness of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) and technetium-99m tetrofosmin (Tc-99m TF) single photon emission computed tomography (SPECT) of neck and chest was evaluated to detect metastatic lesions in well-differentiated thyroid carcinoma after nearly total thyroidectomy and radioiodine (I-131) treatment who present with elevated serum human thyroglobulin levels but negative I-131 whole body scan. MATERIALS AND METHODS: Twenty-three patients with differentiated thyroid carcinoma who underwent nearly total thyroidectomy and I-131 treatments were included in this study. RESULTS: All of the 23 patients had negative I-131 whole body scan and elevated human thyroglobulin levels under thyroid-stimulating hormone stimulation. Metastatic lesions were detected by FDG-PET in 20 patients, while Tc-99m TF SPECT revealed metastatic lesions in only 11 of the 20 patients. Both FDG-PET and Tc-99m TF SPECT failed to demonstrate miliary pulmonary metastases in two of the remaining three patients. The other patient did not show any lesion on FDG-PET, Tc-99m TF SPECT, chest computed tomography, or other imaging techniques. CONCLUSION: This study demonstrated that FDG-PET is more sensitive than Tc-99m TF SPECT to detect metastatic lesions in differentiated thyroid carcinoma with elevated human thyroglobulin but negative I-131 whole body scan. However, miliary pulmonary metastases could be missed by the both techniques.     

Preliminary results of Tc-99m ECD SPECT to evaluate cerebral collateral circulation during balloon test occlusion

PURPOSE: The authors obtained noninvasive quantitative measurements of regional cerebral blood flow using Tc-99m L,L-ethyl cysteinate dimer (Tc-99m ECD) SPECT to evaluate cerebral collateral circulation during balloon test occlusion (BTO) of the internal carotid artery and vertebral artery (VA). METHODS: Five cases associated with an aneurysm and a brain tumor were investigated. After 10 minutes of BTO, a bolus of Tc-99m ECD was injected intravenously and radionuclide angiography was performed. The balloon remained inflated for an additional 5 minutes. After radionuclide angiography was completed, brain SPECT imaging was performed. For quantitative analysis, regions of interest were defined on the transverse images on each side of the anterior cerebral artery and middle cerebral artery territories in cases of occlusion of the internal carotid artery. Regions of interest were defined for the posterior cerebral artery territory and cerebellum in cases of occlusion of the VA. The percentage activity change during BTO was calculated. RESULTS: In two of the three patients in whom BTO of the internal carotid artery was performed, the percentage activity reduction of more than 30% was noted in the anterior cerebral and middle cerebral artery territories. These two patients underwent bypass grafting before carotid occlusion. In one of the two patients in whom BTO of the VA was performed, the percentage activity reduction of 16% was noted in the posterior cerebral artery territory. This patient underwent bypass grafting before occlusion of the VA. CONCLUSION: This noninvasive and quantitative method of cerebral blood flow measurement using Tc-99m ECD during BTO appears to have the potential to help select patients who may tolerate temporary or permanent arterial occlusion.     

P-32 bremsstrahlung SPECT helps assess intracavitary therapy.

A patient underwent intracavitary P-32 chromic phosphate therapy for a chest tumor. Tc-99m sulfur colloid instilled before the P-32 demonstrated uniform distribution of activity throughout the right pleural space, and the P-32 was immediately administered. Ten days later, SPECT imaging using bremsstrahlung radiation of the P-32 showed an unexpected loculation of the P-32. A subsequent chest CT scan demonstrated pleural infolding and fluid localization in the same area as the P-32, indicating that the bremsstrahlung SPECT study had, in fact, documented the final localization of the P-32, which was unexpected and different from the initial localization. The procedure used in this case may be of value in documenting the ultimate distribution of intracavitary P-32.     

Underestimation of regional myocardial perfusion with Tc-99m sestamibi single-day rest-stress SPECT: a "drug washout" pitfall?

Myocardial perfusion scintigraphy with a Tc-99m sestamibi single-day SPECT protocol is a widely used technique to examine patients with possible or known coronary artery disease. A 76-year-old man with a clinical history suggestive of ischemic heart disease underwent Tc-99m sestamibi myocardial SPECT imaging with a same-day rest and stress protocol after temporary discontinuation of his current therapy, which included calcium channel and beta blockers and nitrates. The scintigraphic pattern was consistent with an asymptomatic infarction of the posterolateral myocardial wall and periinfarct ischemia. One week later, the patient had a Tc-99m sestamibi myocardial SPECT study at rest without discontinuing therapy, and scintigraphic images showed normalization of the posterolateral wall perfusion defect. The angiographic study showed a 90% stenosis of the circumflex artery. This case suggests that, during a 1-day cardiac SPECT protocol, washout of therapeutic pharmaceuticals may be responsible for underestimation of myocardial rest perfusion in territory supplied by a coronary artery with a critical stenosis.     

Role of fast data acquisition method with Tc-99m HMPAO brain SPECT in patients with acute stroke

The first data acquisition method for Tc-99m hexamethylpropyleneamineoxime (Tc-99m HMPAO) brain SPECT was used in two patients with acute stroke 5 and 8 hours after the event. In one patient Tc-99m HMPAO fast SPECT showed perfusion defects before the same was manifested on CT. In the other patient, Tc-99m HMPAO fast SPECT showed larger defects than the edema seen on CT. The Tc-99m HMPAO fast SPECT might be feasible for the evaluation of acute stroke patients. Since the time required for fast SPECT is much shorter than usual SPECT, it appears to be more suitable for some patients with acute stroke who are brought to the hospital in a very critical condition.     

Anterior choroidal artery infarction presenting as a progressive cognitive deficit

PURPOSE: The authors describe a patient in whom neuroimaging using Tc-99m HMPAO SPECT, F-18 fluorodeoxyglucose (F-18 FDG) coincidence imaging, and magnetic resonance imaging (MRI) identified an anterior choroidal artery infarction. Neuroimaging played a critical role in confirming this diagnosis, because the patient had symptoms of progressive cognitive decline and satisfied the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for Alzheimer's disease (AD). METHODS: Tc-99m HMPAO brain SPECT was performed using a triple-head gamma camera. F-18 FDG scanning was obtained 40 minutes after intravenous injection of 5 mCi F-18 FDG using a coincidence camera. A brain MRI scan was performed using a 1.5-Tesla scanner. RESULTS: Tc-99m HMPAO SPECT showed focal hypoperfusion to the right parahippocampal cortex. F-18 FDG coincidence imaging showed a more extensive reduction in glucose metabolism compared with SPECT. The MRI scan confirmed the presence of a small segmental choroidal artery infarction. The Tc-99m HMPAO and F-18 FDG scans were not consistent with AD. CONCLUSIONS: This case illustrates the value of the regional cerebral blood flow SPECT for evaluating memory impairment in the elderly. Decreased regional cerebral blood flow to the posterior temporoparietal region is consistent with AD, whereas regional cerebral blood flow diminution in a vascular territory is consistent with vascular dementia. In this case, the patient was clinically diagnosed with AD, and SPECT was performed to establish the baseline regional cerebral blood flow before the cholinesterase inhibitor donepezil was administered. An infarction was diagnosed on the regional cerebral blood flow brain SPECT scan, which was later confirmed by MRI. Infarctions of the parahippocampal cortex may resuft in memory impairment, which can appear clinically similar to AD.