Technetium 99m-labeled Macroaggregated Albumin Research Articles

Establishing Updated Safety Standards for Independent 99mTc-MAA SPECT/CT Treatment Planning in Radioembolization

Significant improvements within radioembolization imaging and dosimetry permit the development of an accurate and personalized pretreatment plan using technetium 99m-labeled macroaggregated albumin (99mTc-MAA) and single-photon emission computed tomography (SPECT) combined with anatomical CT (SPECT/CT). Despite these potential advantages, the clinical transition to pretreatment protocols with SPECT/CT is hindered by their unknown safety constraints. This study aimed to address this issue by establishing novel dose limits for 99mTc-MAA SPECT/CT to enable quantitative pretreatment planning. Stratification criteria to determine images most viable for dosimetry analysis were created from a cohort of 85 patients. SPECT/CT, cone beam CT, and activity calculations derived from the local deposition method were used to create an accurate pretreatment protocol. Planar and SPECT/CT images were compared using linear regression and modified Bland-Altman analyses to convert accepted planar dose limits to SPECT/CT. To validate these new dose limits, activity calculations based on SPECT/CT were compared with those calculated with the body surface area and planar methods for three treatment plans. A total of 38 of 85 patients were deemed viable for dosimetry analysis. SPECT yielded greater lung shunt fractions (LSFs) than planar imaging when LSFs were <4.89%, whereas SPECT yielded lower LSFs than planar imaging when LSFs were >4.89%. Planar to SPECT/CT dose conversions were 0.76×, 0.70×, and 0.55× for the whole liver, normal liver, and lungs, respectively. Patients with SPECT LSFs ≤4.89% were safely treated with the direct application of planar lung dose limits. Activity calculations with the newly established SPECT/CT dose limits were greater than those of the body surface area method by a median range of 33.1% to 61.9% and were lower than planar-based activity calculations by a median range of 12.5% to 13.7% for the whole liver and by 29.4% to 32.2% for the normal liver. This study demonstrated a safe method for translating dose limits from 99mTc-MAA planar imaging to SPECT/CT. A robust pretreatment protocol was further developed guided by the current knowledge in the field. Established SPECT/CT dose limits safely treated 97.5% of patients and permitted the application of independent pretreatment planning with 99mTc-MAA SPECT/CT.

Systematic review of lung shunt fraction quantification comparing SPECT/CT and planar scintigraphy for yttrium 90 radioembolization planning

Yttrium 90-labeled intra-arterial liver therapy is an effective treatment for patients with unresectable primary or metastatic liver malignancy. Optimal radioisotope dose calculation is dependent upon lung shunt fraction (LSF) which is typically estimated by planar scintigraphy. The goal of this systematic review was to compare LSF using 2D planar scintigraphy and 3D SPECT/CT. A secondary outcome was to assess the impact on lung dosimetry. PubMed, SCOPUS and Web of Science database were searched for studies in English language related to lung shunt fraction quantification utilizing technetium 99m-labeled macroaggregated albumin (99mTc-MAA) planar scintigraphy and SPECT/CT, published between January 2010 and November 2020. The review was conducted using the PRISMA statement and QUADAS-2 criteria. A total of 8 studies (one prospective, 4 retrospective studies and 3 abstracts from national conferences) with a sample size of 552 were included in this review. There were 456 patients (82.6%) with hepatocellular carcinoma and 95 patients (17.4%) with hepatic metastasis. A wider range of LSF percentages was noted in planar scintigraphy methodology (range 1.2–33.3%) when compared to SPECT/CT (range 0.4–21.7%). The median LSF percentages were 6.7 and 2.9% using planar scintigraphy and SPECT/CT, respectively. The current clinical assessment of LSF is substantially overestimated by 2D planar scintigraphy when compared to 3D SPECT/CT. However, unclearness of blinding between the index test and reference standard was an area of quality concern. Hence, further randomized or prospective studies are needed to strengthen the role of SPECT/CT in lung shunt fraction estimation.

Prevalence and characteristics of hepatopulmonary syndrome in children with cirrhosis in southern Brazil.

Hepatopulmonary syndrome (HPS) is defined as a triad characterized by arterial deoxygenation, intrapulmonary vascular dilatations (IPVDs), and liver disorder. The aims of this study were to assess the prevalence of HPS in children with cirrhosis, the clinical characteristics of patients with HPS, and the tests used for the diagnosis of IPVD. This was a prospective, cross-sectional study of 40 children with cirrhosis (median age: 44 months). Investigations of HPS included arterial blood gas analysis, contrast-enhanced transthoracic echocardiography (CE-TTE), and perfusion lung scanning using technetium-99m-labeled macroaggregated albumin (Tc-MMA). Patients' clinical characteristics (age, etiology of cirrhosis, and severity of hepatopathy) were assessed. HPS was defined as liver disease; alveolar-arterial oxygen gradient of at least 15 mmHg and/or partial pressure of arterial oxygen less than 80 mmHg; and detection of IPVD by CE-TTE or Tc-MMA scanning. Statistical significance was indicated by a P value less than 0.05. The prevalence of HPS was 42.5% (17/40). Eight patients had moderate HPS (47%) and two patients had severe HPS (12%). In bivariate analysis, biliary atresia (P=0.033) and median age (10 months; P=0.005) were associated with HPS. In multivariate analysis, only age remained statistically significant (prevalence ratio=0.99; 95% confidence interval=0.98-0.99; P=0.010). Sixteen patients with HPS had IPVD detected by CE-TTE (94.1%) and six patients had IPVD detected by Tc-MMA scanning (35.3%), with no significant agreement between these methods (κ=-0.12; P=0.163). HPS is a common complication of cirrhosis in children. A combination of clinical and imaging criteria should be used to diagnose HPS.

Rhinoscintigraphic analysis of nasal mucociliary function in patients with Bell's palsy.

Mucociliary transport (MCT) is an important defense mechanism of the respiratory tract. One of the major factors determining MCT is the ciliary activity of the respiratory epithelium. Rhinoscintigraphy is the most commonly used method for the analysis of mucociliary activity. The aim of this study was to investigate the effect of facial paralysis on the nasal mucociliary clearance. This study included 38 Bell's palsy patients as the study group and 10 subjects without any history of paranasal sinus disease or facial paralysis as the control group. A drop of technetium 99m-labeled macroaggregated albumin (Tc-99m MAA) was placed posterior to the head of the inferior turbinate and followed with a gamma camera. MCT rate was measured as the velocity of Tc-99m MAA drop. The mean MCT rate was 4.27 ± 0.76 millimeters per minute (mm/min) on 20 sides of 10 healthy controls, 4.11 ± 2.91 mm/min on the affected sides of the patients with Bell's palsy, and 6.03 ± 3.13 mm/min on the nonparalyzed sides of the patients. MCT rate was statistically significantly faster in the nonparalyzed side when compared to the paralyzed side in Bell's palsy patients (P = 0.001). MCT rates were not significantly different in the control group and paralyzed sides of the Bell's palsy patients (P = 0.810). The MCT rate was statistically significantly faster in the nonparalyzed sides of Bell's palsy patients when compared to the controls (P = 0.017). This study showed a faster MCT rate on the nonparalyzed side in Bell's palsy patients when compared to the paralyzed side and the control subjects. A compensatory mechanism could be the underlying reason for faster MCT on the nonparalyzed side. Further studies on larger patient groups are needed to investigate the effect of facial paralysis on the MCT and changes of facial nerve function on the opposite, nonparalyzed side of the face.

Effect of Gravity on Drug Distribution after Port-catheter Implantation for Hepatic Arterial Infusion Chemotherapy: Evaluation of the Relationship between the Injection Posture and Intrahepatic Perfusion on Fused Images Acquired with a Combined SPECT/CT System 1

We evaluated the effect of gravity on intrahepatic perfusion (IHP) in patients with a port-catheter system (PCS) implanted for hepatic arterial infusion chemotherapy (HAIC). Using fused single photon-emission computed tomographic (SPECT)/computed tomographic (CT) images, we compared IHP after the injection of technetium-99m-labeled macroaggregated albumin (Tc-99m-MAA) via a PCS with the patient in the upright and decubitus positions. We enrolled 27 patients with metastatic carcinoma of the liver who bore an implantable PCS for HAIC. SPECT/CT images were obtained on the third and seventh postimplantation day; 99mTc-MAA (185 MBq) was delivered with the patient in the upright and decubitus positions. We selected four regions of interest (ROIs) on SPECT images of the superior, inferior, anterior, and posterior regions. The anteroposterior and the superoinferior perfusion ratio (AP ratio, SI ratio) were derived from the mean counts in each ROI. Using an unpaired t-test, we compared these ratios after drug delivery in the upright and decubitus injection positions. We also visually compared IHP and classified the distribution of drugs delivered in the upright and decubitus positions on fused images. Moreover, using World Health Organization criteria, we evaluated the therapeutic response by comparing the tumor size on contrast-enhanced CT images obtained before and 3 months after treatment. The SI ratios in the upright and decubitus injection positions were 1.14 and 0.92, respectively; the corresponding AP ratios were 1.47 and 1.73, respectively, indicating that there was no significant difference in these parameters irrespective of the injection position (SI ratio: P = .27, AP ratio: P = .35). However, in 14 of the 27 patients (52%), the visual appearance of IHP was different in the upright and decubitus positions. A change in the location of the catheter side hole when the decubitus was changed to the upright position produced a difference in IHP. Of 13 patients with identical drug distribution in both injection positions, six (46%) manifested a partial response (PR), five (38%) experienced no change (NC), and two (15%) experienced progressive disease (PD). Among the 14 patients with different drug distribution in the two injection positions, four (28%) achieved PR, five (36%) manifested NC, and the other five (36%) had PD. Although the patient posture affected IHP by changing the position of the infusion catheter side hole in the liver, gravity had no significant effect on IHP in patients bearing an implantable PCS for the delivery of HAIC.

Multiple pathogenic factor-induced complications of cirrhosis in rats: A new model of hepatopulmonary syndrome with intestinal endotoxemia

To develop and characterize a practical model of Hepatopulmonary syndrome (HPS) in rats. The experimental animals were randomized into five feeding groups: (1) control (fed standard diet), (2) control plus intraperitoneal injection with lipopolysaccharide (LPS), (3) cirrhosis (fed a diet of maize flour, lard, cholesterol, and alcohol plus subcutaneously injection with carbon tetrachloride (CCl(4)) oil solution), (4) cirrhosis plus LPS, and (5) cirrhosis plus glycine and LPS. The blood, liver and lung tissues of rats were sampled for analysis and characterization. Technetium 99m-labeled macroaggregated albumin (Tc99m-MAA) was used to test the dilatation of pulmonary microvasculature. Typical cirrhosis and subsequent hepato-pulmonary syndrome was observed in the cirrhosis groups after an 8 wk feeding period. In rats with cirrhosis, there were a decreased PaO(2) and PaCO(2) in arterial blood, markedly decreased arterial O(2) content, a significantly increased alveolar to arterial oxygen gradient, an increased number of bacterial translocated within mesenteric lymph node, a significant higher level of LPS and tumor necrosis factor-alpha (TNF-alpha) in plasma, and a significant greater ratio of Tc99m-MAA brain-over-lung radioactivity. After LPS administration in rats with cirrhosis, various pathological parameters got worse and pulmonary edema formed. The predisposition of glycine antagonized the effects of LPS and significantly alleviated various pathological alterations. The results suggest that: (1) a characteristic rat model of HPS can be non-invasively induced by multiple pathogenic factors including high fat diet, alcohol, cholesterol and CCl(4); (2) this model can be used for study of hepatopulmonary syndrome and is clinically relevant; and (3) intestinal endotoxemia (IETM) and its accompanying cytokines, such as TNF-alpha, exert a crucial role in the pathogenesis of HPS in this model.

Evaluation of nasal mucociliary clearance function in allergic rhinitis patients with technetium 99m-labeled macroaggregated albumin rhinoscintigraphy.

Nasal mucociliary clearance is the first line of defense of the ciliated epithelium of the respiratory tract against inhaled particles. Several rhinopathic conditions involve alterations in nasal mucociliary clearance. The purpose of this study was to assess the clinical role of rhinoscintigraphy in evaluation of nasal mucociliary clearance function in allergic rhinitis patients and in sinusitis patients and healthy controls for comparison. A technetium 99m-labeled macroaggregated albumin (Tc-99m MAA) drop was deposited on the floor of the nasal meatus about 1 cm behind the mucocutaneous junction, and its course was followed with a gamma camera. The nasal mucociliary clearance function was measured as the velocity of the nasal mucociliary transport of the Tc-99m MAA droplet. The mean velocity of nasal mucociliary transport in the allergic rhinitis patients was 2.71 +/- 0.76 mm/min (2.65 +/- 0.76 mm/min in the right nostril; 2.77 +/- 0.76 mm/min in the left nostril). The mean velocity of nasal mucociliary transport in the sinusitis patients was 1.80 +/- 0.64 mm/min (1.79 +/- 0.65 mm/min in the right nostril; 1.82 +/- 0.63 mm/min in the left nostril). The mean velocity of nasal mucociliary transport in the 25 healthy controls was 4.28 +/- 1.38 mm/min (4.30 +/- 1.35 mm/min in the right nostril; 4.27 +/- 1.42 mm/min in the left nostril). A significant difference in nasal mucociliary clearance was observed among the 3 groups. We suggest that Tc-99m MAA rhinoscintigraphy may be a useful noninvasive tool to evaluate the nasal mucociliary clearance function in allergic rhinitis patients.

Extrahepatic regional chemotherapy: use of technetium-99m labeled macroaggregated albumin.

The purpose of this study was to verify the applicability of nuclear techniques with technetium-99m labeled macroaggregated albumin (Tc-99m-MAA) in extrahepatic regional chemotherapy. Of 98 patients in whom arterial Port-a-caths were implanted by transcutaneous access, 13 were treated by regional extrahepatic chemotherapy (breast, one; pancreas, four; kidney, one; uterus, three; vagina, two; bladder, two). In all 13 patients, Tc-99m-MAA was slowly infused intraarterially. The examination showed the perfusion of the area with the neoplasm and excluded the presence of important misperfusions of Tc-99m-MAA to the nearest areas. To detect the presence of an arteriovenous shunt with systemic misperfusion, an anterior image of the thorax was obtained in all patients and an index of misperfusion was calculated. In 12 patients, the index was < 5%; in one patient it was about 40%. In conclusion, our preliminary experience concerns the monitoring of intraarterial infusion chemotherapy of extrahepatic districts. In all 13 patients, we evaluated the correct positioning of the intraarterial catheter and the distribution pattern of the arterial flow, with a semiquantitative indication of arteriovenous shunting. This method gave us an instrument of study that was inexpensive, harmless, and free of collateral complications.

Determination of tumour vascularity using selective hepatic angiography as compared with intrahepatic-arterial technetium-99m macroaggregated albumin scan in hepatocellular carcinoma

A total of 51 patients with hepatocellular carcinoma (HCC) were studied to determine the tumour vascularity as determined by selective hepatic angiography (HAG) and by intrahepatic-arterial technetium-99m-labeled macroaggregated albumin (Tc99m-MAA) scan. The tumour vascularity was graded on the HAG films by an interventional radiologist using a scale ranging from 1 (hypovascular) to 4 (extremely hypervascular). The grades of vascularity on HAG were grade 1 in 5 patients, grade 2 in 13 patients, grade 3 in 24 patients and grade 4 in 9 patients. The tumour vascularity on scintigraphy was determined by quantifying the count rates over the tumour and normal liver areas by an analog/digital gamma-camera, and the resultant tumour-to-normal ratio (T/N ratio) gave a quantitative measure of the vascularity. The range of the T/N ratio was 0.9 to 11.1, with a median of 3.7. There was no correlation between the tumour vascularity grading on HAG and the T/N ratio on the Tc99m-MAA scan (Wilcoxon rank test, P = 0.83). Thus, we conclude that HAG cannot reveal the true vascularity nor reflect the T/N ratio in HCC.