Tc-99m MAA Research Articles

Effects of chronic sleep deprivation on upper respiratory tract mucosal histology and mucociliary clearance on rats.

In this study, we aimed to investigate the effects of chronic sleep deprivation on mucociliary clearance, which is the primary defence mechanism of the upper airway tract and nasal mucosal histology. Forty-two Wistar Albino rats (250-300g), 8 or 12 weeks old, were randomly assigned into three groups as follows. The first sleep-deprivation group consisted of 14 rats (A), another 14 of them were assigned to platform group (B), and the remaining 14 were included to the home cage control group (C). For the two deprivation groups (A and B), the modified multiple platform method (MMPM) was used to induce sleep deprivation for 21days. Tc-99m MAA rhinoscintigraphy was performed to assess mucociliary clearance and the nasal histopathological changes of the sacrificed rats were also examined. Mucociliary clearance was significantly higher in sleep deprivation (A) and deprivation control (B) groups than the control group (C) (p=.037). The ratio of columnar ciliary was significantly higher in group A and B than in the control group (p=.003). The transitional epithelial ratio in groups A and B was also significantly increased compared with group C (p=.04). The control group's squamous epithelial ratio was increased compared to the sleep-deprived groups (p=.003). There was a significantly increased inflammatory response in the ciliated columnar epithelium in groups A and B compared to group C (p=.02). For the first time in the literature, we demonstrated that chronic sleep deprivation has caused a significant increase in mucociliary clearance speed and in the number of ciliary cells.

Abstract No. 562 Temporary reversal of hepatoenteric collaterals during Y90 planning and treatment

A serious complication of Y90 radioembolotherapy (Y90 RE) is nontarget embolization. Current conventional methods to prevent this include coil embolization of hepatoenteric arteries. Temporary redirection of blood towards the liver within these arteries using a balloon catheter in the common hepatic artery provides a safe alternative with prevention of nontarget deposition of Y90 microspheres. Between September 2010 to September 2015, 88 patients with diagnostic or treatment angiograms with attempted use of the balloon occlusion technique were catalogued. A balloon catheter was inflated in the common hepatic artery to temporarily redirect flow from hepatoenteric arteries toward the liver during both diagnostic Tc99m MAA (67 patients) and therapeutic Y90 RE (72 patients) delivery. SPECT/CT nuclear scintigraphy was performed after delivery of each radionuclide. Clinical and laboratory follow-up at 1, 3 and 6 months and imaging follow-up at 3 and 6 months were performed. 72 Y90 RE treatment sessions were performed with use of the balloon technique with either glass (21) or resin (51) microspheres. Tumor types included hepatocellular (26), neuroendocrine (26), colorectal (23), or other (13). Post Y90 RE scintigraphy confirmed no significant extrahepatic activity in any patient. Whole liver, right lobe, left lobe Y90 RE treatments were performed in 58, 15 and 5 sessions respectively. One grade 2 gastrointestinal ulcer was present at 90 day follow-up. Greater than 80% administration of the prescribed dose of was possible in 34/51 resin microsphere sessions and in 20/21 sessions of glass microspheres. Temporary occlusion of the common hepatic artery with a balloon-catheter is a reliable and reproducible alternative to conventional coil embolization of hepatoenteric arteries during both diagnostic Tc99m MAA and therapeutic Y90 RE delivery.

Analysis of differences between 99mTc-MAA SPECT- and 90Y-microsphere PET-based dosimetry for hepatocellular carcinoma selective internal radiation therapy

BackgroundThe aim of this study was to compare predictive and post-treatment dosimetry and analyze the differences, investigating factors related to activity preparation and delivery, imaging modality used, and interventional radiology.MethodsTwenty-three HCC patients treated by selective internal radiation therapy with 90Y glass microspheres were included in this study. Predictive and post-treatment dosimetry were calculated at the voxel level based on 99mTc-MAA SPECT/CT and 90Y-microsphere PET/CT respectively. Dose distribution was analyzed through mean dose, metrics extracted from dose-volume histograms, and Dice similarity coefficients applied on isodoses. Reproducibility of the radiological gesture and its influence on dose deviation was evaluated.Results90Y delivered activity was lower than expected in 67% (16/24) of the cases mainly due to the residual activity. A mean deviation of − 6 ± 11% was observed between the delivered activity and the 90Y PET’s FOV activity. In addition, a substantial difference of − 20 ± 8% was measured on 90Y PET images between the activity in the liver and in the whole FOV. After normalization, 99mTc-MAA SPECT dosimetry was highly correlated and concordant with 90Y-microsphere PET dosimetry for all dose metrics evaluated (ρ = 0.87, ρc = 0.86, P = 3.10−8 and ρ = 0.91, ρc = 0.90, P = 7.10−10 for tumor and normal liver mean dose respectively for example). Besides, mean tumor dose deviation was lower when the catheter position was identical than when it differed (16 Gy vs. 37 Gy, P = 0.007). Concordance between predictive and post-treatment dosimetry, evaluated with Dice similarity coefficients applied on isodoses, significantly correlated with the distance of the catheter position from artery bifurcation (P = 0.04, 0.0004, and 0.05, for 50 Gy, 100 Gy, and 150 Gy isodoses respectively).ConclusionsDiscrepancies between planned activity and activity measured on 90Y PET images were observed and seemed to be mainly related to clinical hazards and equipment issues. Predictive vs. post-treatment comparison of relative dose distributions between tumor and normal liver showed a good correlation and no significant difference highlighting the predictive value of 99mTc MAA SPECT/CT-based dosimetry. Besides, the reproducibility of catheter tip position appears critical in the agreement between predictive and actual dose distribution.

Radiolocalization of atypical lesions for intraoperative identification: technical factors, localization quality, success rates, patient safety, and spectrum of applications

BackgroundTo retrospectively analyze perilesional technetium Tc-99m MAA injection for intraoperative localization of atypical soft-tissue and bone lesions within a single tertiary referral center in order to determine technique, safety, and clinical utility of these procedures.MethodsAn IRB compliant, retrospective electronic chart review (2010–2017) exploring surgical excision of atypical (non-pulmonary, non-breast, non-sentinel node) lesions guided by Tc-99m MAA perilesional injection. Patient demographics, lesion location, lesion size, radiotracer injection technique, radiotracer injection complications, scintigraphy technique, scintigraphic quality, intraoperative time, lesion identification in surgery, and pathological diagnoses were recorded.ResultsTwenty-two atypical radiolocalization exams were identified. Lesion sites included rib (7), lymph node (4), abdominal wall (3), mesenteric (3), gallbladder fossa (1), retroperitoneum (1), parietal pleura (1), anterior mediastinum (1), and iliac bone (1). Average lesion size was 14 mm (range 5–23 mm). Eighteen (82%) radiotracer injections used computed tomography guidance and 4 (18%) used ultrasound guidance. The mean activity of Tc-99m MAA administered was 11.8 MBq (0.32 mCi). A 22-gauge needle was most often used for perilesional injection. No injection complications were reported. The lesions were identified with a hand-held gamma probe during surgery in 100% of cases. Of the samples sent to pathology, 100% were identified and given a diagnosis.ConclusionRadiolocalization of atypical lesions may be a valuable technique, guiding minimally invasive surgical removal of lesions that would otherwise be difficult to identify intraoperatively such as non-palpable rib, central mesenteric nodal, and abdominal wall lesions.

04:21 PM Abstract No. 121 Quantitative and qualitative 99mTc MAA SPECT/CT imaging predicts response to therapy for patients treated with Yttrium-90 (90Y) radioembolization

Selective 90Y radioembolization therapy for hepatic malignancies involves planning angiography and 99mTc macroaggregated albumin scintigraphy (99mTc -MAA) to assess lung shunt fraction and extrahepatic perfusion. The purpose of this study is to assess the relationship between tumor MAA uptake by SPECT/CT and response following radioembolization. 22 patients with primary hepatic malignancies (non-colorectal) or hepatic colorectal metastases underwent 99mTc -MAA hepatic artery perfusion with SPECT/CT. Qualitative evaluation and quantitative evaluation with tumor to disease free liver parenchyma background ratios (TBR) of SPECT were correlated with CT response. Post-radioembolization Bremsstrahlung SPECT imaging was also performed to assess for similar correlations. The mean MAA tumor TBR in the patients that did not progress was 11.0 ±13.8 (n=14), significantly higher than the TBR of patients that progressed (2.7±1.3 (n=8) (P<0.05). The pattern of 99mTc -MAA distribution was predictive of therapy response. In all cases, intense homogeneous uptake was seen in patients who responded; absent uptake was seen in those who progressed. Uptake on post-radioembolization Bremsstrahlung SPECT did not correlate with response. Our findings suggest that the pattern of uptake on planning 99mTc -MAA imaging can predict response to subsequent radioembolization. Bremsstrahlung SPECT imaging, which is not typically performed, did not correlate with response. Evaluation of 99mTc -MAA uptake on routine pre-therapy studies could potentially serve as a critical decision node in the pre-treatment assessment of patients for radioembolization. Such analysis would extend the utility of this routine study beyond a simple assessment for extrahepatic perfusion, thereby leveraging information inherent to the scan.

03:00 PM Abstract No. 112 Y90 radioembolization: do dosimetry and distribution of Tc99m MAA on planning SPECT/CT correlate with that of Y90 on post-treatment PET/CT?

03:00 PM Abstract No. 112 Y90 radioembolization: do dosimetry and distribution of Tc99m MAA on planning SPECT/CT correlate with that of Y90 on post-treatment PET/CT?

Technical Aspects and Practical Approach Toward Same-Day Y90 Radioembolization in the Management of Hepatocellular Carcinoma

Radioembolization with Yttrium-90 (Y90) has been proven safe and effective for the treatment of primary and secondary hepatic malignancies. Standard protocols have necessitated planning angiography with Technetium-99m macroaggregated albumin (Tc99m MAA) administration/scan typically 1-2 weeks prior to the radioembolization therapy. The intent of this practice is to ensure appropriate patient selection and treatment candidacy while also confirming best dosimetry approaches. At our center, we started performing "same-day Y90" in 2008; in a subset of international patients with travel hardship, we performed the planning and treatment procedures consecutively on the same day. In this article, we reveal our practical approach to treating patients on the same day as planning angiography. With more than 160 same-day procedures completed between 2008 and 2017, the safety and efficacy of such a paradigm has been established at our center. This approach is appealing to patients, their families, and referring physicians. Appropriate patient selection and proper preprocedure planning based on baseline imaging are key elements in successful same-day radioembolization treatments.

HEPATOPULMONARY SYNDROME RESOLUTION WITH OCTREOTIDE AND MIDODRINE

SESSION TITLE: Medical Student/Resident Pulmonary Manifestations of Systemic Disease 2 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: Hepatopulmonary Syndrome (HPS) is a pulmonary complication of cirrhosis where patients develop hypoxia as a result of intrapulmonary vascular dilation. We present the case of a patient who underwent liver transplantation and after 2 months of failure to improve, he was started on Octreotide and Midodrine with improvement in oxygenation. CASE PRESENTATION: A 58 year old man with a past medical history of NASH cirrhosis complicated by HPS requiring 10 liters of oxygen with exertion was admitted for a liver transplantation. He underwent an uneventful liver transplant and was extubated on post op day two. His post op course was complicated by increasing high flow oxygen rates despite treatment of alternative causes of hypoxia. Acute liver rejection was ruled out with liver biopsy. After two months, all alternative causes of hypoxia had been treated and he continued to require high flow oxygen, up to 100% FiO2 at rest. Inpatient pulmonology was consulted and recommended obtaining a CT chest which was negative for pulmonary AVMs. He was initially started on Octreotide monotherapy without any apparent response after four days. Pentoxifyine was then added without response. He continued to require high flow nasal cannula and so the decision was made to stop Pentoxifyine and add Midodrine. After being on dual therapy with Midodrine and Octreotide for four days he began to experience significant improvement in his oxygen requirements and he was able to be weaned down to 5 liters on nasal cannula. He was ultimately discharged on 3 liters nasal cannula. DISCUSSION: HPS is characterized by abnormal oxygenation caused by intrapulmonary vascular dilation. The exact cause of HPS is unknown; one proposed mechanism is failure of the damaged liver to clear circulating vasodilators and another is excessive production of circulating vasodilators by the damaged liver. These processes are thought to induce pulmonary capillary vasodilation which induces hypoxemia usually via ventilation-perfusion mismatch, leading patients to develop dyspnea, platypnea and orthodeoxia. The diagnosis is made by detection of intrapulmonary right to left shunting on echocardiography. Liver transplantation is the only definitive treatment for HPS and it is not always effective. Refractory HPS treatment options are limited to maximizing oxygen supplementation and cautious trials of less well validated therapies. Agents such as Pentoxifylline, Octreotide and Midodrine have been theorized to improve HPS with improvement in gas exchange, however none have been reported to consistently result in improvement in oxygenation. CONCLUSIONS: Liver transplantation has been shown to be the only effective treatment however for HPS and it is not always effective at fully reversing the condition. Agents such as Midodrine and octreotide may be useful in helping improve oxygenation in patients who do not respond to transplantation. Reference #1: Clinical Liver Disease. 2014 May;18(2):407-20. Pub 2014 Feb 25. Reference #2: Chest. 2000; 118(3): 116. Hepatopulmonary syndrome: a prospective study of relationships between severity of liver disease, PaO(2) response to 100% oxygen, and brain uptake after (99m)Tc MAA lung scanning. Kroma et al. Reference #3: Pilot study of pentoxifylline in hepatopulmonary syndrome. Tanikella R, Philips GM et al. Liver Transpl. 2008;14(8):1199. DISCLOSURES: No relevant relationships by Mollie Brittan, source=Web Response No relevant relationships by Tammy Wichman, source=Web Response

Is hybrid SPECT/CT necessary for pre-interventional 3D quantification of relative lobar lung function?

BackgroundIn pulmonary malignancies pre-interventional 3D estimation of relative lobar perfusion is established to predict post-interventional functional outcome particularly in patients with borderline lung function. Aim was to test whether quantification from SPECT-scanners (non-hybrid) is as accurate as from SPECT/CT-scanners (hybrid) when using dedicated software.MethodsSixty-one patients suffering from pulmonary tumours underwent lung SPECT/CT using Tc-99m MAA to predict postoperative residual lung function prior to surgical treatment. Quantification was done using “HERMES Hybrid 3D–Lung Lobe Quantification”. In the hybrid approach SPECT and combined lowdoseCT/diagnosticCT were used. In the non-hybrid approach SPECT and diagnosticCTs were used, lowdoseCTs were omitted. Bland Altman analysis was done to test for agreement.ResultsThree hundred five lobes were quantified. Evaluation time was 6:37 ± 0.55 min (hybrid) versus 6:34 ± 0.51 min (non-hybrid). Mean lobar value was 20.0 ± 10.5% (range from 0 to 55%) for hybrid and 20.0 ± 10.6% (range from 0 to 58%) for the non-hybrid approach, mean absolute difference was 1.31%, no significant differences were found when analysing all values (p > 0.9). Correlation was excellent (R = 0.984, slope of the regression line 1.001 (p < 0.0001)). Intraclass correlation coefficient was 0.9843. Bland Altman limits were -3.67% and 3.67%.ConclusionExcellent concordance was found for 3D-quantification of relative lung perfusion when comparing a hybrid vs. non-hybrid approach. Using sophisticated software combining the generally available diagnosticCT and conventional SPECT-data reliable results for lobar perfusion can be obtained without the need for costly investment of SPECT/CT systems for this clinical question.

Impact of missing attenuation and scatter corrections on 99m Tc-MAA SPECT 3D dosimetry for liver radioembolization using the patient relative calibration methodology: A retrospective investigation on clinical images.

To investigate the clinical implication of performing pre-treatment dosimetry for 90 Y-microspheres liver radioembolization on 99m Tc-MAA SPECT images reconstructed without attenuation or scatter correction and quantified with the patient relative calibration methodology. Twenty-five patients treated with SIR-Spheres® at Istituto Europeo di Oncologia and 31 patients treated with TheraSphere® at Istituto Nazionale Tumori were considered. For each acquired 99m Tc-MAA SPECT, four reconstructions were performed: with attenuation and scatter correction (AC_SC), only attenuation (AC_NoSC), only scatter (NoAC_SC) and without corrections (NoAC_NoSC). Absorbed dose maps were calculated from the activity maps, quantified applying the patient relative calibration to the SPECT images. Whole Liver (WL) and Tumor (T) regions were drawn on CT images. Injected Liver (IL) region was defined including the voxels receiving absorbed dose >3.8 Gy/GBq. Whole Healthy Liver (WHL) and Healthy Injected Liver (HIL) regions were obtained as WHL = WL - T and HIL = IL - T. Average absorbed dose to WHL and HIL were calculated, and the injection activity was derived following each Institute's procedure. The values obtained from AC_NoSC, NoAC_SC and NoAC_NoSC images were compared to the reference value suggested by AC_SC images using Bland-Altman analysis and Wilcoxon paired test (5% significance threshold). Absorbed-dose maps were compared to the reference map (AC_SC) in global terms using the Voxel Normalized Mean Square Error (%VNMSE), and at voxel level by calculating for each voxel the normalized difference with the reference value. The uncertainty affecting absorbed dose at voxel level was accounted for in the comparison; to this purpose, the voxel counts fluctuation due to Poisson and reconstruction noise was estimated from SPECT images of a water phantom acquired and reconstructed as patient images. NoAC_SC images lead to activity prescriptions not significantly different from the reference AC_SC images; the individual differences (<0.1 GBq for all IEO patients, <0.6 GBq for all but one INT patients) were comparable to the uncertainty affecting activity measurement. AC_NoSC and NoAC_NoSC images, instead, yielded significantly different activity prescriptions and wider 95% confidence intervals in the Bland-Altman analysis. Concerning the absorbed dose map, AC_NoSC images had the smallest %VNMSE value and the highest fraction of voxels differing less than 2 standard deviations from AC_SC. The patient relative calibration methodology can compensate for the missing attenuation correction when performing healthy liver pre-treatment dosimetry: safe treatments can be planned even on NoAC_SC images, suggesting activities comparable to AC_SC images. Scatter correction is recommended due to its heavy impact on healthy liver dosimetry.

90Y radioembolization dosimetry using a simple semi-quantitative method in intrahepatic cholangiocarcinoma: Glass versus resin microspheres

IntroductionThere are two different types of 90Y Microspheres, glass and resin, in the market for 90Y radioembolization (90Y-RE). This study aimed to investigate the dose of radiation delivered through glass vs. resin-based 90Y-RE to intrahepatic cholangiocarcinoma (ICC). MethodsIn this retrospective study, 10 patients with ICC underwent 90Y-RE, five underwent glass (Glass group) and other 5 resin (Resin group) microspheres. Technetium-99m macro-aggregated albumin (Tc-99m MAA) shunt study was performed two weeks before 90Y-RE. Within 2 h from 90Y-RE, Bremsstrahlung SPECT/CT was obtained. Regions of interest (ROIs) were segmented around the targeted tumor and the liver. Tumor and liver volumes, corresponding radioactive counts, and tumor to liver count ratio were calculated using MIM software and compared between Glass and Resin groups. ResultsMean hepatopulmonary shunt fraction was 7.1 vs. 6.2% for the Glass and Resin groups (p = 0.83), with no extrahepatic activity. There was no difference in the activity and tumor uptake of administered Tc-99m MAA between both groups (p = 0.71 and p = 0.63). Mean administered activity of 90Y in the Glass group was higher than the Resin group (73.2 ± 24.3 vs. 44.5 ± 18.2 mCi, p < 0.001). The tumor 90Y uptake was significantly higher in the Glass group compared to the Resin group (41.3% vs. 33.5%, p < 0.001), corresponding to the mean tumor dose of 205.7 ± 19.7 vs. 128.9 ± 10.6 Gy, respectively (p < 0.001). The tumor to normal liver parenchyma 90Y dose ratio was significantly higher in the Glass group compared to the Resin group, 4.9 ± 0.7 versus 2.4 ± 0.3 respectably (p < 0.001). ConclusionsBoth 90Y glass and resin-based microsphere 90Y-RE are feasible and safe in patients with ICC, while 90Y glass microsphere delivers higher dose of 90Y to the targeted tumors. Advances in knowledgeWhile both 90Y glass and resin-based microsphere yttrium-90 radioembolization are feasible and safe treatment options for in patients with intrahepatic cholangiocarcinoma, 90Y glass microsphere delivers higher dose of 90Y to the targeted tumors. Implications for patient careBoth of 90Y glass and resin-based microsphere can be safely and feasibly used for treatment of intrahepatic cholangiocarcinoma, difference in dose of 90Y delivered to the targeted tumors should be clinically considered while choosing the microsphere type.

Two years of experience of Y90 microspheres SIRT therapies – A truly multidisciplinary endeavour

Selective Internal Radiation Therapy (SIRT) is a targeted treatment for liver tumours that delivers millions of tiny Y90 radioactive beads know as microspheres directly to the liver tumours through the hepatic artery. Y90 is a beta emitter with a half-life of 64 h, maximum energy of 2.27 MeV and produces Bremsstrahlung radiation when interacts with matter. It is a therapy which requires the patient to undergo two angiograms, one for planning and one for the implanting the microspheres, one injection of Tc99m MAA to help plan the therapy and estimate how many of the microspheres could travel to the lungs during the therapy phase, two/three doses of Y90 microspheres delivered to the liver tumours through a catheter, two visits to the nuclear medicine department for imaging, the dispensing of the Y90 microspheres, overnight stay in hospital for the patient and a lot of coordination by a multidisciplinary team of nurses, bed managers, radiographers, medical physicist and consultant radiologists. This presentation will give an overview of our two years of experience of Y90 SIRT therapy which includes the treatment of over 24 patients. The presentation will include details on the risk assessments carried out in advance, the training of staff required, the staff and patient radiation doses, the precautions taken in the interventional laboratory to prevent the contamination of the lab with radioactivity during both angiograms and some of the issues we have discovered with delivering a radionuclide therapy outside of the nuclear medicine department.

Is a Technetium-99m Macroaggregated Albumin Scan Essential in the Workup for Selective Internal Radiation Therapy with Yttrium-90? An Analysis of 532 Patients

PurposeTo determine if baseline patient, tumor, and pretreatment evaluation characteristics could help identify patients who require technetium-99m (99mTc) macroaggregated albumin (99mTc MAA) imaging before selective internal radiation therapy (SIRT). Materials and MethodsIn this retrospective analysis, 532 consecutive patients with primary (n = 248) or metastatic (n = 284) liver tumors were evaluated between 2006 and 2015. Variables were compared between patients in whom 99mTc MAA imaging results contraindicated/modified SIRT administration with yttrium-90 (90Y) resin microspheres and those who were treated as initially planned. The 99mTc MAA findings that contraindicated/modified SIRT were a lung shunt fraction (LSF) > 20%, gastrointestinal 99mTc MAA uptake, or a mismatch between 99mTc MAA uptake and intrahepatic tumor distribution. ResultsLSF > 20% and gastrointestinal MAA uptake were observed in 7.5% and 3.9% of patients, respectively, and 11% presented a mismatch. Presence of a single lesion (odds ratio [OR] = 2.4) and vascular invasion (OR = 5.5) predicted LSF > 20%, and GI MAA uptake was predicted by the presence of liver metastases (OR = 3.7) and 99mTc MAA injection through the common/proper hepatic artery (OR = 4.7). Vascular invasion (OR = 4.1) was the only predictor of LSF > 20% and/or GI MAA uptake (sensitivity = 49.2%, specificity = 80.3%, negative predictive value = 92.4%). Previous antiangiogenic treatment (OR = 2.4) and presence of a single lesion (OR = 2.6) predicted mismatch. ConclusionsImaging with 99mTc MAA is essential in SIRT workup because baseline characteristics may not adequately predict 99mTc MAA results. Nevertheless, the absence of vascular invasion potentially identifies a group of patients at low risk of SIRT contraindication/modification in whom performing SIRT in a single session (ie, pretreatment evaluation and SIRT on the same day) should be explored.

Tumor Dose Response in Yttrium-90 Resin Microsphere Embolization for Neuroendocrine Liver Metastases: A Tumor-Specific Analysis with Dose Estimation Using SPECT-CT

PurposeTo evaluate dose-response relationship in yttrium-90 (90Y) resin microsphere radioembolization for neuroendocrine tumor (NET) liver metastases using a tumor-specific dose estimation based on technetium-99m–labeled macroaggregated albumin (99mTc MAA) single photon emission computed tomography (SPECT)-CT. Materials and MethodsFifty-five tumors (mean size 3.9 cm) in 15 patients (10 women; mean age 57 y) were evaluated. Tumor-specific absorbed dose was estimated using a partition model. Initial (median 2.3 months) follow-up data were available for all tumors; last (median 7.6 months) follow-up data were available for 45 tumors. Tumor response was evaluated using Modified Response Evaluation Criteria in Solid Tumors (mRECIST) on follow-up CT. Tumors with complete or partial response were considered responders. Mean tumor absorbed dose was 231.4 Gy ± 184.3, and mean nontumor liver absorbed dose was 39.0 Gy ± 18.0. ResultsThirty-six (65.5%) and 30 (66.7%) tumors showed response at initial and last follow-up, respectively. Mean absorbed doses in responders and nonresponders at initial and last follow-up were 285.8 Gy ± 191.1 and 128.1 Gy ± 117.1 (P = .0004) and 314.3 Gy ± 195.8 and 115.7 Gy ± 117.4 (P = .0001). Cutoff value of ≥ 191.3 Gy for tumor-specific absorbed dose predicted tumor response with 93% specificity, whereas < 72.8 Gy predicted nonresponse with 100% specificity at last follow-up. Estimated mean absorbed tumor dose per patient was significantly higher in responders versus nonresponders over the follow-up period (224.5 Gy ± 90.3 vs 70.0 Gy ± 28.0; P = .007). ConclusionsTumor-specific absorbed dose, estimated with a partition model, was significantly associated with tumor response in NET liver metastases. An estimated dose ≥ 191.3 Gy predicted treatment response with high sensitivity and specificity.

Asymptomatic calf vein DVT in high risk surgical patients: a single centre study

Asymptomatic deep vein thrombosis (DVT) of calf veins is a known entity in high risk surgical patients, which can lead to fatal pulmonary embolism. The actual incidence of asymptomatic calf vein DVT in high risk surgical patients is not known in Indian population. We had conducted this study with an aim to determine the incidence of asymptomatic calf vein DVT in spite of providing extended prophylaxis against DVT in high risk patients. Our study was a prospective observational study conducted from Oct 2014 to Mar 2016 in a tertiary care teaching Hospital in Bangalore, in Department of surgery with help of Department of Nuclear medicine and Radio diagnosis. We examined more than 100 patients who were due for some surgical procedure and included 100 patients fell in high risk group with a risk stratification score of ≥ 5. All patients screened for asymptomatic DVT with Duplex ultrasonography scan and 99mTc MAA venography. The patients who were detected to have asymptomatic calf vein DVT were therapeutically managed as cases of DVT. In the study 3 patients detected to have asymptomatic calf vein DVT making the incidence of 3.06%. In our study group we found duration of surgery of more than 60 mins being the most common risk factor followed by malignancy. Our incidence of asymptomatic calf vein DVT was 3.06% in high risk surgical patients. Duplex ultrasonography is a useful, easily available, non invasive and safe diagnostic modality in detecting asymptomatic calf vein DVT.

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

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. Fifty-five lung cancer patients (male:female, 37:18; age, 67.8 ± 10.7years) were evaluated. The patients underwent planar scan and SPECT/CT after injection of technetium-99m macroaggregated albumin (Tc-99m-MAA). The % uptake and predicted postoperative percentage forced expiratory volume in 1s (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. 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. 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.

68 Ga-Ca-phytate particles: A potential lung perfusion agent of synthetic origin prepared in a cold kit format.

The objective of this study was to investigate the radiosynthesis of 68 Ga-Ca-phytate particles and then characterize the formulation for radiochemical purity, radioactive particle size distribution, and biodistribution in normal rats. This radiotracer was prepared using a commercial phytate cold kit after reconstitution with saline, 68 Ga-chloride generator eluent, calcium chloride, and air, then heating at 100°C for 30minutes to achieve 99% radiochemical purity of 68 Ga-particles that were 21% 3-5μm, 8% 5-15μm, and 71% >15μm in diameter. This optimal formulation was stable for 2hours at room temperature. Intravenous administration of 68 Ga-particles in rats resulted in an uptake of 93% in the lungs, 4% in the liver plus spleen, and 3% in the carcass after 20minutes. Two-thirds of the carcass activity was radioactive blood, likely to be 68 Ga-transferrin. The positron emission tomography image was superior than the 99m Tc-MAA image because it displayed high lung uptake against a low background. Low uptake by the liver, spleen did not interfere with the diagnostic quality, and faint activity in the submandibular (salivary) glands was due to 68 Ga-transferrin. The preclinical data so far indicate that 68 Ga-Ca-phytate particles have good potential as a lung perfusion imaging agent.

The Caudate Lobe: The Blind Spot in Radioembolization or an Overlooked Opportunity?

The caudate lobe (CL) is impartial to the functional left and right hemi-liver and has outspoken inter-individual differences in arterial vascularization. Unfortunately, this complexity is not specifically taken into account during radioembolization treatment (RE), potentially resulting in under- or overtreatment of the CL. The objective of this study was to evaluate the CL coverage in RE and determine the detection rate of the CL arteries on CT angiography during work-up. In all consecutive patients who underwent RE treatment between May 2012-January 2015, (99m)Tc-MAA SPECT/CT and posttreatment scans ((90)Y-bremsstrahlung SPECT/CT, (90)Y-PET/CT, or (166)Ho-SPECT/CT) were reviewed for activity in the CL. Pretreatment CT angiographies were reviewed for the visibility of the CL arteries. Eighty-two patients were treated. In 32/82 (39%) the CL was involved. In 6/32 (19%) patients, no activity was seen on the posttreatment scan in the CL, whereas in 40/50 (80%) patients without CL tumor involvement, the CL was treated. (99m)Tc-MAA SPECT/CT and final posttreatment scans were discordant in 16/78 (21%). (99m)Tc-MAA SPECT/CT had a positive and negative predictive value of 94% and 46%, respectively, for activity in the CL after RE. In untreated CLs, significant hypertrophy was observed with a median volume increase of 33% (p=0.02). CL arteries were seldom visible on the pretreatment CT; the identification rate was 12-17%. Currently in RE treatments, targeting or sparing of the CL is highly erratic and independent of tumor involvement. Intentional treatment or bypassing of the CL seems worthwhile to either improve tumor coverage or enhancethe functional liver remnant.

Pharmacokinetics of 99mTc-MAA- and 99mTc-HSA-Microspheres Used in Preradioembolization Dosimetry: Influence on the Liver-Lung Shunt.

Perfusion scintigraphy using (99m)Tc-labeled albumin aggregates is mandatory before hepatic radioembolization with (90)Y-microspheres. As part of a prospective trial, the intrahepatic and intrapulmonary stability of 2 albumin compounds, (99m)Tc-MAA (macroaggregated serum albumin [MAA]) and (99m)Tc-HSA (human serum albumin [HSA]), was assessed. In 24 patients with metastatic colorectal cancer, biodistribution (liver, lung) and liver-lung shunt (LLS) of both tracers (12 patients each) were assessed by sequential planar scintigraphy (1, 5, and 24 h after injection). Liver uptake of both albumin compounds decreased differently. Although initial LLSs at 1 h after injection were similar in both groups, MAA-LLS increased significantly from 1 (3.9%) to 5 h (7.7%) and 24 h (9.9%) after injection, respectively. HSA-LLS did not change significantly (1 to 5 h), indicating a steady state of pulmonary and intrahepatic degradation. Compared with (99m)Tc-MAA-microspheres, (99m)Tc-HSA-microspheres are likely more resistant to degradation over time, allowing a reliable LLS determination even at later time points.

Evaluation of nasal mucociliary transport rate according to nasal septum deviation type.

Nasal septum deviation (NSD) may affect mucociliary activity (MCA) to varying degrees, depending upon the severity of the deviation. We used rhinoscintigraphy to determine the impact of the various NSD types on MCA. A recent classification describing 6 different forms of NSD was used to standardize the study. Forty-eight subjects were enrolled. Eight patients for each form of NSD were accrued for further study. Rhinoscintigraphy was performed using technetium 99m macroaggregated albumin ((99m) Tc-MAA) before and 3 months after surgery. Nasal mucociliary transport rate (NMTR), the half-time of (99m) Tc-MAA activity, and clearance rate over a 20-minute period were compared between groups. Preoperative NMTR and clearance rates were significantly lower and half-time was significantly longer in types 4 and 6 than in the other groups. Although the postoperative NMTR and clearance rates increased compared with preoperative values in all groups, the increase was significant only in types 2, 4, and 6. The postoperative half-time increased significantly compared with the preoperative values in types 2, 4, and 6. The postoperative rhinoscintigraphy evaluation revealed no significant differences among groups in NMTR, half-time, or clearance rate. NSD types 4 and 6 had lower preoperative NMTR and clearance rates and a longer half-time compared with the other groups. However, the postoperative values of these parameters were not significantly different among groups. Our results indicate that NSD types 4 and 6 had the greatest impact on MCA, suggesting that these patients may receive the maximum benefit from septoplasty.