18F-FDG PET/CT Parameters for Predicting Prognosis in Esophageal Cancer Patients Treated With Concurrent Chemoradiotherapy.

BACKGROUND AND AIMS: This study evaluated the prognostic value of 18F-fluorodeoxyglucose positron emission tomography with integrated computed tomography (18F-FDG PET/CT) performed before and after concurrent chemoradiotherapy (CCRT) in esophageal cancer. METHODS: We analyzed the prognosis of 50 non-metastatic squamous cell esophageal cancer (T1-4N0-2) patients who underwent CCRT with curative intent at Inje University Busan Paik Hospital and Haeundae Paik Hospital from 2009 to 2019. Median total radiation dose was 54 Gy (range 34-66 Gy). Our aim was to investigate the relationship between PET/CT values and prognosis. The primary end point was progression-free survival (PFS). RESULTS: The median follow-up period was 9.9 months (range 1.7-85.7). Median baseline maximum standard uptake value (SUVmax) was 14.2 (range 3.2-27.7). After treatment, 29 patients (58%) showed disease progression. The 3-year PFS and overall survival (OS) were 24.2% and 54.5%, respectively. PFS was significantly lower (P = 0.015) when SUVmax of initial PET/CT exceeded 10 (n = 22). However, OS did not reach a significant difference based on maximum SUV (P = 0.282). Small metabolic tumor volume (≤14.1) was related with good PFS (P = 0.002) and OS (P = 0.001). Small total lesion of glycolysis (≤107.3) also had a significant good prognostic effect on PFS (P = 0.009) and OS (P = 0.025). In a subgroup analysis of 18 patients with follow-up PET/CT, the patients with SUV max ≤3.5 in follow-up PET/CT showed longer PFS (P = 0.028) than those with a maximum SUV >3.5. CONCLUSION: Maximum SUV of PET/CT is useful in predicting prognosis of esophageal cancer patients treated with CCRT. Efforts to find more effective treatments for patients at high risk of progression are still warranted.

Clinical Impact of Extranodal Metabolic Tumor Volume in 240 Diffuse Large B cell Lymphoma Patients with Extranodal Involvement.

The present study is to investigate whether extranodal (EN) metabolic tumor volume (MTV) would have a specific clinical meaning for survival in EN diffuse large B cell lymphoma (DLBCL) patients. Two hundred forty DLBCL patients with EN involvement received 18F-fluorodeoxygenase (FDG) positron emission tomography/computed tomography (PET/CT) were enrolled. Survival analysis revealed that low EN MTV (PFS [progression-free survival], HR = 0.278, 95% CI = 0.127-0.807, p = 0.001; OS [overall survival], HR = 0.320, 95% CI = 0.145-0.703, p = 0.003), low total MTV (PFS, HR = 0.194, 95% CI = 0.085-0.445, p < 0.001; OS, HR = 0.213, 95% CI = 0.092-0.491, p < 0.007), and high National Cancer Center Network-International Prognostic Index score (PFS, HR = 3.152, 95% CI = 1.732-5.734, p < 0.001; OS, HR = 2.457, 95% CI = 1.363-4.430, p = 0.003) were independently associated with survivals in the patients. Our data showed that EN MTV is a useful and novel prognostic parameter for predicting survival in DLBCL patients with EN involvement.

Potassium-Titanyl-Phosphate (KTP) Laser Photocoagulation Combined with Resection Using an Ultrasonic Scalpel for Pharyngolaryngeal Hemangioma via a Transoral Approach: Case Report and Literature Review.

BACKGROUND Hemangiomas are relatively rare, slow-growing, benign neoplasms that can cause necrosis, ulceration, and infection leading to airway obstruction or intractable hemorrhage. Controversy persists regarding the treatment options for these tumors, which include active observation, corticosteroids, sclerotherapy, laser treatment, and surgical resection. CASE REPORT A 61-year-old man presented with a 6-month history of persistent throat clearing and foreign body sensation in the throat. He was receiving medical treatment and psychotherapy for major depressive disorder and anxiety disorder. Laryngoscopy and computed tomography revealed a large, irregular, lobulated mass covered by bluish mucosa in the hypopharynx and larynx on the right without involvement of the true vocal fold or subglottis. Orotracheal intubation was performed under general anesthesia. The hemangioma abutting the epiglottis and arytenoid was dissected by CO2 laser. The hemangioma in the pharyngoepiglottic fold and aryepiglottic fold was resected using an ultrasonic scalpel. The hemangioma in the ventricle, false vocal fold, and paraglottic space was treated by potassium-titanyl-phosphate (KTP) laser photocoagulation. Pathological examination confirmed hemangioma. There has been no recurrence during 18 months of follow-up. CONCLUSIONS The treatment of pharyngolaryngeal hemangiomas is challenging. It is important to select treatment options considering the characteristics of the treatments and the anatomical and functional relationship between the hemangioma and the surrounding structures. Single-session KTP laser photocoagulation combined with surgical resection using an ultrasonic scalpel via a transoral approach according to anatomic site could be an effective treatment for pharyngolaryngeal hemangioma.

A Case of Extranodal Rosai-Dorfman Disease Presenting as an Isolated Mass on the Base of the Tongue in a 57-Year-old Woman.

BACKGROUND Rosai-Dorfman disease (RDD), is a rare, benign, proliferative, histiocytic disorder characterized by persistent massive lymphadenopathy, which mimics malignant tumors. Diagnosis of extranodal RDD without lymphadenopathy is difficult due to its unusual clinical manifestation and lack of typical histopathologic features. Hence, it requires both a high degree of clinical suspicion and careful histopathologic examination. CASE REPORT A 57-year-old woman presented with an isolated mass on the base of the tongue (BOT) without lymphadenopathy. Laryngoscopic examination revealed a mass on the midline of the BOT. The patient underwent complete surgical excision via suspension laryngoscopy with a CO2 laser. Based on the histopathologic features, including numerous histiocytic infiltrations with emperipolesis and cytoplasmic expression of S100 and CD68 in histiocytes, the diagnosis was confirmed as extranodal RDD. No further treatment was required, and follow-up evaluation revealed no evidence of recurrence. CONCLUSIONS Because no ideal therapeutic approach is available for RDD, treatment should be tailored to the clinical manifestations. To prevent airway obstruction and recurrence, surgery is considered an appropriate option in cases of localized RDD arising on the upper respiratory tract. We report an extremely rare case of extranodal RDD without lymphadenopathy in the BOT, and provide a detailed discussion of its clinical and histopathologic features and treatment with a brief review of the relevant literature.

KSNM/KSID/KOSHIC Guidance for Nuclear Medicine Department Against the Coronavirus Disease 2019 (COVID-19) Pandemic.

The dramatic spread of Coronavirus Disease 2019 (COVID-19) has profound impacts on every continent and life. Due to human-to-human transmission of COVID-19, nuclear medicine staffs also cannot escape the risk of infection from workplaces. Every staff in the nuclear medicine department must prepare for and respond to COVID-19 pandemic which tailored to the characteristics of our profession. This article provided the guidance prepared by the Korean Society of Nuclear Medicine (KSNM) in cooperation with the Korean Society of Infectious Disease (KSID) and Korean Society for Healthcare-Associated Infection Control and Prevention (KOSHIC) in managing the COVID-19 pandemic for the nuclear medicine department. We hope that this guidance will support every practice in nuclear medicine during this chaotic period.

Fluorodeoxyglucose positron emission tomography/computed tomography identifying pericardial metastasis from early-stage p16-positive oropharyngeal cancer.

Pericardial metastasis from HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) without local recurrence is extremely rare. We report about a 69-year-old man exhibiting pericardial metastasis on positron emission tomography/computed tomography (PET/CT). There are currently no reports on the use of PET/CT in patients with pericardial metastasis from p16-positive OPSCCs.

Alterations in the metabolic networks of temporal lobe epilepsy patients: A graph theoretical analysis using FDG-PET.

OBJECTIVE: The aim of this study is to investigate changes in metabolic networks based on fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with drug-resistant temporal lobe epilepsy (TLE) (with and without hippocampal sclerosis [HS]) when compared with healthy controls. METHODS: We retrospectively enrolled 30 patients with drug-resistant temporal lobe epilepsy (17 patients with HS and 13 patients without HS) and 39 healthy controls. All subjects underwent interictal FDG-PET scans, which were analyzed to obtain metabolic connectivity using graph theoretical analysis. We investigated the differences in metabolic connectivity between patients with drug-resistant TLE (with and without HS) and healthy controls. RESULTS: When compared with healthy controls, TLE patients with HS showed alterations of global and local metabolic connectivity. When considering global connectivity, TLE patients with HS had a decreased average degree with increased modularity. When considering local connectivity, TLE patients with HS displayed alterations of betweeness centrality in widespread regions. However, there were no alterations of global metabolic connectivity in TLE patients without HS when compared with healthy controls. In addition, when compared to TLE patients without HS, TLE patients with HS had increased modularity. SIGNIFICANCE: Our study demonstrates more severe alterations in metabolic networks based on FDG-PET in TLE patients with HS than in those without HS and healthy controls. This may represent distinct epileptic networks in TLE patients with HS versus those without HS, although both are drug-resistant focal epilepsy.

Unusual iodine-131 postablation whole-body scintigraphy patterns in patients after robot-assisted/endoscopic thyroidectomy: Case series.

Robot-assisted/endoscopic thyroidectomy causes irritation due to instruments or implantation of thyroid tissue on the anterior chest wall and lower neck. We present three patients who exhibited unexpected focal lesions on postablation Iodine-131 single-photon emission computed tomography/computed tomography without biochemical and structural diseases. Meticulous surgical techniques are important to prevent complications.

Myeloid Sarcoma That Infiltrated a Preexisting Sebaceous Lymphadenoma in the Parotid Gland: Diagnostic Challenges and Literature Review.

Myeloid sarcoma (MS) is a rarely encountered extramedullary localized tumor that is composed of immature myeloid cells. We reported an extremely rare case of MS with concurrent bone marrow (BM) involvement that invaded into a preexisting sebaceous lymphadenoma in the parotid gland and neck lymph nodes. Prompted by this case, we also present a literature review of MS invasion into salivary glands. A 62-year-old man was initially diagnosed with carcinoma that arose in a sebaceous lymphadenoma in the parotid gland, through a total parotidectomy with neck dissection. After an extensive histopathological review that included immunohistochemistry, a pathologic diagnosis of MS with infiltration into the sebaceous lymphadenoma with concurrent BM involvement was confirmed. MS is difficult to diagnose accurately; herein, we analyzed the clinical presentations and effectiveness of the various diagnostic methods with a review of the literature. There are 17 cases, including our case, reported in 13 studies. Of the cases in which the salivary glands were affected, 10 involved the parotid gland, six involved the submandibular gland, and one involved both. Isolated invasion of the salivary gland was found in one case of parotid gland invasion and three cases of submandibular gland invasion. In 13 cases, the salivary glands were affected by various other lesions. Although there were no incidences of isolated MS, six patients were diagnosed with secondary MS and eight patients with MS with BM involvement, including this case. The diagnosis of MS is difficult given its rarity, and a high index of suspicion and integrated radiologic and careful histopathologic evaluation are required. Most cases of MS infiltrating the salivary gland might be indicated by the possibility of BM involvement. MS with BM involvement predicts poor prognosis and the need for intensive systemic treatment.

Port-Site Implantation Diagnosed by Iodine-131 Post-Ablation Single-Photon Emission Tomography-Computed Tomography After Robotic Thyroidectomy: A Case Report.

BACKGROUND Robotic thyroidectomy using remote access approaches is currently regarded as the optimal surgical protocol for highly selected patients. This approach has excellent cosmetic outcomes compared with conventional open transcervical thyroidectomy. Although the remote access approach offers significant benefits, it can cause complications associated with the large working space required for surgery. Such complications can lead to unusual imaging findings. CASE REPORT We report a case of a 37-year-old woman with thyroid cancer who underwent robotic thyroidectomy and demonstrated unusual port-site implantation findings on post-treatment iodine-131 whole-body scintigraphy and single-photon emission computed tomography-computed tomography. Evaluation of stimulated thyroglobulin and additional imaging studies did not reveal any remarkable findings. Through a multidisciplinary discussion, we discovered that the bag had developed a tear during specimen retrieval. Our patient was administered a therapeutic dose of radioiodine, which accumulated within the target area and successfully ablated the implanted tissue. Follow-up imaging and biochemical studies were normal after a follow-up period of 7 years. CONCLUSIONS Port-site seeding is a rare and unexpected surgical complication; however, it can be treated with radioiodine therapy involving a therapeutic dose. Meticulous surgical manipulation is essential to prevent port-site implantation related to spillage and tearing of thyroid or cancer tissue. Awareness and identification of these rare complications, which manifest as unusual imaging findings, are critical for improving the accuracy of interpretation.

Intravascular Papillary Endothelial Hyperplasia of the Vocal Cord: A Case Report and Review of the Literature.

BACKGROUND Intravascular papillary endothelial hyperplasia (IPEH), is a vascular tumor characterized by the proliferation of endothelial cells with papillary formations. It is a rare benign disease; therefore, it is important to exclude malignant vascular neoplasm in order to prevent misdiagnosis and inappropriate overtreatment. CASE REPORT Herein, we describe the case of a 51-year-old male who reported changes in his voice, and who was preoperatively diagnosed with vocal cord polyp and hemorrhagic change based on laryngoscopy. He underwent laryngomicrosurgery and the lesion was completely excised via the microflap surgical method. Histopathology analysis was consistent with IPEH. CONCLUSIONS Herein, we report an extremely rare case of IPEH arising from the true vocal cord, and we provide a brief review of the relevant literature and a detailed discussion of this rare clinical entity.

Long-Term Follow-Up of a Patient with Primary Presacral Neuroendocrine Tumor: A Case Report with Literature Review.

BACKGROUND Primary neuroendocrine tumors (NETs) in the retroperitoneal space are extremely rare. We report the case of a patient diagnosed with primary presacral NET in the retroperitoneum that was initially suspected to be hepatic metastasis, who was followed up for more than 8 years. CASE REPORT A 78-year-old man was referred to our hospital for the treatment of a hepatic mass. Following resection, the patient was diagnosed with a grade 2 well-differentiated NET. A thorough evaluation to identify the primary tumor detected small well-demarcated presacral nodules on In-111 octreotide single-photon emission tomography/computed tomography (SPECT/CT). Metastases to other locations were not observed. Presacral nodules were difficult to remove using the surgical approach; therefore, we decided to follow up closely. After 4 years, the patient was diagnosed with recurrent hepatic metastasis and peritoneal seeding. Although combination therapy of everolimus and octreotide long-acting repeatable was administered, it was discontinued owing to disease progression. Baseline Ga-68 DOTATOC positron emission tomography-computed tomography revealed adequate avidity for the lesions observed on SPECT/CT; therefore, 5 cycles of peptide receptor radionuclide therapy (PRRT) were administered, after which stable disease was maintained. CONCLUSIONS We identified an extremely rare primary retroperitoneal NET on In-111 octreotide SPECT/CT. During long-term follow-up, although the patient presented with recurrent hepatic metastases and peritoneal seeding, PRRT was successful in stabilizing the disease.

Evaluating the Predictive Ability of Initial Staging F-18 FDG PET/CT for the Prognosis of Non-Hodgkin Malignant Lymphoma Patients Who Underwent Stem Cell Transplantation.

OBJECTIVES: This study aimed to determine the value of clinical prognostic factors and semiquantitative metabolic parameters from initial staging fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in non-Hodgkin lymphoma (NHL) patients treated with stem cell transplantation (SCT). METHODS: A total of 39 malignant lymphoma patients who underwent initial staging F-18 FDG PET/CT were enrolled in this study. SUVmax, MTV_wb, and TLG_wb were measured during the initial staging PET/CT. Receiver operating characteristic curve (ROC) analysis was adopted to dichotomize continuous variables. Log-rank test and Cox proportional hazard regression analysis were used to evaluate disease-free survival (DFS) rate. RESULTS: Among the 39 patients with malignant lymphoma, 17 (43.6%) had a relapse. For several clinical factors such as age, ECOG performance score, AMC/ALC score, stages, and revised International Prognostic Index score, differences between the two dichotomized groups were statistically insignificant. In univariate analysis, DFS estimates were 71.0 ± 7.8 months and 18.0 ± 5.9 months in high-SUVmax and low-SUVmax group, respectively (P < 0.01). For MTV_wb, DFS estimates were 46.6 ± 12.4 months and 69.1 ± 8.5 months in high-MTV_wb and low-MTV_wb group, respectively (P = 0.12). For TLG_wb, DFS estimates were 65.3 ± 7.5 months and 13.7 ± 8.6 months in high-TLG_wb and low-TLG_wb group, respectively (P = 0.02). In Cox proportional hazard regression analysis, only MTV_wb showed statistical significance (HR 3.01, 95% CI 1.04-8.74, P = 0.04). CONCLUSION: In NHL patients treated with SCT, the MTV_wb of initial staging F-18 FDG PET/CT was an independent prognostic factor.

Prognostic significance of standardized uptake value on F18-FDG PET/CT in patients with extranodal nasal type NK/T cell lymphoma: A multicenter, retrospective analysis.

OBJECTIVES: The purpose of this study was to evaluate the value of parameters assessed with F18-flurodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in predicting relapse free survival and overall survival in patients with extranodal nasal type NK/T cell lymphoma. METHODS: Thirty-six patients with extranodal nasal type NK/T cell lymphoma, and who underwent PET/CT prior to curative treatment, were enrolled at five institutions. Volumes of interest covering the entire tumor volume were delineated on PET/CT images, and the maximum standardized uptake value (SUVmax), mean SUV (SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured using thresholds of 40% of SUVmax. Furthermore, we compared the difference in F18-FDG avidity according to Epstein-Barr virus (EBV) infection status. RESULTS: The SUVmax (p=0.041) and SUVmean (p=0.049) in patients who died were higher than the respective values of those who survived. A higher TLG (>45.8) was associated with relapse free survival (HR 7.856, p=0.034). Ann Arbor stage (III-IV, HR 14.12, p=0.004), and a higher SUVmax (>12.6, p=0.024) and SUVmean (>6.4, p=0.024) were associated with poor survival. However, neither the MTV nor the TLG (volumetric parameters) were significant predictors of death. The PET parameters SUVmax (p=0.181), SUVmean (p=0.237), MTV (p=0.636), and TLG (p=0.469) did not differ significantly between patients with and without EBV infections. CONCLUSIONS: High TLG was the only significant predictive factor on relapse free survival. The SUVmax and SUVmean measured by F18-FDG PET/CT could be significant prognostic factors in patients with extranodal nasal type NK/T cell lymphoma.

Tumor necrosis and complete resection has significant impacts on survival in patients with limited-stage upper aerodigestive tract NK/T cell lymphoma.

Tumor necrosis (TN) is associated with worse prognosis in several solid cancers. Whether TN predicts poor outcome in natural killer cell / T cell lymphoma (NKTCL) is unclear. We investigated the clinical impact of TN on survival and other novel prognostic parameters in upper aero-digestive tract (UAT) NKTCL of 100 patients with limited stage. TN was significantly associated with poor performance status (p = 0.049), high Korean Prognostic Index score (p = 0.024), high C-reactive protein/albumin ratio (p = 0.003), higher maximum standard uptake value on positron emission tomography/computed tomography (PET/CT) (p = 0.008) and higher metabolic tumor volume (MTV) on PET/CT (p < 0.001). In univariate and multivariate analyses, progression-free survival and overall survival were independently associated with High MTV status (p = 0.001, p = 0.032), TN (p = 0.018, p = 0.009), local tumor invasiveness (p = 0.007, p = 0.035), complete resection (p = 0.020, p = 0.028) and regional lymph node involvement (p < 0.001, p < 0.001). TN and complete resection are concluded to be novel independent prognostic factors in patients with UAT NKTCL.

Erratum to: Incidental Findings of Intense Radioiodine Uptake in Struma Ovarii and Bilateral Non-Lactating Breast Simultaneously on Post-Ablation SPECT/CT for Papillary Thyroid Cancer.

[This corrects the article DOI: 10.1007/s13139-016-0459-0.].

Incidental Findings of Intense Radioiodine Uptake in Struma Ovarii and Bilateral Nonlactating Breasts Simultaneously on Postablation 131I SPECT/CT for Papillary Thyroid Cancer.

A 52-year-old woman diagnosed with papillary thyroid carcinoma was referred for 131I therapy following total thyroidectomy. She was given 4,810 MBq (130 mCi) of 131I following 4 weeks of thyroid hormone withdrawal. A posttherapy scan showed intense, focal activity in the pelvis and intense, diffuse activity on both sides of the chest, which was localized to the right ovary and both breasts on SPECT/CT examination. She had bilateral nipple pain and a history of antidopaminergic drugs as combination medication for her rheumatoid arthritis and prokinetics during radioiodine therapy. On a 123I whole-body scan 9 months later after stopping the drugs, bilateral breast uptake was not visible; however, right ovarian focal uptake was still visualized. Bilateral salpingo-oophorectomy was performed, and revealed struma ovarii with substantial internal necrosis due to radioiodine therapy. This case is interesting as two rare entities, 131I therapy-related struma ovarii and drug-related breast uptake, were simultaneously visualized.

High total metabolic tumor volume in PET/CT predicts worse prognosis in diffuse large B cell lymphoma patients with bone marrow involvement in rituximab era.

Bone marrow involvement (BMI) in diffuse large B cell lymphoma (DLBCL) was naively regarded as an adverse clinical factor. However, it has been unknown which factor would separate clinical outcomes in DLBCL patients with BMI. Recently, metabolic tumor volume (MTV) on positron emission tomography/computed tomography (PET/CT) was suggested to predict prognosis in several lymphoma types. Therefore, we investigated whether MTV would separate the outcomes in DLBCL patients with BMI. MTV on PET/CT was defined as an initial tumor burden as target lesion ≥ standard uptake value, 2.5 in 107 patients with BMI. Intramedullary (IM) MTV was defined as extent of BMI and total MTV was as whole tumor burden. 260.5 cm(3) and 601.2 cm(3) were ideal cut-off values for dividing high and low MTV status in the IM and total lymphoma lesions in Receiver Operating Curve analysis. High risk NCCN-IPI (p<0.001, p<0.001), bulky disease (p=0.011, p=0.005), concordant subtype (p=0.025, p=0.029), high IM MTV status (p<0.001, p<0.001), high total MTV status (p<0.001, p<0.001), and ≥ 2CAs in BM (p=0.037, p=0.033) were significantly associated with progression-free survival (PFS) and overall survival (OS) than other groups. In multivariate analysis, high risk NCCN-IPI (PFS, p=0.006; OS, p=0.013), concordant subtype (PFS, p=0.005; OS, p=0.007), and high total MTV status (PFS, p<0.001; OS, p<0.001) had independent clinical impacts. MTV had prognostic significances for survivals in DLBCL with BMI.

[Synchronous hepatocellular carcinoma and B-cell non-Hodgkin's lymphoma in chronic hepatitis C patient].

Hepatitis C virus (HCV) is one of the main viral causes of hepatocellular carcinoma (HCC) and is associated with lymphoproliferative disorder such as non-Hodgkin's lymphoma (NHL). However, there are only few case reports on concomitantly induced NHL and HCC by HCV. Herein, we report a case of synchronous NHL and HCC in a patient with chronic hepatitis C which was unexpectedly diagnosed during liver transplantation surgery. This case suggests that although intrahepatic lymph node enlargements are often considered as reactive or metastatic lymphadenopathy in chronic hepatitis C patients with HCC, NHL should also be considered as a differential diagnosis.

In vivo bioluminescence imaging for viable human neural stem cells incorporated within in situ gelatin hydrogels.

BACKGROUND: Three-dimensional (3D) hydrogel-based stem cell therapies contribute to enhanced therapeutic efficacy in treating diseases, and determining the optimal mechanical strength of the hydrogel in vivo is important for therapeutic success. We evaluated the proliferation of human neural stem cells incorporated within in situ-forming hydrogels and compared the effect of hydrogels with different elastic properties in cell/hydrogel-xenografted mice. METHODS: The gelatin-polyethylene glycol-tyramine (GPT) hydrogel was fabricated through enzyme-mediated cross-linking reaction using horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). RESULTS: The F3-effluc encapsulated within a soft 1,800 pascal (Pa) hydrogel and stiff 5,800 Pa hydrogel proliferated vigorously in a 24-well plate until day 8. In vitro and in vivo kinetics of luciferase activity showed a slow time-to-peak after D-luciferin administration in the stiff hydrogel. When in vivo proliferation of F3-effluc was observed up to day 21 in both the hydrogel group and cell-only group, F3-effluc within the soft hydrogel proliferated more vigorously, compared to the cells within the stiff hydrogel. Ki-67-specific immunostaining revealed highly proliferative F3-effluc with compactly distributed cell population inside the 1,800 Pa or 5,800 Pa hydrogel. CONCLUSIONS: We examined the in vivo effectiveness of different elastic types of hydrogels encapsulating viable neural stem cells by successfully monitoring the proliferation of implanted stem cells incorporated within a 3D hydrogel scaffold.