Development of a novel castration-resistant orthotopic prostate cancer model in New Zealand White rabbit

BACKGROUND

Prostate cancer (PCa) models in mice and rats are limited by their size and lack of a clearly delineated or easily accessible prostate gland. The canine PCa model is currently the only large animal model which can be used to test new preclinical interventions but is costly and availability is sparse. As an alternative, we developed an orthotopic human prostate tumor model in an immunosuppressed New Zealand White rabbit. Rabbits are phylogenetically closer to humans, their prostate gland is anatomically similar, and its size allows for clinically-relevant testing of interventions.

METHODS

Rabbits were immunosuppressed via injection of cyclosporine. Human PC3pipGFP PCa cells were injected into the prostate via either (a) laparotomy or (b) transabdominal ultrasound (US) guided injection. Tumor growth was monitored using US and magnetic resonance imaging (MRI). Contrast-enhanced ultrasound (CEUS) imaging using nanobubbles and Lumason microbubbles was also performed to examine imaging features and determine the optimal contrast dose required for enhanced visualization of the tumor. Ex vivo fluorescence imaging, histopathology, and immunohistochemistry analyses of the collected tissues were performed to validate tumor morphology and prostate-specific membrane antigen (PSMA) expression.

RESULTS

Immunosuppression and tumor growth were, in general, well-tolerated by the rabbits. Fourteen out of 20 rabbits, with an average age of 8 months, successfully grew detectable tumors from Day 14 onwards after cell injection. The tumor growth rate was 39 ± 25 mm² per week. CEUS and MRI of tumors appear hypoechoic and T2 hypointense, respectively, relative to normal prostate tissue. Minimally invasive US-guided tumor cell injection proved to be a better method compared to laparotomy due to the shorter recovery time required for the rabbits following injection. Among the rabbits that grew tumors, seven had tumors both inside and outside the prostate, three had tumors only inside the prostate, and four had tumors exclusively outside of the prostate. All tumors expressed the PSMA receptor.

CONCLUSIONS

We have established, for the first time, an orthotopic PCa rabbit model via percutaneous US-guided tumor cell inoculation. This animal model is an attractive, clinically relevant intermediate step to assess preclinical diagnostic and therapeutic compounds.

Large pulmonary artery pseudoaneurysm after CardioMEMS implantation: a case report

Background

CardioMEMS heart failure (HF) system is an implantable wireless pressure sensor that is placed in a branch of the pulmonary artery (PA) for remote monitoring of PA pressures in patients with HF. Pulmonary artery injury/haemoptysis can occur during the sensor placement.

Case summary

An 80-year-old male patient with HF with reduced ejection fraction (20%) underwent CardioMEMS HF system implantation for recurrent shortness of breath. He developed haemoptysis and dyspnoea during the procedure, which was managed with furosemide. The patient’s computerized tomographic angiography showed a 3.4 cm pseudoaneurysm with active extravasation from the superior segmental branch of the left PA due to injury during device placement. The decision to embolize the pseudoaneurysm was made after a multi-disciplinary team meeting and discussion with the patient. The embolization procedure was carried out successfully with the final left pulmonary angiogram showed complete stasis and no further filling of the pseudoaneurysm sac.

Discussion

The incidence of mortality in patients with PA injury from CardioMEMS devices is high, and therefore prompt diagnosis and management are critical. Pulmonary artery pseudoaneurysms are uncommon and present with haemoptysis. Transcatheter embolization has been shown to be a practical, effective, and safe therapeutic option in stable patients.

Multidisciplinary Management of Complicated Pancreatitis: What Every Interventional Radiologist Should Know

Management of acute pancreatitis is challenging in the presence of local complications that include pancreatic and peripancreatic collections and vascular complications. This review, targeted for interventional radiologists, describes minimally invasive endoscopic, image-guided percutaneous, and surgical procedures for management of complicated pancreatitis and provides insight into the procedures' algorithmic application. Local complications are optimally managed in a multidisciplinary team setting that includes advanced endoscopists; pancreatic surgeons; diagnostic and interventional radiologists; and specialists in infectious disease, nutrition, and critical care medicine. Large symptomatic or complicated sterile collections and secondary infected collections warrant drainage or débridement. The drainage is usually delayed for 4-6 weeks unless clinical deterioration warrants early intervention. If collections are accessible by endoscopy, endoscopic procedures are preferred to avoid pancreaticocutaneous fistulas. Image-guided percutaneous drainage is indicated for symptomatic collections that are not accessible for endoscopic drainage or that present in the acute setting before developing a mature wall. Peripancreatic arterial pseudoaneurysms should be embolized before necrosectomy procedures to prevent potentially life-threatening hemorrhage. Surgical procedures are reserved for symptomatic collections that persist despite endoscopic or interventional drainage attempts. Understanding these procedures facilitates their integration by interventional radiologists into the complex longitudinal care of patients with complicated pancreatitis.

Role of interventional radiology in the diagnosis and management of congenital extrahepatic portosystemic shunts: Two case reports

Congenital extrahepatic portosystemic shunt (CEPS) is a rare splanchnic venous malformation, wherein the portal venous outflow drains into the systemic venous circulation via a pathologic shunt. CEPS exhibits heterogeneous clinical behavior and angiography is the gold standard for evaluation of the portomesenteric communication to systemic vasculature. The potential severity of complications necessitates shunt closure. Here, we present two cases of CEPS. The first patient presented with an asymptomatic hyperammonemia and was found to have a Type 1 CEPS with absence of intrahepatic portal system. The second patient was asymptomatic and was incidentally found to have a Type 2 CEPS on imaging with normal intrahepatic portal system. Both patients were successfully treated with endovascular occlusion of the CEPS.

Interventional radiology procedural volume changes during COVID-19 initial phase: A tertiary level Midwest health system experience

BACKGROUND

To evaluate Interventional Radiology (IR) procedural volume changes at a large Midwest health system between March 17, 2020 and April 30, 2020 following a state-mandated shutdown of nonessential procedures during the initial phase of COVID-19.

METHODS

IR procedural volumes were compiled, stratified by location and compared with Diagnostic Radiology (DR) volumes during the same timeframe. Procedure volume was categorized by type, including oncology, dialysis interventions, and drainage procedures with comparisons made using Z-score test for proportions. IR and system-wide surgical procedural volume was compared with baseline values.

RESULTS

System-wide IR procedural volume decreased by 35%, with a 41% decrease in outpatient and a 25% decrease in inpatient volume during the state-mandated order. DR volume decreased by 45%, with a 57% decrease in outpatient and a 22% decrease in inpatient volume. Total IR procedural volume during the mandate was 1077 versus 1518 during the preceding six weeks. The proportion of Interventional Oncology and dialysis interventions showed no significant change (p > 0.05) while that of drainage procedures increased (p < 0.05). Compared to baseline values, system-wide procedural volumes for IR, Vascular Surgery, Urology, General Surgery, Gastroenterology and Gynecology decreased by 3%, 11%, 25%, 20%, 38% and 31% in March 2020 and 25%, 47%, 68%, 63%, 79% and 73% in April 2020 respectively.

CONCLUSION

Outpatient IR volumes were less impacted compared to DR during the initial phase of COVID-19. Oncology, dialysis and drainage interventions may be considered essential procedures due to their stability. IR volumes were less affected compared to other procedural specialties.

Ureteroarterial Fistula Presenting as Gross Hematuria during Routine Nephroureteral Stent Exchange

Ureteroarterial fistula (UAF) is an uncommon entity and underrecognized etiology of hematuria in patients with a history of pelvic malignancy, irradiation, and surgery. Herein we report two cases of UAF unexpectedly identified during routine nephroureteral stent exchanges which highlight salient points regarding diagnosis and management.

Interventional radiology preparedness during coronavirus disease (COVID-19) pandemic

The COVID-19 pandemic has affected every sector of healthcare. Interventional Radiology in many instances continues to provide frontline care during this pandemic. The purpose of this article is to assist Interventional Radiologists in their preparation to face the challenges, by summarizing global experiences and guidelines. We provide a basic framework that can be used to prepare institue specific guidelines in coordination with multidisciplinary teams and hospital administration.

Role of imaging in diagnosis and management of left ventricular assist device complications

Heart failure is a clinical condition that is associated with significant morbidity and mortality. With the advent of left ventricular assist device (LVAD), an increasing number of patients have received an artificial heart both as a bridge-to-therapy and as a destination therapy. Clinical trials have shown clear survival benefits of LVAD implantation. However, the increased survival benefits and improved quality of life come at the expense of an increased complication rate. Common complications include perioperative bleeding, infection, device thrombosis, gastrointestinal bleeding, right heart failure, and aortic hemodynamic changes. The LVAD-associated complications have unique pathophysiology. Multiple imaging modalities can be employed to investigate the complications, including computed tomography (CT), positron emission tomography-computed tomography (PET-CT), catheter angiography and echocardiography. Imaging studies not only help ascertain diagnosis and evaluate the severity of disease, but also help direct relevant clinical management and predict prognosis. In this article, we aim to review the common LVAD complications, present the associated imaging features and discuss the role of imaging in their management.

Incidence and interventions for post-thrombotic syndrome

Post-thrombotic syndrome (PTS) is a venous stress disorder that develops from long-term effects from a previous deep venous thrombosis (DVT). The morbidity associated with PTS may be significant and patients can present with edema, chronic pain, swelling, skin changes, and heaviness of the affected limb. PTS can eventually lead to a decreased quality of life and to a marked burden for the healthcare system. This article elaborates on clinical aspects of PTS including the pathophysiology, diagnostic work-up and management of the disease with a particular focus on endovascular options.

In Vivo Transfection and Detection of Gene Expression of Stem Cells Preloaded with DNA-carrying Microbubbles

PURPOSE

To determine whether (a) stem cells loaded with DNA-carrying microbubbles (MBs) can be transfected in vivo, (b) the cells remain alive to express the gene, and (c) gene expression is sufficiently robust to be detected in vivo.

MATERIALS AND METHODS

The study was approved by the Institutional Animal Care and Use Committee. Cationic MBs were prepared, characterized, and loaded with pLuciferase green fluorescent protein (GFP) plasmid. Loading was confirmed with SYBR Gold staining (Life Technologies, Carlsbad, Calif). C17.2 cells were loaded with the DNA-carrying MBs. Two hundred thousand cells suspended in 20 μL phosphate-buffered saline were mixed with 200 μL Matrigel (BD Biosciences, San Jose, Calif) and injected in both flanks of eight nude mice. One of the Matrigel (BD Biosciences) injections contained 50 000 cells pretransfected in vitro by using lipofectamine as a positive control. Nine flanks were exposed to 2.25-MHz ultrasonic pulses at 50% duty cycle for 1 minute at 1 W/cm(2) (n = 3) or 2 W/cm(2) (n = 6), and six flanks served as the negative control. Two days later, bioluminescent images were acquired in each mouse every 3 minutes for 1 hour after the intraperitoneal injection of d-luciferin (Perkin Elmer, Waltham, Mass). Differences between groups were assessed by using the nonparametric Kruskal-Wallis test with Wilcoxon rank sum tests for follow-up comparisons. Mice were then killed, plugs were explanted, and alternate sections were stained with hematoxylin-eosin or stained for GFP expression.

RESULTS

Mean DNA-loaded MB diameter ± standard deviation was 2.87 μm ± 1.69 with the DNA associated with the MB shell. C17.2 cells were associated with 2-4 MBs each, and more than 90% were viable. Peak background subtracted bioluminescent signal was fourfold higher when cells were exposed to 2 W/cm(2) pulses as compared with 1 W/cm(2) pulses (P = .02) and negative controls (P = .002). Histologic examination showed cells within the Matrigel (BD Biosciences) with robust GFP expression only after 2 W/cm(2) ultrasound exposure and lipofectamine transfection.

CONCLUSION

Stem cells loaded with DNA-carrying MBs can be transfected in vivo with ultrasonic pulses and remain alive to demonstrate robust gene expression.

Neural progenitor cells labeling with microbubble contrast agent for ultrasound imaging in vivo

Tracking neuroprogenitor cells (NPCs) that are used to target tumors, infarction or inflammation, is paramount for cell-based therapy. We employed ultrasound imaging that can detect a single microbubble because it can distinguish its unique signal from those of surrounding tissues. NPCs efficiently internalized positively charged microbubbles allowing a clinical ultrasound system to detect a single cell at 7 MHz. When injected intravenously, labeled NPCs traversed the lungs to be imaged in the left ventricle and the liver where they accumulated. Internalized microbubbles were not only less sensitive to destruction by ultrasound, but remained visible in vivo for days as compared to minutes when given free. The extended longevity provides ample time to allow cells to reach their intended target. We were also able to transfect NPCs in vitro when microbubbles were preloaded with GFP plasmid only when cells were insonated. Transfection efficiency and cell viability were both greater than 90%.

Somatic differentiation and MR imaging of magnetically labeled human embryonic stem cells

Magnetic resonance (MR) imaging of superparamagnetic iron oxide (SPIO)-labeled stem cells offers a noninvasive evaluation of stem cell engraftment in host organs. Excessive cellular iron load from SPIO labeling, however, impairs stem cell differentiation. The purpose of this study was to magnetically label human embryonic stem cells (hESCs) via a reduced exposure protocol that maintains a significant MR signal and no significant impairment to cellular pluripotency or differentiation potential. hESCs were labeled by simple incubation with Food and Drug Administration-approved ferumoxides, using concentrations of 50- 200 µg Fe/ml and incubation times of 3-24 h. The most reduced exposure labeling protocol that still provided a significant MR signal comparable to accepted labeling protocols was selected for subsequent studies. Labeled hESCs were compared to unlabeled controls for differences in pluripotency as studied by fluorescence staining for SSEA-1, SSEA-4, TRA-60, and TRA-81 and in differentiation capacity as studied by quantitative real-time PCR for hOCT4, hACTC1, hSOX1, and hAFP after differentiation into embryoid bodies (EBs). Subsequent MR and microscopy imaging were performed to evaluate for cellular iron distribution and long-term persistence of the label. An incubation concentration of 50 µg Fe/ml and incubation time of 3 h demonstrated a significantly reduced exposure protocol that yielded an intracellular iron uptake of 4.50 ± 0.27 pg, an iron content comparable to currently accepted SPIO labeling protocols. Labeled and unlabeled hESCs showed no difference in pluripotency or differentiation capacity. Ferumoxide-labeled hESCs demonstrated persistent MR contrast effects as embryoid bodies for 21 days. Electron microscopy confirmed persistent lysosomal storage of iron oxide particles in EBs up to 9 days, while additional microscopy visualization confirmed the iron distribution within single and multiple EBs. Labeling hESCs with ferumoxides by this tailored protocol reduces exposure of cells to the labeling agent while allowing for long-term visualization with MR imaging and the retention of cellular pluripotency and differentiation potential.

Magnetic resonance imaging of ferumoxide-labeled mesenchymal stem cells in cartilage defects: in vitro and in vivo investigations

The purpose of this study was to (1) compare three different techniques for ferumoxide labeling of mesenchymal stem cells (MSCs), (2) evaluate if ferumoxide labeling allows in vivo tracking of matrix-associated stem cell implants (MASIs) in an animal model, and (3) compare the magnetic resonance imaging (MRI) characteristics of ferumoxide-labeled viable and apoptotic MSCs. MSCs labeled with ferumoxide by simple incubation, protamine transfection, or Lipofectin transfection were evaluated with MRI and histopathology. Ferumoxide-labeled and unlabeled viable and apoptotic MSCs in osteochondral defects of rat knee joints were evaluated over 12 weeks with MRI. Signal to noise ratios (SNRs) of viable and apoptotic labeled MASIs were tested for significant differences using t-tests. A simple incubation labeling protocol demonstrated the best compromise between significant magnetic resonance signal effects and preserved cell viability and potential for immediate clinical translation. Labeled viable and apoptotic MASIs did not show significant differences in SNR. Labeled viable but not apoptotic MSCs demonstrated an increasing area of T2 signal loss over time, which correlated to stem cell proliferation at the transplantation site. Histopathology confirmed successful engraftment of viable MSCs. The engraftment of iron oxide-labeled MASIs by simple incubation can be monitored over several weeks with MRI. Viable and apoptotic MASIs can be distinguished via imaging signs of cell proliferation at the transplantation site.

Depicting adoptive immunotherapy for prostate cancer in an animal model with magnetic resonance imaging

Genetically modified natural killer (NK) cells that recognize tumor-associated surface antigens have recently shown promise as a novel approach for cancer immunotherapy. To determine NK cell therapy response early, a real-time, noninvasive method to quantify NK cell homing to the tumor is desirable. The purpose of this study was to evaluate if MR imaging could provide a noninvasive, in vivo diagnosis of NK cell accumulation in epithelial cell adhesion molecule (EpCAM)-positive prostate cancers in a rat xenograft model. Genetically engineered NK-92-scFv(MOC31)-ζ cells, which express a chimeric antigen receptor specific to the tumor-associated EpCAM antigen, and nontargeted NK-92 cells were labeled with superparamagnetic particles of iron-oxides (SPIO) ferumoxides. Twelve athymic rats with implanted EpCAM positive DU145 prostate cancers received intravenous injections of 1.5×10(7) SPIO labeled NK-92 and NK-92-scFv(MOC31)-ζ cells. EpCAM-positive prostate cancers demonstrated a progressive and a significant decline in contrast-to-noise-ratio data at 1 and 24 h after injection of SPIO-labeled NK-92-scFv(MOC31)-ζ cells. Conversely, tumor contrast-to-noise-ratio data did not change significantly after injection of SPIO-labeled parental NK-92 cells. Histopathology confirmed an accumulation of the genetically engineered NK-92-scFv(MOC31)-ζ cells in prostate cancers. Thus, the presence or absence of a tumor accumulation of therapeutic NK cells can be monitored with cellular MR imaging. EpCAM-directed, SPIO labeled NK-92-scFv(MOC31)-ζ cells accumulate in EpCAM-positive prostate cancers.

Breast cancers: MR imaging of folate-receptor expression with the folate-specific nanoparticle P1133

PURPOSE

To assess the capability of the folate receptor (FR)-targeted ultrasmall superparamagnetic iron oxide (USPIO) P1133 to provide FR-specific enhancement of breast cancers on magnetic resonance (MR) images.

MATERIALS AND METHODS

This study was approved by the institutional Animal Care and Use Committee. The FR-targeted contrast agent P1133 was incubated with various FR-positive human breast cancer cell lines, with and without free folic acid (FFA) as a competitor. Labeling efficiencies were evaluated with MR imaging and inductively coupled plasma mass spectrometry. Subsequently, six athymic rats with implanted FR-positive MDA-MB-231 breast cancers underwent MR imaging at 3 T before and up to 1 hour and 24 hours after injection of P1133. Six athymic rats with implanted FR-positive MDA-MB-231 cancers injected with the non-FR-targeted USPIO P904 and nine athymic rats with implanted FR-negative A549 lung cancers injected with P1133 (n = 6) or P904 (n = 3) served as controls. Data of the in vitro studies were compared for significant differences with the Wilcoxon test for two independent samples. Tumor signal-to-noise-ratios (SNRs) were compared between different experimental groups by using the Kruskal-Wallis test and were correlated with histopathologic findings. Differences with P < .05 were considered significant.

RESULTS

FR-positive breast cancer cells showed a significant P1133 uptake which was inhibited by FFA. MDA-MB-231 cells showed the highest level of P1133 uptake and the strongest T2 effect on MR images. In vivo, all tumors showed an initial perfusion effect. At 24 hours after injection, only MDA-MB-231 tumors injected with P1133 showed significantly decreased SNR data compared with baseline data (P < .05). MR findings were confirmed by using histopathologic findings.

CONCLUSION

The FR-targeted USPIO P1133 demonstrates a specific retention in FR-positive breast cancers. Because FR expression correlates with tumor aggressiveness and prognosis, persistent P1133 tumor enhancement may be used as a noninvasive indicator for tumors with poor outcome.

Optical imaging of the peri-tumoral inflammatory response in breast cancer

PURPOSE

Peri-tumoral inflammation is a common tumor response that plays a central role in tumor invasion and metastasis, and inflammatory cell recruitment is essential to this process. The purpose of this study was to determine whether injected fluorescently-labeled monocytes accumulate within murine breast tumors and are visible with optical imaging.

MATERIALS AND METHODS

Murine monocytes were labeled with the fluorescent dye DiD and subsequently injected intravenously into 6 transgenic MMTV-PymT tumor-bearing mice and 6 FVB/n control mice without tumors. Optical imaging (OI) was performed before and after cell injection. Ratios of post-injection to pre-injection fluorescent signal intensity of the tumors (MMTV-PymT mice) and mammary tissue (FVB/n controls) were calculated and statistically compared.

RESULTS

MMTV-PymT breast tumors had an average post/pre signal intensity ratio of 1.8+/- 0.2 (range 1.1-2.7). Control mammary tissue had an average post/pre signal intensity ratio of 1.1 +/- 0.1 (range, 0.4 to 1.4). The p-value for the difference between the ratios was less than 0.05. Confocal fluorescence microscopy confirmed the presence of DiD-labeled cells within the breast tumors.

CONCLUSION

Murine monocytes accumulate at the site of breast cancer development in this transgenic model, providing evidence that peri-tumoral inflammatory cell recruitment can be evaluated non-invasively using optical imaging.

Improved fluorescence of indocyanine green in vitro and in vivo after simple cooling procedures

Indocyanine green (ICG) is a contrast agent used for detecting angiogenesis with optical imaging (OI). The purpose of this study was to investigate whether cooling procedures increase the signal yield of ICG with OI. Test samples of 0.05 and 0.02 mM ICG in 40% DMSO and 60% DMEM underwent OI at four different temperatures (5, 37, 55 and 75 degrees C). In addition, six athymic rats with an antigen-induced arthritis of the knee and ankle joints underwent OI before and after injection of ICG (10 mg/ml, dose 15 mg/kg) on two separate days with and without cooling of the joints. The fluorescent signals of the test samples and arthritic joints were measured and evaluated for significant differences before and after cooling with a t-test. In vitro studies showed a strong negative correlation between ICG temperature and fluorescent signal. The mean fluorescent signal of arthritic joints (measured in efficiency) was 0.345 before ICG-injection, 4.55 after ICG-injection and before cooling and 9.71 after ICG-injection and after cooling. The fluorescent signal enhancement of arthritic joints with ICG-enhanced OI images increased significantly after cooling (p = 0.02). The signal yield of ICG can be significantly increased by cooling the target pathology. The primary underlying cause of the temperature dependence of ICG is enhanced collisional quenching with increasing temperature. This simple cooling method may be immediately helpful to increase the fluorescence signal yield in current ICG-enhanced OI-studies in patients.

Optical imaging of cellular immunotherapy against prostate cancer

The purpose of this study was to track fluorophore-labeled, tumor-targeted natural killer (NK) cells to human prostate cancer xenografts with optical imaging (OI). NK-92-scFv(MOC31)-zeta cells targeted to the epithelial cell adhesion molecule (EpCAM) antigen on prostate cancer cells and nontargeted NK-92 parental cells were labeled with the near-infrared dye DiD (1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine). The fluorescence, viability, and cytotoxicity of the labeled cells were evaluated. Subsequently, 12 athymic rats with prostate cancer xenografts underwent OI scans before and up to 24 hours postinjection of DiD-labeled parental NK-92 cells or NK-92-scFv(MOC31)-zeta cells. The tumor fluorescence intensity was measured and compared between pre- and postinjection scans and between both groups using t-tests. OI data were confirmed with fluorescence microscopy. In vitro studies demonstrated a significant increase in the fluorescence of labeled cells compared with unlabeled controls, which persisted over a period of 24 hours without any significant change in the viability. In vivo studies demonstrated a significant increase in tumor fluorescence at 24 hours postinjection of tumor-targeted NK-92-scFv(MOC31)-zeta cells but not parental NK cells. Ex vivo OI scans and fluorescence microscopy confirmed a specific accumulation of NK-92-scFv(MOC31)-zeta cells but not parental NK cells in the tumors. Tumor-targeted NK-92-scFv(MOC31)-zeta cells could be tracked to prostate cancer xenografts with OI.

Detection of postoperative granulation tissue with an ICG-enhanced integrated OI-/X-ray System

Background

The development of postoperative granulation tissue is one of the main postoperative risks after lumbar spine surgery. This granulation tissue may lead to persistent or new clinical symptoms or complicate a follow up surgery. A sensitive non-invasive imaging technique, that could diagnose this granulation tissue at the bedside, would help to develop appropriate treatments. Thus, the purpose of this study was to establish a fast and economic imaging tool for the diagnosis of granulation tissue after lumbar spine surgery, using a new integrated Optical Imaging (OI)/X-ray imaging system and the FDA-approved fluorescent contrast agent Indocyanine Green (ICG).

Methods

12 male Sprague Dawley rats underwent intervertebral disk surgery. Imaging of the operated lumbar spine was done with the integrated OI/X-ray system at 7 and 14 days after surgery. 6 rats served as non-operated controls. OI/X-ray scans of all rats were acquired before and after intravenous injection of the FDA-approved fluorescent dye Indocyanine Green (ICG) at a dose of 1 mg/kg or 10 mg/kg. The fluorescence signal of the paravertebral soft tissues was compared between different groups of rats using Wilcoxon-tests. Lumbar spines and paravertebral soft tissues were further processed with histopathology.

Results

In both dose groups, ICG provided a significant enhancement of soft tissue in the area of surgery, which corresponded with granulation tissue on histopathology. The peak and time interval of fluorescence enhancement was significantly higher using 10 mg/kg dose of ICG compared to the 1 mg/kg ICG dose. The levels of significance were p < 0.05. Fusion of OI data with X-rays allowed an accurate anatomical localization of the enhancing granulation tissue.

Conclusion

ICG-enhanced OI is a suitable technique to diagnose granulation tissue after lumbar spine surgery. This new imaging technique may be clinically applicable for postoperative treatment monitoring. It could be also used to evaluate the effect of anti-inflammatory drugs and may even allow evaluations at the bedside with new hand-held OI scanners.