Gd-EOB-DTPA-enhanced MRI for quantitative assessment of liver organ damage after partial hepatic ischaemia reperfusion injury: correlation with histology and serum biomarkers of liver cell injury.

OBJECTIVE: To evaluate Gd-EOB-DTPA-enhanced MRI for quantitative assessment of liver organ damage after hepatic ischaemia reperfusion injury (IRI) in mice. METHODS: Partial hepatic IRI was induced in C57Bl/6 mice (n = 31) for 35, 45, 60 and 90 min. Gd-EOB-DTPA-enhanced MRI was performed 1 day after surgery using a 3D-FLASH sequence. A subgroup of n = 9 animals with 60 min IRI underwent follow-up with MRI and histology 7 days after IRI. The total liver volume was determined by manual segmentation of the entire liver. The volume of functional, contrast-enhanced liver parenchyma was quantified by a region growing algorithm (visual threshold) and an automated segmentation (Otsu's method). The percentages of functional, contrast-enhanced and damaged non-enhanced parenchyma were calculated according to these volumes. MRI data was correlated with serum liver enzyme concentrations and histologically quantified organ damage using periodic acid-Schiff (PAS) staining. RESULTS: The percentage of functional (contrasted) liver parenchyma decreased significantly with increasing ischaemia times (control, 94.4 ± 3.3%; 35 min IRI, 89.3 ± 4.1%; 45 min IRI, 87.9 ± 3.3%; 60 min IRI, 68 ± 10.5%, p < 0.001 vs. control; 90 min IRI, 55.9 ± 11.5%, p < 0.001 vs. control). The percentage of non-contrasted liver parenchyma correlated with histologically quantified liver organ damage (r = 0.637, p < 0.01) and serum liver enzyme elevations (AST r = 0.577, p < 0.01; ALT r = 0.536, p < 0.05). Follow-up MRI visualized recovery of functional liver parenchyma (71.5 ± 8.7% vs. 84 ± 2.1%, p < 0.05), consistent with less histological organ damage on day 7. CONCLUSION: We demonstrated the feasibility of Gd-EOB-DTPA-enhanced MRI for non-invasive quantification of damaged liver parenchyma following IRI in mice. This novel methodology may refine the characterization of liver disease and could have application in future studies targeting liver organ damage. KEY POINTS: • Prolonged ischaemia times in partial liver IRI increase liver organ damage. • Gd-EOB-DTPA-enhanced MRI at hepatobiliary phase identifies damaged liver volume after hepatic IRI. • Damaged liver parenchyma quantified with MRI correlates with histological liver damage. • Hepatobiliary phase Gd-EOB-DTPA-enhanced MRI enables non-invasive assessment of recovery from liver injury.

Assessment of liver ischemia reperfusion injury in mice using hepatic T2 mapping: Comparison with histopathology.

BACKGROUND: Liver ischemia reperfusion injury (IRI) occurs during liver surgery or transplantation resulting in an inflammatory response, tissue damage, and functional impairment of the organ. PURPOSE: To assess the feasibility of T2 mapping for noninvasive quantification of liver edema after partial liver IRI in mice. STUDY TYPE: Prospective, experimental study. ANIMAL MODEL: Partial liver IRI was induced in C57BL/6-mice by transient clamping of the left lateral and median liver lobes for 35 (n = 8), 45 (n = 6), 60 (n = 17), or 90 minutes (n = 5). For comparison, healthy C57BL/6-mice were examined as controls (n = 9). FIELD STRENGTH/SEQUENCE: Functional liver MRI was performed on a 7T scanner using a respiratory-triggered multiecho spin-echo sequence. ASSESSMENT: Healthy control mice and mice with partial liver IRI on day 1 after surgery, and additionally on day 7 in a subgroup with 60 minutes IRI (n = 8) were examined. Maps of T2 relaxation time of liver tissue were used to assess distribution, severity of tissue edema (mean T2 time), and the percentage of edematous liver tissue. STATISTICAL TEST: One-way analysis of variance (ANOVA) with Tukey's honest significant difference (HSD), paired t-tests, Pearson's test for correlation of MRI parameters with levels of liver enzymes, and histopathology, receiver operating characteristic (ROC) analysis. RESULTS: Significant tissue edema induced by liver IRI as compared to the control group was detected by increased mean T2 times in groups with 60 minutes (P < 0.001) and 90 minutes IRI (P < 0.001). The percentage of edematous liver tissue significantly increased with longer ischemia times (controls 3.4 ± 0.4%, 35 minutes 5.3 ± 0.6%, 45 minutes 23.3 ± 7.6%, 60 minutes 39.7 ± 3.6%, 90 minutes 51.3 ± 4.5%). Mean T2 times and the percentage of edematous liver tissue significantly correlated with elevation of liver enzymes (P < 0.001), histological evidence of liver injury (r = 0.80 and r = 0.82, P < 0.001), and neutrophil infiltration (r = 0.70 and r = 0.74, P < 0.001). In the subgroup with follow-up, the severity (P < 0.01) and extent of liver edema decreased significantly over time (P < 0.01). DATA CONCLUSION: T2 mapping allows quantification and follow-up of liver injury in mice. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1586-1594.

18F-FDG PET/CT for Molecular Imaging of Hepatoblastoma in Beckwith-Wiedemann Syndrome.

Beckwith-Wiedemann syndrome (BWS) is a rare congenital overgrowth disorder variably characterized by macrosomia, macroglossia, congenital hypoglycemia, and hemihyperplasia. The BWS predisposes affected individuals to embryonal tumors during childhood. The BWS is caused by abnormal gene regulation in a particular region of chromosome 11. We present the case of a 1-year-old boy with BWS who underwent an F-FDG PET/CT scan for restaging of hepatoblastoma. On the F-FDG PET scan, increased tracer accumulation was observed in hepatoblastoma lesions. In addition, marked hemihyperplasia was noted. This case highlights the usefulness of F-FDG PET/CT for restaging of hepatoblastoma in BWS.

PSA-stratified detection rates for [68Ga]THP-PSMA, a novel probe for rapid kit-based 68Ga-labeling and PET imaging, in patients with biochemical recurrence after primary therapy for prostate cancer.

PURPOSE: [68Ga]Tris(hydroxypyridinone)(THP)-PSMA is a novel radiopharmaceutical for one-step kit-based radiolabelling, based on direct chelation of 68Ga3+ at low concentration, room temperature and over a wide pH range, using direct elution from a 68Ge/68Ga-generator. We evaluated the clinical detection rates of [68Ga]THP-PSMA PET/CT in patients with biochemically recurrent prostate cancer after prostatectomy. METHODS: Consecutive patients (n=99) referred for evaluation of biochemical relapse of prostate cancer by [68Ga]THP-PSMA PET/CT were analyzed retrospectively. Patients underwent a standard whole-body PET/CT (1 h p.i.), followed by delayed (3 h p.i.) imaging of the abdomen. PSA-stratified cohorts of positive PET/CT results, standardized uptake values (SUVs) and target-to-background ratios (TBRs) were analyzed, and compared between standard and delayed imaging. RESULTS: At least one lesion suggestive of recurrent or metastatic prostate cancer was identified on PET images in 52 patients (52.5%). Detection rates of [68Ga]THP-PSMA PET/CT increased with increasing PSA level: 94.1% for a PSA value of ≥10 ng/mL, 77.3% for a PSA value of 2 to <10 ng/mL, 54.5% for a PSA value of 1 to <2 ng/mL, 14.3% for a PSA value of 0.5 to <1 ng/mL, 20.0% for a PSA value of >0.2 to <0.5, and 22.2% for a PSA value of 0.01 to 0.2 ng/mL. [68Ga]THP-PSMA uptake (SUVs) in metastases decreased over time, whereas TBRs improved. Delayed imaging at 3 h p.i. exclusively identified pathologic findings in 2% of [68Ga]THP-PSMA PET/CT scans. Detection rate was higher in patients with a Gleason score ≥8 (P=0.02) and in patients receiving androgen deprivation therapy (P=0.003). CONCLUSIONS: In this study, [68Ga]THP-PSMA PET/CT showed suitable detection rates in patients with biochemical recurrence of prostate cancer and PSA levels ≥ 2 ng /mL. Detections rates were lower than in previous studies evaluating other PSMA ligands, though prospective direct radiotracer comparison studies are mandatory particularly in patients with low PSA levels to evaluate the relative performance of different PSMA ligands.

Renal ischemia-reperfusion injury causes hypertension and renal perfusion impairment in the CD1 mice which promotes progressive renal fibrosis.

Renal ischemia-reperfusion injury (IRI) is a severe complication of major surgery and a risk factor for increased morbidity and mortality. Here, we investigated mechanisms that might contribute to IRI-induced progression to chronic kidney disease (CKD). Acute kidney injury (AKI) was induced by unilateral IRI for 35 min in CD1 and C57BL/6 (B6) mice. Unilateral IRI was used to overcome early mortality. Renal morphology, NGAL upregulation, and neutrophil infiltration as well as peritubular capillary density were studied by immunohistochemistry. The composition of leukocyte infiltrates in the kidney after IRI was investigated by flow cytometry. Systemic blood pressure was measured with a tail cuff, and renal perfusion was quantified by functional magnetic resonance imaging (fMRI). Mesangial matrix expansion was assessed by silver staining. Following IRI, CD1 and B6 mice developed similar morphological signs of AKI and increases in NGAL expression, but neutrophil infiltration was greater in CD1 than B6 mice. IRI induced an increase in systemic blood pressure of 20 mmHg in CD1, but not in B6 mice; and CD1 mice also had a greater loss of renal perfusion and kidney volume than B6 mice ( P < 0.05). CD1 mice developed substantial interstitial fibrosis and decreased peritubular capillary (PTC) density by day 14 while B6 mice showed only mild renal scarring and almost normal PTC. Our results show that after IRI, CD1 mice develop more inflammation, hypertension, and later mesangial matrix expansion than B6 mice do. Subsequently, CD1 animals suffer from CKD due to impaired renal perfusion and pronounced permanent loss of peritubular capillaries.

Assessment of acute kidney injury with T1 mapping MRI following solid organ transplantation.

OBJECTIVES: To evaluate T1 mapping as a non-invasive, functional MRI biomarker in patients shortly after solid organ transplantation to detect acute postsurgical kidney damage and to correlate T1 times with renal function. METHODS: 101 patients within 2 weeks after solid organ transplantation (49 kidney transplantation, 52 lung transplantation) and 14 healthy volunteers were examined by MRI between July 2012 and April 2015 using the modified Look-Locker inversion recovery (MOLLI) sequence. T1 times in renal cortex and medulla and the corticomedullary difference were compared between groups using one-way ANOVA adjusted for multiple comparison with the Tukey test, and T1 times were correlated with renal function using Pearson's correlation. RESULTS: Compared to healthy volunteers T1 times were significantly increased after solid organ transplantation in the renal cortex (healthy volunteers 987 ± 102 ms; kidney transplantation 1299 ± 101 ms, p < 0.001; lung transplantation 1058 ± 96 ms, p < 0.05) and to a lesser extent in the renal medulla. Accordingly, the corticomedullary difference was diminished shortly after solid organ transplantation. T1 changes were more pronounced following kidney compared to lung transplantation, were associated with the stage of renal impairment and significantly correlated with renal function. CONCLUSIONS: T1 mapping may be helpful for early non-invasive assessment of acute kidney injury and renal pathology following major surgery such as solid organ transplantation. KEY POINTS: • Renal cortical T1 relaxation times are prolonged after solid organ transplantation. • Cortical T1 values increase with higher stages of renal function impairment. • Corticomedullary difference decreases with higher stages of renal function impairment. • Renal cortical T1 relaxation time and corticomedullary difference correlate with renal function. • T1 mapping may be helpful for non-invasive assessment of post-operative renal pathology.

Patterns of relapse as determined by 68Ga-PSMA ligand PET/CT after radical prostatectomy : Importance for tailoring and individualizing treatment.

PURPOSE: To evaluate the patterns of relapse and impact on the intended treatment when using 68Ga-prostate-specific membrane antigen (PSMA) ligand positron emission tomography/computed tomography (PET/CT) imaging for restaging of disease in patients with biochemical relapse after radical prostatectomy (RP) before salvage radiotherapy (sRT). METHODS: In all, 39 patients with biochemical recurrence after RP who had no primary indication for adjuvant RT due to the absence of biologically unfavorable disease (e.g., extracapsular extension, seminal vesicle invasion, positive margins, or lymph node involvement) underwent a 68Ga-PSMA ligand PET/CT for planning of sRT. RESULTS: PET/CT was positive in 84.6% (33/39) of patients. A total of 61 lesions were observed in these patients (on average 1.8 lesions per patient); 30.3% (10/33) of patients had locally recurrent disease in the prostatic bed. The clinical TNM stage (TNM: tumour-lymph nodes-metastasis-classification) was altered in 69.7% (23/33) of patients following PET, resulting in individualized treatment concepts. A prostate-specific antigen (PSA) >1.0 ng/mL was significantly associated with an increased risk of extrapelvic metastatic disease (p = 0.048). The PSA level at the time of PSMA ligand PET/CT correlated with the peak standardized uptake value (SUVpeak; p = 0.002). According to current clinical guidelines, the remaining 15.4% (6/39) of patients without evidence of disease on PET received sRT with a dose of 66.0 Gy. CONCLUSION: Our results suggest that in patients with biochemical recurrence who did not receive early sRT, a 68Ga-PSMA ligand PET/CT for restaging of disease allows for tailoring and individualizing treatment. Particularly in patients with PSA levels above 1.0 ng/mL, a 68Ga-PSMA ligand PET/CT should be performed for therapy planning, since patients often have metastases not confined to the pelvis.

Evaluation of MRI/Ultrasound Fusion-Guided Prostate Biopsy Using Transrectal and Transperineal Approaches.

PURPOSE: To evaluate transrectal (TR) and transperineal (TP) approaches for MRI/ultrasound (MRI/US) fusion-guided biopsy to detect prostate cancer (PCa). MATERIALS AND METHODS: 154 men underwent multiparametric MRI and MRI/US fusion-guided biopsy between July 2012 and October 2016. 79/154 patients were biopsied with a TR approach and 75/154 with a TP approach. MRI was retrospectively analyzed according to PI-RADS version 2. PI-RADS scores were compared with histopathological results. Descriptive statistics, accuracy, and negative and positive predictive values were calculated. Histopathological results of first, second, and third MRI targeted biopsy cores were compared to evaluate the impact of one verus multiple targeted cores. RESULTS: Detection rates of PCa were 39% for TR biopsy and 75% for TP biopsy. Sensitivity/specificity for tumor detection with PI-RADS ≥ 4 were 81/69% for TR biopsy and 86/84% for TP biopsy. In 31% for TR biopsy and 19% for TP biopsy, PCa was found in the second or third MRI targeted biopsy core only. CONCLUSION: MRI/US fusion-guided biopsy may be conducted with the TR as well as the TP approach with high accuracy, giving more flexibility for diagnosis and the option for focal treatment of PCa.

68Ga-DOTA-TATE PET/CT for Molecular Imaging of Somatostatin Receptor Expression in Extra-adrenal Paraganglioma in a Case of Complete Carney Triad.

Carney triad is a very rare syndrome characterized by the synchronous or metachronous occurrence of gastrointestinal stromal tumors, pulmonary chondroma, and extra-adrenal paraganglioma. We present the case of a 36-year-old woman with complete Carney triad who underwent a Ga-DOTA-TATE PET/CT scan for restaging of metastasizing extra-adrenal paraganglioma and for evaluation of targeted radionuclide therapy potential. On the Ga-DOTA-TATE PET scan, increased tracer accumulation was observed in paraganglioma metastases. This case highlights the usefulness of Ga-DOTA-TATE PET/CT for restaging of metastasizing paraganglioma in Carney triad and the option of targeted radionuclide therapy in this entity.

18F-FDG PET for Detection of Primary Tracheobronchial T-/Natural Killer-Cell-Derived Posttransplant Lymphoproliferative Disorder After Lung Transplantation.

Posttransplant lymphoproliferative disorder (PTLD) is a rare, but potentially devastating complication of solid organ transplantation. Epstein-Barr virus-associated PTLDs of T-cell origin are exceedingly rare. We present the case of a 20-year-old man with extranasal T-/natural killer-cell-derived PTLD after lung transplantation who underwent an F-FDG PET/CT scan for staging of disease. The F-FDG-PET scan demonstrated an unusual pattern of lymphomatous involvement limited to the recipients tracheobronchial tree without concomitant involvement of the donor's bronchi. This case highlights the potential of F-FDG PET/CT for sensitive detection and staging of uncommon manifestations of PTLD.

68Ga-DOTA-TATE PET/CT for Molecular Imaging of Somatostatin Receptor Expression in Metastasizing Epithelioid Hemangioendothelioma: Comparison With 18F-FDG.

Epithelioid hemangioendothelioma (EHE) is a rare tumor originating from vascular endothelial or pre-endothelial cells. It has the potential to metastasize. We present the case of a 51-year-old woman with metastasizing EHE who underwent both F-FDG and Ga-DOTA-TATE PET/CT for staging of disease and for evaluation of targeted radionuclide therapy potential. On Ga-DOTA-TATE PET scans, intense tracer accumulation was observed in metastases. Besides the increased glucose metabolism in EHE, this case highlights the potential of Ga-DOTA-TATE PET/CT for restaging of EHE and the option of targeted radionuclide therapy in this entity.

Pulmonary vascular volume, impaired left ventricular filling and dyspnea: The MESA Lung Study.

BACKGROUND: Evaluation of impaired left ventricular (LV) filling has focused on intrinsic causes of LV dysfunction; however, pulmonary vascular changes may contribute to reduced LV filling and dyspnea. We hypothesized that lower total pulmonary vascular volume (TPVV) on computed tomography (CT) would be associated with dyspnea and decrements in LV end-diastolic volume, particularly among ever-smokers. METHODS: The Multi-Ethnic Study of Atherosclerosis recruited adults without clinical cardiovascular disease in 2000-02. In 2010-12, TPVV was ascertained as the volume of arteries and veins in the lungs detectable on non-contrast chest CT (vessels ≥1 mm diameter). Cardiac measures were assessed by magnetic resonance imaging (MRI). Dyspnea was self-reported. RESULTS: Of 2303 participants, 53% had ever smoked cigarettes. Among ever-smokers, a lower TPVV was associated with a lower LV end-diastolic volume (6.9 mL per SD TPVV), stroke volume, and cardiac output and with dyspnea (all P-values <0.001). Findings were similar among those without lung disease and those with 0-10 pack-years but were mostly non-significant among never-smokers. TPVV was associated smaller left atrial volume but not with LV ejection fraction or MRI measures of impaired LV relaxation. In a second sample of ever-smokers, a lower pulmonary microvascular blood volume on contrast-enhanced MRI was also associated with a lower LV end-diastolic volume (P-value = 0.008). CONCLUSION: Reductions in pulmonary vascular volume were associated with lower LV filling and dyspnea among ever-smokers, including those without lung disease, suggesting that smoking-related pulmonary vascular changes may contribute to symptoms and impair cardiac filling and function without evidence of impaired LV relaxation.

Integrating MRI and Chemokine Receptor CXCR4-Targeted PET for Detection of Leukocyte Infiltration in Complicated Urinary Tract Infections After Kidney Transplantation.

Complicated urinary tract infections (UTIs) are frequent in immunosuppressed patients after kidney transplantation and may lead to allograft failure or urosepsis. Noninvasive detection of allograft involvement as well as localization of the primary site of infection are challenging. Therefore, we sought to determine whether molecularly targeted PET, combined with diffusion-weighted MRI, enables detection of leukocytes in renal allografts. Methods: Thirteen kidney transplant recipients with complicated UTIs underwent both PET with a specific CXCR4 ligand, 68Ga-pentixafor, and diffusion-weighted MRI. The spatial distribution and intensity of CXCR4 upregulation in renal allografts as determined by SUVs on PET and diffusion restriction as determined by apparent diffusion coefficients (ADCs) on MRI were analyzed and compared with urinalysis, clinical chemistry and bacteriology, and biopsy, if available. Results: Combined PET/MRI detected acute allograft infection in 9 patients and lower UTI/nonurologic infections in the remaining 4 patients. Leukocyte infiltration was identified by areas of CXCR4 upregulation compared with unaffected parenchyma in PET (SUVmean, 4.6 vs. 3.7; P < 0.01), corresponding to areas with increased cell density in MRI (ADCmin, 0.89 vs. 1.59 × 10-3 mm2/s, P < 0.01). Allograft CXCR4 signal was paralleled by CXCR4 upregulation in lymphoid organs. Histopathologic evaluation supported a correlation between CXCR4 signal and presence of leukocytes. Conclusion: Combined CXCR4-targeted PET/MRI with 68Ga-pentixafor may enable the noninvasive detection of leukocytes in renal allografts. This novel methodology may refine the characterization of infectious and inflammatory kidney diseases and may serve as a platform for future clinical studies targeting allograft infection.

Longitudinal evaluation of perfusion changes in acute and chronic renal allograft rejection using arterial spin labeling in translational mouse models.

PURPOSE: To examine the longitudinal changes of renal perfusion due to acute and chronic renal allograft rejection by using arterial spin labeling (ASL) MRI in translational mouse models of isogenic and allogenic kidney transplantation (ktx). MATERIALS AND METHODS: Acute rejection was induced by allogenic ktx of C57BL/6 (B6)-kidney grafts to BALB/c-recipients with prolonged cold ischemia (CIT) of 60 minutes (n = 13). To induce chronic rejection BALB/c-kidneys were transplanted into B6-recipients with short CIT of 30 minutes (n = 22). Isogenic grafts without rejection (n = 14 with prolonged, n = 9 with short CIT) and normal kidneys (n = 22) were used for comparison. Perfusion was measured on a 7T small-animal magnetic resonance imaging (MRI) scanner using flow-sensitive alternating inversion recovery (FAIR) ASL-sequences at day 1 and 6 (acute) or at week 3 and 6 (chronic) after surgery. Histological analyses of grafts included inflammation, vascular changes, and fibrosis. RESULTS: In the acute ktx model, ASL showed perfusion impairment in isogenic and allogenic kidney grafts. Perfusion of allografts further decreased until day 6 and remained stable in isografts without rejection (allogenic ktx 62 ± 21 vs. isogenic ktx 181 ± 39 ml/min/100g, P < 0.01). In the chronic ktx model, perfusion in isografts was similar to normal kidneys over the entire observation period. Perfusion was severely reduced in allografts compared to isografts (week 3: 28 ± 7 vs. 310 ± 46 ml/min/100g, P < 0.001, week 6: 32 ± 5 vs. 367 ± 72 ml/min/100g, P < 0.001). Histological analysis revealed severe inflammation, vascular occlusion, and rejection in allografts. Chronic rejection grafts showed endothelialitis, peritubular capillaritis, interstitial fibrosis, and tubular atrophy. CONCLUSION: ASL allows longitudinal assessment of renal perfusion impairment due to acute and chronic renal allograft rejection in translational mouse models. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1664-1672.

Home-based drainage of refractory ascites by a permanent-tunneled peritoneal catheter can safely replace large-volume paracentesis.

BACKGROUND AND AIM: Refractory ascites has a poor prognosis. Recurrent large-volume paracentesis is the current standard of care; however, it results in circulatory dysfunction and renal dysfunction, and hospitalization is commonly required. Transjugular intrahepatic portosystemic shunt placement is not an option in a substantial number of patients because of contraindications. The placement of a tunneled peritoneal drainage catheter has been shown to be effective in patients with malignant ascites. However, data in patients with nonmalignant refractory ascites are rare. PATIENTS AND METHODS: We followed 24 consecutive patients in whom tunneled peritoneal drainage catheters were placed in the Endoscopy Unit at Hannover Medical School between June 2013 and December 2014. RESULTS: Catheters were placed in 24 patients with refractory ascites in end-stage liver disease and with a contraindication to transjugular intrahepatic portosystemic shunt placement. Placement was technically successful in all patients. The dosage of diuretics could be reduced significantly. The number of paracentesis decreased from 2.2±1 to 0 per week, although the volume of daily ascites removal remained stable (2 l). Despite frequent drainage of ascites, kidney function, serum sodium, and serum albumin remained stable. Seven adverse events occurred in six (25%) patients. Five patients listed for liver transplantation underwent successful transplantation without a negative impact. CONCLUSION: The tunneled peritoneal drainage catheter placement is a viable and effective treatment alternative in patients with refractory ascites because of end-stage liver disease, reducing diuretic intake and the need for paracentesis. The procedure avoids hyponatremia, worsening kidney function, and albumin infusions without an increased risk of spontaneous bacterial peritonitis.

Functional MRI for characterization of renal perfusion impairment and edema formation due to acute kidney injury in different mouse strains.

PURPOSE: The purpose was to characterize acute kidney injury (AKI) in C57BL/6 (B6)- and 129/Sv (Sv)-mice by noninvasive measurement of renal perfusion and tissue edema using functional MRI. METHODS: Different severities of AKI were induced in B6- and Sv-mice by renal ischemia reperfusion injury (IRI). Unilateral clamping of the renal pedicle for 35 min (moderate AKI) or 45 min (severe AKI) was done. MRI (7-Tesla) was performed 1, 7 and 28 days after surgery using a flow alternating inversion recovery (FAIR) arterial spin labeling (ASL) sequence. Maps of perfusion and T1-relaxation time were calculated. Relative MRI-parameters of the IRI kidney compared to the contralateral not-clipped kidney were compared between AKI severities and between mouse strains using unpaired t-tests. In addition, fibrosis was assessed by Masson Trichrome and collagen IV staining. RESULTS: After moderate AKI relative perfusion impairment was significantly higher in B6- than in Sv-mice at d7 (55±7% vs. 82±8%, p<0.05) and d28 (76±7% vs. 102±3%, p<0.01). T1-values increased in the early phase after AKI in both mouse strains. T1-increase was more severe after prolonged ischemia times of 45 min compared to 35 min in both mouse strains, measured in the renal cortex and outer stripe of outer medulla. Kidney volume loss (compared to the contralateral kidney) occurred already after 7 days but proceeded markedly towards 4 weeks in severe AKI. Early renal perfusion impairment was predictive for later kidney volume loss. The progression to chronic kidney disease (CKD) in the severe AKI model was similar in both mouse strains as revealed by histology. CONCLUSION: Quantification of renal perfusion and tissue edema by functional MRI allows characterization of strain differences upon AKI. Renal perfusion impairment was stronger in B6- compared to Sv-animals following moderate AKI. Prolonged ischemia times were associated with more severe perfusion impairment and edema formation in the early phase and progression to CKD within 4 weeks of observation.

Visualization of Posttraumatic Splenosis on Chemokine Receptor CXCR4-Targeted PET/CT.

The C-X-C motif chemokine receptor 4 (CXCR4) is expressed by a variety of inflammatory and malignant cells. We report the case of a 54-year-old woman with recurrent urinary tract infection who underwent a Ga-pentixafor PET/CT for detection of occult infectious foci. As a secondary finding, multiple CXCR4 abdominal lesions could be seen, consistent with the diagnosis of long-known posttraumatic splenosis. It is important to be aware that CXCR4-directed imaging may identify splenic tissue based on the presence of inflammatory cells and that both benign and malignant cells may show CXCR4 expression to avoid misinterpretation.

68Ga-DOTA-TATE PET/CT for Molecular Imaging of Somatostatin Receptor Expression in Metastasizing Chordoma: Comparison With 18F-FDG.

Chordoma is a rare slow-growing neoplasm of neuroectodermal origin, which frequently recurs after removal and has the potential to metastasize. We present the case of a 53-year-old man with metastasizing chordoma who underwent F-FDG and Ga-DOTA-TATE PET/CT for restaging of disease and for evaluation of targeted radionuclide therapy potential. On both F-FDG and Ga-DOTA-TATE PET scans, increased tracer accumulation was observed in chordoma metastases. Besides the increased glucose metabolism in chordoma, this case highlights the potential of Ga-DOTA-TATE PET/CT for restaging of chordoma as well the option of targeted radionuclide therapy in this entity.