Functional evaluation of transplanted kidneys using arterial spin labeling MRI.

PURPOSE: To investigate non-contrast-enhanced arterial spin labeling (ASL) MRI for functional assessment of transplanted kidneys at 1.5 Tesla (T) and 3T. MATERIALS AND METHODS: This study was approved by the local ethics committee, and written informed consent was obtained from all participants. Ninety eight renal allograft recipients (mean age, 51.5 ± 14.6 years) were prospectively included in this study. ASL MRI was performed at 1.5T (n = 65) and 3T (n = 33) using a single-slice flow-sensitive alternating inversion recovery true-fast imaging with steady-state precession (FAIR True-FISP) sequence in the paracoronal plane. ASL perfusion was regional analyzed for the renal cortex on parameter maps. ASL was compared between patients with good or moderate allograft function (Group a; estimated glomerular filtration rate [eGFR] > 30 mL/min/1.73 m(2)) and patients with heavily impaired allograft function (Group b; eGFR ≤ 30 mL/min/1.73 m(2)) and correlated to renal function as determined by eGFR. RESULTS: ASL perfusion and eGFR were comparable at 1.5T (246.9 ± 66.8 mL/100 g/min and 41.9 ± 22.7 mL/min/1.73 m(2)) and 3T (236.5 ± 102.3 mL/100 g/min and 35.9 ± 22.9 mL/min/1.73 m(2)). ASL perfusion was significantly higher in group a (282.7 ± 60.8 mL/100 g/min) as compared to group b (178.2 ± 63.3 mL/100 g/min) (P < 0.0001). ASL perfusion values exhibited a significant correlation with renal function as determined by eGFR (r = 0.59; P < 0.0001). CONCLUSION: Cortical ASL perfusion values differ between patients with good or moderate allograft function and poor allograft function and correlate significantly with allograft function. Our results highlight the potential of ASL MRI for functional evaluation of renal allografts.

CT-guided biopsy of thoracic lesions with a novel wire-based needle guide device - initial experiences.

BACKGROUND: Biopsies guided by computed tomography (CT) play an important role in clinical practice. A short duration, minimal radiation dose and complication rate are of particular interest. Purpose To evaluate the potential of a novel self-manufactured wire-based needle guide device for CT-guided thoracic biopsies with respect to radiation dose, intervention time and complication rate. MATERIAL AND METHODS: Forty patients that underwent CT-guided biopsies of thoracic lesions were included in this study and assigned to two groups. Patients in group A (n = 20, mean age 69 ± 8.4 years) underwent biopsies with a novel wire-based needle guide device, while patients in group B (n = 20, mean age 68.4 ± 10.1 years) were biopsied without a needle guide device. The novel self-manufactured needle guide device consists of an iron/zinc wire modelled to a ring with a flexible arm and an eye at the end of the arm to stabilize the biopsy needle in the optimal position during intervention. Predefined parameters (radiation dose, number of acquired CT-slices, duration of intervention, complications) were compared between both groups. RESULTS: Mean radiation dose (CTDIvol 192 mGy versus 541 mGy; P ≤ 0.001) and the number of acquired slices during intervention (n = 49 ± 33 vs. n = 126 ± 78; P ≤ 0.001) were significantly lower in group A compared with group B. Intervention time in group A (13.1 min) was significantly lower than in group B (18.5 min, P < 0.01). A pneumothorax as peri-interventional complication was observed less frequent after device assisted biopsies (n = 4 vs. n = 8, n.s.). CONCLUSION: The novel wire-based needle guide device is a promising tool to facilitate CT-guided thoracic biopsies reducing radiation dose, intervention time, and related complications. Further studies are mandatory to confirm these initial results.

Assessment of early cartilage degeneration after slipped capital femoral epiphysis using T2 and T2* mapping.

BACKGROUND: T2 and T2* mapping are novel tools to assess cartilage quality. PURPOSE: To evaluate hip cartilage quality in the long-term follow-up of patients with slipped capital femoral epiphysis (SCFE) with T2 and T2* mapping. MATERIAL AND METHODS: Thirty-three patients (19 men, 14 women, mean age 24 ± 6.0 years, range 18-51 years) with a history of SCFE in 41 hips and 10 healthy controls (seven men, mean age 22 ± 4 years) were included. Follow-up period was 12 ± 6 (range 4-39 years) years. Coronal T2 and T2* mapping were performed on a 1.5 T scanner. T2 and T2* values of the hip articular cartilage were determined in the medial, central, and lateral portion of the hip within the weight bearing zone. Clinical symptoms including pain were assessed with the Harris hip score. Statistical analysis was performed using Mann-Whitney U test and Spearman rank sum test. RESULTS: In hips after SCFE T2 (central portion: 25.71 ms ± 4.84 ms vs. 29.71 ms ± 7.04 ms, p<0.05) and T2* (central portion: 20.76 ms ± 3.17 ms vs. 23.06 ms ± 2.68 ms, P<0.01) of cartilage were significantly lower, compared to controls. The differences were most apparent in the lateral portion of the hip articular cartilage. Abnormal cartilage T2 and T2* were not associated with hip pain or impaired hip function. SCFE was unilateral in 23 cases (70%). In the patients' unaffected hips without SCFE, areas of significantly reduced T2 (central portion: 26.07 ms ± 4.27 ms, P<0.05) and T2* (lateral portion: 23.23 ms ± 2.45 vs. 25.11 ms ± 3.01 ms, P<0.05) were noted. CONCLUSION: T2 and T2* mapping of the hip in patients after SCFE are significantly different from healthy controls and may offer additional information about cartilage quality.

Quantification of renal allograft perfusion using arterial spin labeling MRI: initial results.

OBJECTIVE: To quantify renal allograft perfusion in recipients with stable allograft function and acute decrease in allograft function using nonenhanced flow-sensitive alternating inversion recovery (FAIR)-TrueFISP arterial spin labeling (ASL) MR imaging. METHODS: Following approval of the local ethics committee, 20 renal allograft recipients were included in this study. ASL perfusion measurement and an anatomical T2-weighted single-shot fast spin-echo (HASTE) sequence were performed on a 1.5-T scanner (Magnetom Avanto, Siemens, Erlangen, Germany). T2-weighted MR urography was performed in patients with suspected ureteral obstruction. Patients were assigned to three groups: group a, 6 patients with stable allograft function over the previous 4 months; group b, 7 patients with good allograft function who underwent transplantation during the previous 3 weeks; group c, 7 allograft recipients with an acute deterioration of renal function. RESULTS: Mean cortical perfusion values were 304.8 +/- 34.4, 296.5 +/- 44.1, and 181.9 +/- 53.4 mg/100 ml/min for groups a, b and c, respectively. Reduction in cortical perfusion in group c was statistically significant. CONCLUSION: Our results indicate that ASL is a promising technique for nonenhanced quantification of cortical perfusion of renal allografts. Further studies are required to determine the clinical value of ASL for monitoring renal allograft recipients.

Correlation of biexponential diffusion parameters with arterial spin-labeling perfusion MRI: results in transplanted kidneys.

PURPOSE: The purpose of the present study was to explore the correlation between diffusion parameters assessed by biexponential analysis and the tissue perfusion measured by arterial spin labeling (ASL) imaging in renal allografts. MATERIAL AND METHODS: Seventeen recipients of renal allograft (11 men and 6 women; mean [SD] age, 53.6 [14.1] years) were included in this study. For diffusion-weighted imaging, a paracoronal echo-planar imaging sequence was acquired with 16 b values (range, b = 0-750 s/mm²) and 6 averages at 1.5 T. For the quantitative assessment of transplanted kidney perfusion, a flow-sensitive alternating inversion recovery true fast imaging with steady precession-ASL technique was applied. No respiratory gating was used. For quantitative analysis, region of interest measurements were performed on parameter maps. The Spearman correlation coefficients were calculated to determine the association between mean serum creatinine levels, estimated glomerular filtration rate, the apparent diffusion coefficient (ADC) of pure diffusion, the ADC of pseudodiffusion, the monoexponential ADC, the fraction of pseudodiffusion, and the tissue perfusion ASL values. RESULTS: In the renal cortex, the fraction of pseudodiffusion was 17.4% ± 4.0%, the apparent diffusion coefficient of pure diffusion was 160.7 ± 15.0 × 10⁻5 mm²/s, the monoexponential ADC was 193.2 ± 16.7 × 10⁻5 mm²/s, and the ADC of pseudodiffusion was 1421.0 ± 237.7 × 10⁻5 mm²/s. Mean cortical perfusion of renal allografts, as assessed with ASL imaging, was 247.2 ± 75.0 mL/100 g/min. There was a significant correlation between ASL perfusion and the fraction of pseudodiffusion (r = 0.68; P < 0.005) but not with the other diffusion coefficients. Both ASL perfusion and the fraction of pseudodiffusion exhibited a significant correlation with serum creatinine levels (r = 0.51 and r= 0.53, respectively; P < 0.05) and estimated glomerular filtration rate (r = 0.63 and r = 0.54, respectively; P < 0.05). CONCLUSIONS: This is the first study that shows a significant correlation between renal allograft perfusion, as assessed with ASL perfusion measurements, and the fraction of pseudodiffusion derived from biexponential diffusion-weighted imaging measurements.