Perfusion in Peripheral Musculoskeletal Structures From Dynamic Volumetric Computed Tomography Using an En Bloc Approach:

Intraprocedural, Intra-Arterial CT Foot Perfusion Examination for Assessment of Endovascular Therapy in Patients With Critical Limb Ischemia: A Prospective Pilot Study

BACKGROUND

Current techniques to evaluate computed tomography (CT) foot perfusion in patients with critical limb ischemia use high contrast doses and cannot be used during endovascular procedures. CT perfusion of the foot with intra-arterial contrast injection during endovascular treatment in a hybrid angiography CT suite might solve these problems.

PURPOSE

The main objective of this study was to evaluate whether intra-arterial CT foot perfusion using a hybrid CT angiosystem is feasible during endovascular treatment for critical limb ischemia.

MATERIAL AND METHODS

This prospective pilot study investigated intraprocedural, intra-arterial CT perfusion of the foot using a hybrid CT angiosystem in 12 patients before and after endovascular treatment for critical limb ischemia. Time to peak (TTP) and arterial blood flow were measured before and after treatment and compared using a paired t test.

RESULTS

All 24 CT perfusion maps could be calculated adequately. The contrast volume used for one perfusion CT scan was 4.8 ml. The mean TTP before treatment was 12.8 seconds (standard deviation [SD] 2.8) and the mean TTP posttreatment was 8.4 seconds (SD 1.7), this difference being statistically significant (p=.001). Tendency toward increased blood flow after treatment, 340 ml/min/100 ml (SD 174) vs 514 ml/min/100 ml (SD 366) was noticed (p=.104). The mean effective radiation dose was 0.145 mSv per scan.

CONCLUSION

Computed tomography perfusion of the foot with low contrast dose intra-arterial contrast injection during endovascular treatment in a hybrid angiography CT suite is a feasible technique.Clinical ImpactIntra-arterial CT foot perfusion using a hybrid CT-angiography system is a feasible new technique during endovascular therapy for critical limb ischemia to assess the results of the treament. Future research is necessary in defining endpoints of endovascular treatment and establishing its role in limb salvage prognostication.

Dynamic Volume Perfusion CT of the Foot in Critical Limb Ischemia: Response to Percutaneous Revascularization

OBJECTIVE. The purpose of this study was to assess the reproducibility and validity of quantitative perfusion parameters derived from dynamic volume perfusion CT in patients with critical limb ischemia (CLI) and to evaluate perfusion parameter changes before and after endovascular revascularization. SUBJECTS AND METHODS. Patients with CLI referred for unilateral extremity endovascular arterial recanalization were enrolled in this study. CT examinations obtained 1-3 days before the procedure and then within 1 week after the treatment were evaluated at two reading sessions. Blood flow (BF), blood volume (BV), and time to peak (TTP) were measured on color-coded maps and compared statistically. Intraobserver agreement was assessed using intraclass correlation coefficient (ICC) and Bland-Altman analysis. RESULTS. Endovascular treatment was technically successful for all 16 patients. The posttreatment BF and BV showed a statistically significant increase in both dermal and muscle areas (p < 0.05). The posttreatment TTP shortened at a statistically significant level (p < 0.05). In the 3-month clinical follow-up period, the limb salvage rate was 81% and the percentage change in BF and BV of patients with poor response to treatment had no statistically significant increase after treatment, consistent with the clinical assessment. The percentage change in BF and BV correlated well with the improvement of the clinical condition (r = 0.673-0.901). ICC values showed excellent agreement in the range of 0.95-0.98. CONCLUSION. As a reproducible method, dynamic volume perfusion CT of the foot may enable quantitative evaluation of the perfusion of soft tissues and also provide a novel approach to assessing response to endovascular recanalization in CLI.

CT-perfusion in peripheral arterial disease - Correlation with angiographic and hemodynamic parameters

Objective

The purpose of this study was the assessment of volumetric CT-perfusion (CTP) of the lower leg musculature in patients with symptomatic peripheral arterial disease (PAD) of the lower extremities, comparing it with established angiographic and hemodynamic parameters.

Materials and methods

Thirty-five consecutive patients with symptomatic PAD of the lower extremities requiring interventional revascularization were assessed prospectively. All patients underwent a CTP scan of the lower leg, and hemodynamic and angiographic assessment. Hemodynamic parameters, specifically ankle-brachial pressure index (ABI), ankle blood pressure (ABP), peak systolic velocity (PSV), and segmental pulse oscillography (SPO) level, were determined. Lesion length and degree of collateralization were assessed by interventional angiography. CTP parameters were calculated with a perfusion software, acting on a no outflow assumption. A sequential two-compartment model was used. Differences in CTP parameters and correlations between CTP, hemodynamic and angiographic parameters were assessed with non-parametric tests.

Results

The cohort consisted of 27 subjects with an occlusion, and eight with a high-grade stenosis. The mean blood flow (BF) was 7.71 ± 2.96 ml/100ml*min^-1, mean blood volume (BV) 0.71 ± 0.33 ml/100ml, and mean mean transit time (MTT) 7.22 ± 2.66 s. BF and BV were higher in subjects with longer lesions, and BV was higher in subjects with lower ABI. Significant correlations were found between lesion length and BV (r = 0.65) and BF (r = 0.52). Significant inverse correlations were found between BV and ABI and between BV and ABP (r = -0.56, for both correlations).

Conclusions

In our study, we have shown the feasibility of CTP for the assessment of PAD. In the future, this quantitative method might serve as a non-invasive method, possibly complementing the diagnostic workup of patients with peripheral arterial disease.

Quantitative Assessment of Foot Blood Flow by Using Dynamic Volume Perfusion CT Technique: A Feasibility Study

PURPOSE

To demonstrate the feasibility of foot blood flow measurement by using dynamic volume perfusion computed tomographic (CT) technique with the upslope method in an animal experiment and a human study.

MATERIALS AND METHODS

The human study was approved by the institutional review board, and written informed consent was obtained from all patients. The animal study was approved by the research animal care and use committee. A perfusion CT experiment was first performed by using rabbits. A color-coded perfusion map was reconstructed by using in-house perfusion analysis software based on the upslope method, and the measured blood flow on the map was compared with the reference standard microsphere method by using correlation analysis. A total of 17 perfusion CT sessions were then performed (a) once in five human patients and (b) twice (before and after endovascular revascularization) in six human patients. Perfusion maps of blood flow were reconstructed and analyzed. The Wilcoxon signed rank test was used to prove significant differences in blood flow before and after treatment.

RESULTS

The animal experiment demonstrated a strong correlation (R(2) = 0.965) in blood flow between perfusion CT and the microsphere method. Perfusion maps were obtained successfully in 16 human clinical sessions (94%) with the use of 32 mL of contrast medium and an effective radiation dose of 0.31 mSv (k factor for the ankle, 0.0002). The plantar dermis showed the highest blood flow among all anatomic structures of the foot, including muscle, subcutaneous tissue, tendon, and bone. After a successful revascularization procedure, the blood flow of the plantar dermis increased by 153% (P = .031). The interpretations of the color-coded perfusion map correlated well with the clinical and angiographic findings.

CONCLUSION

Perfusion CT could be used to measure foot blood flow in both animals and humans. It can be a useful modality for the diagnosis of peripheral arterial disease by providing quantitative information on foot perfusion status.

Perfusion-based assessment of disease activity in untreated and treated patients with aortitis and chronic periaortitis: correlation with CT morphological, clinical and serological data

OBJECTIVE

To evaluate the role of perfusion-based assessment of inflammatory activity in patients with treated and untreated aortitis and chronic periaortitis as compared with clinical and serological markers.

METHODS

35 patients (20 females; median age 66 years) with (peri) aortitis were retrospectively evaluated. All patients had clinical symptoms prompting at the time of imaging. All patients first underwent whole-body contrast-enhanced CT and subsequently segmental volume perfusion CT for assessment of the degree of vascularization of (peri) aortitis as a surrogate marker for inflammatory activity. Blood flow, blood volume, volume transfer constant (k-trans), time to peak and mean transit time were determined. The thickness of the increased connective tissue formation was measured. Perfusion data were correlated with clinical symptoms and acute-phase inflammatory parameters such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and leukocyte number.

RESULTS

21 of 35 patients were untreated and 14 of 35 had previous/ongoing immunosuppression. The interobserver agreement was good (κ = 0.78) for all perfusion parameters. Average values of perfusion parameters were higher in untreated patients but remained abnormally elevated in treated patients as well. Perfusion data and ESR and CRP correlated well both in aortitis (p < 0.05) and in periaortitis (p < 0.05). In periaortitis, perfusion parameters agreed well with ESR and CRP values (p < 0.05) only in untreated patients.

CONCLUSION

Perfusion CT parameters in untreated aortitis and chronic periaortitis correlate well with serological markers with respect to disease activity assessment. However, in treated periaortitis, correlations were weak, suggesting an increased role for (perfusion-based) imaging.

ADVANCES IN KNOWLEDGE

Volume perfusion CT may be used for diagnosis of aortitis/periaortitis.

An en bloc approach to CT perfusion for the evaluation of limb ischemia

We examine volumetric CT perfusion in soft tissues of the entire foot with an en bloc technique to provide a meaningful measure of differentiation between mild and major vascular impairment. With Institutional Review Board approval, 22 healthy male subjects between the ages of 21 and 50 (mean 37) were enrolled. Volumetric computed tomography using an en bloc technique was conducted on 14 subjects for validation while unilateral vascular obstruction was simulated in the calves of the remaining 8 subjects. Perfusion estimates were made using in-house software and differences in perfusion estimates between feet were evaluated with Student's t-test at 95% confidence. Subjects with simulated major vascular obstruction (calf blood pressure cuff inflated to 200 mmHg) showed significantly higher ratios of perfusion estimates between the unobstructed and obstructed foot compared to subjects with simulated mild vascular obstruction (cuff inflated to 120 mmHg), mean 4.6, SD 2.6 vs. mean 1.3, SD 0.2; P = 0.05. CT perfusion using an en bloc technique shows promise for the future evaluation of patients with critical limb ischemia and particularly for re-characterization post medical, surgical or endovascular intervention.

Reduced perfusion in pulmonary infiltrates of high-risk hematologic patients is a possible discriminator of pulmonary angioinvasive mycosis: a pilot volume perfusion computed tomography (VPCT) study

RATIONALE AND OBJECTIVES

The aim of this study was to assess perfusion parameters in atypical pneumonia of heavily immunocompromised hematologic patients suspected of having invasive mycosis using volume perfusion computed tomography and establish their diagnostic role.

MATERIALS AND METHODS

Volume perfusion computed tomographic data from 21 consecutive immunocompromised patients presenting with atypical parenchymal opacity of consolidation were analyzed with respect to the degree of perfusion of their pneumonias. All patients presented with clinical and laboratory signs of infection. Seventeen patients (10 men, seven women; mean age, 57 years; age range, 19-76 years) were found with proven (n = 9), probable (n = 2), or possible (n = 6) angioinvasive mycosis. One patient was diagnosed with bronchoinvasive aspergillosis. Four patients (all men; mean age, 71 years; age range, 67-79 years) were diagnosed with bacterial pneumonia. Volume perfusion computed tomography of the involved pulmonary areas was performed at 80 kV and 60 mAs, with 26 measurement points distributed over 65.9 seconds. Fifty milliliters of contrast material was injected at a rate of 5 mL/s, followed by a 50-mL saline chaser. Entire coverage of the pneumonic parenchymal consolidation was obtained in all patients, with the generation of parametric maps of blood flow (BF) using the maximal slope model and blood volume (BV) using Patlak analysis. The results of perfusion measurements were then analyzed and evaluated for all patients.

RESULTS

Patients with proven, probable, or possible angioinvasive pulmonary fungal infection revealed very low levels of perfusion of their parenchymal consolidations, with BFs ranging from 0.01 to 23.86 mL/100 mL tissue/min and BVs ranging from 0.88 to 10.67 mL/100 mL tissue, lower than those of the adjacent thoracic musculature and of bacterial pneumonias. Bacterial pneumonias showed all increased perfusion parameters, with BFs ranging from 30.49 to 41.65 mL/100 mL tissue/min and BVs ranging from 10.07 to 49.90 mL/100 mL tissue. The cutoff BF value for differentiation was 23.89 mL/100 mL tissue/min, and the cutoff BV value was 9.6 mL/100 mL tissue.

CONCLUSIONS

Patients with angioinvasive pulmonary mycosis showed lower perfusion parameters on volume perfusion computed tomography compared to those experiencing bacterial pneumonia.