Multimodality imaging of lower extremity peripheral arterial disease: current role and future directions

Radiation dose and image quality with new protocol in lower extremity computed tomography angiography

PURPOSE

To compare radiation dose and image quality of lower extremity computed tomography angiography (CTA) between cranio-caudal acquisition with single-source CT (SSCT) and flash caudo-cranial acquisition with dual-source CT (DSCT).

MATERIALS AND METHODS

In this prospective study, 60 patients were randomly assigned to Group A (control) or Group B (experimental) to undergo lower extremity CTA for peripheral obliterative arterial disease. Group A received protocol 1 (P1) with SSCT cranio-caudal acquisition. Group B received protocol (P2) with DSCT flash caudo-cranial acquisition. Intravascular attenuation (IVA), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and image noise were compared. Two radiologists assessed the image quality. Computed tomography volume dose index (CTDI_vol) and dose-length product (DLP) were also compared.

RESULTS

IVA with P2 was higher than with P1 (586.8 ± 140.3 vs. 496.1 ± 129.3 HU, p = 0.011), as was SNR (33.0 ± 11.3 vs. 27.4 ± 12.3; p = 0.042), CNR (30.1 ± 13.3 vs. 24.2 ± 10.3; p = 0.029) and image quality score of small arteries below the knee (3.8 ± 0.2 vs. 3.1 ± 0.2; p = 0.001). Radiation dose was significantly lower in P2 than in P1 with CTDI_vol reduction of 40.9% (1.3 ± 0.1 vs. 2.2 ± 0.3 mGy; p = 0.006) and DLP reduction of 42.8% (148.7 ± 21.9 vs 260.2 ± 59.1 mGy * cm; p = 0.018).

CONCLUSION

Lower extremity CTA with DSCT flash caudo-cranial acquisition allows lower radiation dose with higher IVA, SNR, CNR and better image quality for small arteries below the knee than SSCT cranio-caudal acquisition.

Non-contact dynamic diffuse optical tomography imaging system for evaluating lower extremity vasculature

A novel multi-view non-contact dynamic diffuse optical tomographic imaging system for the clinical evaluation of vasculature in the lower extremities is presented. The system design and implementation are described in detail, including methods for simultaneously obtaining and reconstructing diffusely reflected and transmitted light using a system of mirrors and a single CCD camera. The system and its performance using numeric simulations and optical phantoms. Measurements of a healthy foot in vivo demonstrates the potential of the system in assessing perfusion within the foot.

Pulse Oximetry as a Screening Test for Hemodynamically Significant Lower Extremity Peripheral Artery Disease in Adults with Type 2 Diabetes Mellitus

Objective

The main objective is to determine if digital pulse oximetry is an acceptable screening tool to detect hemodynamically significant lower extremity peripheral artery disease (PAD) in patients 50 years old and above with type 2 diabetes mellitus (T2DM) seen at the University of Santo Tomas Hospital (USTH).

Methodology

A total of 78 subjects (155 limbs) were included. Using duplex ultrasonography as the reference standard for the presence of hemodynamically significant lower extremity PAD, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were obtained for abnormal percent oxygen saturation (SpO₂) gradients and for ankle-brachial index (ABI).

Results

Of the 155 limbs, 38.7% had hemodynamically significant stenosis. Pulse oximetry had 76.7% sensitivity (95% CI, 65.2% to 88.1%), 85.3% specificity (95% CI, 78.0% to 92.6%), 76.7% PPV (95% CI, 66.5% to 84.4%) and 85.3% NPV (95% CI, 78.4% to 90.2%). ABI had 40.7% sensitivity (95% CI, 30.1% to 51.3%), 88.2% specificity (95% CI, 80.0% to 96.3%), 68.6% PPV (95% CI, 53.6% to 80.4%) and 70.1% NPV (95% CI, 65.1% to 74.5%). Combining both produces 88.1% sensitivity (95% CI, 78.5% to 97.8%), 74.2% specificity (95% CI, 65-83.4%), 68.4 PPV (95% CI, 60.3% to 75.6%) and 90.8% NPV (95% CI, 83.0% to 95.2%).

Conclusion

The results of this study suggest that pulse oximetry has a higher sensitivity than ABI as a screening tool for hemodynamically significant lower extremity PAD in T2DM patients 50 years old and above. Combining these two tests may be done to achieve a higher sensitivity.

Innovative Multi-Site Photoplethysmography Analysis for Quantifying Pulse Amplitude and Timing Variability Characteristics in Peripheral Arterial Disease

Photoplethysmography (PPG) is a simple-to-perform vascular optics measurement technique that can detect blood volume changes in the microvascular bed of tissue. Beat-to-beat analysis of the PPG waveform enables the study of the variability of pulse features, such as the amplitude and the pulse arrival time (PAT), and when quantified in the time and frequency domains, has considerable potential to shed light on perfusion changes associated with peripheral arterial disease (PAD). In this pilot study, innovative multi-site bilateral finger and toe PPG recordings from 43 healthy control subjects and 31 PAD subjects were compared (recordings each at least five minutes, collected in a warm temperature-controlled room). Beat-to-beat normalized amplitude variability and PAT variability were then quantified in the time-domain using two simple statistical measures and in the frequency-domain bilaterally using magnitude squared coherence (MSC). Significantly reduced normalized amplitude variability (healthy control 0.0384 (interquartile range 0.0217–0.0744) vs. PAD 0.0160 (0.0080–0.0338) (p < 0.0001)) and significantly increased PAT variability (healthy control 0.0063 (0.0052–0.0086) vs. PAD 0.0093 (0.0078–0.0144) (p < 0.0001)) was demonstrated for the toe site in PAD using the time-domain analysis. Frequency-domain analysis demonstrated significantly lower MSC values across a range of frequency bands for PAD patients. These changes suggest a loss of right-to-left body side coherence and cardiovascular control in PAD. This study has also demonstrated the feasibility of using these measurement and analysis methods in studies investigating multi-site PPG variability for a wide range of cardiac and vascular patient groups.

ImmunoPET of CD146 in a Murine Hindlimb Ischemia Model

Peripheral arterial disease (PAD) consists of a persistent obstruction of lower-extremity arteries further from the aortic bifurcation attributable to atherosclerosis. PAD is correlated with an elevated risk of morbidity and mortality as well as of deterioration of the quality of life with claudication and chronic leg ischemia being the most frequent complications. Therapeutic angiogenesis is a promising therapeutic strategy that aims to restore the blood flow to the ischemic limb. In this context, assessing the efficacy of pro-angiogenic treatment using a reliable noninvasive imaging technique would greatly benefit the implementation of this therapeutic approach. Herein, we describe the angiogenesis and perfusion recovery characteristics of a mouse model of PAD via in vivo positron emission tomography (PET) imaging of CD146 expression. For that, ischemia was generated by ligation and excision of the right femoral artery of Balb/C mice and confirmed through laser Doppler imaging. The angiogenic process, induced by ischemia, was noninvasively monitored and quantified through PET imaging of CD146 expression in the injured leg using a ⁶⁴Cu-labeled anti-CD146 monoclonal antibody, ⁶⁴Cu-NOTA-YY146, at post-operative days 3, 10, and 17. The CD146-specific character of ⁶⁴Cu-NOTA-YY146 was verified via a blocking study performed in another cohort at day 10 after surgery. Tracer uptake was correlated with in situ CD146 expression by histological analysis. PET scan results indicated that ⁶⁴Cu-NOTA-YY146 uptake in the injured leg was significantly higher, with the highest uptake with a value of 14.1 ± 2.0 %ID/g at post-operative day 3, compared to the normal contralateral hindlimb, at all time points (maximum uptake of 2.2 ± 0.2 %ID/g). The pre-injection of a blocking dose resulted in a significantly lower tracer uptake in the ischemic hindlimb on day 10 after surgery, confirming tracer specificity. CD146/CD31 immunofluorescent co-staining showed an excellent correlation between the high uptake of the tracer with in situ CD146 expression levels and a marked co-localization of CD146 and CD31 signals. In conclusion, persistent and CD146-specific tracer accumulation in the ischemic hindlimb was observed, confirming the feasibility of ⁶⁴Cu-NOTA-YY146 to be used as an imaging agent to monitor the progression of angiogenesis and recovery in future PAD research.

Prospects of Contrast-Enhanced Ultrasonography for the Diagnosis of Peripheral Arterial Disease: A Meta-analysis

OBJECTIVES

Contrast-enhanced ultrasonography (CEUS) is a modern diagnostic method that can also be used to study microperfusion. This study compared the time to peak intensity measured by CEUS in patients with peripheral arterial disease (PAD) and healthy control participants.

METHODS

After a comprehensive literature search in multiple electronic databases and study selection, a random-effect meta-analysis was performed to compare the time to peak intensity measured by CEUS in patients with PAD and healthy controls, which followed meta-regression analyses for identification of factors affecting the outcomes.

RESULTS

Fourteen studies (data for 322 patients with PAD and 314 healthy individuals) were used for the meta-analysis. The age of this sample of patients with PAD was 64.92 (95% confidence interval, 62.53, 67.31) years, and that of the healthy controls was 55.32 (51.67, 58.98) years. The times to peak intensity were 18.55 (15.62, 21.48) seconds in healthy controls, 33.40 (27.65, 39.15) seconds in patients with PAD, and 76.22 (36.23, 116.22) seconds in patients with PAD and diabetes mellitus. The difference between patients with PAD and healthy controls in the time to peak intensity was statistically significant (mean difference, 24.80 [10.16, 39.44] seconds; P < .00009). The ABI was not significantly associated with the time to peak intensity in patients with PAD. Age and sex were also not significantly associated with the time to peak intensity.

CONCLUSIONS

Contrast-enhanced ultrasonography is a valuable tool for the diagnosis of PAD based on its ability to differentiate the time to peak intensity between patients with PAD and healthy individuals, but little data are yet available to assess its diagnostic ability in clinical practice.

T2 , T1ρ and TRAFF4 detect early regenerative changes in mouse ischemic skeletal muscle

The identification of areas with regenerative potential in ischemic tissues would allow the targeting of treatments supporting tissue recovery. The regeneration process involves the activation of several cellular and molecular responses which could be detected using magnetic resonance imaging (MRI). However, to date, magnetic resonance (MR) relaxation parameters have received little attention in the diagnosis and follow-up of limb ischemia. The purpose of this study was to evaluate the feasibility of different MRI relaxation and diffusion tensor imaging parameters in the detection of areas showing early signs of regeneration in ischemic mouse skeletal muscles. T₂ and T_1ρ relaxation time constants, together with T_RAFFn , T₁ and diffusion tensor imaging, were evaluated to differentiate areas of regeneration in a mouse hind limb ischemia model before and 0, 1, 4, 7, 14 and 30 days after ischemia. All the measured relaxation times were longer in the areas of early regeneration compared with normal muscle tissue. The relaxation times increased after ischemia in the ischemic muscles, reaching a maximum at 4-7 days after occlusion, coinciding with the appearance of early signs of regeneration. Fractional anisotropy decreased significantly (p < 0.05) on days 1-4, whereas mean diffusivity, λ₁ and λ₂ decreased later, starting at day 7 after ischemia compared with the pre-operational time point. The percentages of areas with different tissue morphologies were determined based on histological analysis of the ischemic muscle cross-sections, and correlations between the percentages obtained and different relaxation times were calculated. The highest correlation between relaxation times and histology was achieved with T₂ , T_1ρ and T_RAFF4 (R² = 0.96, R² = 0.92 and R² = 0.84, respectively, p < 0.01)_. Early regenerative changes were visible using T₂ , T_1ρ and T_RAFF4 MR relaxation time constants in skeletal muscle after ischemia. These markers could potentially be used for the identification of targets for therapies supporting muscle regeneration after ischemic injury.

Effect of Patient Characteristics on Vessel Enhancement at Lower Extremity CT Angiography

Objective

To evaluate the effect of patient characteristics on popliteal aortic contrast enhancement at lower extremity CT angiography (LE-CTA) scanning.

Materials and Methods

Prior informed consent to participate was obtained from all 158 patients. All were examined using a routine protocol; the scanning parameters were tube voltage 100 kVp, tube current 100 mA to 770 mA (noise index 12), 0.5-second rotation, 1.25-mm detector row width, 0.516 beam pitch, and 41.2-mm table movement, and the contrast material was 85.0 mL. Cardiac output (CO) was measured with a portable electrical velocimeter within 5 minutes of starting the CT scan. To evaluate the effects of age, sex, body size, CO, and scan delay on the CT number of popliteal artery, the researchers used multivariate regression analysis.

Results

A significant positive correlation was seen between the CT number of the popliteal artery and the patient age (r = 0.39, p < 0.01). A significant inverse correlation was observed between the CT number of the popliteal artery and the height (r = −0.48), total body weight (r = −0.52), body mass index (r = −0.33), body surface area (BSA) (r = −0.56), lean body weight (r = −0.56), and CO (r = −0.35) (p < 0.001 for all). There was no significant correlation between the enhancement and the scan delay (r = 0.06, p = 0.47). The BSA, CO, and age had significant effects on the CT number (standardized regression: BSA −0.42, CO −0.22, age 0.15; p < 0.05, respectively).

Conclusion

The BSA, CO, and age are significantly correlated with the CT number of the popliteal artery on LE-CTA.

Lower Extremity Arterial Duplex, Toe-Brachial Index, and Computed Tomography Angiography Examinations in Peripheral Arterial Disease: A Case Presentation

Peripheral arterial disease (PAD) commonly results from progressive narrowing of arteries in the extremities because of atherosclerosis. More than 8 million people in the United States have PAD. The majority of individuals with PAD are seniors with one or more cardiovascular disease risk factors. Because patients with PAD may be asymptomatic, the true incidence of PAD may be underreported. Accurate and timely diagnosis of PAD is very important for optimal treatment.

CT Angiography of Peripheral Arterial Disease by 256-Slice Scanner: Accuracy, Advantages and Disadvantages Compared to Digital Subtraction Angiography

BACKGROUND

Peripheral arterial occlusive disease (PAOD) may cause disabling claudication or critical limb ischemia. Multidetector computed tomography (CT) technology has evolved to the level of 256-slice CT scanners which has significantly improved the spatial and temporal resolution of the images. This has provided the capability of chasing the contrast bolus at a fast speed enabling angiographic imaging of long segments of the body. These images can be reconstructed in various planes and various modes for detailed analysis of the peripheral vascular diseases which helps in making treatment decision.

PURPOSE

The aim of this retrospective study was to compare the CT angiograms (CTAs) of all cases of PAOD done by 256-slice CT scanner at a tertiary care vascular center and comparing these images with the digital subtraction angiograms (DSAs) of these patients.

MATERIALS AND METHODS

The retrospective study included 53 patients who underwent both CTA and DSA at our center over a period of 3 years from March 2013 to March 2016.

RESULTS

The CTA showed high sensitivity (93%) and specificity (92.7%) for overall assessment of degree of stenosis in a vascular segment in cases of aortic and lower limb occlusive disease. The assessment of lesions of infrapopliteal segment was comparatively inferior (sensitivity 91.6%, accuracy 73.3%, and positive predictive value 78.5%), more so in the presence of significant calcification. The advantages of CTA were its noninvasive nature, ability to image large area of body, almost no adverse effects to the patients, and better assessment of vessel wall disease. However, the CTA assessment of collaterals was inferior with a sensitivity of only 62.7% as compared to DSA. Overall, 256-slice CTA provides fast and accurate imaging of vascular tree which can restrict DSA only in few selected cases as a problem-solving tool where clinico-radiological mismatch is present.

Current Status and Outcomes of Iliac Artery Endovascular Intervention

Aortoiliac occlusive disease (AIOD) is widely prevalent and leads to significant limitations in patient quality of life. All patients with aortoiliac occlusive disease should be managed with approved medical therapies in addition to a supervised exercise program. Persistence of significant symptoms despite noninvasive therapy should prompt further management with endovascular revascularization. Although patients with the most complex cases of AIOD anatomy may ultimately require surgery, advances in endovascular techniques have made it possible to treat most of these patients with AIOD using an endovascular-first approach.

Assessment and validation of a novel angiographic scoring system for peripheral artery disease

BACKGROUND

Angiography is used routinely in the assessment of lower-limb arteries, but there are few well validated angiographic scoring systems. The aim of this study was to develop and validate a novel angiographic scoring system for peripheral artery disease.

METHODS

An angiographic scoring system (the ANGIO score) was developed and applied to a sample of patients from a single vascular surgical department who underwent CT angiography of the lower limbs. The reproducibility of the ANGIO score was compared with those of the Bollinger and Trans-Atlantic inter-Society Consensus (TASC) IIb systems in a series of randomly selected patients. Associations between the ANGIO score and lower-limb ischaemia, as measured by the ankle : brachial pressure index (ABPI), and outcome events (major lower-limb amputations and cardiovascular events - myocardial infarction, stroke and cardiovascular death) were assessed.

RESULTS

Some 256 patients undergoing CT angiography were included. The interobserver reproducibility of the ANGIO score was better than that of the other scoring systems examined (κ = 0·90, P = 0·002). There was a negative correlation between the ANGIO score and ABPI (ρ = -0·33, P = 0·008). A higher ANGIO score was associated with an increased risk of major lower-limb amputation (hazard ratio (HR) for highest versus lowest tertile 9·30, 95 per cent c.i. 1·95 to 44·38; P = 0·005) and cardiovascular events (HR 2·73, 1·31 to 5·70; P = 0·007) following adjustment for established risk factors.

CONCLUSION

The ANGIO score provided a reproducible and valid assessment of the severity of lower-limb ischaemia and risk of major amputation and cardiovascular events in these patients with peripheral artery disease.

Categorisation of tibial artery disease on computer tomography angiography according to the TASC II classification

Purpose Computer tomography angiography is used to assess peripheral arterial disease. Its preference over other imaging modalities is based upon its rapid acquisition and high spatial resolution, along with ease of access. TASC II have recently updated their vascular lesion classification to include infrapopliteal lesions, and our aim is to assess the reproducibility of TASC II on infrapopliteal disease when using computer tomography angiography. Methods A retrospective analysis of a series of consecutive computer tomography angiographies was performed by seven assessors (three consultant radiologists, two consultant vascular surgeons and two vascular specialty trainees). Each assessor was asked to classify the target vessel based on the TASC II classification. Statistical analysis was performed using Cohen's weighted kappa. Results Seven assessors analysed 48 target vessels in 25 patients (20 men), with a mean age of 72.9 years. Twenty posterior tibial, 27 anterior tibial and one peroneal artery were analysed. Poor agreement was demonstrated between the two vascular consultants, with a kappa of 0.094. Weak agreement was demonstrated among the radiologists, with a kappa of 0.547. The total group of assessors had a kappa of 0.176. Conclusion This study showed poor agreement between assessors when applying the TASC II classification to infrapopliteal lesions on computer tomography angiography. TASC II should not be used to classify lesions, for clinical or research purposes, with this image modality.

CT Angiography in Patients with Peripheral Arterial Disease: Effect of Small Focal Spot Imaging and Iterative Model Reconstruction on the Image Quality

RATIONALE AND OBJECTIVES

We investigated the effects of small focal spot (SFS) imaging and iterative model reconstruction (IMR) on the image quality of computed tomography angiographs (CTA) in patients with peripheral arterial disease.

MATERIALS AND METHODS

We divided 60 consecutive patients with suspected or confirmed peripheral artery disease into two equal groups. One group underwent large focal spot scanning under our standard CTA protocol with hybrid iterative reconstruction (iDose(4)) (protocol 1), and the other underwent scanning with the SFS protocol and IMR (protocol 2). Quantitative image quality parameters, ie, arterial computed tomography attenuation, image noise, and the contrast-to-noise ratio, were compared and the visual image quality (depiction of each vessel) was scored on a 5-point scale.

RESULTS

There was no significant difference in the arterial attenuation among all evaluated slice levels. The mean image noise was significantly lower under protocol 2 and the contrast-to-noise ratio was significantly higher at all slice levels. The visual scores assigned to the two protocols for the depiction of large vessels, such as the abdominal aorta and iliac artery, were comparable. However, the mean visual scores for small vessels in the lower extremities were significantly higher under protocol 2.

CONCLUSION

CTA with SFS and IMR yielded significantly better qualitative and quantitative image quality especially for small vessels.

Semiquantitative assessment of tibial artery calcification by computed tomography angiography and its ability to predict infrapopliteal angioplasty outcomes

OBJECTIVE

Tibial artery calcification (TAC) is associated with increased risk of amputation and mortality in peripheral artery disease. We sought to investigate whether the severity of TAC based on semiquantitative analysis of computed tomography angiography (CTA) can predict outcomes of endovascular therapy in patients with critical limb ischemia.

METHODS

We reviewed medical records of 124 patients who underwent lower extremity CTA before intervention. Based on CTA, TAC severity was categorized into three groups: minimal calcification (MC; n = 43), intermediate calcification (IC; n = 36), or extensive calcification (EC; n = 45). Immediate and late outcomes of infrapopliteal interventions were compared, and predictors of the outcomes were investigated.

RESULTS

The categorized severity of target TAC correlated with the log-transformed TAC score (r = 0.873; P < .001). The EC group was younger and had more diabetes and chronic kidney disease compared with the MC or IC group (all P < .001). The technical success was lower in the EC group (71.1%) than in the MC (95.3%) or IC (91.7%) group (P = .001). The survival free of unplanned amputations at 2 years was significantly lower in the EC group (58.9%) than in the MC (79.0%) or IC (95.3%) group (P < .001). Extensive TAC was an independent predictor of technical success (hazard ratio, 0.02; 95% confidence interval, 0.00-0.45; P = .014) and unplanned amputation (hazard ratio, 9.90; 95% confidence interval, 2.05-47.75; P = .004).

CONCLUSIONS

The categorized severity of TAC by semiquantitative analysis of CTA correlated with TAC score, and extensive TAC was associated with a lower technical success rate of angioplasty and an increased incidence of unplanned amputation.

Diagnostic performance and radiation dose of lower extremity CT angiography using a 128-slice dual source CT at 80 kVp and high pitch

BACKGROUND

Multi-detector computed tomography (MDCT) angiography is now used for the diagnosing patients with peripheral arterial disease. The dose of radiation is related to variable factors, such as tube current, tube voltage, and helical pitch.

PURPOSE

To assess the diagnostic performance and radiation dose of lower extremity CT angiography (CTA) using a 128-slice dual source CT at 80 kVp and high pitch in patients with critical limb ischemia (CLI).

MATERIAL AND METHODS

Twenty-eight patients (mean, 64.1 years; range, 39-80 years) with CLI were enrolled in this retrospective study and underwent CTA using a 128-slice dual source CT at 80 kVp and high pitch and subsequent intra-arterial digital subtraction angiography (DSA), which was used as a reference standard for assessing diagnostic performance.

RESULTS

For arterial segments with significant disease (>50% stenosis), overall sensitivity, specificity, and accuracy of lower extremity CTA were 94.8% (95% CI, 91.7-98.0%), 91.5% (95% CI, 87.7-95.2%), and 93.1% (95% CI, 90.6-95.6%), respectively, and its positive and negative predictive values were 91.0% (95% CI, 87.1-95.0%), and 95.1% (95% CI, 92.1-98.1%), respectively. Mean radiation dose delivered to lower extremities was 266.6 mGy.cm.

CONCLUSION

Lower extremity CTA using a 128-slice dual source CT at 80 kVp and high pitch was found to have good diagnostic performance for the assessment of patients with CLI using an extremely low radiation dose.

Re-assessing the enhanced permeability and retention effect in peripheral arterial disease using radiolabeled long circulating nanoparticles

As peripheral arterial disease (PAD) results in muscle ischemia and neovascularization, it has been claimed that nanoparticles can passively accumulate in ischemic tissues through the enhanced permeability and retention (EPR) effect. At this time, a quantitative evaluation of the passive targeting capabilities of nanoparticles has not been reported in PAD. Using a murine model of hindlimb ischemia, we quantitatively assessed the passive targeting capabilities of (64)Cu-labeled PEGylated reduced graphene oxide - iron oxide nanoparticles ((64)Cu-RGO-IONP-PEG) through the EPR effect using positron emission tomography (PET) imaging. Serial laser Doppler imaging was performed to monitor changes in blood perfusion upon surgical induction of ischemia. Nanoparticle accumulation was assessed at 3, 10, and 17 days post-surgery and found to be highest at 3 days post-surgery, with the ischemic hindlimb displaying an accumulation of 14.7 ± 0.5% injected dose per gram (%ID/g). Accumulation of (64)Cu-RGO-IONP-PEG was lowest at 17 days post-surgery, with the ischemic hindlimb displaying only 5.1 ± 0.5%ID/g. Furthermore, nanoparticle accumulation was confirmed by photoacoustic imaging (PA). The combination of PET and serial Doppler imaging showed that nanoparticle accumulation in the ischemic hindlimb negatively correlated with blood perfusion. Thus, we quantitatively confirmed that (64)Cu-RGO-IONP-PEG passively accumulated in ischemic tissue via the EPR effect, which is reduced as the perfusion normalizes. As (64)Cu-RGO-IONP-PEG displayed substantial accumulation in the ischemic tissue, this nanoparticle platform may function as a future theranostic agent, providing both imaging and therapeutic applications.

Intra-arterial Ultra-low-Dose CT Angiography of Lower Extremity in Diabetic Patients

PURPOSE

To image lower extremity arteries by CT angiography using a very low-dose intra-arterial contrast medium in patients with high risk of developing contrast-induced nephropathy (CIN).

MATERIALS AND METHODS

Three cases with long-standing diabetes mellitus and signs of lower extremity atherosclerotic disease were evaluated by CT angiography using 0.1 ml/kg of the body weight of contrast medium given via 10-cm-long 4F introducer by puncturing the CFA. Images were evaluated by an interventional radiologist and a cardiovascular surgeon. Density values of the lower extremity arteries were also calculated. Findings in two cases were compared with digital subtraction angiography images performed for percutaneous revascularization. Blood creatinine levels were followed for possible CIN.

RESULTS

Intra-arterial CT angiography images were considered diagnostic in all patients and optimal in one patient. No patient developed CIN after intra-arterial CT angiography, while one patient developed CIN after percutaneous intervention.

CONCLUSION

Intra-arterial CT angiography of lower extremity might be performed in selected patients with high risk of developing CIN. Our limited experience suggests that as low as of 0.1 ml/kg of the body weight of contrast medium may result in adequate diagnostic imaging.

Peripheral Arterial Disease in Patients with Type 2 Diabetes Mellitus

Peripheral arterial disease (PAD) in patients with type 2 diabetes mellitus (T2DM) exhibits broad clinical characteristics and various consequences and is known as one of the major macrovascular complications of T2DM. Atherosclerosis is recognized as the most direct and important cause of PAD, but acute or chronic limb ischemia may be the result of various risk factors. In light of the increasing number of patients who undergo peripheral vascular procedures, the number of subjects who are exposed to the risks for PAD and related complications is increasing. In this review, we will discuss the clinical and epidemiological characteristics of PAD, as well as the clinical significance of PAD in T2DM subjects.

Diagnostic confidence of run-off CT-angiography as the primary diagnostic imaging modality in patients presenting with acute or chronic peripheral arterial disease

Objectives

To investigate the reliability of CT-angiography of the lower extremities (run-off CTA) to derive a treatment decision in patients with acute and chronic peripheral artery disease (PAD).

Materials and Methods

314 patients referred for run-off CTA were includ-ed in this retrospective study. First, diagnostic confidence of run-off CTA to derive a treat-ment decision was assessed in an interdisciplinary vascular conference using a 2 point scale (sufficient or not sufficient diagnostic confidence) and compared with the image quality eval-uated by two readers in consensus in four different levels (abdominopelvic, thigh, calf, foot arteries). Second, reliability of treatment decision was verified in all patients undergoing re-vascularization therapy.

Results

Diagnostic confidence of run-off CTA to derive a treatment deci-sion was sufficient in all patients with acute and in 97% of patients (215/221) with chronic PAD, whereas the rate of run-off CTA with non-diagnostic image quality was considerably higher in the calf and foot level (acute vs. chronic; calf: 28% vs.17%; foot: 52% vs. 20%). Reliability of treatment decision was superior for patients with chronic (123/133 = 92%) than for patients with acute PAD (64/78 = 82%, P = 0.02).

Conclusion

Run-off CTA is a reliable imaging modality for primary diag-nostic work-up of patients with acute and chronic PAD.

Vascular imaging: the evolving role of the multidisciplinary team meeting in peripheral vascular disease

This article reviews the importance of preinterventional cross-sectional imaging in the evaluation of peripheral arterial disease, as well as discussing the pros and cons of each imaging modality. The importance of a multidisciplinary team approach is emphasized.

CT angiography after 20 years: a transformation in cardiovascular disease characterization continues to advance

Through a marriage of spiral computed tomography (CT) and graphical volumetric image processing, CT angiography was born 20 years ago. Fueled by a series of technical innovations in CT and image processing, over the next 5-15 years, CT angiography toppled conventional angiography, the undisputed diagnostic reference standard for vascular disease for the prior 70 years, as the preferred modality for the diagnosis and characterization of most cardiovascular abnormalities. This review recounts the evolution of CT angiography from its development and early challenges to a maturing modality that has provided unique insights into cardiovascular disease characterization and management. Selected clinical challenges, which include acute aortic syndromes, peripheral vascular disease, aortic stent-graft and transcatheter aortic valve assessment, and coronary artery disease, are presented as contrasting examples of how CT angiography is changing our approach to cardiovascular disease diagnosis and management. Finally, the recently introduced capabilities for multispectral imaging, tissue perfusion imaging, and radiation dose reduction through iterative reconstruction are explored with consideration toward the continued refinement and advancement of CT angiography.

Radiotracer imaging of peripheral vascular disease

Peripheral vascular disease (PVD) is an atherosclerotic disease affecting the lower extremities, resulting in skeletal muscle ischemia, intermittent claudication, and, in more severe stages of disease, limb amputation and death. The evaluation of therapy in this patient population can be challenging, as the standard clinical indices are insensitive to assessment of regional alterations in skeletal muscle physiology. Radiotracer imaging of the lower extremities with techniques such as PET and SPECT can provide a noninvasive quantitative technique for the evaluation of the pathophysiology associated with PVD and may complement clinical indices and other imaging approaches. This review discusses the progress in radiotracer-based evaluation of PVD and highlights recent advancements in molecular imaging with potential for clinical application.