Contrast-induced nephropathy (CIN) has long been observed in both experimental and clinical studies. However, recent observational studies have questioned the prevalence and severity of CIN following ...intravenous contrast exposure. Initial studies of acute kidney injury following intravenous contrast were limited by the absence of control groups or contained control groups that did not adjust for additional acute kidney injury risk factors, including prevalent chronic kidney disease, as well as accepted prophylactic strategies. More contemporary use of propensity score–adjusted models have attempted to minimize the risk for selection bias, although bias cannot be completely eliminated without a prospective randomized trial. Based on existing data, we recommend the following CIN risk classification: patients with estimated glomerular filtration rates (eGFRs) ≥ 45mL/min/1.73m2 are at negligible risk for CIN, while patients with eGFRs<30mL/min/1.73m2 are at high risk for CIN. Patients with eGFRs between 30 and 44mL/min/1.73m2 are at an intermediate risk for CIN unless diabetes mellitus is present, which would further increase the risk. In all patients at any increased risk for CIN, the risk for CIN needs to be balanced by the risk of not performing an intravenous contrast-enhanced study.
Efforts to develop novel cell-based therapies originated with the first bone marrow transplant on a leukemia patient in 1956. Preclinical and clinical examples of cell-based treatment strategies have ...shown promising results across many disciplines in medicine, with recent advances in immune cell therapies for cancer producing remarkable response rates, even in patients with multiple treatment failures. However, cell-based therapies suffer from inconsistent outcomes, motivating the search for tools that allow monitoring of cell delivery and behavior in vivo. Noninvasive cell imaging techniques, also known as cell tracking, have been developed to address this issue. These tools can allow real-time, quantitative, and long-term monitoring of transplanted cells in the recipient, providing insight on cell migration, distribution, viability, differentiation, and fate, all of which play crucial roles in treatment efficacy. Understanding these parameters allows the optimization of cell choice, delivery route, and dosage for therapy and advances cell-based therapy for specific clinical uses. To date, most cell tracking work has centered on imaging modalities such as MRI, radionuclide imaging, and optical imaging. However, X-ray computed tomography (CT) is an emerging method for cell tracking that has several strengths such as high spatial and temporal resolution, and excellent quantitative capabilities. The advantages of CT for cell tracking are enhanced by its wide availability and cost effectiveness, allowing CT to become one of the most popular clinical imaging modalities and a key asset in disease diagnosis. In this review, we will discuss recent advances in cell tracking methods using X-ray CT in various applications, in addition to predictions on how the field will progress.
Objective
Evaluation of image characteristics at ultra-low radiation dose levels of a first-generation dual-source photon-counting computed tomography (PCCT) compared to a dual-source dual-energy CT ...(DECT) scanner.
Methods
A multi-energy CT phantom was imaged with and without an extension ring on both scanners over a range of radiation dose levels (CTDI
vol
0.4–15.0 mGy). Scans were performed in different modes of acquisition for PCCT with 120 kVp and DECT with 70/Sn150 kVp and 100/Sn150 kVp. Various tissue inserts were used to characterize the precision and repeatability of Hounsfield units (HUs) on virtual mono-energetic images between 40 and 190 keV. Image noise was additionally investigated at an ultra-low radiation dose to illustrate PCCT’s ability to remove electronic background noise.
Results
Our results demonstrate the high precision of HU measurements for a wide range of inserts and radiation exposure levels with PCCT. We report high performance for both scanners across a wide range of radiation exposure levels, with PCCT outperforming at low exposures compared to DECT. PCCT scans at the lowest radiation exposures illustrate significant reduction in electronic background noise, with a mean percent reduction of 74% (
p
value ~ 10
−8
) compared to DECT 70/Sn150 kVp and 60% (
p
value ~ 10
−6
) compared to DECT 100/Sn150 kVp.
Conclusions
This paper reports the first experiences with a clinical dual-source PCCT. PCCT provides reliable HUs without disruption from electronic background noise for a wide range of dose values. Diagnostic benefits are not only for quantification at an ultra-low dose but also for imaging of obese patients.
Key Points
PCCT scanners provide precise and reliable Hounsfield units at ultra-low dose levels.
The influence of electronic background noise can be removed at ultra-low-dose acquisitions with PCCT.
Both spectral platforms have high performance along a wide range of radiation exposure levels, with PCCT outperforming at low radiation exposures.
Purpose
Phantoms are a basic tool for assessing and verifying performance in CT research and clinical practice. Patient‐based realistic lung phantoms accurately representing textures and densities ...are essential in developing and evaluating novel CT hardware and software. This study introduces PixelPrint, a 3D printing solution to create patient‐based lung phantoms with accurate attenuation profiles and textures.
Methods
PixelPrint, a software tool, was developed to convert patient digital imaging and communications in medicine (DICOM) images directly into FDM printer instructions (G‐code). Density was modeled as the ratio of filament to voxel volume to emulate attenuation profiles for each voxel, with the filament ratio controlled through continuous modification of the printing speed. A calibration phantom was designed to determine the mapping between filament line width and Hounsfield units (HU) within the range of human lungs. For evaluation of PixelPrint, a phantom based on a single human lung slice was manufactured and scanned with the same CT scanner and protocol used for the patient scan. Density and geometrical accuracy between phantom and patient CT data were evaluated for various anatomical features in the lung.
Results
For the calibration phantom, measured mean HU show a very high level of linear correlation with respect to the utilized filament line widths, (r > 0.999). Qualitatively, the CT image of the patient‐based phantom closely resembles the original CT image both in texture and contrast levels (from −800 to 0 HU), with clearly visible vascular and parenchymal structures. Regions of interest comparing attenuation illustrated differences below 15 HU. Manual size measurements performed by an experienced thoracic radiologist reveal a high degree of geometrical correlation of details between identical patient and phantom features, with differences smaller than the intrinsic spatial resolution of the scans.
Conclusion
The present study demonstrates the feasibility of 3D‐printed patient‐based lung phantoms with accurate organ geometry, image texture, and attenuation profiles. PixelPrint will enable applications in the research and development of CT technology, including further development in radiomics.
Computed tomography (CT) is one of the most commonly used clinical imaging modalities. There have recently been many reports of novel contrast agents for CT imaging. In particular, the development of ...gold nanoparticles (AuNP) as CT contrast agents is a topic of intense interest. AuNP have favorable characteristics for this application such as high payloads of contrast generating material, strong X-ray attenuation, excellent biocompatibility, tailorable surface chemistry, and tunable sizes and shapes. However, there have been conflicting reports on the role of AuNP size on their contrast generation for CT. We therefore sought to extensively investigate the AuNP size-CT contrast relationship. In order to do this, we synthesized AuNP with sizes ranging from 4 to 152 nm and capped them with 5 kDa m-PEG. The contrast generation of AuNP of different sizes was investigated with three clinical CT, a spectral photon counting CT (SPCCT) and two micro CT systems. X-ray attenuation was quantified as attenuation rate in Hounsfield units per unit concentration (HU/mM). No statistically significant difference in CT contrast generation was found among different AuNP sizes via phantom imaging with any of the systems tested. Furthermore, in vivo imaging was performed in mice to provide insight into the effect of AuNP size on animal biodistribution at CT dose levels, which has not previously been explored. Both in vivo imaging and ex vivo analysis with inductively coupled plasma optical emission spectroscopy (ICP-OES) indicated that AuNP that are 15 nm or smaller have long blood circulation times, while larger AuNP accumulated in the liver and spleen more rapidly. Therefore, while we observed no AuNP size effect on CT contrast generation, there is a significant effect of size on AuNP diagnostic utility.
Gadolinium-based contrast agents (GBCAs) improve the diagnostic capabilities of magnetic resonance imaging. Although initially believed to be without major adverse effects, GBCA use in patients with ...severe chronic kidney disease (CKD) was demonstrated to cause nephrogenic systemic fibrosis (NSF). Restrictive policies of GBCA use in CKD and selective use of GBCAs that bind free gadolinium more strongly have resulted in the virtual elimination of NSF cases. Contemporary studies of the use of GBCAs with high binding affinity for free gadolinium in severe CKD demonstrate an absence of NSF. Despite these observations and the limitations of contemporary studies, physicians remain concerned about GBCA use in severe CKD. Concerns of GBCA use in severe CKD are magnified by recent observations demonstrating gadolinium deposition in brain and a possible systemic syndrome attributed to GBCAs. Radiologic advances have resulted in several new imaging modalities that can be used in the severe CKD population and that do not require GBCA administration. In this article, we critically review GBCA use in patients with severe CKD and provide recommendations regarding GBCA use in this population.
Abstract Gold nanoparticles (AuNP) have been proposed for many applications in medicine. Although large AuNP (>5.5 nm) are desirable for their longer blood circulation and accumulation in diseased ...tissues, small AuNP (<5.5 nm) are required for excretion via the kidneys. We present a novel platform where small, excretable AuNP are encapsulated into biodegradable poly di(carboxylatophenoxy)phosphazene (PCPP) nanospheres. These larger nanoparticles (Au-PCPP) can perform their function as contrast agents, then subsequently break down into harmless byproducts and release the AuNP for swift excretion. Homogeneous Au-PCPP were synthesized using a microfluidic device. The size of the Au-PCPP can be controlled by the amount of polyethylene glycol-polylysine (PEG-PLL) block co-polymer in the formulation. Synthesis of Au-PCPP nanoparticles and encapsulation of AuNP in PCPP were evaluated using transmission electron microscopy and their biocompatibility and biodegradability confirmed in vitro . The Au-PCPP nanoparticles were found to produce strong computed tomography contrast. The UV–Vis absorption peak of Au-PCPP can be tuned into the near infrared region via inclusion of varying amounts of AuNP and controlling the nanoparticle size. In vitro and in vivo experiments demonstrated the potential of Au-PCPP as contrast agents for photoacoustic imaging. Therefore, Au-PCPP nanoparticles have high potency as contrast agents for two imaging modalities, as well as being biocompatible and biodegradable, and thus represent a platform with potential for translation into the clinic.
Patients with chest pain have a high hospital admission rate, but often no cardiac cause is found. In this trial, coronary CT angiography accurately identified patients who were free from coronary ...disease and could be safely discharged from the emergency department.
Patients who present to the emergency department with signs and symptoms consistent with a possible acute coronary syndrome pose a diagnostic dilemma.
1
–
6
Despite the introduction of clinical decision rules
6
–
15
and the improved sensitivity of cardiac markers,
15
–
17
most patients are admitted to the hospital so that an acute coronary syndrome can be ruled out, even though for most of these patients, the symptoms are ultimately found not to have a cardiac cause.
The absence of evidence of coronary disease on invasive coronary angiography is associated with a low risk of future cardiac events.
18
,
19
Coronary computed tomographic angiography . . .
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