Table 1.
Summary of techniques with the advantages and limitations
| Methods | Parameters | Agents | References | Advantages | Limitations |
|---|---|---|---|---|---|
| Perfusion CT/Dynamic CT | BV, PE, TTP, SLOPE, ΔH, TBR, AUC, MTT, and PSAP | Iodine Iomeprol Iopromide Iopamidol |
31, 32, 33, | Fast speed of image acquisition Easily repeatable Widespread availability Morphological evaluation and physiological evaluation can be made in single scan |
High ionizing radiation Lack of uniform standard |
| Spectral CT | IC | Iohexol | 34 | Provide more image information than conventional CT Provide material decomposed images with a single CT scan |
High demands of clinical systems Low resolution Spectral variations of the X-ray beam may result in artifacts |
| DCE-MRI/MRA | BV, VD, Ktrans, RSI, AUC, Vp, Ve, PS, peak, slope, iAUC60, and ΔSO2 | Gadolinium Gadodiamide Gadoterate meglumine Gadobutrol |
32, 42, 44–50, 52, 54–57 | No ionizing radiation Daily or weekly repeats Without the depth limitations of optical techniques Achieve the same spatial resolution and higher contrast-to-noise ratio with a shorter imaging time |
Cannot resolve vessels at the capillary level Lack of consensus Easily be affected by various methodological and technological issues Slow speed of image acquisition |
| BOLD-MRI | R2* value | – | 58 | Provide information of interstitial oxygen state Deoxyhemoglobin as a natural contrast agent No contrast agent |
Indirectly reflects rather than directly displaying vascular changes |
| ECT | BF, BV, HV, metabolism, and SUVmax |
18F-FMISO 18F-FDG [15O]H2O Arg-Gly-Asp |
60, 62, 68, 72 | Provide information about metabolism and function Display angiogenesis based on the expression and functional activity of proteins |
Need to improve the stability, target affinity, and specificity Tracers’ accumulation in tumors is slow, and tracers have short half-life of the isotopes and a considerable amount of radioactive metabolites |
| DCE-US | AUC, IPK, TPK, WIR, W OR, BV, σf, PI, MTT, VM, VT, PE, and RT | Microbubble | 78, 79, 82, 84–87, 90, 91, 93–95 | Easily repeatable without risk and with low cost Simultaneously display the morphology and function of blood vessels |
Influenced by intestine gas Unable to accurately monitor the BF of abdominal and pelvic foci |
| Plasma/serum | PlGF, VEGF, sVEGFR-1, Ang2, sTie2, MMP-10, bFGF, s VEGFR2, SDF1α, and collagen IV | – | 39, 44, 54, 56, 100 | More convenient Simultaneously predicts prognosis and recurrence Display changes in body metabolism and mechanisms |
Has not yet formed a unified standard Different agents or types of tumors may have effects on serum proteins |
Notes: σf, shape parameter; ΔH, density difference before and after tissue enhancement; iAUC60, initial area under the curve for 60 seconds after injection; IPK, peak intensity; Ktrans, volume transfer constant between extracellular extravascular space and blood plasma; PS, vascular permeability; R2* value, transverse relaxation rate of water; ΔSO2, oxygen saturation levels and tissue oxygen consumption before and after treatment; SLOPE, slope of the time–density curve; SUVmax, standardized uptake values; TPK, time-to-peak intensity; Ve, fractional extravascular volume; and Vp, fractional plasma volume.
Abbreviations: AUC, area under the contrast enhancement curve; BF, blood flow; BOLD-MRI, blood oxygenation level-dependent MRI; BV, blood volume; DCE-MRI, dynamic contrast-enhanced magnetic resonance imaging; DCE-US, dynamic contrast-enhanced ultrasonography; ECT, emission computed tomography; HV, hypoxic volume; IC, iodine concentration; MRA, magnetic resonance angiography; MTT, mean transit time; PE, peak enhancement; PI, peak intensity; PSAP, permeability surface-area product; ROI, region of interest; RSI, relative signal intensity; RT, retention time; soluble vascular endothelial growth factor receptor 2; TBR, tissue–blood ratio; TTP, time to peak enhancement; VD, vessel diameter; VM, vascular morphologic; VT, vascular tortuous; WIR, wash-in rate; WOR, wash-out rate.