Phase delay imaging

The data in Figure B11.1.1 were acquired with a frequency-domain FLIM instrument working in homodyne mode. In this mode, the modulation frequency of the intensifier (40 MHz) is identical to that of the excitation light (40 MHz). The phase and modulation are calculated from a series of images taken at different phase delays between the excitation light and the intensifier. 

Fig. 13.19. Abalone shell (a) AFM (b) UFM (c) W-UFM (d) AFM (e) HFM amplitude (f) HFM phase. All images 2(tm x 2//m the second row is of a different area. The ultrasonic frequency was 9.5 MHz the difference frequency for HFM was 2.7 kHz. In the HFM phase image the full greyscale corresponds to a phase delay of 10 ns. The arrows in the HFM images indicate features attributed to bifurcation of layers (sample courtesy of Mehmet Sarikaya).

In a retrospective study including 46 patients with locally advanced or metastatic breast cancer, Takamura et al. evaluated the significance of [ Tc]MIBI uptake in early and delayed images in predicting tumor response to chemotherapy with epirubicin and cyclophosphamide or docetaxel [87]. Before starting chemotherapy, the patients underwent a [ Tc]MIBI SPECT study. The parameters extracted from SPECT images were the tumor-to-nor-mal tissue ratios (T/N) of [ Tc]MIBI uptake at 10 min (early phase) and at 180 min (delayed phase) and the retention index (RI) was calculated as follows RI = (T/N(d))/(T/N(e)). After chemotherapy, tumor response was determined by clinical examination. 

Sulfur-colloid liver scintigraphy may show large filling defects in the hepatic parenchyma, with prominent tracer avidity at the site of the tumor within a few seconds of the appearance of the bolus in the abdominal aorta. This increased activity persists into the venous phase. Hepatoblastomas may demonstrate increased uptake on delayed imaging, but this is rare (Suchy 2003). 

Patients are injected with radioisotope and imaged after a suitable delay (usually 2-4 h). Single phase bone imaging is used to assess the skeleton by demonstrating the osteophyte activity which occurs in the interval between radiopharmaceutical administration and scan. 

Similarly, FNH lesions typically enhance following MnDPDP. On early phase imaging (start delay of 20 min) lesions may appear isointense or hyperintense to normal liver and are usually hyperintense to normal liver parenchyma on delayed imaging (start delay of 24 h) (King et al. 2002). Non-enhancing central scar or septa are frequently demonstrated. 

Fig. 13.5a-d. Small, overt hepatocellular carcinoma. The lesion, not visible in the baseline image (a), appears hyperattenuating in the arterial phase spiral CT image (b) and hypoattenuating in the portal venous (c) and delayed phase (d) images... 

Fig. 13.10a-d. Infiltrative type hepatocellular carcinoma. The lesion is depicted by baseline (a), arterial phase (b), portal venous phase (c) and delayed phase (d) images as an uneven area with irregular borders and inhomogeneous enhancement which strands into surrounding tissue... 

Fig. 20.2. Hepatocyte-specific contrast agents such as Gd-EOB-DTPA (Primovist, Schering, Germany) may enhance the efficacy of lesion detection. Immediately after the injection of the contrast agent perfusion phenomena known from classic Gd-chelates can be seen such as ring-like enhancement (arrowhead). Delayed imaging, during the uptake and hepatocellular storage phase, may reveal additional findings such as a further metastasis. [Note the contrast within the biliary ducts based on the biliary elimination of the contrast agent (arrowhead)]...

When an interferogram is formed between images acquired at different times, any change in range due to movement of the ground between the acquisitions will contribute to the interferometric phase each displacement of half the wavelength of the carrier signal away from the satellite will increase the phase delay by one more phase cycle (Fig. 3) ... 

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