Perfusion scanning

About: Perfusion scanning is a research topic. Over the lifetime, 9496 publications have been published within this topic receiving 223860 citations. The topic is also known as: perfusion imaging.

Perfusion CT allows prediction of therapy response in non-small cell lung cancer treated with conventional and anti-angiogenic chemotherapy

Abstract: To determine whether CT can depict early perfusion changes in lung cancer treated by anti-angiogenic drugs, allowing prediction of response Patients with non-small cell lung cancer, treated by conventional chemotherapy with (Group 1; n = 17) or without (Group 2; n = 23) anti-vascular endothelial growth factor (anti-VEGF) drug (bevacizumab) underwent CT perfusion before (TIME 0) and after 1 (TIME 1), 3 (TIME 2) and 6 (TIME 3) cycles of chemotherapy The CT parameters evaluated included: (1) total tumour vascular volume (TVV) and total tumour extravascular flow (TEF); (2) RECIST (Response Evaluation Criteria in Solid Tumours) measurements Tumour response was also assessed on the basis of the clinicians’ overall evaluation In Group 1, significant reduction in perfusion was identified between baseline and: (1) TIME 1 (TVV, P = 00395; TEF, P = 0015); (2) TIME 2 (TVV, P = 00043; TEF, P < 00001); (3) TIME 3 (TVV, P = 00034; TEF, P = 00005) without any significant change in Group 2 In Group 1: (1) the reduction in TVV at TIME 1 was significantly higher in responders versus non-responders at TIME 2 according to RECIST (P = 00128) and overall clinicians’ evaluation (P = 00079); (2) all responders at TIME 2 had a concurrent decrease in TVV and TEF at TIME 1 Perfusion CT demonstrates early changes in lung cancer vascularity under anti-angiogenic chemotherapy that may help predict therapeutic response • Perfusion CT has the potential of providing in vivo information about tumour vasculature • CT depicts early and specific perfusion changes in NSCLC under anti-angiogenic drugs • Specific therapeutic effects of anti-angiogenic drugs can be detected before tumour shrinkage • Early perfusion changes can help predict therapeutic response to anti-angiogenic treatment • Perfusion CT could be a non-invasive tool to monitor anti-angiogenic treatment

Susceptibility Contrast and Arterial Spin Labeled Perfusion MRI in Cerebrovascular Disease

Abstract: Purpose. To directly compare dynamic susceptibility contrast (DSC) and continuous arterial spin labeled (CASL) magnetic resonance (MR) perfusion techniques in patients with known cerebrovascular disease, with the goals of identifying possible pitfalls in interpretation and determining potential for a complementary role in this setting. Methods. DSC and CASL MR perfusion studies were performed and compared in 11 patients with acute and/or chronic cerebrovascular disease. Using an automated segmentation technique, Pearson correlation coefficients were generated for CASL perfusion measurements compared to DSC perfusion maps (time-to-peak [TTP], relative cerebral blood volume [rCBV], cerebral blood flow [rCBF], and mean transit time [MTT]) by hemisphere and vascular territory. Results. TTP maps obtained using DSC perfusion MR correlated best both subjectively and objectively with CASL perfusion MRmeasurements when all patients studied were considered. If patients with a major transit delay were excluded, DSC rCBF correlated best with CASL CBF measurements. Conclusion. There may be a complementary role for CASL and DSC perfusion MR methods in cerebrovascular disease, especially in the setting of a marked transit delay.

Noninvasive methods of measuring bone blood perfusion

Abstract: Measurement of bone blood flow and perfusion characteristics in a noninvasive and serial manner would be advantageous in assessing revascularization after trauma and the possible risk of avascular necrosis. Many disease states, including osteoporosis, osteoarthritis, and bone neoplasms, result in disturbed bone perfusion. A causal link between bone perfusion and remodeling has shown its importance in sustained healing and regrowth following injury. Measurement of perfusion and permeability within the bone was performed with small and macromolecular contrast media, using dynamic contrast-enhanced magnetic resonance imaging in models of osteoarthritis and the femoral head. Bone blood flow and remodeling was estimated using (18)F-Fluoride positron emission tomography in fracture healing and osteoarthritis. Multimodality assessment of bone blood flow, permeability, and remodeling by using noninvasive imaging techniques may provide information essential in monitoring subsequent rates of healing and response to treatment as well as identifying candidates for additional therapeutic or surgical interventions.

Perfusion mapping with multiecho multishot parallel imaging EPI

Abstract: Dynamic susceptibility contrast (DSC)-based perfusion-weighted imaging (PWI) can visualize cerebrovascular hemodynamics. Therefore, it may be an important asset to determine “tissue-at-risk” in acute stroke patients. When used with diffusion-weighted imaging (DWI), it can help to triage patients who would potentially benefit from IV tPA treatment or mechanical thrombectomy (1). In DSC imaging, an exogenous paramagnetic tracer (e.g., Gd-DTPA or Dy-DTPA) is rapidly injected into the venous system and its passage is tracked through concentration-related T2* changes in the cerebral vascular bed (2–4). The arterial input concentration curve, as measured in a large cranial vessel, defines the arterial input function (AIF) (5), which is necessary to define the arrival and non-ideal shape of the impulse bolus injection as it reaches the imaging volume. The undesired temporal smearing of the concentration curve is undone via deconvolving the AIF from the signal course. This leaves the tissue residue function, which can be used to infer important information about the hemodynamic state of the tissue, such as the cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT). In order to sufficiently track the first-pass contrast concentration changes, which typically occur over a time span of approximately 10 s, rapid time-series imaging is required. This has made single-shot echo-planar imaging (ssEPI) (6) the method of choice for most DSC perfusion imaging. However, the use of ssEPI suffers from several well-known problems, some of which are exacerbated in DSC imaging. The T2* decay of the signal during the EPI readout widens the sampling’s point-spread function (PSF), blurring the output images and effectively limiting resolution (7,8). Further, due to the T2* decay, the signal exists for only a short period of time, which places an absolute upper limit on the possible resolution. The introduction of the tracer greatly decreases T2*, generating significant vessel blooming during the bolus passage due to the larger susceptibility gradients. This resolution decay is most notable cortically, as a result of the venous drainage of the agent, and near the major cranial arteries, leading to an apparent widening of vessels. EPI suffers from well-described geometric image distortions due to the low sampling bandwidth in the phase-encoding direction. Aside from global distortions, local areas of magnetic field susceptibility gradients (e.g., near the sinuses and the auditory canals), which are most egregious at air/tissue interfaces, suffer from image voids, with signal energy “piled-up” nearby. For DSC PWI this is highly problematic since the signal from the carotid siphon or the inferior cerebral arteries in the sella region, such as the internal carotid artery (ICA) and middle cerebral artery (MCA), are commonly used to define the AIF. These areas are often markedly distorted due to the strong susceptibility gradients. Due to the relatively long TEs needed for optimal T2* contrast in brain parenchyma, the contrast material in the arteries during bolus passage can so greatly reduce T2* that the contribution from the additive, rectified noise floor is comparable to the Rician-distributed MR magnitude signal. This leads to an underestimation of the tracer concentration curves (9). During bolus passage, the difference in susceptibility between the tissue and the paramagnetic material in the large arterial vessels causes significant local resonance frequency shifts. Combined with EPI’s low pixel bandwidth in the phase-encoding direction, significant shifts of the vessel can be observed, causing degradation of the AIF curve shape. These image-quality issues associated with EPI can preclude accurate determination of the AIF, affecting the veracity of the measured CBV, MTT, and CBF. In this work an interleaved EPI acquisition with parallel imaging (PI) reconstruction is used to overcome both the image-quality and contrast-mapping drawbacks found in ssEPI. Through PI, the temporal resolution of the interleaved EPI acquisitions can be accelerated above that of ssEPI, with the added benefit of acquiring multiple echoes of each slice in each volume. Since the reduced readout lengths of PI-enhanced EPI scans allow multiple echoes to be acquired without a penalty in time resolution, unbiased R2* mapping is possible. This avoids incorrect estimation of tracer concentration due to signal saturation or T1-shortening effects. It can be anticipated that rapid volumetric EPI for DSC can be performed using this pseudo-ssEPI acquisition, with the effective T2* blur and susceptibility distortions being reduced to the magnitude of a multiple-interleaf EPI sequence. Improved image quality, combined with the additional echo information, results in improved DSC mapping of the hemodynamic parameters.