PMID- 34122123
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20210615
IS  - 1664-042X (Print)
IS  - 1664-042X (Electronic)
IS  - 1664-042X (Linking)
VI  - 12
DP  - 2021
TI  - Transit Time Measurement in Indicator Dilution Curves: Overcoming the Missing 
      Ground Truth and Quantifying the Error.
PG  - 588120
LID - 10.3389/fphys.2021.588120 [doi]
LID - 588120
AB  - The vascular function of a vessel can be qualitatively and intraoperatively 
      checked by recording the blood dynamics inside the vessel via fluorescence 
      angiography (FA). Although FA is the state of the art in proving the existence of 
      blood flow during interventions such as bypass surgery, it still lacks a 
      quantitative blood flow measurement that could decrease the recurrence rate and 
      postsurgical mortality. Previous approaches show that the measured flow has a 
      significant deviation compared to the gold standard reference (ultrasonic flow 
      meter). In order to systematically address the possible sources of error, we 
      investigated the error in transit time measurement of an indicator. Obtaining in 
      vivo indicator dilution curves with a known ground truth is complex and often not 
      possible. Further, the error in transit time measurement should be quantified and 
      reduced. To tackle both issues, we first computed many diverse indicator dilution 
      curves using an in silico simulation of the indicator's flow. Second, we 
      post-processed these curves to mimic measured signals. Finally, we fitted 
      mathematical models (parabola, gamma variate, local density random walk, and 
      mono-exponential model) to re-continualize the obtained discrete indicator 
      dilution curves and calculate the time delay of two analytical functions. This 
      re-continualization showed an increase in the temporal accuracy up to a 
      sub-sample accuracy. Thereby, the Local Density Random Walk (LDRW) model 
      performed best using the cross-correlation of the first derivative of both 
      indicator curves with a cutting of the data at 40% of the peak intensity. The 
      error in frames depends on the noise level and is for a signal-to-noise ratio 
      (SNR) of 20 dB and a sampling rate of f (s) = 60 Hz at fs-1 . 0.25(+/-0.18) , so 
      this error is smaller than the distance between two consecutive samples. The 
      accurate determination of the transit time and the quantification of the error 
      allow the calculation of the error propagation onto the flow measurement. Both 
      can assist surgeons as an intraoperative quality check and thereby reduce the 
      recurrence rate and post-surgical mortality.
CI  - Copyright (c) 2021 Naber, Reiss and Nahm.
FAU - Naber, Ady
AU  - Naber A
AD  - Institute of Biomedical Engineering, Karlsruhe Institute of Technology, 
      Karlsruhe, Germany.
FAU - Reiss, Michael
AU  - Reiss M
AD  - Institute of Biomedical Engineering, Karlsruhe Institute of Technology, 
      Karlsruhe, Germany.
FAU - Nahm, Werner
AU  - Nahm W
AD  - Institute of Biomedical Engineering, Karlsruhe Institute of Technology, 
      Karlsruhe, Germany.
LA  - eng
PT  - Journal Article
DEP - 20210528
PL  - Switzerland
TA  - Front Physiol
JT  - Frontiers in physiology
JID - 101549006
PMC - PMC8194354
OTO - NOTNLM
OT  - blood flow velocity
OT  - fluorescence angiography
OT  - indicator dilution curve
OT  - mathematical fits
OT  - sub-frame rate accuracy
OT  - transit time
COIS- The authors declare that the research was conducted in the absence of any 
      commercial or financial relationships that could be construed as a potential 
      conflict of interest.
EDAT- 2021/06/15 06:00
MHDA- 2021/06/15 06:01
PMCR- 2021/05/28
CRDT- 2021/06/14 09:35
PHST- 2020/06/28 00:00 [received]
PHST- 2021/03/22 00:00 [accepted]
PHST- 2021/06/14 09:35 [entrez]
PHST- 2021/06/15 06:00 [pubmed]
PHST- 2021/06/15 06:01 [medline]
PHST- 2021/05/28 00:00 [pmc-release]
AID - 10.3389/fphys.2021.588120 [doi]
PST - epublish
SO  - Front Physiol. 2021 May 28;12:588120. doi: 10.3389/fphys.2021.588120. eCollection 
      2021.