http://www.k-wave.org/forum/topic/negative-part-of-a-photoacoustic-signal Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:22:27 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/negative-part-of-a-photoacoustic-signal#post-4137 Sun, 24 Nov 2013 16:13:17 +0000 Bradley Treeby 4137@http://www.k-wave.org/forum/ <p>Hi Tim,</p> <p>I think that looks ok. If you look in Fig. 7 in [1], for a homogeneous cylindrical absorber with a delta function pulse, the magnitude of the peak negative pressure is greater than the magnitude of the peak positive pressure.</p> <p>Brad.</p> <p>[1] Hoelen, C.G.A., de Mul, F.F.M., 1999. A new theoretical approach to photoacoustic signal generation. J. Acoust. Soc. Am. 106, 695–706. </p> http://www.k-wave.org/forum/topic/negative-part-of-a-photoacoustic-signal#post-4130 Fri, 22 Nov 2013 16:59:56 +0000 tim_man 4130@http://www.k-wave.org/forum/ <p>Hi Dr. Treeby, </p> <p>apologies for the delay. </p> <p>The output data averaged across the sensor's elements result to the shape of the pressure profile as you can see here: <a href="http://imageshack.com/a/img191/2164/4x4d.png" rel="nofollow">http://imageshack.com/a/img191/2164/4x4d.png</a></p> <p>Thank you - Best Regards,<br /> Tim </p> http://www.k-wave.org/forum/topic/negative-part-of-a-photoacoustic-signal#post-4095 Wed, 20 Nov 2013 10:10:28 +0000 Bradley Treeby 4095@http://www.k-wave.org/forum/ <p>Hi Tim,</p> <p>I'm not sure I completely follow what you mean. Do you mean comparing the results of:</p> <pre><code>mean(sensor_data(sensor_data &gt; 0)) mean(sensor_data(sensor_data &lt; 0))</code></pre> <p>Also, is your output data summed or averaged across your semicircular sensor?</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/negative-part-of-a-photoacoustic-signal#post-4083 Wed, 06 Nov 2013 13:49:53 +0000 tim_man 4083@http://www.k-wave.org/forum/ <p>Dear Dr. Treeby and Dr. Cox,</p> <p>I use k-wave to simulate an absorbing sphere in 2D (homogeneous medium) using the <code>kspaceFirstOrder2D</code> function with a semicircular sensor centered on the grid.<br /> I'm considering about the negative part of the photoacoustic signal. Does it make sense to you, the average negative part of the pressure from all the sensor's elements to be in absolute value bigger than the positive part? Let me know if you need futher information or/and a plot of the signal. </p> <p>Thank you in advance.<br /> Best Regards,<br /> Tim </p>