**1. Introduction**

The recent technological developments in the field of microelectronics have revolutionized the development and deployment of biomedical implants, mobile healthcare, and biomedical scanners. In this framework, a variety of highperformance PET scanners have been proposed and realized during the last decade [1–3]. PET imaging is evolving the overall influence of nuclear medicine [1]. It is because of its superior performance, in terms of resolution, compared to the Single Photon Emission Computed Tomography (SPECT). Additionally, it is the rapidly

#### *Integrated Circuits/Microchips*

growing nuclear diagnostic field [1]. It is a valuable metabolic imaging approach that is probably using the most suitable radiopharmaceutical [1].

discussed in Section 3. Section 4 presents the experimental results. Section 5 makes

*Computationally Efficient Hybrid Interpolation and Baseline Restoration of the Brain-PET Pulses*

**Figure 1** displays a block diagram of the proposed system. It illustrates that in the intended patient body "1" an appropriately controlled quantity of the radioactive tracer "2" is injected. The radioactive tracer used in this analysis is 18F-FDG. Most of this tracer is distributed through contaminated brain cells after a certain time [5]. It originates β+, which is annihilated with electrons of medium. Every annihilation emits two 511-keV energy γ-rays. These are simultaneously released at about 180° relative angle and interact with crystal scintillators of the detection sensors "4." Scintillators convert energies of γ-rays into photons of light. Afterward, photo-detectors pick up these photons and turn them into electrical pulses [8–13]. A determined number of sensors are used in a detection ring "3." The front-end electronics, located in the detection sensors "4," further prepare and process PET pulses emanating from photo-detectors. For the construction of tomographs, the selected pulses with extracted parameters like addresses of the intended crystal and

The detection ring consists of a group of four sensors, arranged axially around an

"B" axis in a circle. Most contemporary PET scanners are built from radially arranged scintillators [15, 23]. The use of scintillator axial arrangements with the

a discussion and concludes the chapter.

*DOI: http://dx.doi.org/10.5772/intechopen.92193*

the involved sensor are conveyed to the IRM "5."

**2. Materials and methods**

**2.1 The detection ring**

**Figure 1.**

**175**

*Block diagram of the proposed system.*

Moreover, PET renders high-quality tomographs, which cannot be attained by SPECT or non-nuclear counterparts [1–3]. It has a significant clinical impact, which is evident from a variety of well-conducted case studies. Oncologists, using PET imaging services, appreciate its usefulness. PET is used in a number of critical clinical applications, including cancer diagnosis and monitoring, management of cardiology and cardiac surgery, and neurology and psychiatry.

Brain-PET scanner is an imaging device used for analysis and observation of the brain metabolic activity [1–3]. The concept is to inject a controlled volume of the radioactive tracer into the patient. Brain-PET frequently uses the tracer fluorine-18 fluorodeoxyglucose (18F-FDG) [4, 5]. After a certain period, a significant amount of this tracer is accumulated across the tumor cells. Tracer releases β + positrons, annihilated by medium electrons. As a result of each annihilation, two γ-rays of 511 keV energies are emitted. These are released at about 180° relative angles at the same time. Crystal scintillators absorb energy from emitted γ-rays [6, 7]. They are turning the energy into photons of light. In the next step, photo-detectors pick up these photons, which transform them into electrical pulses [8–13].

The shape and amplitude of electrical pulses produced by photo-detectors enable undesirable interactions to be reduced [2, 3, 11, 14]. In this context, sophisticated PET pulses readout and conditioning are used to maximally preserve this information [12–15].

The PET pulses, produced by photo-detectors, are conditioned and processed to extract the information such as energies and timestamps. The extracted parameters are onward passed to the Image Reconstruction Module (IRM). It combines all pairs of γ-rays, produced by same annihilations, to generate the Line-of-Responses (LORs) [11, 15, 16]. It also uses energies of the PET pulses to measure the Depths of Interactions (DOIs) [1–3]. Afterward, IMR treats these LORs and DOIs to produce three-dimensional tomographs.

PET pulses readout introduces artifacts [11, 12, 16]. It degrades the exactitude of measuring the PET pulses energies and timestamps [11]. It influences device consistency in calculating DOIs and LORs, which lowers the scanner's sensitivity and resolution [11, 12, 16]. BLRs, pile-up correctors, and high-precision timestamp calculators are being used to resolve these deficits [11, 16–21].

The readout of photo-detectors' generated PET pulses produces a shift in the baseline of the signal. It diminishes the energy resolution and the precession of DOI calculation. BLRs are utilized in this framework. Various BLRs have been suggested, ranging from analog approaches to adaptive solutions based on digital filters [11, 12, 16–21].

Another primary method in PET scanners is the measurement of annihilation timestamps. It allows the collection of adequate annihilations to create LORs and also prevents the processing of ineffective information at IRM [11, 12]. Various timestamp calculators were suggested for this purpose. These are essentially formed by using discriminators and time to digital converters (TDCS) [11, 22–27].

The timestamp calculators based on analog discriminators do not face a problem with the temporal resolution of the input signal. This problem arises, however, in the case of timestamp calculators based on digital discriminators [11, 23]. The performance of the system relates directly to the temporal resolution of the input signal and the discriminatory algorithm. The interpolation and multithreshold discriminators are used to achieve accurate measurement of digital timestamps [11, 28].

The remaining chapter is set out as follows. Section 2 explains the materials and methods. The VHDL-based system implementation and synthesis on FPGA are

*Computationally Efficient Hybrid Interpolation and Baseline Restoration of the Brain-PET Pulses DOI: http://dx.doi.org/10.5772/intechopen.92193*

discussed in Section 3. Section 4 presents the experimental results. Section 5 makes a discussion and concludes the chapter.
