# State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios
## 5 Results and Discussion
Since the gamma image reconstruction can take minutes and since multi-rotors have very low autonomy (16 min), the importance of developing a 4\(\pi\) Compton camera to obtain the contamination image inside a building is highlighted. For the source \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Gamma Camera** & **Mobile Platform** & **Weight** & **\(\Delta E\)/\(E\) \% (662 keV)** & **Acquisition Time** & **Scenario** & **Ref.** \\ \hline Compton Camera: & & & & & & \\ SCoTSS with arrays of & & & & & & \\ CsI(Tl) and NaI(Tl) in the & & Truck & 15 kg & 7.5–7.9 & Under 3 s & A,B & [182; 183] \\
3\(\times\)3 configuration & & & & & & \\ \hline
2 arrays of Ce:GAGG & Unmanned & & & & & \\ coupled to SiPM & & helicopter & Lightweight & 6.5 & 5 min & A & [178; 184] \\ \hline
2 arrays of Ce:GAGG & Multi-rotor & 1.9 kg & 9 & \(\sim 10\) min & A & [185] \\ \hline
2 arrays of Ce:GAGG & Multi-rotor & 1.5 kg & - & \(\sim 10\) min & A & [186; 187] \\ \hline VCI based on HPGe & Mobile & - & - & - & A,B & [188] \\ \hline VCI & Robot & - & - & - & A & [190; 191] \\ \hline VCI using Ce:GAGG & Crawler robot & - & - & - & A & [192; 193] \\ \hline
2 arrays of Ce:GAGG & Handheld & 1 kg & - & 10 s & A & [22] \\ \hline Si/CdTe Compton camera & - & 10 kg & 2.2 & 30 min & A & [194] \\ \hline Polaris-H (pixelated CZT & & & & & & \\ detectors) & Handheld & 4 kg & 1.1 & \(\sim 2\) min 1  & A & [195] \\ \hline Compton camera/Coded-aperture & & & & & & \\ camera: & & & & & \\ VCI (based in CZT crystals & & & & & \\ with active mask for & & & & & \\ coded-aperture mode) & & & & & \\ \hline Coded-aperture camera: & & & & & \\ SORDS-3D (with passive & & & & & \\ mask) & Cargo trailer & - & 6.13 & - & B & [179] \\ \hline SORIS (with active mask) & Van & - & 8 & - & B & [196] \\ \hline GAMPIX (MOBISIC & & & & & \\ project) & Mutirotor & 70 g & - & 300 s & B & [197] \\ \hline Pinhole camera: & & & & & & \\ Pinhole & Truck & - & - & - & A & [198] \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Resume of the gamma cameras described in the literature considering the scenario types (described in Section 2). searching and mapping on unknown environments or to localize sources inside objects, a 3D Compton imaging system was also developed, which used scene data fusion of the gamma image with a 3D scene reconstruction using a Kinect sensor, a photogrammetry software, or a 3D-LiDAR. SLAM techniques are used to obtain the position and posture of the imaging system. In addition to the use of Ce:GAGG crystals for VCI, the use of HPGe detectors and a high-efficiency multimode imager, which allows both coded-aperture and Compton imaging modes, is also reported and described. Despite the fact that VCI are being implemented in handheld equipment and in mobile platforms, improvements are still necessary in the 3D scene data fusion, an important tool not only for detection and mapping gamma sources but also other particles (e.g., neutrons). * Coded-aperture camera. To detect weak sources at larger distances, as is the case of scenario B, larger gamma cameras were developed to be carried in a cargo trailer (SORDS-3D) or by a van (SORIS). While the former used coded-aperture camera composed by CsI(Na) scintillation crystals and a passive mask, the latter used NaI crystals and an active mask used not only to attenuate the incident gamma-ray but also for spectroscopy purpose (increased efficiency). The use of a lightweight coded-aperture gamma camera (GAMPIX) coupled to a multi-rotor is also referred to in the literature. * Pinhole camera. Since pinhole cameras are heavy and low efficiency equipment (thick collimation system), they have few applicability to mobile platforms. The use of gamma cameras for autonomous mapping and hotspot localization using mobile platforms is still limited by the long acquisition times, poor angular resolution, difficulty in detecting distant hotspots when intense sources are nearby the camera or when considering measurements with a moving source/camera (blurred images).