**3. Representative cases**

### **3.1. Case 1 (Figure 2)**

We examined the normal reconstructed images and statistical mapping of IMP SPECT. After the intravenous injection of 222 Megabecquerel (MBq) of 123I-IMP, the early (15 minutes) and delayed (3 hours) images were acquired using a multi-detector SPECT machine (E.CAM, Siemens Medical, Erlangen, Germany) and a high resolution collimator (LEHR, Siemens Medical, Erlangen, Germany). The Butterworth pre-correction filter and the Chang method were used for pre- and post-attenuation corrections. The Ramp filter was used for reconstruc‐ tion. The image matrices, the pixel sizes and the slice thickness of the IMP SPECT were 128 x 128, 3.31 mm and 6.62 mm, respectively. All SPECT data were saved in the Digital Imaging and Communication in Medicine (DICOM) format. The DICOM data were transferred to a newly developed software program, the iNeurostat+ (Nihon Medi-physics, Hyogo, Japan), which runs on a Windows personal computer. The SPECT data were anatomically standar‐ dized on normal brain images. The increased uptakes of IMP were statistically mapped on the tomographic images of the normal brain. The image quality, diagnostic ability and imaging

**Fig 1: Automatic Process Flow of iNeurostat+** 

Comparison Z‐score calculation

Statistical Mapping on tomographic MRI

Statistical Mapping on surface image (3DSSP)

Age matched Normal Data Base (mean+SD)

Magnetic resonance imaging (MRI) data were acquired with 1.5 Tesla instrument (Gyroscan NT Intera, Philips, Amsterdam, The Netherlands). The tumor diameters and size were measured using gadolinium-diethyltriaminepentaacetic acid (Gd-DTPA)-enhanced T1-

artifacts were evaluated by a visual inspection (Figure 1).

Anatomical Standardization

96 Tumors of the Central Nervous System – Primary and Secondary

Original SPECT

**Figure 1.** Automatic Process Flow of iNeurostat+

weighted MRI.

A 58-year-old female had a Gd-enhanced MRI scan, which showed a homogenously enhanced tumor at the left putamen. Delayed IMP SPECT showed tumor uptake, however, other normal brain uptake was also detected. Statistical mapping of IMP SPECT data demonstrated hot tumor uptake and no uptake into the normal brain. A tumor biopsy revealed a pathological diagnosis of PCNSL.

**Fig 2: Case 1: 58 Woman: PCNSL**

**Figure 2.** 58 Woman: PCNSL

#### **3.2. Case 2 (Figure 3)**

A 71-year-old female underwent a Gd-enhanced MRI scan, which showed a homogeneously enhanced tumor at the left cerebellum. Delayed IMP SPECT did not show clear uptake into the cerebellar lesion. Statistical mapping of IMP SPECT demonstrated clear uptake of IMP into the tumor. The tumor was pathologically diagnosed as PCNSL by biopsy.

**5. Discussion**

25 to 30 mm in diameter.

was not described.

**5.1. Sensitivity and specificity of IMP SPECT**

Statistical Mapping

Our results revealed a high sensitivity (80%) and high specificity (100%) of IMP SPECT in the diagnosis of PCNSL. Our IMP SPECT of 3.31 mm in pixel size could not detect one small supratentorial tumor less than 5 mm. Because our patient series included only one patient with a tumor less than 20 mm in diameter, the detection threshold could not be demonstrated. However, two cerebellar tumors more than 30 mm in diameter could be detected with the usual IMP SPECT, while two cerebellar tumors smaller than 25 mm in diameter could not be detected. Based on our results, the detection threshold of cerebellar tumors seems to be around

**Table 1**

New Application of 123I-Iodoamphetamine SPECT for the Diagnosis of Primary Central Nervous System Lymphoma

Original IMP PCNSL other unknown uptake + 16 0 2 uptake - 4 26 1

uptake + 18 0 2 uptake - 2 26 1

Sensitivity 80%, specificity 100%, Chi‐test p<0.01

Sensitivity 90%, specificity 100%, Chi‐test p<0.01

PCNSL other unknown

http://dx.doi.org/10.5772/58321

99

Akiyama reported that the PCNSL larger than 3 ml could be detected in delayed IMP SPECT [1]. Their patient series included some patients with brain stem tumors and no patients with cerebellar tumor. Shinoda reported the IMP SPECT findings in 10 patients with PCNSL [9]. There were two patients with cerebellar tumors in their study, but the tumor size or volume

SPECT has some physical and radiological limitations. The absorption of gamma rays in each tissue decreases the detected signal. Scattering radiation from the gamma ray source leads to low spatial resolution of the reconstructed SPECT images. The posterior fossa is covered by a thick area of the skull, so the signal from the brain stem and cerebellum is attenuated more than that from the cerebrum. Homogeneous attenuation correction could not correct for the low signal from the posterior fossa. These reasons might underlie the low sensitivity at the cerebellum. Some methods of correcting the absorption and scattering have been employed, however, all of these correction methods are associated with some limitations [4]. In our facility, the scatter was corrected with a Butterworth filter, and the absorption and attenuation were corrected with the chang method. The chang method assumes homogenous attenuation, however, the head is not homogenously attenuated. Therefore, using the Chang method leads to an overestimation of the regional CBF values in IMP SPECT in low CBF regions and an

**Fig 3: Case 2: 71 Woman: PCNSL**

**Figure 3.** 71 Woman: PCNSL
