Yoshihiro Shimonishi

Advantages of upright position imaging with medium-energy collimator for sentinel node lymphoscintigraphy in breast cancer patients

Objective: To evaluate the advantage of upright position imaging with a medium-energy collimator for the detection of sentinel lymph node (SLN).Methods: Thirty-four patients with operable breast cancer underwent sentinel node lymphoscintigraphy with99mTc-tin colloid. Images were obtained in 5 different positions and paired images from the same patient were compared using side-by-side interpretation. Images were compared in 3 groups: group 1 (anterior view); supine (SAV) vs. upright (UAV), group 2 (oblique view); supine (SOV) vs. upright (UOV), and group 3 (oblique view); modified supine (MOV) vs. UOV. Image quality was evaluated using a 3-grade scale of clear, faint, and equivocal depiction, and correlated to 3 parameters: distance from injection site to lymph node (hot node), counts in hot node, and image contrast. Parameters in group 1 were compared by classifying the primary tumor site into 4 subregions.Results: Image quality in all 3 groups was more enhanced on the image obtained in the upright position than that in the supine position. Obtaining images in an upright position increased the mean distances by 1.5–3.2 cm, and mean contrasts were significantly increased by 0.13–0.31 (p<0.05). It was shown that image quality was more greatly affected by image contrast than by counts in the hot node. Image contrast of 0.5 seemed an appropriate threshold level for detection of the hot node. On comparison of tumor sites, the upper outer quadrant (C) region of the 4 subregions demonstrated greater contrast enhancement on upright position images.Conclusion: Clinical images obtained in an upright position with a mediumenergy collimator were superior to those obtained in a supine position. Use of this procedure is recommended to enhance lymph node detection on sentinel node lymphoscintigraphy.

Thallium and FDG uptake by atelectasis with bronchogenic carcinoma

We report a case of bronchogenic carcinoma with atelectasis studied by Tl-SPECT and FDG-PET. In the carcinoma, abnormally high uptake of Tl and FDG were detected, but in the region of atelectasis, an abnormally high uptake of Tl with a relatively low uptake of FDG were observed. On quantitative analyses, the Tl retention indexes of the tumor and atelectasis were 29.7 and 42.0. The mean SUVs of FDG of the tumor and the atelectasis were 8.92 and 1.28. Tl-SPECT could not distinguish the atelectasis from the carcinoma. FDG-PET was superior to Tl-SPECT in this case in detecting malignancy and distinguishing it from atelectasis.

Clinical Usefulness of (15O)H2O in Positron Emission Computed Tomography.

The clinical usefulness of [15O] H2O was evaluated in 59 patients (16 patients with brain disease, 19 with neck disease, 4 with chest disease, and 20 with abdominal disease) . [15O] H2O was produced in a medical cyclotron (AMWR01, NKK Co., Tokyo, Japan) . The images by positron emission computed tomography with [15O] H2O were judged clinically useful (“fairly useful” or better) in 14 (88%) of the 16 patients with brain disease, all 19 patients with neck disease, all 4 patients with chest disease, and 19 (95%) of the 20 patients with abdominal disease (19 with chronic liver disease) . In 14 of the patients with liver disease, hepatic arterial blood flow and portal blood flow were measured in the same session. The mean portal blood flow in cirrhotic patients with varices was significantly lower than that in cirrhotic patients without varices. There were no side effects during or after the computed tomography. Positron emission computed tomography with [15O] H2O was clinically useful.

Relationship between Imaging Condition and Diagnostic Information in Bone Scintigrams.

Image quality of scintigrams is influenced by several imaging conditions. But, the relationship between image quality and diagnostic information has been not clearly evaluated. Therefore the diagnostic information was evaluated visually by radiologists using bone scintigrams changing the imaging conditions : total counts, image density, and distance from collimator to patient surface. The diagnostic information was considered the point of whether normal or abnormal scintigrams and in the abnormal scintigrams, the information of abnormal position, the abnormal area and the abnormal radioactive distribution on the bone scintigrams. Analysis of variance for the diagnostic information was performed. We concluded that using our methods the relationship between imaging condition and diagnostic informaton is analyzed quantitatively and the base of imaging technique is evaluated objectively.

Relationship between image quality and changes in spatial resolution for the gamma camera.

空間分解能の劣化と視覚的な画質との関係を定量的に検討した。コリメータと検体を密着した時のFWHMを基準にして, 離した時のFWHMとの差を△FWHMとすると, 画質上の変化を認識できる割合 (ρ) は, △FWHMが大きくなるに従いsigmoid curveを描いて大となった。Dendyらの方法およびファジィ理論を適用して, 画質の違いを充分認識できる最小△FWHMを検討すると, △FWHM=0.5mmとなった。この値はコリメータから約2cm離れた時の値に相当した。

(p, 5n) 反応によって製造した123Iを用いたSPECTに関する基礎的検討

The effects of higher-energy photon from 123I (p, 5n) on the SPECT image quality were evaluated. The quality was evaluated by image contrast and %rms. Image contrast had similar tendency to planar and SPECT FWHM value. %rms was affected by septal penetration. Using 140 keV high resolution collimator (140 keV HR), image contrast was superior to that for 300 keV medium energy collimator (300 keV ME), but septal penetration rate (SPR) was 18% and %rms was 10.5. When quantitation is required, the collimator with less SPR than 18% is recommended for SPECT imaging. Using 300 keV ME, SPR was 0.05%, but spatial resolution and image contrast were inferior to that for 140 keV HR.