Pathology of human organic mercury poisoning: Lessons from an autopsy case.

We had an opportunity to perform a general autopsy of a case with chronic organic mercury toxicosis in 2017. He had been engaged in synthesizing a variety of organic mercury compounds throughout the four years from 1966 and developed chronic organic mercury poisoning in 1969. Almost forty years on, he still remained to complain of persistent paresthesia at finger tips and tongue, and of narrowed visual field. Neurological examinations clarified a rise of two-point discrimination thresholds, a systemic increase of touch thresholds, constriction of the visual field caused by general visual depression, and sensorineural hearing loss while primary modalities of his somatic, visual, and auditory sensations were preserved. These symptoms and signs are characteristic of human organic mercury poisoning. Furthermore, he had difficulty in processing a lot of visual and auditory information at a time. His two-point discrimination thresholds and systemic elevation of touch thresholds were comparable to those of mild organic mercury poisoning cases. He had slight sensory ataxia, but not cerebellar ataxia. Brain [18F]-2-fluorodeoxyglucose positron emission tomography analysis exhibited marked hypometabolism at bilateral postcentral gyrus, striate cortex, and superior temporal gyrus, but not the cerebellum. Histopathological studies revealed considerable decrease of granular neurons and neuronal networks in bilateral primary somatosensory, visual, and auditory cortices. Those characteristic brain lesions fairly explain increase of thresholds of somatic, visual, and auditory sensations, and degradation of integrating sensory information. It is noted that damages to the peripheral nervous system and the cerebellum were not detected and that his intellectual faculties were preserved.

[Correction of Partial Volume Effect Using CT Images in Brain 18F-FDG PET].

PURPOSE: We performed partial volume effect correction of PET images using 18F-FDG-PET and CT images taken consecutively, compared it with correction using MRI images, and investigated the usefulness of correction using CT images. METHODS: A total of 9 clinically normal subjects were included in the study, and the CT and MRI images of each subject were segmented and normalized. PET images were coregistered to each morphological image and then normalized. The normalized morphological images of each subject were used to mask the brain atlas and to correct for the partial volume effect. For each brain region, comparison of counts, two-group test between CT- and MRI-corrected groups, and correlation analysis were performed. RESULTS: As a result of correction, some error was observed between the two groups. Correlation analysis showed strong positive correlations in many areas, but weak correlations were found in some areas. In the region where significant differences were found, the two groups showed strong positive correlation, and in the region where weak correlation was found, the error tended to be small. CONCLUSION: It is suggested that the correction by CT can be performed with the same accuracy, although some errors are generated compared with MRI.

Impact of FDG-PET/CT imaging on nodal staging for head-and-neck squamous cell carcinoma.

PURPOSE: To evaluate the impact of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) imaging on nodal staging for head-and-neck squamous cell carcinoma (SCC). METHODS AND MATERIALS: The study population consisted of 23 patients with head-and-neck SCC who were evaluated with FDG-PET/CT and went on to neck dissection. Two observers consensually determined the lesion size and maximum standardized uptake value (SUVmax) and compared the results with pathologic findings on nodal-level involvement. Two different observers (A and B) independently performed three protocols for clinical nodal staging. Methods 1, 2, and 3 were based on conventional modalities, additional visual information from FDG-PET/CT images, and FDG-PET/CT imaging alone with SUV data, respectively. RESULTS: All primary tumors were visualized with FDG-PET/CT. Pathologically, 19 positive and 93 negative nodal levels were identified. The SUVmax overlapped in negative and positive nodes <15 mm in diameter. According to receiver operating characteristics analysis, the size-based SUVmax cutoff values were 1.9, 2.5, and 3.0 for lymph nodes <10 mm, 10-15 mm, and >15 mm, respectively. These cutoff values yielded 79% sensitivity and 99% specificity for nodal-level staging. For Observer A, the sensitivity and specificity in Methods 1, 2, and 3 were 68% and 94%, 68% and 99%, and 84% and 99%, respectively, and Method 3 yielded significantly higher accuracy than Method 1 (p = 0.0269). For Observer B, Method 3 yielded the highest sensitivity (84%) and specificity (99%); however, the difference among the three protocols was not statistically significant. CONCLUSION: Imaging with FDG-PET/CT with size-based SUVmax cutoff values is an important modality for radiation therapy planning.

The diagnostic efficacy of FDG-PET in the local recurrence of hilar bile duct cancer.

BACKGROUND/PURPOSE: It is frequently difficult to make an accurate diagnosis of the local recurrence of hilar bile duct cancer (HBC). We assessed the efficacy of fluorodeoxyglucose-positron emission tomography (FDG-PET) in diagnosing the local recurrence of HBC. METHODS: Among 18 patients who had previously undergone resection of HBC, 5 were suspected of having a recurrence. These 5 patients were examined for recurrence by computed tomography (CT) and FDG-PET. A definitive diagnosis was determined either by pathological studies or by clinical follow-up. RESULTS: Whereas CT showed a recurrent mass in only 1 patient, FDG-PET revealed the high uptake of FDG in all patients. Histopathological and/or cytological examinations confirmed the local recurrence of HBC in 4 patients. One false-positive result occurred in a patient with reflux cholangitis. One patient with a recurrent tumor was followed by FDG-PET after irradiation therapy. The high level of FDG uptake, which had been seen in that patient before irradiation, completely disappeared after treatment. CONCLUSIONS: When used in combination with other modalities, FDG-PET offered useful information for the diagnosis of a local recurrence of HBC. This highly sensitive imaging approach also appeared to be useful for follow-up examination after irradiation therapy.

[Current situation and problems of PET examinations].

In recent years, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has become a remarkable new modality for use in preventive medicine. FDG-PET examinations have many characteristics that are not available through conventional examinations, including the diagnosis of cancer. However, devices and examination techniques that take advantage of the merits of FDG-PET examinations are still required. In addition, many problems related to the management of facilities need to be solved. Therefore, we introduce the current situation of FDG-PET examinations in our facility and discuss our problem-solving efforts. FDG-PET examinations are very useful as screening examinations for cancer, and, in the future, FDG-PET will combine with other techniques and examinations in preventive medicine to provide a general cancer-screening system. For the future development of FDG-PET, we need to focus on the effective utilization of FDG-PET examinations and to establish evidence of their effectiveness. Moreover, we must create guidelines for the improvement of technology and the standardization of PET examination facilities.

[Clinical evaluation of gastric diverticulum on indirect radiograph for gastric mass survey].

The aim of this study was to evaluate the clinical conditions of gastric diverticulum. Fifty-four patients with gastric diverticulum (20 men and 34 women among 34,314 patients who underwent medical check-ups) were evaluated on indirect radiographs, for an incidence of 0.16% among the total number of examined cases, a rate lower than that of previous reports. Almost all cases were asymptomatic, had a single diverticulum, and showed a saccular shape. The age distribution indicated higher frequencies in the 5th and 6th decades, and the posterior wall of the fornix was the most common location. Size ranged from 0.6 cm to 12 cm, and 41 cases (75.9%) were between 1.0 cm and 4.0 cm in size. This entity should be kept in mind when reading radiographs of upper gastrointestinal series as well as recognition of pseudodiverticulum and aberrant pancreas as noted for the stomach in several past report. Diverticulum on the cardia, which was previously classified as gastric diverticulum, should be excluded because of the possibility of normal variation.