Terue Okamura

Diagnostic usefulness of FDG PET for pancreatic mass lesions

The purpose of this study was to investigate the feasibility of [18F]2-deoxy-2-fluoro-d-glucose (FDG) positron emission tomography (PET) in patients with a pancreatic mass by comparing the results with those of X-ray computed tomography (CT) and magnetic resonance (MR) imaging.Methods: Eighty-six patients with pancreatic lesions, included 65 malignant tumors and 21 benign masses (55 masses were proven histologically and the others were diagnosed clinically), were studied. The diagnostic factors of CT and MR imaging were evaluated, and those of FDG PET were also evaluated for malignant and benign masses by visual interpretation and quantitative interpretation with the standardized uptake value (SUV) and SUV gluc which was designed to reduce the effects of a high blood sugar level. Visual interpretations were evaluated only in FDG PET images, and quantitative interpretations were evaluated by referring to CT and/or MR imaging. The correlation between SUV and the degree of histological differentiation in pancreatic ductal adenocarcinoma was investigated.Results: Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for CT imaging were 91, 62, 88, 68 and 84%, and for MR imaging 78, 70, 88, 54 and 76%, respectively. In visual interpretation of FDG PET images, the sensitivity, specificity, PPV, NPV and accuracy were 82, 81, 93, 59 and 81%, respectively. Significant differences between malignant and benign lesions existed in SUV and SUV gluc (p<0.0001, each). With the cutoff value of SUV as 2.1 and SUV gluc as 2.2, the accuracy of diagnosis was maximal. With that cutoff value, the sensitivity, specificity, PPV, NPV and accuracy for SUV were 89, 76, 92, 70 and 86%, and for SUV gluc 91, 76, 92, 73 and 87%, respectively. The sensitivity and NPV of SUV gluc were higher than those of SUV, which suggests that SUV gluc may be more useful in reducing the number of overlooked malignant tumors. The specificity and PPV of FDG PET were superior to those of CT and MR imaging. There were no significant differences between the SUVs of moderately differentiated adenocarcinomas and those of well differentiated adenocarcinomas.Conclusion: To improve the diagnostic procedure for classifying masses, FDG PET with not only SUV but also SUV corrected by the blood sugar level is required in addition to morphological diagnosis by CT and/or MR imaging.

Thallium‐201‐chloride thyroid scintigraphy to evaluate benign and/or malignant nodules usefulness of the delayed scan

The purpose of this study is to evaluate benign and/or malignant thyroid tumors with 201TI thyroid scan. We studied 76 cases of histologically verified thyroid tumors, all seen as cold nodules on the 123I thyroid scan. 201TI thyroid scan was performed 5–15 minutes (early scan) and 3–5 hours (delayed scan) after intrayenous administration of 1.5–2.0 mCi of 201TI. In 35 (94.6%) of 37 malignant tumors (anaplastic carcinoma, six; papillary carcinoma, 23; follicullar carcinoma, five; epidermoid carcinoma, one; malignant lymphoma, 1), 201TI accumulated in the cold nodule of the 123I thyroid scan on both early and delayed scans. On the other hand, the delayed 201TI scan was negative in 35 out of 39 (89.7%) benign tumors. Employing early and delayed 201TI scans, we were able to differentiate most malignant thyroid tumors from those which were benign. False‐negative and ‐positive cases are discussed.

Fluorine-18-fluorodeoxyglucose positron emission tomography for assessment of patients with unresectable recurrent or metastatic lung cancers after CT-guided radiofrequency ablation: Preliminary results

ObjectivesWe compared the diagnostic value of fluorine-18-fiuorodeoxyglucose positron emission tomography (FDG-PET) with that of computed tomography (CT) following radiofrequency ablation (RFA) of inoperable recurrent or metastatic cancers in the lung.MethodsTwelve patients (9 males and 3 females; 5 had recurrent lung cancer and the other 7 had metastatic nodules from a variety of primary cancers) were treated by RFA for 17 pulmonary nodules. FDG-PET was performed before and 2 months after RFA, and the mean standardized uptake value (SUV) was calculated. The response evaluation was based on the percent reduction relative to the baseline and the absolute values of SUV on FDG-PET performed at 2 months after RFA. We compared the response evaluations made based on findings of FDG-PET and CT at 2 and ≥6 months (mean 10.2) after RFA.ResultsThe percent reduction in uptake at 2 months was significantly lower in nodules considered progressive (69.6± 18.6%) than nonprogressive disease (38.7 ± 12.5%; p < 0.01) based on CT findings at >6 months after RFA. The absolute SUV at 2 months was significantly higher in nodules considered progressive (2.61 ±0.75) than nonprogressive disease (1.05 ±0.67; p<0.01) based on CT findings at ≥6 months post-RFA.ConclusionAlthough our pilot study comprised few cases of various histopathological types of cancers in the lung, the results suggest that FDG-PET could predict regrowth on subsequent follow-up CT. Regrowth could be diagnosed earlier by FDG-PET than by CT, and nodules with residual uptake and with <60% reduction of uptake relative to baseline on FDG-PET at 2 months after ablation might require additional therapy.

Evaluation of treatment effects in brain abscess with positron emission tomography: comparison of fluorine-18-fluorodeoxyglucose and carbon-11-methionine.

Positron emission tomography (PET) imaging is in common use preoperatively to clinically evaluate patients who present with central nervous system mass lesions. The usefulness of PET is also recognized as a method to detect intracranial tumorous lesions. A number of papers report that some inflammatory processes also showed the uptake of Fluorine-18-Fluorodeoxyglucose (FDG) and Carbon-11-Methionine (Met) tracers. We performed two PET studies before and after treatment in 4 patients with brain abscess. PET showed the uptake of both tracers to the brain abscess before treatment. The area showing an increased uptake of Met corresponded closely to the enhanced area on both CT and MR images. FDG-PET visually showed an uptake of FDG in a small area corresponding to an enhanced lesion within the CT and MR images. After treatment the area of lesions became small on enhancement CT or MRI and both PET studies showed reduced lesion and decreased uptake. The mechanism of Met uptake in the inflammatory area may be related to the higher metabolic rate and the active transport of amino acids as well as disruption of the blood brain barrier. Furthermore, it appears that the mechanism of FDG uptake is also related to a higher metabolic rate and, in addition, is related to the increased density of inflammatory cells. PET studies, more directly, reflect the degree of inflammatory response in brain abscess than enhancement CT or MRI. Therefore, PET is useful in detecting the inflammatory lesion and assessing the clinical effects of antibiotics treatment on brain abscesses.

Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography Imaging of Parotid Mass Lesions

Using X-ray CT or magnetic resonance imaging (MRI), fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) studies were performed in 28 patients with parotid lesions. All lesions except two showed higher accumulation of FDG than normal parotid gland. High accumulation was found in all of 5 carcinomas, all of 6 Warthins tumors, and 8 of 12 pleomorphic adenomas, with standardized uptake values (SUVs) over 3.0. The mean SUVs of carcinomas, Warthins tumors, and pleomorphic adenomas were 5.92 +/- 2.05, 7.03 +/- 2.49, and 4.07 +/- 1.55, respectively. On the other hand, all 5 inflammatory lesions demonstrated low accumulation, with mean SUVs of 1.66 +/- 0.89. It is thus difficult to differentiate malignant from benign parotid lesions by SUV on FDG-PET.

Clinical evaluation of digital radiography based on a large-area cesium iodide-amorphous silicon flat-panel detector compared with screen-film radiography for skeletal system and abdomen

Abstract. The aim of this clinical study was to compare the image quality of digital radiography using the new digital Bucky system based on a flat-panel detector with that of a conventional screen-film system for the skeletal structure and the abdomen. Fifty patients were examined using digital radiography with a flat-panel detector and screen-film systems, 25 for the skeletal structures and 25 for the abdomen. Six radiologists judged each paired image acquired under the same exposure parameters concerning three observation items for the bone and six items for the abdomen. Digital radiographic images for the bone were evaluated to be similar to screen-film images at the mean of 42.2%, to be superior at 50.2%, and to be inferior at 7.6%. Digital radiographic images for the abdomen were judged to be similar to screen-film images at the mean of 43.4%, superior at 52.4%, and inferior at 4.2%; thus, digital radiographic images were estimated to be either similar as or superior to screen-film images at over 92% for the bone and abdomen. On the statistical analysis, digital radiographic images were also judged to be preferred significantly in the most items for the bone and abdomen. In conclusion, the image quality of digital radiography with a flat-panel detector was superior to that of a screen-film system under the same exposure parameters, suggesting that dose reduction is possible with digital radiography.

Monitoring of Response to Radiotherapy with Fluorine-18 Deoxyglucose PET of Head and Neck Squamous Cell Carcinomas

We examined the usefulness of positron emission tomography (PET) using fluorine-18 deoxyglucose (FDG) in determining the therapeutic effects of irradiation and chemotherapy on head and neck malignant tumors. Twenty-two patients with head and neck lesions who underwent histological examinations were studied. Squamous cell carcinoma was histologically diagnosed in all cases. Sixteen of them underwent radiotherapy with approximately 40 Gy in combination with carboplatin therapy. The remaining 6 patients underwent radiotherapy alone. After these treatments, 11 underwent surgery. For PET study, each patient was injected with intravenous FDG 185-370 MBq. We evaluated the degree of FDG accumulation using scanned images taken 40-55 min after the injection. We measured the standardized uptake value (SUV), a semiquantative evaluation, ROI activity divided by the dosage per weight of each patient. FDG-PET, CT and MRI were performed twice for each patient, before and after treatment. FDG uptake, but not the tumor size in CT or MRI, was significantly reduced in each patient after the treatment. Therefore, our findings have clearly demonstrated that FDG-PET provides for more valuable therapeutic outcomes than conventional imaging such as CT and MRI. FDG-PET should thus provide a new dimension in the management of head and neck malignant tumors.

Positron emission tomography using 2-[18F] fluoro-2-deoxy-d-glucose in the diagnosis of uterine leiomyosarcoma: A case report

Abstract The preoperative diagnosis of uterine leiomyosarcoma (LMS) is very difficult. Magnetic resonance (MR) imaging is usually used for it; however, precise diagnosis by MR imaging is limited to typical LMS with coagulative tumor cell necrosis. We presented a case of LMS that was diagnosed preoperatively by positron emission tomography (PET) using 2-[ 18 F] fluoro-2-deoxy-d-glucose (FDG).

The usefulness of18F-FDG PET images obtained 2 hours after intravenous injection in liver tumor

Liver tumors, especially hepatocellular carcinomas (HCCs), often exhibit no contrast with surrounding non-tumorous liver tissue in F-18-fluoro-2-deoxy-2-fluoro-d-glucose (FDG) positron emission tomography (PET) images obtained at the usual interval of one hour after intravenous FDG injection. We evaluated the usefulness of FDG PET studies of liver tumors performed 2 hours after intravenous injection.Methods and Materials: Fifteen pretherapeutic patients with 33 liver tumors were studied, including 11 patients with 18 HCCs, and 4 patients with 15 metastatic liver tumors (METAs) from 3 colorectal carcinomas and 1 esophageal carcinoma. After transmission scans, emission scans were obtained 45–55 minutes and 115–125 minutes after intravenous injection of 185–370 MBq FDG as early images and delayed FDG PET images, respectively. Visual analysis of early and delayed images was performed, and the FDG uptake in the tumor to that in nontumorous liver ratio (T/N ratio), the FDG uptake in tumor to that in soft-tissue ratio (T/S ratio) and the FDG uptake in non-tumorous liver to that in soft-tissue ratio (N/S ratio) were calculated for each image.Results: In visual analysis, visual improvement seen in images was observed in 6 of 18 HCC lesions and all 15 META lesions. In quantitative analysis, the mean T/S ratio and T/N ratio of HCCs in early images were 4.97 and 1.90, respectively, and those in delayed images were 6.24 and 2.20, respectively. The mean T/S ratio and T/N ratio of METAs in early images were 5.97 and 2.21, respectively, and those in delayed images were 6.99 and 3.80, respectively. The T/S ratio of HCCs and T/S ratio and T/N ratio of METAs were significantly higher in delayed images than in early images. The mean N/S ratios of HCC cases were 2.58 in the early images and 2.57 in the delayed images, but the ratio showed no constant tendency in the images. All N/S ratios of META cases were decreased in delayed images, although the significance of the small number of cases.Conclusion: FDG PET studies performed 2 hours after intravenous injection were useful for clear visualization of liver tumors, especially metastatic liver tumors.

Physiological FDG uptake in the palatine tonsils

In clinical F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) studies of the head and neck region, remarkable symmetric tonsillar FDG uptake is sometimes observed. We determined the incidence and degree of tonsillar FDG uptake and investigated the significance of tonsillar FDG uptake. Between June 1998 and August 1998, we obtained informed consent from 17 patients who were scheduled to undergo a FDG-PET study for their own disease (11 men and 6 women; aged 22 to 77 yr) and who did not have head and neck disease to perform FDG-PET scanning of the head and neck region in addition to their target organs. The incidence and degree of tonsillar FDG uptake were determined. Remarkable tonsillar FDG uptake was found in 9 patients. The SUVs of these FDG uptakes ranged from 2.48 to 6.75, with a mean of 4.29±1.20 (SD). Tonsillar FDG uptakes in the remaining 8 patients were not remarkable, and their SUVs ranged from 1.93 to 3.31, with a mean of 2.46±0.45. Head and neck disease does not appear to have been responsible for the increase in tonsillar FDG uptake. Differences among tonsillar FDG uptake in these 17 patients without head and neck disease appear to reflect differences in activity of “physiological” inflammation of the palatine tonsils.