Carl K. Hoh

Regional cerebral activity in normal and pathological perception of visceral pain

BACKGROUND & AIMS To characterize the cerebral processing of noxious visceral events, changes in regional cerebral blood flow associated with perception of intestinal pain were examined. METHODS The effects of rectal pressure stimuli on regional cerebral blood flow were assessed with 15O-water positron emission tomography (PET) in 12 subjects, half with irritable bowel syndrome (IBS). PET scans were obtained at baseline and during both actual and simulated delivery of anticipated stimuli. Changes in regional cerebral blood flow were interpreted using statistical parametric mapping and region of interest methods of analysis. RESULTS In healthy subjects, perception of pain during actual or simulated delivery of painful stimuli was significantly associated (P < 0.01) with activity of the anterior cingulate cortex (ACC; Brodmanns areas 24 and 32), whereas no ACC response to perception of nonpainful stimuli was observed. In patients with IBS, the ACC failed to respond to the same stimuli, whereas significant activation (P < 0.01) of the left prefrontal cortex (maximal in Brodmanns area 10) was seen. CONCLUSIONS The perception of acute rectal pain is associated with activation of the ACC in healthy subjects, and patients with IBS show an aberrant brain activation pattern both during noxious rectal distention and during the anticipation of rectal pain.

Cancer detection with whole-body PET using 2-[18F]fluoro-2-deoxy-D-glucose.

Objective This study was done to determine the feasibility and potential utility of whole-body PET using the glucose analogue 2-[18F]fluoro-2-deoxy-D-glucose (FDG) for the detection of primary malignancies and metastatic lesions. Materials and Methods This was a prospective, nonrandomized study of whole-body FDG-PET imaging carried out at a large university teaching hospital in Los Angeles, CA, U.S.A. The study group consisted of all patients referred for PET imaging (87) with a suspected diagnosis of primary or recurrent malignancy and who had eventual histological confirmation of their lesions. Results In the 87 patients, whole-body PET studies were positive (presence of focal FDG uptake relative to surrounding tissues uptake) in 61 of 70 patients (87%) with subsequent biopsy-confirmed primary or recurrent malignant lesions, including carcinomas of breast, lung, ovary, prostate, colon, urinary bladder, and gallbladder origin, as well as malignant melanoma, carcinoid, osteosarcoma, lymphoma, and spinal cord astrocytoma. The PET images revealed no focal hypermetabolism at the known site of tumor in patients with primary prostate carcinoma (two), microscopic ovarian carcinoma (two), breast carcinoma (one), low-grade carcinoid tumors (two), and one patient with recurrent microscopic osteogenic sarcoma. The PET studies detected the primary lesion in 15 of 17 patients with breast carcinoma and in 6 of 6 patients with primary lung carcinoma. Of the 17 patients with benign biopsies, 13 patients had FDG-PET studies without focal areas of uptake. Conclusion Because of the high glycolytic rate of malignant tissue, the whole-body FDG-PET technique has promise in the detection of a wide variety of both primary and metastatic malignancies. The presence of FDG uptake in benign inflammatory conditions may limit the specificity of the technique. The sensitivity for the detection of malignant lesions was 87% and the positive predictive value was 94%. The whole-body FDG-PET method is promising both in determining the nature of a localized lesion and in defining the systemic extent of malignant disease.

Targeting and retention of magnetic targeted carriers (MTCs) enhancing intra-arterial chemotherapy

MTCs were magnetically targeted and retained at a region of interest in a swine model after intra-arterial infusion. MTCs did not redistribute after removal of the magnetic field. Histopathology results demonstrated high particle density in the area of the magnetic field. Particles were observed in the interstitium and occasionally intra-arterially. Regional delivery of chemotherapeutic drugs will be tested with this technology.

Analytical decision model for the cost-effective management of solitary pulmonary nodules.

PURPOSE AND METHODS Multiple strategies are currently being used to manage patients who present with indeterminate solitary pulmonary nodules (SPN). We have used decision-analysis models to assess the cost-effectiveness of various strategies for the diagnosis and management of SPN. Four decision strategies were compared: a wait and watch strategy, a surgery strategy, a computed tomography (CT)-based strategy, and a CT-plus-positron emission tomography (PET) strategy. An incremental cost-effectiveness ratio (ICER) was used to compare all strategies to the wait and watch strategy. RESULTS A CT-plus-PET strategy was the most cost-effective over a large pretest likelihood (probability of having a malignant nodule), with a range of 0.12 to 0.69. Furthermore, within this likelihood range, the potential cost savings of using the CT-plus-PET strategy over the CT strategy ranged from

PET in oncology: will it replace the other modalities?

91 to

The application of positron emission tomographic imaging with fluorodeoxyglucose to the evaluation of breast disease.

2,200 per patient. This translates to a yearly national savings of approximately

COMPARISON OF HELICAL COMPUTERIZED TOMOGRAPHY, POSITRON EMISSION TOMOGRAPHY AND MONOCLONAL ANTIBODY SCANS FOR EVALUATION OF LYMPH NODE METASTASES IN PATIENTS WITH PROSTATE SPECIFIC ANTIGEN RELAPSE AFTER TREATMENT FOR LOCALIZED PROSTATE CANCER

62.7 million. CONCLUSION Decision-analysis modeling indicates the potential cost-effectiveness of [18F]2-fluoro-2-deoxy-D-glucose (FDG)-PET in the management of SPN. Furthermore, the decision trees developed can be used to model various features of the management of SPN, including modeling the cost-effectiveness of other newly emerging technologies.

Noninvasive Quantification of Myocardial Blood Flow in Humans A Direct Comparison of the [13N]Ammonia and the [15O]Water Techniques

Medical imaging technology is rapidly expanding and the role of each modality is being redefined constantly. PET has been around since the early sixties and gained clinical acceptance in oncology only after an extreme number of scientific publications. Although PET has the unique ability to image biochemical processes in vivo, this ability is not fully used as a clinical imaging tool. In this overview, the role of PET in relation to other tumor imaging modalities will be discussed and the reported results in the literature will be reviewed. In predicting the future of PET, technical improvements of other imaging modalities need to be dealt with. The fundamental physical principles for image formation with computed tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), photon-emission tomography (PET), and single photon emission CT (SPECT) will not change. The potential variety of radiopharmaceuticals which may be developed is unlimited, however, and this provides nuclear imaging techniques with a significant advantage and adaptive features for future biologic imaging. The current applications of PET in oncology have been in characterizing tumor lesions, differentiating recurrent disease from treatment effects, staging tumors, evaluating the extent of disease, and monitoring therapy. The future developments in medicine may use the unique capabilities of PET not only in diagnostic imaging but also in molecular medicine and genetics. The articles discussed in this review were selected from a literature search covering the last 3 years, and in which comparisons of PET with conventional imaging were addressed specifically. PET studies with the glucose analogue fluorine-18-labeled deoxyglucose (FDG) have shown the ability of detecting tumor foci in a variety of histological neoplasms such as thyroid cancer, breast cancer, lymphoma, lung cancer, head and neck carcinoma, colorectal cancer, ovarian carcinoma, and musculoskeletal tumors. Also, the contribution of the whole body PET (WBPET) imaging technique in diagnosis will be discussed. In the current health care environment, a successful imaging technology must not only change medical management but also demonstrate that those changes improve patient outcome.

POSITRON EMISSION TOMOGRAPHY IN UROLOGICAL ONCOLOGY

Positron emission tomography (PET) is a computer-aided tomographic imaging technique that uses positron-emitting compounds to trace biochemical processes of tissue, and construct images based on them. The authors applied a whole-body PET imaging technique to patients with breast masses or mammographic abnormalities using the isotope 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG), in a clinical trial to evaluate the feasibility of using PET to identify primary breast cancer, axillary lymph node involvement, and systemic metastases, before surgical resection. Fourteen patients have been entered on this study, 10 of whom proved to have breast cancer. Positron emission tomography correctly predicted the nature of 12 of the 14 primary breast lesions, and correctly determined the lymph node status of 11 of the 14 patients. The authors conclude that PET with FDG has potential as a diagnostic modality for detection of primary breast cancer, particularly in the patient with radiodense breasts by conventional mammography, and that it has potential for the preoperative identification of axillary lymph node metastases.

Positron emission tomography with fluorodeoxyglucose to evaluate tumor response and control after radiation therapy

PURPOSE We compare the detection of metastatic disease by helical computerized tomography (CT), positron emission tomography (PET) with F-18 fluorodeoxyglucose and monoclonal antibody scan with 111indium capromab pendetide in patients with an elevated prostate specific antigen (PSA) after treatment for localized prostate cancer. MATERIALS AND METHODS A total of 45 patients with an elevated PSA (median 3.8 ng./ml.) were studied following definitive local therapy with radical prostatectomy in 33, radiation therapy in 9 and cryosurgery in 3. CT of the abdomen and pelvis, and whole body PET were performed in all patients, of whom 21 also underwent monoclonal antibody scan. Lymph nodes 1 cm. in diameter or greater on CT were considered abnormal and were sampled by fine needle aspiration in 12 patients. RESULTS PET and CT were positive for distant disease in 50% of 22 patients with PSA greater than 4, and in 4 and 17%, respectively, of 23 with PSA less than 4 ng./ml. The detection rate for metastatic disease was similar for CT and PET, and higher overall than that for monoclonal antibody scan. Monoclonal antibody scan was true positive in only 1 of 6 patients, while PET was true positive in 6 of 9 with CT guided fine needle aspiration proved metastases. CONCLUSIONS CT and PET each detected evidence of metastatic disease in 50% of all patients with a high PSA or PSA velocity (greater than 4 ng./ml. or greater than 0.2 ng./ml. per month, respectively). Both techniques are limited for detecting metastatic disease in patients with a low PSA or PSA velocity. Our data suggest that monoclonal antibody scan has a lower detection rate than CT or PET.