Michael L. Waller

The diagnostic value of positron emission tomography (PET) with radiolabelled fluorodeoxyglucose (18F-FDG) in head and neck cancer.

Positron emission tomography (PET) scanning has recently been introduced into clinical practice but its usefulness in the management of head and neck cancer is not well defined. The aim of this prospective preliminary study was to examine the clinical value of fluorodeoxyglucose (FDG)--PET in patients with head and neck cancer treated by radiotherapy with surgery in reserve by (i) relating quantitative uptake of isotope to tumour type and histological grade and (ii) comparing the imaging findings of PET and magnetic resonance imaging (MRI) in post-radiotherapy assessment of tumour response. Twenty-one patients had pre-treatment PET and MRI scans and these were repeated four and eight months after treatment if there was no clinical relapse. Pre-treatment uptake of FDG using tumour to cerebellar ratio parameters was significantly related to the histological grade of squamous cancer (p = 0.04) but not to tumour type. Discordance of post-treatment PET/MRI findings in one case indicates a possible role for PET in the early detection of tumour recurrence. Other potential uses of PET scanning in the management of head and neck cancer are discussed.

High-resolution [18F]fluoride positron emission tomography of the distal interphalangeal joint in psoriatic arthritis—a bone–enthesis–nail complex

OBJECTIVE This study used high-resolution PET to explore the pattern of DIP joint bone metabolism to test the hypothesis that the nail was functionally integrated with the bone, based on patterns of distal phalange (DP) bone metabolism in PsA compared with OA and normal joints. METHODS A total of 234 DIP joints were scanned in 30 subjects (10 PsA, 10 OA, 10 healthy control) with [18F]fluoride using the quad-high-density avalanche chamber nano PET scanner. The images were assessed blinded to diagnosis and symptoms for site and intensity of increased [18F]fluoride uptake. RESULTS [18F]fluoride uptake in the DP was strong relative to the intermediate phalange in both PsA and OA. In PsA there was a trend for uptake to occur in a diffuse pattern involving the entire DP. There was also greater uptake at the enthesis, the periosteum and at the tufts of the DP of PsA compared with OA. In OA, uptake was greatest in the subchondral region adjacent to known sites of osteophytosis and erosions. Both PsA and OA joints with uptake at the subchondral or periosteal bone are likely to be more symptomatic. CONCLUSION This exploratory study suggested diffuse increased bone metabolism involving the entire DP, periosteum and entheses, especially in PsA. The subchondral bone and periosteum at the DP have large concentrations of enthesis attachments, including attachments from the nail, supporting the concept of an integrated nail and joint apparatus leading to a wide area of abnormal bone metabolism in PsA.

An assessment of finger doses received by staff while preparing and injecting radiopharmaceuticals.

Good working practice and legal obligation impose a duty on nuclear medicine departments to check syringe activities before administration to a patient. If syringe guards are used to reduce staff exposure while drawing up injections, the guard has to be removed to measure the activity in a conventional reentrant ionization chamber type calibrator. Alternatively, the activity may be checked in a purpose-built syringe calibrator which allows the assay of the activity in the syringe without the need to remove the syringe guard. Finger doses received during the dose preparation and injection are a cause for concern. This study investigated the finger and whole-body doses received when using each of these calibrators, and compared the results with those obtained by an operator who did not measure the dose at all. The results demonstrated that although the finger doses are small, measurement of the syringe activities in a conventional ionization chamber increases the dose by a factor of 2 above that which would occur if no activity measurements were made, whereas the use of the specialized syringe calibrator gave finger doses only marginally above those obtained with no activity measurement.

Registration of PET and MR hand volumes using bayesian networks

A method for the non-rigid, multi-modal, registration of volumetric scans of human hands is presented. PET and MR scans are aligned by optimising the configuration of a tube based model using a set of Bayesian networks. Efficient optimisation is performed by posing the problem as a multi-scale, local, discrete (quantised) search, and using dynamic programming. The method is to be used within a project to study the use of high-resolution HIDAC PET imagery in investigating bone growth and erosion in arthritis.

Technical note: simultaneous multislice imaging with an additional slice gradient in the readout stage: an idea for multislice FLASH.

Conventional two-dimensional Fourier transform spin-echo multislice imaging can be performed in a time efficient manner by taking advantage of the relatively long repetition time (TR) compared with the sequence time (i.e. the time from excitation to end of signal acquisition), to observe other slices. Thus, given a sequence time of 1/n of TR, n slices can be observed with no time penalty. For some applications, however, e.g. cardiac imaging, it would be desirable to collect data for all slices of interest simultaneously and not sequentially. One method of simultaneous multislice imaging has previously been proposed (Muller, 1988). This method uses a multifrequency rf pulse to excite all the slices of interest simultaneously. Separation of the slices is then achieved by addition or subtraction of the time domain signals by altering the phase of the slice selection pulses. For n slices, the basic imaging sequence has to be repeated n times. We present here an alternative method to acquire multislice images ...