Need for radiologists to interpret orthopedic total joint radiographs.

We applaud the aim of Nayak and colleagues: to use our scarce economic resources as judiciously as possible. We have suggested several alternatives that would save more of our scarce health care dollars. We would be delighted to take part in a properly designed prospective randomized trial to address the issues presented in this paper. We believe the literature would be strengthened by the publication of a collegial paper, coauthored by orthopedic and radiology departments, addressing the issue of saving health care dollars by omitting unnecessary or redundant procedures.

Experimental and theoretical x-ray imaging performance comparison of iodine and lanthanide contrast agents.

Contrast agents based on the lanthanide elements gadolinium and holmium have recently been developed for magnetic resonance imaging (MRI). Because of the increased atomic number of these elements relative to iodine, these new compounds, used as x-ray contrast agents, may yield higher radiographic contrast, and hence improved x-ray image quality, relative to conventional iodinated compounds, for clinically useful x-ray spectra. This possibility has been investigated, in independent experimental and theoretical studies, for two x-ray imaging systems: a digital radiographic system, using an x-ray image intensifier (XRII) and charge-coupled device (CCD) detector; and a conventional screen/film system, using a Lanex Regular screen. Iodine, gadolinium, and holmium contrast agents were investigated over a wide range of concentration-thickness products (0.1-0.6 M cm) and diagnostic x-ray spectra (60-120 kVp). A simple theoretical model of x-ray detector response predicts the experimental radiographic contrast measurements with a mean absolute error of 8.0% for the XRII/CCD system and 5.9% for the screen/film system, and shows that the radiographic contrast for these two systems is representative of all XRII and screen/film systems. An index of image quality is defined, and its dependence on radiographic contrast, x-ray fluence per unit dose, and detective quantum efficiency (DQE) is shown. Theoretical values of the index, predicted by our model, are then used to compare the performance of the three contrast agents for the two systems investigated. In general, iodine performance decreases steadily with increasing kVp, gadolinium performance has a broad maximum near 85 kVp, and gadolinium outperforms holmium. Gadolinium outperforms iodine for spectra above (and vice versa below) about 72 kVp, depending slightly on spectrum filtration, object thickness, and detector type. Thus, raising the kVp to shorten exposure times or reduce x-ray tube heat loading results in a loss of image quality with iodine, but not with gadolinium. Similarly, beam-hardening artifacts in performing video densitometry with iodine would be reduced with gadolinium. Gadolinium-based contrast agents are thus shown to offer several practical advantages over conventional iodinated contrast agents.

Contrast use: waste not--want not.

Efficient use of low-osmolar contrast media is essential, owing to their cost and increasing substitution for conventional agents. A study was undertaken in three radiology departments to examine use of intravascular contrast media. Over a one-month period in the summer of 1987, the amount of intravascular contrast medium used and discarded was measured in one community hospital and two university-affiliated hospitals in southwestern Ontario. The major part of the waste occurred in the angiography suite, while minimal wastage was recorded in computed tomography. Much less contrast was wasted in the community hospital than in the teaching hospitals. Thirteen percent of all contrast material used by the three hospitals was discarded. Some wastage appears inevitable. Multidose dispensing systems as well as variety in bottle sizes have been proposed to reduce waste. Individual departments need to be aware of the problem and analyze their own patterns of contrast use.

Digital teleradiology: Seaforth--London network.

A total digital teleradiology system using a prototype DuPont laser beam scanner (DTR 2000) and a Bell Canada digital transmission network was evaluated. A total of 489 radiographic and ultrasonographic examinations were transmitted for interpretation from a 41-bed rural community hospital in Seaforth to the University Hospital in London, Ontario, 80 km away. There was concurrence in 98% of these examinations, i.e. the laser-sensitive facsimile film clearly duplicated the original film findings and allowed a confident interpretation to be made. We conclude that this system could readily serve the needs of family physicians in rural communities for radiologic consultation, diagnosis, management, and triage of patients 24 hours per day.

Arterial flow characterization with a photodiode array based imaging system.

An x-ray imaging system is described that can be used for obtaining arterial blood flow information. The system consists of a linear photodiode array image detector, simple optical and mechanical components, and a data acquisition microcomputer that connect to a conventional x-ray image intensifier based fluorography system. Flow information is obtained by detecting the movement of a small, locally injected bolus of radio-opaque contrast agent. This is done by determining the bolus mass, integrated over the cross-sectional area, at each of 1024 positions along the length of the artery with a sampling rate of up to 200 samples per s. It is shown in a phantom study that the peak flow velocity can be measured with an accuracy of +/- 5% by detecting the bolus arrival times at each of the 1024 positions. The mean velocity is obtained with similar accuracy using a cross-correlation technique and a modified form of the Stewart-Hamilton principle. In addition, it is shown that the separation and reattachment points resulting from flow separation near a stenosis can be determined from the bolus clearance times. The locations of these points are consistent with theoretical values for the cosine shaped symmetric 89% stenosis used in this study.

Low osmolar contrast media--a challenge for cardiology.

Low osmolar contrast media have been available in Canada for several years. Their introduction has lead to considerable controversy because of the substantive increase in costs compared to conventional ionic media. This increased cost is in the order of 13 times per gram of iodine. There is extensive scrutiny by both the medical profession and Government because of this added cost, estimated to be +17 million annually for cardiology. A challenge is presented to Canadian cardiology to help solve this problem.

A scanning x-ray imaging system for quantitative arteriography and blood flow measurements.

The authors have developed a new x-ray imaging system for quantitative arterial imaging and blood flow measurements. The system is based on the scanned projection technique and employs an x-ray beam collimated into a fan of radiation and an x-ray image intensifier optically coupled to a 1024-element linear photo-diode detector array. The system has two modes of operation: quantitative projection imaging and blood flow measurements. In the first mode of operation, low-noise, quantitative images are obtained by irradiating small regions of interest to minimize the detection of scattered radiation and intensifier tube veiling glare. System performance is optimized by making use of the large dynamic range (8,000:1) and response linearity of the solid-state photo-detector. In the second mode of operation, flow information is obtained by detecting the passage of a small bolus of iodine contrast agent.

A new system for quantitative arterial imaging and blood flow measurements.

A new x-ray imaging system is being developed for quantitative arterial imaging and blood flow measurements. The system consists of an x-ray image intensifier optically coupled with a 1024-element photo-diode detector array. Low-noise, quantitative images are obtained by irradiating small regions of interest to minimize the detection of scattered radiation and intensifier tube veiling glare, and by making use of the large dynamic range (8000:1) and response linearity of the solid-state photo-detector. In the first of two modes of operation, low-noise scanned projection images are produced. Stenosis size (reduction of lumen area) in phantoms is determined with a maximum uncertainty of 10% over a range of iodine contrast agent concentrations of 4 to 100 mg/ml in a 1.0 cm2 cross-sectional area tube, independent of stenosis orientation and size. In the second mode, flow information is obtained by detecting the movement of a small, locally injected iodine bolus. Peak flow velocity and locations of flow separation and turbulence resulting from simulated stenoses are determined with stenosis sizes ranging from 0 to 84% area reduction.

Dose and quality control (DQC) in diagnostic radiology.

Dose and quality control in diagnostic radiology can play an important role in reducing x-ray exposure and costs whilst maintaining a high level of imaging quality and diagnostic benefit. It can also become very costly. Current government regulations demand unnecessary accuracy in the measurement and performance of certain parameters of x-ray generators whilst ignoring others which are more important. They totally neglect imaging systems. We urge a more critical approach to the requirements for dose and quality control programs. We propose the exchange of information through a user's club and a less regulatory but equally important role for government.

Percutaneous transluminal dilatation of the renal artery: follow-up studies on renovascular hypertension.

Percutaneous transluminal dilatation of 80 renal artery stenoses was attempted in 68 patients. The procedure was technically successful in 58 (85%) patients. Fifty (86%) of the 58 patients were initially cured or improved. Life-table analysis of this group gives a cumulative success rate of 81% for a 3 year period. Hypertension recurred in only seven patients. There were no deaths related to the procedure, but four major complications occurred, including two secondary nephrectomies.

Intermittent percutaneous infusion into the hepatic artery of cytotoxic drugs for hepatic tumours.

Between June 1, 1976 and Apr. 30, 1981, 157 patients were treated for inoperable cancer of the liver by intermittent percutaneous infusion of chemotherapeutic agents into the hepatic artery. The majority of these patients had metastatic colorectal cancer. The regimen of chemotherapeutic infusion evolved during the study and is described. The survival of the total group of patients is analysed according to type of cancer, extent of disease, dosage and combination of drugs. This therapeutic modality appears to benefit patients with metastases from colorectal cancer confined to the liver. The complication rate for this procedure is relatively low. The results from this study suggest that intermittent percutaneous infusion of cytotoxic agents into the hepatic artery is worthwhile for selected patients and should be studied further in combination with other forms of therapy.