Should we obtain informed consent for examinations that expose patients to radiation?

OBJECTIVE: Concern about the radiation-related risks associated with medical imaging is currently a hot topic in both the scientific and lay press as well as gaining a growing awareness from regulatory and legislative organizations. As a result, there is a growing debate about whether or not we should obtain informed consent from patients-in particular, children and their parents-for examinations that expose patients to radiation. In this article, we will discuss the difficulties and challenges of informed decision making and obtaining consent for radiologic examinations. CONCLUSION: We provide our perspectives about the issue of whether informed consent should be required for diagnostic imaging procedures in children, although many of the points also apply to the adult population, and we discuss the dilemmas related to the process of designing and obtaining informed consent for radiologic procedures.     

Should nuclear medicine physicians give the results of radioisotope examinations directly to patients?

Patients often ask for the results after a radioisotope procedure, which can make nuclear medicine physicians feel uncomfortable. In Belgium, nuclear medicine physicians are not supposed to disclose results directly to patients, but to send them to the referring physician. We undertook this work to determine the official rules and practical attitudes in other countries. An introductory letter and a questionnaire were sent to 103 eminent nuclear medicine specialists from 37 countries. Seventy responses (32 countries) were received. Official rules seemed to exist in only seven countries. Most of the respondents indicated that their attitude depended on the clinical situation and the results of the test. Many respondents emphasized that, while in some situations the results should be communicated directly to patients in order to initiate treatment rapidly, in other situations, such as cancer, the referring physician was better suited to disclose the results. The advantages and drawbacks of different attitudes are discussed. Practically and universally applicable rules are difficult to establish, but choosing one solution remains preferable to no standardized attitude at all. An official body, including the medical community, representatives of the population and legal experts, should define an official rule which should be widely communicated, stressing its advantages and drawbacks. In practice, all nuclear medicine physicians would have to do would be to stick to the rule.     

Should an MR scan be performed routinely after a normal clearance CT scan in the trauma patient? Experience with 59 cases

Magnetic resonance (MR) imaging is not routinely used to exclude ligamentous and other soft tissue injury in the unconscious trauma patient. In order to determine the frequency and types of soft tissue injuries detected by MR imaging but not by computed tomography (CT), we performed a retrospective investigation comparing the MR findings in 59 trauma patients, either alert or unconscious, who previously had undergone a negative clearance multislice CT study of the cervical spine. Six patients had abnormalities not identified on the CT studies, including four cases of ligamentous injury.     

Should the justification of medical exposures take account of radiation risks from previous examinations?

With the growing availability of dose histories for patients, the question of whether previous diagnostic radiation exposures should affect decisions on future examinations is coming into sharper focus. This article discusses ways in which cumulative dose information may affect our thinking in justifying exposures. Based on a common tendency to see a connection between past and future events even where we know them to be independent—the gambler''s fallacy—we may find ourselves treating past risks as if they contribute to the present risk. We take the example of two patients scheduled for CT scans, one with no previous diagnostic radiation exposures, the other with a history of previous CT scans, to show that the risks, and justification process, are equivalent in both cases. For the patient with a history of diagnostic exposures, there are only two possibilities: either harm has been caused or there has been no effect. If previous CT examinations have not caused harm, then, as past risks, they are irrelevant. The patient is in precisely the same position with regard to risk as a patient with no dose history. If harm has been caused, avoiding further diagnostic exposures does not change this outcome; again in this case, a justified radiation examination should proceed. We argue that bringing dose history into the decision process for justifying examinations is contrary to our understanding of risk for low-dose radiation and, rather than improving patient safety, would unnecessarily restrict access to radiation-based diagnostic examinations.With the growing availability of dose histories for patients, the question of whether previous diagnostic radiation exposures should affect decisions on future diagnostic radiation examinations is coming into sharper focus. Durand et al,¹ in a recent article, highlight the danger of cumulative dose estimates affecting the justification of future exposures, emphasizing that histories have no place in a rational decision-making process. The argument that justification should not take account of past exposures follows from the stochastic risk model described by the linear no threshold (LNT) hypothesis. According to this model, the probability of a low-dose exposure causing cancer is proportional to the radiation dose and, crucially for the argument being made here, each exposure is a statistically independent event.^2,3 However, despite the logical difficulties Durand et al describe, there can be a strong temptation to include cumulative exposures in the decision-making process. In this article, we look at how cumulative dose information might erroneously affect our thinking in justifying exposures and, taking an example of CT scans, set out the counter argument. The argument refers to risks that are modelled stochastically and follows the LNT hypothesis for low-dose exposures. Cumulative dose in high-dose procedures, where repeat exposures in a short time frame may accumulate to exceed a deterministic threshold for a tissue or organ, follows a different risk process and are not considered as part of this discussion.It is important to draw a distinction between the imaging information and the radiation exposure from past radiographic examinations. The justification process includes careful consideration of the benefit of the examination and how it will contribute to a patient''s clinical management. A key step in this process is the consideration of previous imaging to establish whether the clinical question can be answered without recourse to further radiation exposure or with a lower dose diagnostic examination. In the examples outlined in this commentary, it is assumed that this part of the justification process has been completed.There can be a tendency, however, to treat past dose information in the same way as previous imaging and assume that it should play a role in whether or not the patient should have further imaging with ionising radiation. We know, for example, that five CT scans carry a greater risk than one CT scan. It may seem reasonable to take the risks of the previous four scans into account when justifying the fifth scan. As our thinking subtly shifts towards consideration of the previous scans, the fifth CT scan begins to seem a different proposition to the first CT scan. In the back of our minds, the risk associated with the fifth scan becomes, notionally at least, somehow conflated with the risks from the previous four scans.Part of the thinking here is based on a logical error, sometimes referred to as the gambler''s fallacy. We have a strong tendency to assume that past events have an influence on future events, even when we know that each event is independent. A common example used to illustrate this point is the toss of a coin. Assuming it is a fair coin, the chances of getting tails on a coin toss is 50–50. However, if we get tails, there can be an inclination to believe that on the second toss of the coin, the probability of tails coming up again is less than 50–50. But this is not the case. The coin has no “knowledge” of past events, and its chance of coming up heads remains 50–50, so long as it is a fair coin, regardless of the history. The fallacy of believing we are due heads after several throws resulting in tails (i.e. that the odds of getting heads has changed) is also a factor when we consider further radiographic exposures.Take the situation of a patient who is scheduled for a fifth CT scan. The gambler''s fallacy leads us to believe that patients getting their fifth CT scan are in a different position with regard to the risk for that scan than they were for their first CT scan. We are, in a sense, considering the risk of all five scans together, although four of those scans were in the past and have no bearing on the risk for the fifth scan that we are being asked to justify. Of course, if we were actually comparing the risk of all five scans to the risk of one scan, then five scans carry the higher risk. But we are not in this position. Justifying a fifth CT scan should not be confused with justifying five CT scans. A previous scan is relevant if it provides the diagnostic information we are looking for, thus abrogating the need for a new scan; there is no basis under LNT for considering a previous radiation exposure as a modifier to the risk for the current scan.The argument can be brought out more clearly with an example. Assume we have two patients of equal size who have been scheduled for the same examination on the same CT scanner using the same technique factors. The scan has been properly justified for each patient. Patient A is to have their first CT scan. Patient B has had four previous CT scans. For the purpose of this argument, we take the risk of inducing cancer from a CT scan to be a standard value for each scan, say 1 in 2000.For Patient A, who has not had previous scans, we have justified the CT scan, and the examination goes ahead.What about Patient B? The scan has been clinically justified, but there is hesitancy because of the previous scans. Should we consider these? Is it correct to treat these two patients differently because of the previous radiation dose to Patient B?There are two possible outcomes in terms of the radiation risk for Patient B after four CT scans. Treating each outcome in turn with regard to its relevance to the fifth scan, we get the following:The first possibility is that Patient B has not had cancer induced by the previous CT examinations. The patient''s chance of getting cancer from the new scan is entirely unaffected by this history (the patient might have got cancer from the previous scans, but in this case did not: those four CT scans and their attendant risks are now past). Just as on a fair die, all previous rolls have no bearing on the probable outcome of future rolls, so too with stochastic cancer induction: the past scans where cancer was not induced have no affect one way or the other on the new scan. The risk probability for the fifth scan is not altered. Patient B is at precisely the same risk as Patient A. Given that the risks are equivalent for both patients, we have no basis for proceeding differently on each patient.The second possibility is that Patient B has had cancer induced by one or more of the previous scans. The new CT scan has no impact on this outcome. If we proceed, there is a chance of causing harm as before; if we do not scan the patient, then they still have cancer from the previous scan, and they lose the benefit from the CT scan that we have not given them. So in this case, we should also proceed with the scan.We do not know which of the two situations pertains to Patient B, but according to the LNT model, it is one or the other of the two cases. And as we have shown, we should proceed with a justified CT in either case. Thus, under the present understanding of risk as a stochastic process for low-dose radiation, previous dose history should not influence the justification of future radiographic exposures.The example above is intentionally artificial. We assume that each CT scan delivers the same dose and that it carries the same simplified risk quoted. This allows us to concentrate on the point in question—whether the history of risk is relevant—without getting sidetracked by the complexities of dose calculations. It also keeps the point general. Our argument attempts to show that, as a general rule, taking account of risk from previous scans should not affect the justification process. The justification process already includes risk–benefit analysis and the consideration of alternate strategies, and rightly focuses on the particular examination in question.This article makes the case that including the history of radiation risks in the justification process is contrary to our understanding of risk for low-dose radiation. Allowing cumulative dose estimates to influence whether a patient should get a scan would be tantamount to introducing dose limits for patients and, rather than improving patient safety, would unnecessarily restrict access to radiation-based diagnostic examinations.     

Can body volume be determined by PET?

Purpose

To avoid dependence on body weight, the standardised uptake value (SUV) in positron emission tomography (PET) can instead be normalised to the lean body mass (LBM), which can be determined from body volume and mass. This study was designed to answer the following questions: Firstly, can the total body volume in principle be determined using PET? Secondly, is the precision of this measurement comparable to that achieved using an established standard method.

Methods

Ten patients were examined during oncological whole-body PET examinations. The whole-body volume of the patients was determined from the transmission scan in PET. Air displacement plethysmography with BOD POD was used for comparison as the standard method of volume determination.

Results

In all patients, the whole-body volumes could be determined using PET and the standard method. Bland and Altman [23] analysis for agreement between the volumes determined by the two methods (presentation of differences vs means) revealed a very small difference of ?0.14 l. With a mean patient volume of 71.81±15.93 l, the relative systematic error is only <0.1%. On this basis, equality of the volume values determined by the two methods can be assumed.

Conclusion

PET can be used as a supplementary method for experimental determination of whole-body volume and total body fat in tumour patients. The fat content can be used to calculate the LBM and to determine body weight-independent SUVs (SUV_LBM).     

Can proprioception really be improved by exercises?

There is little question that ankle disc training can improve ankle muscle motor performance in a unipedal balance task, most likely through improved strength and coordination [62] and possibly endurance. How much of the observed improvement in motor performance is due to improved ankle proprioception remains unknown. We have reviewed a number of theoretical ways in which training might improve proprioception for moderately challenging weight-bearing situations such as balancing on one leg. Although the relevant experiments have yet to be performed to test this hypothesis, any improvement would theoretically help to reduce injuries at these moderate levels of challenge. We question, however, whether these exercises can ever improve the reactive response required to prevent injury under the most challenging time-critical situations. If confirmed, this limitation needs to be acknowledged by authors and practitioners alike. Alternative protective strategies for the most challenging time-critical situations should be sought. We conclude that, despite their widespread acceptance, current exercises aimed at "improving proprioception" have not been demonstrated to achieve that goal. We have outlined theoretical scenarios by which proprioception might be improved, but these are speculative. The relevant experiments remain to be conducted. We argue that even if they were proven to improve proprioception, under the best circumstances such exercises could only prevent injury under slow to intermediate rate provocations to the joint musculoligamentous complex in question.     

Should fine needle aspiration cytology in breast assessment be abandoned?

Fine needle aspiration cytology (FNAC) has been used extensively in the U.K. for the diagnosis of breast lesions over the past 15 years. More recently, large gauge needle biopsy has been used to address many of the problems which have been encountered with fine needle aspiration. This paper reviews the evolution of the use of these procedures and the advantages and disadvantages of each. In considering whether to abandon the use of fine needle aspiration cytology in breast assessment, each individual unit should make a decision based upon their own audited results. However, even if FNAC is retained, it is important to be able to complement cytological diagnosis with core biopsy as there are indisputable advantages, e.g. in the diagnosis of mammographically detected microcalcification. As always, a multi-disciplinary approach is ultimately essential for effective patient management.     

Small bowel hydro‐MR imaging for optimized ileocecal distension in Crohn's disease: Should an additional rectal enema filling be performed?

PURPOSE: To assess the impact of an additional rectal enema filling in small bowel hydro-MRI in patients with Crohn's disease. MATERIALS AND METHODS: A total of 40 patients with known Crohn's disease were analyzed retrospectively: 20 patients only ingested an oral contrast agent (group A), the other 20 subjects obtained an additional rectal water enema (group B). For small bowel distension, a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol was used. In all patients, a breathhold contrast-enhanced T1w three-dimensional volumetric interpolated breathhold examination (VIBE) sequence was acquired. Comparative analysis was based on image quality and bowel distension as well as signal-to-noise ratio (SNR) measurements. MR findings were compared with those of conventional colonoscopy, as available (N = 25). RESULTS: The terminal ileum and rectum showed a significantly higher distension following the rectal administration of water. Furthermore, fewer artifacts were seen within group B. This resulted in a higher reader confidence for the diagnosis of bowel disease, not only in the colon, but also in the ileocecal region. Diagnostic accuracy in diagnosing inflammation of the terminal ileum was 100% in group B; in the nonenema group there were three false-negative diagnoses of terminal ileitis. CONCLUSION: Our data show that the additional administration of a rectal enema is useful in small bowel MRI for the visualization of the terminal ileum. The additional time needed for the enema administration was minimal, and small and large bowel pathologies could be diagnosed with high accuracy. Thus, we suggest that a rectal enema in small bowel MR imaging be considered.     

Which radiological investigations should be performed to identify fractures in suspected child abuse?

AIMS: To determine which radiological investigations should be performed and which children should be investigated. MATERIALS AND METHODS: An all language literature search of original articles; from 1950-October 2005. Two reviewers independently reviewed each article. A third was carried out on disagreement. Each study was assessed using standardised data extraction, critical appraisal and evidence forms. RESULTS: Thirty-four studies were included. Fifteen addressed the question: which investigation has a higher yield, skeletal surveys (SS) or bone scintigraphy (BS)? Studies gave conflicting results. Overall neither investigation is as good as the two combined. BS predominately missed skull, metaphyseal and epiphyseal fractures, whereas SS commonly missed rib fractures. Two studies showed that a repeat SS 2 weeks after the initial study provided significant additional information about tentative findings, the number and age of fractures. A comparative study evaluated additional oblique views of ribs in 73 children and showed improved diagnostic sensitivity, specificity and accuracy. Four studies addressed the diagnostic yield for occult fractures with respect to age. This was significant for children under 2-years old. CONCLUSIONS: In children under 2-years old, where physical abuse is suspected, diagnostic imaging of the skeleton should be mandatory. SS or BS alone is inadequate to identify all fractures. It is recommended that all SS should include oblique views of the ribs. This review suggests that the following options would optimize the diagnostic yield. However, each needs to be evaluated prospectively: SS that includes oblique views, SS and BS, a SS with repeat SS or selected images 2 weeks later or a BS plus skull radiography and coned views of metaphyses and epiphyses.