The role of proper patient positioning for head CT
examination in children (on the base of illustrative case series)
Tymon Skadorwa
1,2, Mikołaj Eibl
1, Elżbieta Zygańska
1, Bogdan Ciszek
1,21
Department of Pediatric Neurosurgery, Bogdanowicz Memorial Hospital for Children, Warsaw, Poland
2
Department of Descriptive and Clinical Anatomy, The Medical University of Warsaw, Warsaw, Poland
Author’s Address: Tymon Skadorwa, Department of Descriptive and Clinical Anatomy, The Medical University of Warsaw, Chałubińskiego 5 Str., 02-004 Warsaw, Poland, e-mail: tskadorwa@nieklanska.pl
Summary
The implementation of computed tomography (CT) scanners to most of pediatric trauma centers resulted in an increasing number of performed examinations. There exist numerous situations in which raw pictures must be assessed immediately after acquisition and when detailed radiological interpretation is not available: emergency departments, surgical planning, follow-up controls for ambulatory patients. On the other hand, there exist important difficulties with pediatric patients not only as for their head dimensions, but also lesser compliance and sensibility for radiation.
Therefore, the proper head positioning plays an important role in order to obtain accurate, reliable data. The article is an analysis of a problem of improper patient positioning and describes difficulties with interpretation of misplaced examinations. A series of cases discussed in the article presents the role of precision in performing CT scans in pediatric patients. Ignorance and negligence in this field may result in unnecessary additional procedures, excessive radiation or dangerous misinterpretations.
Background
Computed tomography (CT) examination has become a golden standard in majority of cases of traumatic head injury [1–8]. Fast and easy to perform, it gives answers for most of procedure-influencing questions at the emergency departments. It is used to establish the patient’s condition and chances for quick recovery, the etiology of a number of complaints from simple headaches to complex neurological deficits. Fast and reliable CT scans may save the patient’s life – in minutes for intracranial hemorrhage or in weeks for malignant brain tumors. The CT scans are also used for routine diagnostic and treatment procedures, especially at neurological, neurosurgical or ENT departments. Being one of the least complicated neuroimaging methods, they can facilitate the diagnosis, focus the examination on impor- tant points or enable to assess the post-operative state- ment. It may be used both for adults and children, no mat- ter on their general health condition. A standard position of the head during CT examination is clearly described in literature [9]. The main goal in proper head positioning is further ability to obtain reliable and symmetrical images.
Such patient placement gives a lot of advantages to image analyzing radiologist, decision-making emergency staff or operating surgeon. The importance of proper head posi- tioning is hard to overestimate, on the other side however, it seems really hard to underestimate the danger of false image interpretation resulting from negligence in this basic duty.
The Importance of Proper Head Positioning
In many cases CT images are first available, before the radiological description. They are used for quick decision- making especially in case of delay in transmitting data between workstations in hospitals. There exist clinical statements, i.ex. stroke, intracerebral hemorrhage or cervi- cal spine injury, with which every medical individual has to be familiar. The following interpretation, made by experi- enced radiologist, often adds important findings to the raw image. There exist however a number of situations in which raw images are the first and only result of performed exam- ination or the written result is not sufficient for making a clinical decision. These include for example: 1) emergency situations with unconsciousness or increasing headache;
2) operative room when surgeon makes himself a decision concerning the range of resection or plans the most appro- priate approach; 3) routine follow-up visits in clinics where patients present their neuroimaging examinations to their local doctors. In all of these cases obtained images must be technically correct and answer the clinical questions in details [10,11]. The more precisely performed, the more use- ful they are in further processing. It is important to note, that any technical deficiencies (resulting from low dose of radiation or patient misplacements) can be corrected during processing by well-equipped modern workstations, which is useful for radiologists [12,13]. Simple image users however, with no possibilities to add some contrast to the image nor to create 3D-rendered reconstructions, often have to inter- pret the images as they are, which may present doubts. The
proper head positioning enables to get a straight diagnosis by providing all details needed in any case. It also dimin- ishes the risk of excessive radiation to the patient, who does not require any additional scanning [14].
The rules of proper head positioning in pediatric patient include symmetry and immobility of the head and depend on specific examination mode [13,15–17]. First component is achieved by correct head placement according to marked lines and crossings which in all types of scanners are simi- lar. The head should also be blocked by additional tapes or straps with the use of soft rubber or sponge-filled blocks, placed on both sides and around the front. The blocks should be placed on the same level regarding the head and symmetrically to each other. The head should lie in the cen- ter of the designated area with the front facing forward.
The angle between horizontal plane of the examined head and the plane of scans is variable and depends on the examination mode, which means the purpose of CT scan- ning [12,18,19]. For example, if the scans are focused on orbits and anterior cranial fossa, the angle is different from 0°, but if the inner ear or paranasal sinuses are the target, then the scanning plane should be more parallel. In prac- tice, many of these solutions are specific for each radiology unit and depend on the type of CT scanner. The immobility of the patient is usually achieved by the implementation of short-term general anesthesia.
Difficulties in Pediatric Head CT Examination
Pediatric patients constitute a complex and diverse group for head CT examination. This is because of large range of age, each with distinct characteristics in CT scans, and lesser compliance, which in some cases prevents perform- ing CT examination without prior anesthesia. In addition, young patients may present various developmental fea- tures which, regarding their tiny dimensions, require pre- cise description and often detailed morphometrical studies.
All of these reasons brought together show the difficulty in finding reliable and wide-ranged references for head CT examination in pediatric patients [20].
Material and Methods
We have analyzed images of 5 patients investigated in our department. The patients underwent head CT examina- tion performed with Siemens 8-row scanner. Pictures were recorded in DICOM standard mode and examined using Siemens Magic Web Browser equipped with measurement tools. The interpretation of these CT scans was difficult due to suboptimal position of the head during imaging proce- dure. We want to present and comment the most common problems and following complications related to position- ing of the patients.
Figure 1. Patient AZ: False atlanto-axial dislocation due to improper head positioning.
Figure 4. Patient AZ: Further analysis of CT scan showed asymmetrical position of the head.
Figure 2. Patient AZ: Coronal aspect of false atlanto-axial dislocation.
Figure 3. Patient AZ: Control X-ray aimed at C1-C2 junction showed
no real dislocation.
Interpretation Problems in Misplaced Patients: A Series of Cases
There exist numerous situations in which wrong patient positioning may promote misinterpretations. They include inaccuracy in dimensions of intracranial changes, CSF spaces or bony structures, questionable cranioverte- bral dislocations or false signs of brain oedema and mass effects. In the course of the study we found distinct inter- pretational difficulties which will be commented on 5 cases.
Case 1 – Vertebral dislocation
Patient AZ, 7 year old boy, admitted to the neurosurgi- cal unit due to a street accident (pedestrian hit by a car).
Performed CT scan showed mild C1-C2 dislocation with no neurological deficit. The boy was equipped with orthopedic neck support, removed on the third day of hospital stay, after control X-ray aimed at C1-C2 junction. The further CT scan analysis showed that initial images were not sym- metrical and the head was not properly blocked at designed space in CT scanner (Figures 1–4).
Case 2 – Diagnostics of hemorrhagic brain contusion Patient KM, 1 year 10 months boy, admitted to the hospital after he had collapsed on the street. An initial CT examina- tion revealed a small focal hemorrhagic contusion in the right frontal lobe. In CT scans performed after 12 hours, small enlargement of hemorrhage was observed. However, control scans were not performed at the same plane, therefore measured dimensions might have differed a bit.
Luckily the child was in good general statement and surgi- cal treatment was not introduced (Figure 5).
Case 3 – Impossible tympanic cavity comparison Patient OO, 5 year old girl, presented to the neurological department with peripheral facial nerve palsy on the right side. She underwent a routine CT examination to check whether the middle ear is involved. However, direct com- parison was not possible because of asymmetrical images (Figure 6).
Case 4 – Post-operative control CT scanning after EDH surgery
Patient SK, 15 years old boy, admitted to Intensive Care Unit (ICU) after a car crash. He suffered from a head inju- ry with a closed epidural hematoma (EDH) and was oper- ated in a local hospital but the removal of the hematoma was not total. The primary and secondary control CT scans did not give any answer about the possible increase of epi- dural bleeding. Obtained scans (Figure 7) were focused on the level of the midbrain and the ambient cistern but the appearance of blood clots remains totally different. Proper and adequate conclusion about the future treatment of an unconscious ICU patient was impossible with such results.
The patient underwent another control CT scanning which showed the stabilization and reduction of the hematome and did not require any re-operation.
Case 5 – Pineal tumor follow-up
Patient MW, 16 years old girl with an abnormal mass in a pineal region, treated conservatively, with no neurological symptoms, nor mass effects, presented to the hospital for a control CT scanning. Obtained images showed an additional mass around the pineal gland and current dimensions of the change have been given. Such performed examination
Figure 5. Patient KM: a small focal hemorrhagic brain contusion. (A) – 1 hour after collapsing; (B) – 12 hours later; (C) – control CT scan performed
with such head supporting materials producing doubts about the reliability of obtained images.
A B C
Figure 6. Patient OO: direct comparison of tympanic cavities is
impossible because of image asymmetry.
was still problematic even for consulting neurosurgeon, because the planes of X-ray beam were distinct from the scans obtained 2 years before (Figure 8). Detailed analysis of the head position showed the difference between pic- tures (Figure 9).
Discussion
Negligence in proper patient positioning produces unnec- essary doubts and nervousness. The problem of improper head placement in CT scanner can be analyzed at three aspects: this of emergency situations, this of surgical pro- cedures and this of long-term treatment.
First of these problematic points of view includes decision- making at the emergency unit and further first few hours after the accident. Cases 1–3 show the procedure after the patient undergoes the initial CT examination, which gives a first look into the problem. Then the doubts begin – is the operative treatment necessary, are the signs of nerve palsy due to central lesion? The question of very first hours after admission is: does the problem increase? Reliable exami- nations are essential to assess the patient’s condition and determine further decisions and prognosis. This is espe- cially in case of small rated intracranial bleedings, which may become dangerous after they grow to large dimensions [21,22].
Figure 7. Patient KS: post-operative control CT scans (A – primary control, B – secondary control 4 days after) performed in different planes – the reliable interpretation of the increment/regression of EDH is impossible. M – midbrain, Amb – ambient cistern, white arrows mark the EDH territory.
A
B
Figure 8. Patient MW: follow-up scanning of pineal region tumor (marked by an asterisk). Direct comparison of the tumor dimensions is impossible. A – scan from 2007; B – scan from 2009.
A
B
Second aspect of misinterpretations due to wrong patient positioning is related to post-operative assessment or surgi- cal planning (case 4). Standard CT examination after sur- gery brings an important information concerning further prognosis. Surprising signs due to patient misplacement may result in additional drug introduction, unnecessary methods of conservative or surgical treatment. Depending on patient’s statement the false findings may cause addi- tional decisions about the positioning in bed of unconscious
patient. On the other hand, the difficulties in assessment of intracranial lesions, such as their dimensions or dynam- ics, may delay surgical procedures. It is also important for successful planning and choosing the most appropriate approach, which becomes complicated with unreliable CT scans [23].
The last point of view concerns long-term follow-up vis- its of patients with chronic diseases or after surgical procedures (case 5). This situation often requires compa- rable images to decide whether the surgery was success- ful and to estimate dynamics of disease or improvement of patient’s general condition. Wrongly performed CT scans are useless in such assessment because they did not answer the questions.
It is important to note that wrong positioning for head CT examination results also in further image processing, i.ex.
3D reconstructions. Although rendered pictures are always secondary to raw CT scans, they may promote misinterpre- tations in cases that need an overall view of a disease (i. ex.
skull shape in craniosynostoses). Improper head placement may also result in producing radiological signs of non- existing pathologies (case 1) which often promotes intro- duction of unnecessary procedures.
It seems that the problem of wrong positioning of head for CT examination is more important in pediatric than adult patients. Lesser dimensions and compliance make these patients more exposed to threats associated with misinter- pretation. Children are more likely to disguise the disease for longer than adults (i.ex. by head enlargement in hydro- cephalus) but on the other hand, many disorders develop more rapidly [24]. For this reason, a proper head position- ing seems one of the most important element of every CT examination.
Conclusions
Proper head positioning plays an important role for further decision-making and assessment of patient’s well-being.
Pediatric patients seem to be a group the most demand- ing because of their lesser ability to cooperate and dimen- sions of examined structures. An emphasis on this problem should be put during professional courses for technicians responsible for preparing and performing CT scanning of pediatric patients.
Figure 9. Patient MW: planes of head CT scans. A – scan from 2007;
B – scan from 2009. H – head/up direction, F – foot/down direction.
A
B
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