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Case Study Brain Tumour

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					     Case Study
    Brain Tumour
             Victor Micallef
BSc (hon.) Health Sciences (Radiography)
       MSc Medical Imaging (CT)
                                             time to compensate for the presence of
Case history and clinical                    the tumour. A malignant tumour will
indication                                   become symptomatic when it reaches an
                                             average volume of about 100ml (Vanel
A Caucasian 72 year old female was           and Stark, 1993).
referred for a brain CT examination by the
neurologist. For the last three months she   The most common clinical presentation of
had been suffering from throbbing            a brain tumour is generalized headache
headaches which woke her up in early         and often predominant at the site of the
mornings.      The     headaches     were    tumour.
sometimes accompanied by nausea. It
was noted by the patient that she felt       A common fundoscopic sign in adults with
different to her usual self and although     increased intracranial pressure is bilateral
lethargic she had become very short          papilledema.
tempered, which contrasted with her
usual calm predisposition. In the last       In advanced stages of cerebral neoplastic
weeks the patient complained of right        disease, patients may present with
upper limb weakness.                         arterial hypertension, bradycardia and
                                             depressed respiratory rate.
Signs and symptoms caused by brain
tumours may be due to one or more of         In the later stages of the disease patients
various reasons which we can classify        may also have tentorial herniation.
into three types. First and most obvious
reason can be due to the invasion and        Seizures may occur at any stage of the
destruction of the cerebral parenchyma       disease in about a third of all brain
by the tumour. Second cause can be due       tumour patients.
to compression of the normal brain by the
bulk of the tumour or its surrounding        Other signs and symptoms of brain
edema. The third effect is due to remote     tumour may be behavioural changes,
effects of the tumour on;                    memory deficits and other cognitive
                                             disorders such as aphasia and apraxia.
o vascular supply or drainage of normal
  brain by compression or direct
  invasion of arteries and/or veins,
o cerebrospinal fluid (CSF) pathways
  and CSF overproduction leading to
  secondary hydrocephalus
o and increased intracranial pressure by
  the volume mass of the tumour or any
  of its secondary effects.

The growth rate of the tumour is a
determining factor of the type of clinical
manifestation. Tumours with a slow
growth rate will reach a large size before
giving off symptoms while a faster
growing tumour will become symptomatic
sooner as the normal brain is not given
                                                                                       2
Patient consideration                        An intravenous cannula was inserted
                                             using a vein in the cubital fossa area prior
The patient was very much anxious on         to positioning the patient to avoid
arrival to the hospital. She was reassured   movement after positioning. The patient
and comforted by the staff and on            was told what to expect on contrast
questioning she was found to be anxious      injection (warm flush sensation and bitter
about the results of the scan rather than    taste). The patient’s position for the scan
the scan itself. The radiographer            was supine head first into the gantry. A
explained the procedure for the scan and     cushioned head cradle was used and
explained the importance of not moving       chin and forehead straps were used to
during the scan. It was decided by the       minimise head movements. A thigh
radiologist to scan the patient pre and      supporting cushion was also used for the
post contrast administration so she was      patient’s comfort. After the pre-contrast
asked a set of screening questions to rule   scans, the patient was given the IV
out any allergies and complication,.         contrast using the pre-prepared cannula.
These questions related to                   Prior to the injection she was instructed
                                             and reminded not to move her head
   •   general allergies,                    during the injection. After the scan the
   •   allergies to shell fish,              cannula was left in situ for about twenty
   •   diabetes (particularly the use of     minutes just in case of a delayed allergic
       metformine)                           reaction to the contrast.
   •   general kidney function and
   •   history of previous contrast media
       administration.




                                                                                       3
Scanning protocol

          CT Scanner                                      Siemens Emotion Duo
          Anatomy                                         Posterior fossa   Cerebrum
                            Acquisition                   Contiguous        Contiguous
                            Kilovolts (kVp)               130               130
                            Milliamperage (mA)            173               173
                            Milliampere-seconds (mAs)     260               260
                            Rotation time (ms)            1500              1500
                            Exposure time (ms)            1500              1500
           Scan




                            Focal Spot (mm)               .95               .95
                            Scan Field of View            502.17            502.17
                            Gantry tilt                   -19               -19
                            Increment (mm)                2                 8
                            Slice thickness (mm)          2                 8
                            Slice gap                     0                 0
                            Display field of View (mm)    212               217
           Reconstruction




                            Algorithm                     H30s              H30s
             & display




                            Matrix                        512 by 512        512 by 512
                            Window width                  200/3200          80/3200
                            Window level                  40/700            35/700
Table 1 - Parameters for Case 1

                                                         included). The Siemens Emotion scanner
Optimisation                                             uses a simple beam-hardening correction
                                                         algorithm which reduces the artefact to
The patient was told to remove any                       some extent. Some manufacturers utilise
hairpins she was wearing in her hair to                  a sophisticated two-pass beam-hardening
avoid metal artefacts of the scans.                      correction algorithm which substantially
Position of the patient was supine with                  reduce this artefact (Bushberg et al.,
chin tucked down so the baseline is as                   2002). Another artefact which may affect
close to vertical as possible. The brain                 the posterior fossa and also the vertex of
was scanned from the foramen magnum                      the cranium is partial volume averaging.
to the skull vertex with the gantry tilted               Thin slices of 2mm thickness were used
about 10° above the orbito-meatal (OM)                   for the posterior fossa thus minimising
line to reduce exposure of the eye lenses.               this artefact. Motion artefact was
                                                         eliminated through complete patient
Beam hardening artefact in the posterior                 cooperation, helped by fast scanning
fossa was seen on some images (not
                                                                                                 4
times and the use of restrainer straps on     Appropriate window width and level used
the chin and forehead.                        for supratentorial brain and for the brain
                                              in the posterior fossa. Although the
Although the machine used is of spiral        radiologist examined all images in bone
technology, normal contiguous scans           window to exclude any bone secondary
were performed. This is in line with the      lesions, this window was not hardcopied.
departmental policy which is aimed at
eliminating helical artefacts in the vertex
area.

50cc of Omnipaque 350 was hand
injected and a 90 second delay was
allowed between injection and the
beginning of the scan. Volume of contrast
used is also restricted by departmental
policy which can be overridden by the
radiologist.




                                                                                      5
Evaluation of presented images

Pre-contrast image                              Post-contrast image




        Image 1 - Pre Contrast Image                   Image 2 - Post contrast image

   1. White matter oedema resulting                1. Contrast enhanced tumour tissue
      from B-B-B breakdown                            in the right of the midline,
   2. 4th ventricle                                   completely compressing the lateral
   3. Posterior horns of lateral ventricles           ventricle
                                                   2. Sub falx herniation of tumour from
Anterior horns of lateral ventricles are              the left to the right intimate to the
completely compressed. Choroid plexus                 corpus callosum
in the posterior horns of the lateral              3. Necrotic tissue in the middle of the
ventricles is seen calcified, a common                tumour
normal occurrence in adults. Falx cerebri          4. Enhancing tumour tissue
is slightly shifted to the right and there is      5. Oedema
mild sulcal effacement on the left side of
the brain with the lateral sulcus (Sylvian      A bolus of 50 ml of non-ionic contrast
fissure) being completely indiscernible,        agent (Omnipaque 350) was used. There
both      signs      indicating    increased    was enhancement of the tumour seen as
intracranial pressure on the left side.         hyperdensity around a hypodense area
                                                (Image 23). The hypodense area
                                                indicates necrosis in the core of the
                                                tumour. This contrast accumulation in the
                                                                                         6
tumour is the result of leakage of the         along white matter tracts away from the
contrast into the interstitium of the tumour   tumour (Image 23, label 5). Together with
because of the absence of a blood brain        the tumour mass, the oedema is also
barrier within the tumour neovascularity       contributing to the increased left sided
(Kirkwood, 1990).                              intracranial pressure. The tumour is
                                               involving the corpus callosum and
The oedema shown on both pre and post          crosses the midline producing the
contrast images is also a result of the        “butterfly” pattern characteristic of a high
breakdown in the blood-brain-barrier in        grade glioblastoma. Other characteristics
the neovascularity of the tumour, allowing     to such a tumour are the extensive
leakage of proteins and other solutes into     oedema, the contrast enhancement,
the surrounding extra-cellular space of        corpus callosum involvement and the
the white matter. The oedema has spread        central necrosis (Kirkwood, 1990).
                                               (1952) grading of glial tumours, a contrast
                                               enhancing tumour with oedema such as
                                               this one is a Grade III or Grade IV
                                               malignant tumour.

                                               Histological confirmation of the diagnosis
                                               for this case will never be established as
                                               on follow up of the case it was found the
                                               patient and her family opted for no
                                               treatment and she passed away fourteen
                                               weeks after diagnosis. Glucocorticoid
                                               therapy in an attempt to reduce the brain
                                               oedema was the only treatment the
                                               patient was given.

                                               Radiologist Report

                                               There is a well defined enhancing lesion
                                               to the left side of the midline in the frontal
                                               region which is partly cystic and partly
                                               solid. The solid part lies to the right of the
        Image 3 - Post contrast image          midline and is intimately related to the
                                               corpus callosum. Adjacent ventricles are
   1. Upper border of right part of the        compressed and there is moderate
      tumour                                   amount of oedema associated.
   2. left part of the tumour
   3. Necrotic changed in the core of the      Conclusion is of a large aggressive
      tumour                                   gliomatous focus in the frontal region that
   4. Left lateral border of the tumour.       has crossed the midline and lies at the
                                               level of the corpus callosum.
While on the first two images the left
component of the tumour is seen crossing
                                               Differential diagnosis
the midline, the third image shows the
tumour contained in the left side by the
                                               Occasionally a metastatic tumour may
falx cerebri. According to Kernohan et al.,
                                               present itself in similar manner as
                                                                                  7
described here, and without a biopsy it       brain tumour is clinically suspected. This
might be impossible to differentiate. A       approach can be guided if the radiologist
biopsy was never performed for this           is able to answer to the following five
patient. If the enhancing ring was more       questions (Vanel and Stark, 1993).
regular and thin around the central
hypodense area, diagnosis of a brain              1. Sensitivity: Is an intracranial
abscess might have been considered.                  lesion     causing    the     clinical
                                                     symptoms?
CT versus MRI                                     2. Specificity: What is the lesion? Is
                                                     it a neoplasm? Is it benign or
CT and MRI are the two imaging                       malignant?
modalities which best visualise the brain         3. Location:     Where is the growth
(Vanel and Stark, 1993). In Malta both               and what are its precise limits? Is it
are available in NHS but the CT is more              one growth or multiple?
readily available as more radiographers           4. Treatment: If the tumour is to be
are trained to use it and thus is operated           irradiated, biopsied or resected,
round the clock unlike the MRI which is              which is the best approach?
closed at night.                                  5. Monitoring: How         can        the
                                                     neuroradiologist    monitor       and
All CT examinations for suspected                    evaluate the efficacy of the
intracranial lesions should include a pre            treatment?
and post CM study (Vanel and Stark,
1993). When imaging calcified lesions,        The structural changes of the brain and
the relative subtle increase in density of    changes to the CSF pathways are the
contrast enhancement is overwhelmed by        morphologic abnormalities that suggest
the high density of the calcification. This   the presence of brain tumour. These
is contrasted by CM in MRI where              changes are visible on both CT and MRI
calcifications have very low signal           and can be direct signs of abnormal
intensity on a T1 weighted image making       density on CT or abnormal signal
enhancement easy to detect even in            intensity on MRI or indirect changes like
heavily calcified lesions.
                                              1   alteration of normal structures
Where readily available MRI should be         2   mass effect
the modality of choice when looking for       3   displacement
brain tumours because of its                  4   deformation of ventricular system
                                              5   sulcal effacement
1   great sensitivity                         6   cisternal distortion or filling
2   capability of multiplanar imaging
3   good anatomical depiction of normal       On both CT and MRI certain tumour
    and diseased brain                        characteristics    will   be sought
4   high contrast resolution                  systematically. These are
5   sensitivity to flow
6   detection of vascular elements            o lesion border definition
                                              o homogeneous or non-homogeneous
Strategy of diagnosis                           appearance
                                              o presence of associated haemorrhage
The most effective strategic approach to      o cystic elements
diagnosis has to be reached whenever a        o intratumoral necrosis
                                                                                         8
o calcifications                             1.2 (adapted from Vanel and Stark, pg.
o associated edema                           33).
o extension across midline
                                             Table 2 - CT attenuation of cerebral masses
This systematic assessment may be
facilitated by using a table such as Table




                                                                                           9
CT Attenuation of Cerebral Masses Relative to Normal Brain
(adapted from Chapman and Nakielny 1995 pg. 411)
                Neoplasms
                     I. Meningioma 95%
   Hyperdense
                    II. Microglioma (primary lymphoma).
                   III. Metastases 30%
                   IV.  Glioma 10% (most glioblastomas           show    mixed
                        attenuation).
                    V. Ependymoma
                   VI. Papilloma
                  VII. Medulloblastoma 80%
                  VIII. Pituitary adenoma 25%
                   IX. Craniopharyngioma (if solid)
                    X. Acoustic neuroma 5%
                Haematoma – if two weeks old or less
                Giant aneurism
                Colloid cyst – 50%
                Neoplasms
                      Acoustic neuroma 95%
                     I.
   Isodense




                      Pituitary adenoma 65%
                    II.
                      Glioma 10%
                   III.
                   IV.Metastases 10%
                    V.Chordoma
                   VI.Pinealoma
                Haematoma – if between two and four weeks old weeks old or
                less
                Tuberculoma
                Colloid cyst – 50%
                Tumours
                      Craniopharyngioma
                     I.
                      Glioma (95% of astrocytomas).
                    II.
   Hypodense




                      Metastases
                   III.
                   IV.Prolactinoma
                    V.Haemangioblastoma
                   VI.Lipoma
                  VII.Epidermoid
                      Dermoid
                  VIII.
                Haematoma – could be if more than four weeks old
                Abscess – pyogenic
                Tuberculoma
                Cyst
                     I. Arachnoid
                    II. Porencephalic
                   III. Hydatid
                                           Radiographic data together with the
                                           relevant clinical information may result in
                                           a statistically accurate diagnosis but all
                                                                                   10
                                             Tumour characteristics on CT
                                 CT findings
     Histopathology                                                Edema    Cyst       Haemorrhage Mass
                                 -c                    +c
     Pilocytic astrocytoma       iso/hypo              ++          +        +++        -              +/-
     Cerebellar astrocytoma      iso/hypo              +           +/-      +++        -              +/-       and Stark, 1993).
     Astrocytoma grade I         hypo                  -(+)        +/-      -(+)       -              +/-
     Subependymal astrocytoma iso/hyper                +++         +        -          -              +
     Astrocytoma grade II        hypo                  +/-         +/-      +/-        -              +/-
     Astrocytoma grade III       hypo/iso              ++          +        +          +/-            +
     Glioblastoma                hypo/iso/hyper        ++/+++      +++      +          ++             ++
     Oligodendroglioma I and II hypo/iso/hyper         -/+         +/-      +          ++             +/-
                                                                                                                diagnosis of intracranial pathologies must
                                                                                                                have a histological confirmation (Vanel




     Oligodendroglioma III and
                                hypo/iso/hyper         ++          ++       +++        +++            ++
     IV
     Ependymoma                 iso/hyper              +           ++       +/-        +/-            ++
     Medulloblastoma             hyper                 ++          +        +/-        ++             +
     Primary lymphoma            hyper                 +++         +++      -          -              ++
     Pineal tumours              iso/hyper             +++         +/-      -          +/-            +/-
     Choroid plexus papilloma    iso/hyper             +++         +/-      -          -              ++
     Epidermoid                  hypo                  -           -        -          -              +/-
     Dermoid                     hypo/hyper            -           -        +/-        -              +
     Teratoma                    iso/hyper             -(+)        -        +/-        -              +
                                                                                                                  (Vanel & Stark, 1993 p. 33)




     Lipoma                      hypo                  -           -        -          -              +/-
     Metastases                  hypo/iso/hyper        +/++        ++/+++   +          +              +/++
                                                                                                                                                Table 3 - Tumour characteristics on CT




     +, present; -, absent; iso, isodense or isointense; hypo, hypodense or hypointense; hyper, hyperdense or
     hyperintense.




11
 Other imaging modalities

Besides plain and contrast enhanced CT
and MR imaging, which to date remain
the modalities of choice for various
reasons (including availability and cost),

One can mention PET which is
particularly   superior    to  both   in
differentiating radiation necrosis from
tumour recurrence as it can depict the
actual metabolic activity.




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