* BRAIN-USEFUL TIPS *

1*CAREFUL QUALITY CONTROL IS NECESSARY, INCLUDING PAPER CHROMATOGRAPHY OF THE 99mTc HMPO PRIOR TO INJECTION. INJECTION SHOULD BE PERFORMED IMMEDIATELY AFTER PREPARATION, PREFERABLY INTO A FREE FLOWING IV LINE. BLOOD SHOULD NOT BE WITHDRAWN INTO SYRINGE PRIOR TO INJECTION*

2*THE PATIENT'S HEAD SHOULD ALWAYS BE IMMOBILIZED FIRMLY WITH TAPE OR VECRO TO THE HEAD-REST PRIOR TO THE STUDY. SMALL CHILDREN OR SEVERELY DEMENTED PATIENTS MAY REQUIRE SEDATION, WHICH SHOULD BE GIVEN AFTER THE TRACER INJECTION, BUT BEFORE SCANNING. THE PATIENT SHOULD NOT BE LEFT UNATTENDED*

3*STRENUOUS ATTEMPTS SHOULD BE MADE TO ENSURE CORRECT POSITIONING. SOME CAMERAS CONTAIN LASER LIGHT BEAMS WHICH HELP. SOME ALSO CONTAIN SOFTWARE WHICH CAN PERFORM A DEGREE OF TILT CORRECTION. THE PATIENT'S POSITION SHOULD BE CHECKED FROM THE FOOT OF THE TABLE*

4*THE USUAL COUNT RATE OBTAINED ON THE CAMERA SHOULD BE RECORDED WITH BRAIN SPECT STUDIES AT THE BEGINNING OF ACQUISITION. IF THE COUNT RATE IN A STUDY FALLS SIGNIFICANTLY BELOW THE EXPECTED, THE SCANNING TIME PER FRAME SHOULD BE INCREASED PROPORTIONALLY*

5*REGULAR CHECKING OF HIGH-COUNT-RATE PHANTOMS (BOTH PLANAR AND SPECT) IS ESSENTIAL, AS ARE REGULAR CENTRE OF ROTATION CORRECTIONS*

6*IT IS IMPORTANT TO STANDARDIZE THE ANGLE AT WHICH TRANSAXIAL SLICES ARE PRODUCED. ONE WAY IS TO USE A PLANE FROM A LINE CONNECTING THE INFERIOR SURFACES OF THE FRONTAL AND OCCIPITAL LOBES ON A SAGITTAL OR LATERAL IMAGE. EXTERNAL MARKERS MAY ALSO BE PLACED ON THE PATIENT'S FACE TO MARK A LINE CONNECTING THE EXTERNAL CANTHUS OF THE EYE WITH THE TRAGUS OF THE EAR*

7*THE PROCESSING PARAMETERS USED WILL DEPEND ON THE CAMERA AND THE TYPE AND INJECTED DOSE OF RADIOTRACER. TO OBTAIN THE OPTIMUM COMBINATION, TRIAL AND ERROR IS USUALLY REQUIRED INITIALLY, TOGETHER WITH THE ADVICE OF THE CAMERA MANUFACTURER, BUT, ONCE FOUND, IT SHOULD BE ADHERED TO WHEREVER POSSIBLE*

8*THE USER SHOULD ADHERE TO A SINGLE COLOUR SCHEME. IN THIS WAY EACH USER'S LEVEL OF 'NORMALITY' WILL GRADUALLY BE SET FOR THIS SCHEME. WHERE POSSIBLE, IMAGES SHOULD BE VIEWED ON THE MONITOR, SINCE THIS REDUCE THE PROBLEM OF IMAGE SATURATION. IMAGES SHOULD BE VIEWED IN ALL SLICES, WITH THE DISPLAY SET TO THE MAXIMUM IN THE ENTIRE BODY, NOT ON A FRAME-BY-FRAME BASIS. IF CT OR MRI STUDIES ARE AVAILABLE, THEY SHOULD BE VIEWED CONCURRENTLY. THE COLOUR SCALE SHOULD ALWAYS BE DISPLAYED AND CHANGES IN COLOUR (eg RED TO YELLOW) SHOULD BE CORRELATED WITH PERCENTAGE CHANGES IN CEREBRAL BLOOD FLOW*

9*IN A NORMAL STUDY:
*NO TRACER SHOULD ENTER LATERAL VENTRICLES*
*TRACER SHOULD HAVE FLOWED OVER THE CEREBRAL CORTEX BY 24 HOURS*

10*AN INFARCT MAY NOT INVOLVE AN ENTIRE VASCULAR TERRITORY*
*VASCULAR TERRITORIES SHOW SOME VARIATION BETWEEN INDIVIDUALS*

11*CEREBRAL PERFUSION STUDIES ARE ABNORMAL IMMEDIATELY FOLLOWING THE STROKE, AND OFTEN 24-48 HOURS BEFORE CT OR MRI ABNORMALITIES APPEAR*

12*THE EXTENT OF ABNORMALITIES SEEN ON BRAIN SPECT IMAGING OFTEN EXCEEDS THOSE SEEN ON CT/MRI*
*HYPOPERFUSION OF THE CONTRALATERAL CEREBELLAR HEMISPHERE IS OFTEN SEEN SO -CALLED 'CROSSED CEREBELLAR DIASCHISIS'. THIS OCCUR MOST COMMONLY IN MOTOR CORTEX INFARCTS, BUT CAN BE SEEN IN OTHER CONDITIONS*

13*WHEN THE STATIC BRAIN SCAN IMAGES ARE ATYPICAL, THE PRESENCE OF MARKEDLY DECREASED BLOOD FLOW TO THAT AREA WILL INCREASE THE PROBABILITY OF A CEREBRAL INFARCT, BECAUSE THE MAIN DIFFERENTIAL DIAGNOSIS, A GLIOMA, WILL ALMOST ALWAYS HAVE INCREASED BLOOD FLOW*
*WHEN THE STATIC RADIONUCLIDE BRAIN SCAN IS EQUIVOCALLY ABNORMAL, WITH NO SPECIFIC FEATURES, THE CLEAR-CUT LOSS OF RIGHT MIDDLE CEREBRAL PERFUSION MAKES AN ACUTE CEREBRAL INFARCT ALMOST CERTAIN*

14*OCCASIONALLY, THE STATIC BRAIN SCAN MAY BE COMPLETELY NORMAL. THE VASCULAR STUDY SHOWING LOSS OF BLOOD FLOW TO THE LEFT SIDE IN A PATIENT WHO HAS RECENTLY DEVELOPED RIGHT-SIDED PARESIS WILL EXCLUDE A MALIGNANT SPACE-OCCUPYING LESION AS THE CAUSE WITH A HIGH DEGREE OF CERTAINTY*

15*MOST CEREBRAL INFARCTS SHOW DECREASED BLOOD FLOW. HOWEVER, THE RIGHT-SIDED CEREBRAL INFARCT SHOWS INCREASED BLOOD FLOW, SO CALLED 'LUXURY' PERFUSION. THE CLINICAL MUST BE AWARE OF THIS POSSIBILITY SO AS TO AVOID REPORTING AN INFARCT AS A PROBABLE TUMOUR. AN IMPORTANT DIFFERENTIAL POINT IN THIS CASE IS THE SHAPE OF THE LESION ON THE LATERAL VIEW AND THE FACT THAT IT LIES DISCRETELY WITHIN POSTERIOR BRANCHES OF THE MIDDLE CEREBRAL ARTERY TERRITORY*

16*INCREASED PERFUSION ('LUXURY' PERFUSION) CAN SOMETIME BE SEEN IN SUBACUTE INFARCTS. IT IS MAXIMAL AT ABOUT 20 DAYS, AND IS PROBABLY DUE TO PERI-INFARCT LOSS OF VASOMOTOR CONTROL AND INGROWTH OF NEW CAPILLARIES*

17*NOT ALL BBB BRAIN SCANS OF CEREBRAL INFARCTS RESOLVE, AND SOME MAY REMAIN POSITIVE INDEFINITELY. THEREFORE THE PRESENCE OF AN INFARCT ON THE SCAN DOSE NOT INDICATE A RECENT EVENT*

18*THE DISTRIBUTION OF CEREBRAL HEMORRHAGE MAY CROSS VASCULAR TERRITORIES*
*MARKED WHITE MATTER HYPOPERFUSION, WITH RETAINED CORTICAL HYPOPERFUSION, SUGGESTS HEMORRHAGE OR WHITE MATTER INFARCTION*

19*BBB AGENT SCANS ARE USUALLY NORMAL IN PATIENTS WITH TIAS UNLESS THERE IS A SEVERE CAROTID STENOSIS*
*SCANS WITH CEREBRAL PERFUSION AGENTS ARE ONLY ABNORMAL IN 50-70% OF CASES WITH ABSENCE OF INFARCTION*
*POSITIVE SCANS ARE MORE LIKELY TO BE OBTAINED IF THE PATIENT IS SCANNED WHILE SYMPTOMATIC, OR SOON AFTER RECOVERY*
*ABNORMALITIES SHOULD FOLLOW VASCULAR TERRITORIES*
*SOME CENTERS ADVOCATE THE USE OF CEREBRAL VASODILATOR AGENTS SUCH AS CO2 OR ACETAZOLOMIDE TO INCREASE THE SENSITIVITY OF HMPAO SCANS IN TIAS/CAROTID STENOSES*

20*BRAIN PERFUSION STUDIES MAY BE USED TO DETECT VASOSPASM AND TO MONITOR THERAPY*
*SEVER VASOSPASM IS ASSOCIATED WITH A POOR PROGNOSIS*
*BBB AGENT STUDIES ARE NORMAL IN SUBARACHNOID HEMORRHAGE*

21*AVMS DO NOT ACCUMULATE 99mTc-HMPO, AND SO APPEAR AS SPACE-OCCUPYING LESIONS*

22*CRITERIA FOR BRAIN DEATH:
*NO INTRACEREBRAL ARTERIAL, CAPILLARY OR VENOUS FLOW ON DYNAMIC STUDY*
*NO VISUALIZATION OF SAGITTAL SINUS ON IMMEDIATE POST-INJECTION IMAGES*

23*99mTc-HMPAO IS PREFERRED TO A BBB AGENT TO ASSESS BRAIN DEATH*

24*SMALL BILATERAL CHRONIC SUBDURAL HEMATOMAS MAY EASILY BE MISSED BECAUSE OF THEIR SYMMETRICAL APPEARANCES. POINTS TO NOTE ARE:
*THE BLOOD FLOW STUDY SHOWING COMPRESSION OF THE CEREBRAL CORTEX*
*ON DELAYED IMAGES, THE LOSS OF FRONTAL LUCENCY ON THE LATERAL VIEW, SINCE THE REGION AT THE FRONTAL LOBE SHOULD NORMALLY BE MORE PHOTON-DEFICIENT THAN THE PARIETAL AND TEMPORAL LOBES*

25*FOCAL UNILATERAL OR BILATERAL HYPOPERFUSION IN THE FRONTAL OR PARIETAL REGIONS IN A NON-VASCULAR DISTRIBUTION IS SUSPICIOUS OF SUBDURAL/EXTRADURAL HEMATOMAS*
*THE PRESENCE OF HYPOPERFUSION SUGGESTS THAT A KNOWN HEMATOMA IS OF SUFFICIENT SIZE TO COMPROMISE CEREBRAL PERFUSION*

26*BRAIN PERFUSION STUDIES ARE VERY SENSITIVE TO LOCALIZING CEREBRAL CONTUSIONS IN ACUTE AND CHRONIC HEAD INJURIES*
*ABNORMALITIES ARE USUALLY FOCAL AND ASYMMETRICAL*
*ABNORMALITIES ARE OFTEN MORE EXTENSIVE AND NUMEROUS THAN THE CT ABNORMALITIES*

27*TYPICAL, BILATERAL TEMPORAL AND PARIETAL HYPOPERFUSION IS SEEN IN Alzheimer's DISEASE*
*PERFUSION IS USUALLY RETAINED IN THE FRONTAL LOBES IN EARLY DISEASE, AS WELL AS IN THE BASAL GANGLIA, VISUAL AND SENSORIMOTOR CORTEX AND CEREBELLUM*

28*THE ABNORMALITIES IN EARLY DISEASE ARE OFTEN SUBTLE, AND ARE BEST SEEN ON THE SAGITTAL SLICES*
*ASYMMETRIC DISEASE IS COMMON, BUT A PURELY UNILATERAL ABNORMALITY SHOULD RAISE THE POSSIBILITY OF STROKE OR EVEN SUBDURAL HEMATOMA*

29*THE FRONTAL LOBES MAY BE INVOLVED IN SEVERE DISEASE. EVENTUALLY, A PATTERN OF MARKED PAN-CORTICAL HYPOPERFUSION MAY BE SEEN IN VERY ADVANCED CASES*

30*SIMILAR PATTERNS TO ALZHEIMER'S DISEASE CAN BE SEEN IN BILATERAL PARIETAL SUBDURAL OR STROKES. CT SCANNING MAY BE REQUIRED TO EXCLUDE THESE*
*PARKINSON'S DISEASE WITH DEMENTIA APPEARS SIMILAR TO ALZHEIMER'S DISEASE ON BRAIN PERFUSION IMAGING. THE BASAL GANGLIA ARE TYPICALLY NORMALLY PERFUSED*

31*THE LESION OF MID ARE FOCAL, USUALLY IN BOTH HEMISPHERES AND ASYMMETRICAL*
*LESIONS SHOULD REMAIN WITHIN VASCULAR TERRITORIES IF THERE IS CORTICAL INVOLVEMENT*
*THE NUMBER OF FOCAL PERFUSION DEFECTS WILL VARY CONSIDERABLY FROM APPARENTLY SINGLE LESIONS TO WIDESPREAD ABNORMALITIES (eg BINZWANGER'S DISEASE)*

32*PERSONALTY CHANGE MAY BE THE ONLY FEATURE OF A FRONTAL LOBE TUMOUR, AND THERE MAY NOT BE ANY OBVIOUS FOCAL NEUROLOGICAL SIGNS*

33*TRACER IN THE VENTRICLES IS ALWAYS ABNORMAL*
*IN COMMUNICATING HYDROCEPHALUS TRACER IS SEEN IN THE LATERAL VENTRICLES AT 4 HOURS, REMAINING AT 24 HOURS*
*DELAYED IMAGING AT 48 HOURS IS OCCASIONALLY REQUIRED*
*IN SEVERE DISEASE THERE MAY BE DELAYED ASCENT OF THE TRACER OVER THE HEMISPHERES*
*IN CEREBRAL ATROPHY RADIOTRACER MAY PASS INTO THE LATERAL VENTRICLES, BUT IT RAPIDLY EMPTIES*

34*INTERICTAL SCANS SHOW HYPOPERFUSION AT THE SITE OF THE SEIZURE FOCUS IN 60-75% OF PATIENTS WITH FOCAL SEIZURES*
*THE COMMONEST SITE IS THE TEMPORAL LOBE*
*THE ABNORMALITY OFTEN INVOLVES AN EXTENSIVE AREA*
*SLICES ORIENTATED ALONG THE AXIS OF THE TEMPORAL LOBE ARE HELPFUL, AS ARE CORONAL SLICES*

35*HYPOPERFUSION IS SEEN AT THE SITE OF THE SEIZURE FOCUS IN AN ICTAL STUDY*
*AN EXTENSIVE AREA OF BRAIN MAY BE INVOLVED, ESPECIALLY IF THE SEIZURE BECOMES GENERALIZED, AND CAUTION MUST BE USED IN INTERPRETATION*
*OCCASIONALLY BILATERAL ABNORMALITIES ARE SEEN TO BE SECONDARY ACTIVATION OF OTHER AREAS. THE INTERICTAL STUDY MAY BE HELPFUL IN THIS CASE*
*EARLY POST-ICTAL (WITHIN 1-5 MINUTES) STUDIES MAY LOCALIZE MORE ACCURATELY*
*EEG MONITORING AT THE TIME OF INJECTION IS REQUIRED FOR ACCURATE INTERPRETATION OF ICTAL STUDIES*

36*ALTHOUGH THE CT SCAN HAS A HIGHER SENSITIVITY THAN THE RADIONUCLIDE STUDY FOR DETECTION OF CEREBRAL SPACE-OCCUPYING LESIONS, THE SENSITIVITY OF THE RADIONUCLIDE STUDY IS NEVERTHELESS STILL HIGH, AT GREATER THAN 90%. THE RADIONUCLIDE STUDY IS USUALLY NOT AS GOOD AT DEFINING THE PATHOLOGICAL ENTITY AS CT*
*A VERY LARGE SOLITARY SPACE-OCCUPYING LESION IN THE BRAIN IS MUCH MORE LIKELY TO BE A PRIMARY TUMOUR THAN A SECONDARY DEPOSIT. THE LATTER LESION IS MORE FREQUENTLY SMALL AND MULTIPLE*

37*BENIGN LESIONS VERY RARELY CROSS THE MIDLINE*

38*THE BRAIN SCAN WILL BE NORMAL IN A PATIENT WITH SIGNS DUE TO A PARANEOPLASTIC SYNDROME*

39*THE POSTERIOR FOSSA IS BOUNDED SUPERIORLY BY THE TENTORIUM, NOT BY THE VENOUS SINUSES. THEREFORE, THE VERMIS LESION MAY APPEAR TO BE ABOVE THE POSTERIOR FOSSA*

40*201Tl IS A NON-SPECIFIC TUMOUR IMAGING AGENT*
*201Tl MAY BE USEFUL IN DISTINGUISHING A MALIGNANT LESION FROM AN INFECTION OR NECROSIS*
*LOW-GRADE TUMOURS MAY EXHIBIT LOW 201Tl UPTAKE*

41*IN ANT PATIENT WITH A KNOWN NEOPLASM THAT MAY METASTASIZE, ALMOST ANY NEUROLOGICAL SIGN OR SYMPTOM JUSTIFIES A BRAIN SCAN, SINCE THE PRESENTATION OF A CEREBRAL METASTASIS IS EXTREMELY VARIABLE*

42*CEREBRAL TUMOURS USUALLY APPEAR AS NON-SPECIFIC FOCAL PERFUSION DEFECTS ON BRAIN PERFUSION IMAGING. OCCASIONALLY THE TUMOURS MAY HAVE UPTAKE EQUAL TO OR EXCESS OF THE SURROUNDING CORTEX. IF THE DEFECTS CROSS VASCULAR TERRITORIES, METASTASES RATHER THAN MULTIPLE INFARCTIONS SHOULD BE SUSPECTED*

43*DIFFERENTIATION BETWEEN A MENINGIOMA AND AN INTRACEREBRAL INFARCT CAN BE DIFFICULT. DIFFERENTIAL POINTS TO NOTE ARE THAT IN AT LEAST ONE VIEW (THE LATERAL) THE MENINGIOMA IS APPARENTLY SPHERICAL, WHEREAS THE CEREBRAL INFARCT KEEPS TO THE DISTRIBUTION OF THE MIDDLE CEREBRAL ARTERY TERRITORY. FURTHER, ON THE POSTERIOR VIEW, THE MENINGIOMA APPEARS TO BE EXTENDING TOWARDS THE MIDLINE. BLOOD FLOW STUDIES ARE ALSO OF VALUE, AS THESE SHOW INCREASED BLOOD FLOW TO A MENINGIOMA AND DECREASED BLOOD FLOW TO AN INFARCT*

44*UNFORTUNATELY, NOT ALL GLIOMAS HAVE AN INCREASE BLOOD SUPPLY. A USEFUL POINT OF DIFFERENTIATION IS THE FACT THAT THE LESION ON THE ANTERIOR VIEW CROSSES THE MIDLINE TO THE LEFT SIDE*

45*MENINGIOMA DOSE NOT CROSS THE MIDLINE, AND ARISES FROM A SITE IN THE MENINGES, AND THERE IS A MASSIVE DRAINAGE VEIN ASSOCIATED WITH IT. GLIOMA, ON THE OTHER HAND, CAN BE CLEARLY SEEN INVASIVELY CROSSING THE MIDLINE, WHICH WOULD BE RARE FOR A MENINGIOMA*

46*MANY LESIONS WILL BECOME PROGRESSIVELY MORE PROMINENT AS A RESULT OF RELATIVELY GREATER TRACER AVIDITY; HOWEVER, BECAUSE THE HALF-LIFE OF 99mTc IS ONLY 6 HOURS, THERE IS LIMIT TO THE BENEFIT WHICH WILL BE OBTAINED FROM PROLONGED WAITING*

47*IT HAS OFTEN BEEN SAID THAT THE APPEARANCE OF A DONUT SIGN INDICATES A CEREBRAL ABSCESSES MAY INDEED SHOW THIS SIGN, THE FINDING IS NON-SPECIFIC, BECAUSE OF THE PREVALENCE OF DISEASE, THE DONUT SIGN WILL MORE OFTEN BE FOUND IN ASSOCIATION WITH TUMOUR*

48*BONY INVOLVEMENT OF THE SKULL IS A WELL-RECOGNIZED CAUSE OF A FALSE-POSITIVE BRAIN SCAN FOR SUBDURAL COLLECTION, AND IS MOST OFTEN SEEN IN ASSOCIATION WITH EITHER METASTASES OR PAGET'S DISEASE. A RADIONUCLIDE BONE SCAN WILL OFTEN CLARIFY THE SITUATION*
*MOST NON-CEREBRAL,ie SKULL AND SCALP, LESIONS ARE PROMINENT BECAUSE OF THE VASCULAR SPACE WITHIN THEM. THEREFORE MOST OF THESE LESIONS WILL SHOW DECREASED TRACER UPTAKE WITH INCREASING TIME BETWEEN INJECTION AND IMAGING*

49*THE IMPORTANCE OF CLINICAL EXAMINATION ONCE THE STUDY HAS BEEN PERFORMED, LESIONS COULD BE EASILY LOCALIZED BY MANUAL PALPATION*
*SKULL AND SCALP LESIONS MAY OFTEN PROVIDE A CLUE AS TO THEIR ORIGIN BY DISTORTING THE SMOOTH OUTER MARGIN OF THE SKULL ON ONE OF THE BRAIN SCAN VIEWS. INTRACEREBRAL LESION NEVER DO THIS*

*BRAIN IMAGING INTERPRETATION*
*BRAIN CLINICAL APPLICATIONS*
* CISTERNOGRAGHY-USEFUL TIPS *
*CISTERNOGRAGHY IMAGING INTERPRETATION*
* CENTRAL NERVOUS SYSTEM *