Материал: part03

>>Include Table 8.8-1 “Code Sequence Macro Attributes”.​DCID 7215 “Spectroscopy Purpose of Reference”.​

C.8.14.1.1 MR Spectroscopy Attribute Multiplicity Ordering​

ThefollowingAttributesmayhaveaValueMultiplicityofoneortwodependingwhetheroneortwofrequencyaxesareusedasspecified​ by the value of Data Point Rows (0028,9001):​

Transmitter Frequency (0018,9098)​

Resonant Nucleus (0018,9100)​

Spectral Width (0018,9052)​

Chemical Shift Reference (0018,9053)​

De-coupled Nucleus (0018,9060)​

De-coupling Frequency (0018,9061)​

De-coupling Chemical Shift Reference (0018,9063)​

Time Domain Filtering (0018,9065)​

Number of Zero Fills (0018,9066)​

Value 1 shall contain the value corresponding to the sampling time axis (the axis along a data point row).​

Value 2, if present, shall contain the value corresponding to the evolution time axis (the axis along a data point column).​

C.8.14.1.2 MR Spectroscopy Zero Fill Explanation​

Zero filling is a data processing technique where zero points are appended to the time domain data before Fourier transformation.​ The effect of zero filling is to increase the digital resolution in the spectrum. Since the zeros contain no new information, there is no​ new information added to the spectrum. It is artificially increasing the acquisition time after the data collection without adding any new​ information or true resolution to the spectrum. See Figure C.8.14.1-1, Figure C.8.14.1-2 and Figure C.8.14.1-3.​

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Zero Points

Figure C.8.14.1-1. Example Result without and with Zero Filling​

Echo Acquisition time

Acquired Signal

(Signal Domain = TIME)

Data Point Columns

(0018,9002)

Echo Peak Position

(0018,xx02)

Time Domain Filtering

Zero Fill

Number of Zero Fills

(0018,9066)

Fourier Transformation

Frequency Spectrum

(Signal Domain = FREQUENCY)

Data Point Columns

(0018,9002)

Figure C.8.14.1-2. Echo Acquisition with Applying Zero Fill​

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Acquired Signal

(Signal Domain = TIME)

Data Point Columns

(0018,9002)

Echo Peak Position

(0018,xx02)

Time Domain Filtering

Zero Fill

Number of Zero Fills

(0018,9066)

Fourier Transformation

Frequency Spectrum

(Signal Domain = FREQUENCY)

Data Point Columns

(0018,9002)

Figure C.8.14.1-3. Free Induction Decay Acquisition with Applying Zero Fill​

C.8.14.1.3 MR Spectroscopy Water Reference Data Clarification​

MR Spectroscopy is using diagnostic data and water reference data. The water reference data is acquired and used to correct the​ phaseofthediagnostictimedomaindatabeforetheFouriertransformationtothefrequencydomain.Therelationbetweenthedifferent​ spectroscopy objects is given in Figure C.8.14.1-4.​

When Water Reference Acquisition (0018,9297) equals REFERENCED, it means that instances are available that were or can be​ used for Water Phase Correction. All other values mean that there are no instances available although data might have been used​ for water phase correction, see Water Referenced Phase Correction (0018,9199).​

The water reference data can also be used for quantification of the signal strength of the diagnostic data.​

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Figure C.8.14.1-4. Relation Between Spectroscopy Instances​

C.8.14.1.4 Water Reference Acquisition​

The value of Water Reference Acquisition (0018,9297) specifies the intent of the spectroscopy data acquired.​

Enumerated Values:​

WATER_REFERENCE​This instance is acquired to be used as water reference and can be used by other spectroscopy data in the​ Study for water phase correction.​

USED_DISCARDED​The phase of this spectroscopic instance is corrected with water reference data. The water reference data​ used is discarded after correction and no longer available.​

REFERENCED​ This spectroscopic instance has water reference data available for phase correction or the phase is already​ corrected with water reference data. The water reference data shall be specified in the Referenced Instance​ Sequence (0008,114A).​

NONE​ This spectroscopic instance has not been corrected for the water phase signal and water reference data has​ not been acquired.​

C.8.14.2 MR Spectroscopy Pulse Sequence Module​

The primary purpose of this Module is to identify the pulse sequence and variations that were used in creation of the spectroscopic​ data. Terminology is intended to be neutral, and allow equivalent pulse sequences provided by different vendors to be classified to-​ gether.​

Table C.8-103 specifies the Attributes of the MR Spectroscopy Pulse Sequence Module.​

Table C.8-103. MR Spectroscopy Pulse Sequence Module Attributes​

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Enumerated Values:​

YES​

NO​

Required if Image Type (0008,0008) Value 1 is ORIGINAL or MIXED and​

Echo Pulse Sequence (0018,9008) equals SPIN or BOTH.​

Otherwise may be present if Image Type (0008,0008) Value 1 is DERIVED​ and Echo Pulse Sequence (0018,9008) equals SPIN or BOTH.​

Enumerated Values:​

YES​

NO​

Required if Image Type (0008,0008) Value 1 is ORIGINAL or MIXED. May​ be present otherwise.​

Steady State Pulse​ (0018,9017)​ 1C​ Steady State Sequence.​

Sequence​

Defined Terms:​

FREE_PRECESSION​

TRANSVERSE​

TIME_REVERSED​

LONGITUDINAL​

NONE​

Required if Image Type (0008,0008) Value 1 is ORIGINAL or MIXED. May​ be present otherwise.​

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