如何在PyDICOM中获取超声DICOM图像的像素/cm²缩放比例

我有多个存储超声图像的DICOM文件，需要提取图像的缩放信息（即像素/cm²）。请问是否存在对应的DICOM标签存储该信息？还是需要通过计算得出？

我的DICOM数据集如下：

Dataset.file_meta -------------------------------
(0002, 0000) File Meta Information Group Length  UL: 196
(0002, 0001) File Meta Information Version       OB: b'\x00\x01'
(0002, 0002) Media Storage SOP Class UID         UI: Ultrasound Multi-frame Image Storage
(0002, 0003) Media Storage SOP Instance UID      UI: 1.2.840.113619.2.391.51208.1686298501.4.21
(0002, 0010) Transfer Syntax UID                 UI: JPEG Baseline (Process 1)
(0002, 0012) Implementation Class UID            UI: 1.2.276.0.48.20000.2
(0002, 0013) Implementation Version Name         SH: 'TomTecArena v2'
(0002, 0016) Source Application Entity Title     AE: 'TTCLIENT'
-------------------------------------------------
(0008, 0008) Image Type                          CS: ['DERIVED', 'PRIMARY', '', '0001']
(0008, 0016) SOP Class UID                       UI: Ultrasound Multi-frame Image Storage
(0008, 0018) SOP Instance UID                    UI: 1.2.840.113619.2.391.51208.1686298501.4.21
(0008, 0020) Study Date                          DA: '20230609'
(0008, 0021) Series Date                         DA: '20230609'
(0008, 0023) Content Date                        DA: '20230609'
(0008, 002a) Acquisition DateTime                DT: '20230609081459'
(0008, 0030) Study Time                          TM: '081459'
(0008, 0031) Series Time                         TM: '081459'
(0008, 0033) Content Time                        TM: '081459'
(0008, 0050) Accession Number                    SH: ''
(0008, 0060) Modality                            CS: 'US'
(0008, 0070) Manufacturer                        LO: 'GE Vingmed Ultrasound'
(0008, 0090) Referring Physician's Name          PN: ''
(0008, 1090) Manufacturer's Model Name           LO: 'Vivid E95'
(0008, 2142) Start Trim                          IS: '1'
(0008, 2143) Stop Trim                           IS: '32'
(0008, 2144) Recommended Display Frame Rate      IS: '30'
(0010, 0010) Patient's Name                      PN: '3001'
(0010, 0020) Patient ID                          LO: '3001'
(0010, 0030) Patient's Birth Date                DA: ''
(0010, 0040) Patient's Sex                       CS: ''
(0012, 0062) Patient Identity Removed            CS: 'YES'
(0012, 0063) De-identification Method            LO: 'GEVU anonymization'
(0018, 0040) Cine Rate                           IS: '30'
(0018, 0072) Effective Duration                  DS: '1.04'
(0018, 1020) Software Versions                   LO: 'Vivid E95:201.84.0'
(0018, 1063) Frame Time                          DS: '33.5484'
(0018, 1066) Frame Delay                         DS: '0.0'
(0018, 1088) Heart Rate                          IS: '95'
(0018, 1242) Actual Frame Duration               IS: '33'
(0018, 1244) Preferred Playback Sequencing       US: 0
(0018, 6011)  Sequence of Ultrasound Regions  1 item(s) ---- 
   (0018, 6012) Region Spatial Format               US: 1
   (0018, 6014) Region Data Type                    US: 1
   (0018, 6016) Region Flags                        UL: 0
   (0018, 6018) Region Location Min X0              UL: 213
   (0018, 601a) Region Location Min Y0              UL: 70
   (0018, 601c) Region Location Max X1              UL: 803
   (0018, 601e) Region Location Max Y1              UL: 658
   (0018, 6020) Reference Pixel X0                  SL: 295
   (0018, 6022) Reference Pixel Y0                  SL: 0
   (0018, 6024) Physical Units X Direction          US: 3
   (0018, 6026) Physical Units Y Direction          US: 3
   (0018, 602c) Physical Delta X                    FD: 0.0238278
   (0018, 602e) Physical Delta Y                    FD: 0.0238278
   (0018, 6030) Transducer Frequency                UL: 1670
   ---------
(0018, 6060) R Wave Time Vector                  FL: [313.3869934082031, 1000.0260009765625]
(0020, 000d) Study Instance UID                  UI: 1.2.840.113619.2.391.51208.1686298500.4.1
(0020, 000e) Series Instance UID                 UI: 1.2.840.113619.2.391.51208.1686298500.4.2
(0020, 0010) Study ID                            SH: '202306090814'
(0020, 0011) Series Number                       IS: '1'
(0020, 0013) Instance Number                     IS: '19'
(0020, 0020) Patient Orientation                 CS: ''
(0028, 0002) Samples per Pixel                   US: 3
(0028, 0004) Photometric Interpretation          CS: 'YBR_FULL_422'
(0028, 0006) Planar Configuration                US: 0
(0028, 0008) Number of Frames                    IS: '32'
(0028, 0009) Frame Increment Pointer             AT: (0018, 1063)
(0028, 0010) Rows                                US: 708
(0028, 0011) Columns                             US: 1016
(0028, 0014) Ultrasound Color Data Present       US: 0
(0028, 0100) Bits Allocated                      US: 8
(0028, 0101) Bits Stored                         US: 8
(0028, 0102) High Bit                            US: 7
(0028, 0103) Pixel Representation                US: 0
(0028, 2110) Lossy Image Compression             CS: '01'
(0028, 2112) Lossy Image Compression Ratio       DS: '95.0'
(7fe0, 0010) Pixel Data                          OB: Array of 2521450 elements
(fffc, fffc) Data Set Trailing Padding           OB: b'\x00\x00'

解答 #

没有直接存储像素/cm²的DICOM标签，需要通过现有标签计算得出，步骤如下：

• 确认物理单位：查看(0018, 6024)和(0018, 6026)标签（Physical Units X/Y Direction），值为3，对应毫米（mm）（DICOM标准中US类型值3代表毫米）。
• 获取像素物理长度：在(0018, 6011)（Sequence of Ultrasound Regions）序列下，(0018, 602c)（Physical Delta X）和(0018, 602e)（Physical Delta Y）的值均为0.0238278，即每个像素对应0.0238278毫米。
• 计算缩放信息：
  1. 单位转换：将毫米转为厘米，0.0238278 mm = 0.00238278 cm
  2. 每厘米像素数：1 ÷ 0.00238278 ≈ 420 像素/cm
  3. 像素/cm²：(420)² ≈ 176400 像素/cm²

内容的提问来源于stack exchange，提问作者mik.ro